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Natural halloysite nanotubes /chitosan based bio-nanocomposite for delivering norfloxacin, an anti-microbial agent in sustained release manner
... The sample of blank MNP-based nanocomposite beads showed distinctively different pXRD spectra from the drug's spectra, as sharp peaks were completely absent in the blank formulation. The XRD spectra of blank MNP beads showed no drug peak, which verified the absence of the drug [35]. Figure 10 shows the pXRD spectra of aceclofenac, F1, F2, and blank. ...
... The sample of blank MNP-based nanocomposite beads showed distinctively different pXRD spectra from the drug's spectra, as sharp peaks were completely absent in the blank formulation. The XRD spectra of blank MNP beads showed no drug peak, which verified the absence of the drug [35]. Magnetochemistry 2025, 11, x FOR PEER REVIEW 13 of 22 Figure 10. ...
... This suggests that the blank sample contained magnetite, and the decrease in peak intensity is likely due to the entrapment of magnetite in the bead. Additionally, the blank sample did not show any significant peaks related to aceclofenac, which confirms the absence of the drug in the sample [35]. The range between 3000 and 3600 cm −1 displays the vibrations of O-H bonds stretching of Na-alginate [21,44,45]. ...
Iron oxide-based nanoparticles, such as magnetic nanoparticles (MNPs), have gained significant attention in the area of drug delivery due to their unique magnetic properties, allowing for precise targeting and controlled release of therapeutic agents. Several successful research studies were reported with combinations of magnetic nanoparticles and polysaccharides such as sodium alginate, chitosan, cellulose, etc. The presented research work is based on synthesising MNPs via the co-precipitation method and their successful encapsulation within alginate beads, serving as a promising drug delivery system for aceclofenac, a model drug. The physical and chemical characteristics of both the prepared magnetite nanoparticles and the aceclofenac-loaded MNPs alginate beads were thoroughly examined using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), and vibrating sample magnetometry (VSM). Furthermore, a drug release study was conducted to evaluate the release kinetics of aceclofenac from the prepared MNP alginate beads. The magnetic characteristics of magnetite and MNP beads shed light on the potential application of novel drug delivery systems for magnetically targeted therapeutic interventions. The present research offers valuable insights into the development of magnetic nanoparticle-based drug carriers, paving the way for enhanced drug delivery strategies in the field of pharmaceutical sciences.
... Fig. 1 displays the FT-IR spectra of the pristine (i.e., unfunctionalized) HNTs, the F-HNTs catalytic support, and the HSiW@F-HNTs catalyst. In all three spectra, the absorption bands at 3695 and 3625 cm − 1 are associated with the stretching vibration modes of hydroxyl functional groups (e.g., Al− OH) [41][42][43]. The absorption bands at 2930 cm − 1 and 1027 cm − 1 in the spectra of F-HNTs and HSiW@F-HNTs can be attributed to the stretching vibration modes of − CH 2 (as a result of APTES incorporation) and Si− O− Si bonds, respectively [42]. ...
... In all three spectra, the absorption bands at 3695 and 3625 cm − 1 are associated with the stretching vibration modes of hydroxyl functional groups (e.g., Al− OH) [41][42][43]. The absorption bands at 2930 cm − 1 and 1027 cm − 1 in the spectra of F-HNTs and HSiW@F-HNTs can be attributed to the stretching vibration modes of − CH 2 (as a result of APTES incorporation) and Si− O− Si bonds, respectively [42]. The sharp absorption band at 537 cm − 1 corresponds to the Al− O− Si deformation vibration mode observed within the spectra of all three samples, indicating the presence of HNTs [44]. ...
... Peppas model) and statistical (ex. Log-Logistic and Weibul model) mathematic models have been derived [64][65][66]. Depending on the hydrophilicity of the drug, the characteristics of the drug carriers and the drug release medium, the mechanism of drug release can be changed, thus the model that correctly describes it can also be different [64][65][66][67]. ...
... Log-Logistic and Weibul model) mathematic models have been derived [64][65][66]. Depending on the hydrophilicity of the drug, the characteristics of the drug carriers and the drug release medium, the mechanism of drug release can be changed, thus the model that correctly describes it can also be different [64][65][66][67]. ...
The main objective of this research is to investigate how curcumin liposomal nanocarriers influence the drug release behaviour of PVA/PEG hydrogels in relation to physico-mechanical properties. For this purpose, optimal nanoliposomes from drug loading and release viewpoints, prepared by the thin-film hydration method, were incorporated into the hydrogel composition. Hydrogel samples were physically crosslinked using the freeze–thaw procedure. According to the dynamic laser scattering, atomic force microscopy and field-emission scanning electron microscopy observations, negative nanoliposomes with negative surface charges showed a spherical morphology with an average particle size of about 100 nm and narrow size distribution. The X-ray diffraction results revealed that adding nanoliposomes to the hydrogel increases the degree of PVA chains crystallinity, enhances tensile modulus and tensile strength of the hydrogel, while decreasing swelling and dehydration rates. SEM micrographs observation displayed that the porosity in the hydrogel structure in the presence of nanoliposomes increases. Nevertheless, in agreement with physical properties, drug release from nanoliposome-in-hydrogel is slower and more controlled as compared to that from free curcumin hydrogel, especially in the early stages. The MTT assay results indicated that although all hydrogel samples are non-toxic, human foreskin fibroblast cell proliferation on hydrogel in the presence of curcumin-loaded nanoliposomes has improved somewhat.
... This translates to excellent compatibility within the biological environment, allowing for gradual degradation over time [14,15]. These properties make chitosan a valuable material in bone tissue engineering, complementing functionalities crucial for the process [16]. Additionally, chitosan sponges offer the added advantage of preventing infection during the healing process [17]. ...
This study investigates the impact of curcumin extract incorporation on the properties of PVA/Collagen/Chitosan/HAp nanofiber scaffolds for bone tissue engineering applications. Nanofibers were fabricated via electrospinning using PVA, collagen, chitosan, hydroxyapatite (HAp), and curcumin. Their morphology, mechanical properties, wettability, degradation rate, and antibacterial activity were comprehensively evaluated. Fourier transform infrared (FTIR) spectroscopy confirmed the successful incorporation of all components into the nanofibers and the potential for interactions between their functional groups. Scanning Electron Microscopy (SEM) revealed bead-free, fine nano-fibers with a decrease in diameter ranging from 139 nm to 108 nm. Simultaneously, enhanced mechanical properties were observed, with ultimate strength increasing from 2.8 MPa to 8.8 MPa as the diameter decreased. Notably, 15% curcumin extract maintained favorable hydrophilicity and degradation rates, crucial factors for tissue regeneration. Antibacterial activity was also enhanced, with an inhibition zone of 6.71 mm against E.coli observed at 15% curcumin treatment. Staphylococcus aureus exhibited the largest zone of inhibition (8.74 mm) at 15% curcumin concentration. This research demonstrates the feasibility of incorporating curcumin into nanofiber scaffolds for bone tissue engineering applications.
... They are biocompatible, with low toxicity, and high mechanical properties. In addition, they are a low-cost alternative compared to other drug delivery systems (Barman et al., 2020;Bertolino et al., 2020;Danyliuk et al., 2020;Fakhruddin et al., 2021;Massaro et al., 2021). ...
Objective
The purpose of the study was to compare the fluoride release in two conventional glass ionomer cements (Ionobond, Ketac Molar) and two resin-modified glass ionomer cements (Vitrebond, Fuji II LC) adapted with halloysite nanotubes preloaded with sodium fluoride at different concentrations.
Methods
In total, 96 samples were prepared and distributed into four control groups and eight experimental groups (5 % and 10 %). Totals of 10 % and 5 % of the total weight of ionomer powder needed to prepare the samples were replaced with nanotubes, preloaded at 2,000 parts per million, respectively. The experimental groups were followed for 120 days at seven time intervals. All the samples were stored at 37 °C.
Results
All the experimental groups showed significant differences compared with the control groups; likewise, differences were observed between the concentrations of 5% and 10%.
Conclusion
The experimental groups (conventional and resin-modified glass ionomer cements adapted with preloaded nanotubes) released a higher and more constant amount of fluoride compared to the control groups.
... This means that, in the future, the foods should not only be protected but also preserved for a longer period before being consumed or wasted. The most trendy and promising method for this achievement is to use bio-based materials [3,[5][6][7]. Such food additives are naturally abundant antioxidant/antibacterial phytochemical extracts and essential oils (EOs) [8,9]. ...
The use of natural raw substances for food preservation could provide a great contribution to food waste reduction, circular economy enhancement, and green process application widening. Recent studies indicated that the use of porous materials as adsorbents for natural essential oils provided nanohybrids with excellent antioxidant and antimicrobial properties. Following this trend in this work, a thymol oil (TEO) rich SBA-15 nanohybrid was prepared and characterized physiochemically with various techniques. This TEO@SBA-15 nanohybrid, along with the pure SBA-15, was extruded with low-density polyethylene (LDPE) to develop novel active packaging films. Results indicated that TEO loading was higher than other porous materials reported recently, and the addition of both pure SBA-15 and TEO@SBA-15 to the LDPE increased the water/oxygen barrier. The film with the higher thyme-oil@SBA-15 nanohybrid content exhibited a slower release kinetic. The antioxidant activity of the final films ignited after 48 h, was in the range of 60-70%, and was almost constant for 7 days. Finally, all tests indicated a sufficient improvement by the addition of thyme-oil@SBA-15 nanohybrids in the pure LDPE matrix and the concentration of wt. 10% of such nanocarriers provided the optimum final LDPE/10TEO@SBE-15 active packaging film. This material could be a potential future product for active packaging applications.
... [18] In addition, typical signals related to aluminosilicate nanotubes, such as bands related to OH groups, are evident: the peak at 1037 cm À 1 is ascribable to the AlÀ OÀ OH vibration, and the peak at 750 cm À 1 is assigned to the stretching mode of apical SiÀ O bonds. [19] In the end, it is essential to highlight the signal related to the carbonyl bridge at 1750 cm À 1 , which emphasizes the successful functionalization of the loofah fibers with halloysite nanotubes. [14] Indeed, this band is absent in the TiO 2 /L sample. ...
Volatile organic compounds (VOCs), recognized as hazardous air contaminants, prompt the exploration of sustainable air purification methods. Solar photocatalytic oxidation emerges as a promising solution, utilizing semiconductor photocatalysts like titanium dioxide (TiO2). However, the raw material crisis necessitates reduced TiO2 usage, leading to investigations into TiO2 modification techniques. The study introduces a novel approach by employing natural fibers, specifically loofah sponge, as a TiO2 support. This method aims to maintain photocatalytic activity while minimizing TiO2 content. The article explores using halloysite, a natural clay mineral, as a supportive material, enhancing mechanical strength and adsorption properties. The resulting TiO2/loofah–halloysite composites are evaluated for their efficacy in gas‐phase photocatalytic oxidation of toluene and ethanol, chosen as representative VOCs. The conversion of toluene and ethanol on the composite was 88 % and 39 %, respectively, with high selectivity toward CO2. In addition to its high performance, the bio–composite was stable for several conversion cycles, keeping the conversion activity unchanged. The study contributes to developing green hybrid materials for VOC removal, showcasing potential applications across industries.
... Biocompatibility, biodegradability, long-term stability, mucoadhesive capacity, non-toxicity, cationic nature, and the presence of amino and hydroxyl groups are the most critical characteristics that make chitosan an active and promising polysaccharide for various drug delivery (Barman et al., 2020;Hameed et al., 2022). Advances in drug delivery systems are attracting growing interest from researchers, and point to the need to develop innovative and improved materials using chitosan-based nanocomposites to enhance drug delivery efficiency. ...
For many years, chitosan has been widely regarded as a promising eco-friendly polymer thanks to its renewability, biocompatibility, biodegradability, non-toxicity, and ease of modification, giving it enormous potential for future development. As a cationic polysaccharide, chitosan exhibits specific physicochemical, biological, and mechanical properties that depend on factors such as its molecular weight and degree of deacetylation. Recently, there has been renewed interest surrounding chitosan derivatives and chitosan-based nanocomposites. This heightened attention is driven by the pursuit of enhancing efficiency and expanding the spectrum of chitosan applications. Chitosan’s adaptability and unique properties make it a game-changer, promising significant contributions to industries ranging from healthcare to environmental remediation. This review presents an up-to-date overview of chitosan production sources and extraction methods, focusing on chitosan’s physicochemical properties, including molecular weight, degree of deacetylation and solubility, as well as its antibacterial, antifungal and antioxidant activities. In addition, we highlight the advantages of chitosan derivatives and biopolymer modification methods, with recent advances in the preparation of chitosan-based nanocomposites. Finally, the versatile applications of chitosan, whether in its native state, derived or incorporated into nanocomposites in various fields, such as the food industry, agriculture, the cosmetics industry, the pharmaceutical industry, medicine, and wastewater treatment, were discussed.
... Barman et al., [11] prepared films made of chitosan nanocomposite loaded with norfloxacin (an antibiotic drug) for sustained release of the drug. This biofilm showed good antimicrobial activity and high biocompatibility and also, it was reported in the literature that the water uptake of the film was limited, which indicates the behaviour of sustained release of the incorporated drug, which supports the present study. ...
Introduction
Routine wound management in maxillofacial trauma with soft-tissue injury needs to be addressed in a systematic way to prevent untoward complications. In this study, we examined the effects of a novel surgical dressing material on pain, wound healing and scar and its feasibility to common people. Our aim is to compare the efficacy and potency of the nano-chitosan membrane and collagen–chitosan membrane as surgical dressing materials for soft-tissue wounds in the maxillofacial region.
Materials and Methods
Thirty participants who sustained soft-tissue injury in the maxillofacial region were included in the study. Post-suturing, Group A participants were treated with nano-chitosan membrane impregnated with chlorhexidine, Group B participants were treated with collagen–chitosan membrane impregnated with chlorhexidine and Group C participants had received chlorhexidine powder as conventional wound care management and recalled and evaluated for wound healing, pain and scar at seventh day, one month and three months postoperatively.
Results
The wound healing efficacy of both Group A and B participants was nearly comparable and Group A had better wound healing ( P = 0.043) when compared to conventional chlorhexidine dressing material. In relation to pain intensity, Group A was reported with a low intensity of pain and also with better results in scar assessment at the third-month follow-up.
Discussion
This study had proven that even though the wound healing efficacy of both nano-chitosan and collagen–chitosan membranes is nearly comparable, nano-chitosan shows better results on the evaluation of parameters such as wound healing, pain and scar. Nano-chitosan membrane has better wound healing when compared to conventional chlorhexidine dressing material.
... Sigmoid-shaped release pattern was observed that was confirmed using the Weibull equation which indicated the sustained release of halloysite nanotubes, using an in-vitro release kinetic study. These nanocomposites could be used in patients who need long-term catheterization, and an antibacterial drug like norfloxacin could be used to treat bacterial infection in those sites with sustained drug delivery [89]. Wang et al. synthesized a magnetic chitosan hydrogel (MCH) with an in-situ hybridization method. ...
... CS is the utmost significant polysaccharide for drug delivery related applications due to its positively charged (cationic) features and the existence of only amino groups. These features are accountable for several of their required properties which mainly include the adhesion property of these biomaterials, easiness of permeability towards metabolites, in situ gelation and controlled/targeted drug release ability (Barman et al., 2020). The incorporation of approximately 100 nm or less sized biopolymers during the fabrication of CS-based nanocomposites certainly provide enhanced hemostatic response towards any injury. ...
The attention to polymer-based biomaterials, for instance, chitosan and its derivatives, as well as the techniques
for using them in numerous scientific domains, is continuously rising. Chitosan is a decomposable naturally
occurring polymeric material that is mostly obtained from seafood waste. Because of its special ecofriendly,
biocompatible, non- toxic nature as well as antimicrobial properties, chitosan-based materials have received a lot
of interest in the field of biomedical applications. The reactivity of chitosan is mainly because of the amino and
hydroxyl groups in its composition, which makes it further fascinating for various uses, including biosensing,
textile finishing, antimicrobial wound dressing, tissue engineering, bioimaging, gene, DNA and drug delivery and
as a coating material for medical implants. This study is an overview of the different types of chitosan-based
materials which now a days have been fabricated by applying different techniques and modifications that
include etherification, esterification, crosslinking, graft copolymerization and o-acetylation etc. for hydroxyl
groups’ processes and acetylation, quaternization, Schiff’s base reaction, and grafting for amino groups’ reactions. Furthermore, this overview summarizes the literature from recent years related to the important applications of chitosan-based materials (i.e., thin films, nanocomposites or nanoparticles, sponges and hydrogels)
in different biomedical applications.
... More precisely, the peaks observed at 3624 cm − 1 and 3693 cm − 1 are for the inner surface inner Al-OH stretching. The Si-O-Si deformational bands are seen at 1114cm-1 and 1007 cm − 1 [22]. Earlier to modification strong peaks at 900 cm − 1 and 745 cm − 1 are attributed to in-plane stretching of Si-O and O-H of inner hydroxyls [23]. ...
The present study brings out the affirmative knowledge on covalently modified halloysite nanotube (HNT) with the biopolymer pectin and their poly (vinyl alcohol) nanocomposite films. The kaolin grouped HNTs have rooted a path for incorporation of pectin-functionalised-HNTs (Pec-f-HNT) into a PVA matrix. The polymer nanocomposite films along with plane PVA were followed up for cell adhesion and cell proliferation with mouse fibroblast (NIH3T3) cells and the results have been confirmed their potential usability in tissue engineering applications.
Food packaging industries are growing to meet consumer demand and prevent pollution by adopting significant biopolymer advancements. Therefore, this study aimed to develop functionally active chitosan (CS)/polyvinyl alcohol (PVA)-based biopolymer films and evaluate the effect of Justicia Adhatoda extract (JAE), pure quercetin (Q), and CS-capped quercetin nanoparticles ((Q)CS NPs) on sustainable bread packaging. CS was successfully loaded onto (Q) by the one-pot method, which was confirmed by light absorption spectroscopy (UV), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The fabricated films were examined using different analytical techniques. FTIR and XRD patterns confirmed that the CS/PVA matrix had molecular interactions through hydrogen bonds with JAE, (Q), and (Q)CS NPs. SEM micrograms revealed a uniform distribution and denser surface with small aggregations by adding (Q)CS NPs. The (Q)CS NPs added CPE(Q)CS nanocomposite exhibited excellent UV light shielding (99.99 % UV-A and UV-B blocking), water resistance ability (contact angle:99.44, WVP:3.68^10−7 gh−1m−1Pa−1), and oxygen (0.614^10−6 gh−1 m−1 atm−1) barrier properties. Adding (Q)CS NPs enhanced the antimicrobial properties of CPE(Q)CS against foodborne microbes (E. coli:15.45 mm, P. aeruginosa:14.50 mm, B. subtilis:14.25 mm, S. aureus:13.52 mm, and C. albicans:15.16 mm). In addition, incorporating (Q)CS NPs, increased the shelf life of bread compared to unpacked and polyethylene-packed bread samples.
Halloysite nanotubes (HNTs) are naturally occurring aluminosilicate minerals, known for their unique tubular structure, which have garnered significant interest for a wide range of applications. This study explores the morphological changes of HNTs when subjected to thermal treatment ranging from 25 °C to 1100 °C using a combination of experimental characterization techniques and molecular dynamics simulations. Techniques such as solid-state NMR (SSNMR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) surface area measurements, and Fourier Transform Infrared Spectroscopy (FT-IR) were employed to analyse the structural evolution. The results reveal two major transitions: the first occurring between 400 and 500 °C, corresponding to the release of intercalated water and partial distortion of the HNT structure, and the second occurring between 900 and 1000 °C, marked by the collapse of the tubular structure and the exposure of alumina on the surface. These findings provide significant insights into the thermal stability of HNTs, informing future applications, especially in high-temperature environments.
Lung cancer has become the leading cause of cancer‐related deaths, surpassing all other forms of cancer. Among lung cancers, non‐small cell lung cancer (NSCLC) accounts for approximately 85% of cases. The use of tobacco, genetic traits, and radiation exposure are amongst the major reasons of lung cancer. The ongoing research in the medical field has considered the efficacy of nanocarriers in targeting various cancer cells. Among several biomaterials, lipid‐based nanocarriers have gained special attention due to their excellent compatibility, improved targeting efficacy, and encapsulation ability of diverse therapeutic agents. Phospholipids are naturally occurring amphiphilic moieties found in all living creatures. The presence of phospholipids in biomembrane aids the permeability of phospholipid‐based drug carrier. It can also facilitate targeting of therapeutic agents to cancer microenvironment without degrading the encapsulated drug. Phospholipids can be employed to develop conjugated nanocarriers and vesicular nanoformulation that can result in prolonged circulatory half‐life and controlled release of drugs. Phospholipids are also suitable biomaterials to attach a ligand for tissue‐specific targeting. Recent researches have reported effective targeting of chemotherapeutic agents, genes, and vaccines through phospholipid‐based nanocarriers to lung cancer cells. This review focuses on the rationality and applications of phospholipid‐based nanocarriers in lung cancer therapy.
Achieving sustainable and controllable drug delivery is a highly effective disease treatment approach. Chitosan
hydrogels, with their unique three-dimensional (3D) porous structures, offer tunable capacity, controllable
degradation, various stimuli sensitivities, and the ability to encapsulate therapeutic agents. These characteristics
provide chitosan hydrogels with inherent advantages as vehicles for drug delivery systems. In recent years, there
has been a notable shift toward embracing the “back-to-nature” ethos, with biomass materials emerging as
promising candidates for constructing chitosan hydrogels used in controlled drug release applications. This trend
is sustained by their biodegradability, biocompatibility, and non-toxic properties, emphasizing their unique
benefts and innovative features. These hydrogels exhibit sensitivity to various factors such as temperature, pH,
ion concentration, light, magnetic felds, redox, ultrasound, and multi-responsiveness, offering opportunities for
fnely tuned drug release mechanisms. This review comprehensively outlines fabrication methods, properties,
and biocompatibility of chitosan hydrogel, as well as modifcation strategies and stimuli-responsive mechanisms.
Furthermore, their potential applications in subcutaneous (wound dressing), parental (transdermal drug delivery), oral (gastrointestinal tract), and facial (ophthalmic and brain) drug delivery are briefly discussed. The
challenges in clinical application and the future outlook of chitosan-based smart hydrogel are also highlighted.
Nanocomposite materials are emerging as key players in addressing critical challenges in healthcare, energy storage, and environmental remediation. These innovative systems hold great promise in engineering effective solutions for complex problems. Nanocomposites have demonstrated various advantages such as simplicity, versatility, lightweight , and potential cost-effectiveness. By reinforcing synthetic and natural polymers with nanomaterials, a range of nanocomposites have exhibited unique physicochemical properties, biocompatibility, and biodegradability. Current research on nanocomposites has demonstrated promising clinical and translational applications. Over the past decade, the production of nanocomposites has emerged as a critical nano-structuring methodology due to their adaptability and controllable surface structure. This comprehensive review article systematically addresses two principal domains. A comprehensive survey of metallic and nonmetallic nanomaterials (nanofillers), elucidating their efficacy as reinforcing agents in polymeric matrices. Emphasis is placed on the methodical design and engineering principles governing the development of functional nanocomposites. Additionally, the review provides an exhaustive examination of recent noteworthy advancements in industrial, environmental , biomedical, and clinical applications within the realms of nanocomposite materials. Finally, the review Med Res Rev. 2024;1-53. wileyonlinelibrary.com/journal/med
Intercalation compounds represent a unique class of materials that can be anisotropic (1D and 2D-based topology) or isotropic (3D) by their guest/ host superlattice repetitive organization. Intercalation refers to the...
Abstract
In the modern healthcare system, the therapeutic options of cancer management have gained much attention. Several chemotherapeutic agents and anticancer drugs are in use to combat cancer and many of them have shown promising results. The direct targeting of anticancer drugs may enhance the side effects and limit the efficacy of the therapeutic agents. The efficacy of various drug carriers are investigated for successful drug targeting of therapeutic moieties. Amongst several drug carriers, nanofibers are recently being investigated by many researchers due to their favorable physicochemical properties, increased surface area, and ability to control the release of therapeutic molecules at target site. Chitosan, being a biodegradable marine polysaccharide, offers excellent biocompatibility alongside decreased immunogenicity and easy large scale production. Chitosan nanofibers are easily prepared employing electrospinning and other techniques. This review focuses on the fabrication techniques, suitability of chitosan nanofibers in targeting therapeutic molecules in tumor microenvironment alongside the recent advancements in chitosan nanofibers for effective cancer targeting.
Purpose
The purpose of this paper is to prepare a multifunctional nanocomposite that is slow-release and resistant to seawater corrosion and biofouling corrosion and to explore the synergistic effect between the two corrosion inhibitors.
Design/methodology/approach
The morphology, structure and release properties of CAP@HNTs, BTA@HNTs and CAP/BTA@HNTs were investigated by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, specific surface area analysis and UV spectrophotometry. The corrosion resistance and antimicrobial properties were investigated by electrochemical measurements and bioinhibition rate tests, and the synergistic effect between the two corrosion inhibitors was explored by X-ray photoelectron spectroscopy.
Findings
The CAP/BTA@HNTs are responsive to acidic environments and have significantly improved antibacterial and corrosion resistance compared with CAP@HNTs and BTA@HNTs. CAP and BTA have a positive synergistic effect on anticorrosion and antifouling.
Originality/value
Two types of inhibitors, anticorrosion and antifouling, were loaded into the same nanocontainer to prepare a slow-releasable and multifunctional nanocomposite with higher resistance to seawater corrosion and biocorrosion and to explore the synergistic effect of CAP and BTA on corrosion resistance.
Smart self-healing coatings offer a revolutionary approach to mitigating metal corrosion, a problem with significant economic and environmental impacts. Divided into intrinsic and extrinsic types, these coatings autonomously rectify the damage. Intrinsic variants utilize reversible bonds to achieve ongoing repair, while extrinsic ones incorporate micro/nanocontainers that activate upon environmental triggers to mend micro-cracks, their efficacy dictated by the encapsulated healing agents’ volume. This review dissects the rapidly evolving sector of stimuli-responsive self-healing coatings, emphasizing the progress in micro/nano container technology. It discusses the synthesis and encapsulation processes of different micro/nanocontainers and charts the transition from single to multistimulus-responsive systems, which enhances the coatings’ sensitivity and functionality. The addition of multifunctional traits such as self-reporting and anti-microbial actions further broadens their industrial applicability. The review provides a succinct overview of the field’s current state and future potential, envisioning a paradigm shift in corrosion protection through advanced smart coatings.
Halloysite nanotubes (HNTs) are natural aluminosilicate clay minerals with the formula of Al2Si2O5(OH)4 nH2O. HNTs, which can be obtained naturally as well as synthetically, occur in layered, spherical, flat and other forms. HNTs with an outer diameter of 50 nm and a length ranging from 500 to 1000 nm have a hollow and nanotube-shaped structure. It has natural deposits in Brazil, Turkey, New Zealand, China, the United States, Korea, Japan, and France, and it is a low-cost material that can be obtained through ore purification. Thanks to their high surface area, large pore volume, rheological properties, high interactions, and high binding capacities with biopolymers, HNTs are used in a wide range of areas. For example, HNTs have become a frequently used material in environmental applications such as wastewater treatment and removal of organic contaminants and dyes. It is also used in the production of nanoelectronics and nanocomposites, catalytic studies, flame retardants in make-up materials, forensic sciences and biomedical fields. The specific properties of HNT used in the biomedical field lead to numerous applications. In this review, it is aimed to present the advantages of HNTs for use in drug delivery systems, immune therapy, anti-infection applications, cancer therapy, bioimaging, biosensing applications, tissue engineering applications, implants and hygiene-cosmetics materials.
In this work, banana flour (BF)-based composite films were formulated by loading halloysite
nanoparticles (HS) and essential oil carvacrol (CR). HS nanoclay was selected since it has abilities
to improve the mechanical and water vapor barrier properties of the prepared films. CR was used
since it demonstrates powerful antimicrobial activity against foodborne pathogens. Results reveal
successful incorporation of HS and CR in the composite films that display an improved melting
temperature (Tm) and rough surface. The water solubility of the films significantly reduced
whereas the contact angle significantly improved with the impregnation of both HS and CR. The
XRD diffractograms indicated pre-dominant amorphous characteristics of all the prepared films.
These changes reflected well on the mechanical properties, wherein the tensile strength and Elas�tic modulus increased by ∼47% and ∼206%, respectively. The presence of HS and CR also re�duced the films' water vapor transmission rate by about 62%. In addition, as a case study, BF/HS/
CR dispersions were coated on a capsicum fruit to test their protecting ability. The incorporation
of HS and CR in the BF-based biopolymeric matrix resulted in a significant reduction in the
%weight loss, from 50.96 ± 2.40% (control: without coating) to 37.42 ± 3.75% (with the coat�ing), along with an improvement in the firmness (N) from 5.04 ± 0.92 N (control: without coat�ing) to 7.47 ± 0.25 N (with the coating), during 12 days of storage. The outcome promises BF/
HS/CR based films and dispersions as natural food packaging materials to extend the shelf life of
food systems.
Sustainably derived nanoparticles and their nanohybrids are cruicial for devolping energy efficient polymeric materials. In this study, a promicing nanohybrid of iron oxide nanoparticles (IONPs) supported over cellulose nanofibers (CNFs)...
In traditional drug delivery systems, poor targeting and the need for repeated administration are major issues. In this paper, an injectable chitosan/3,4-dihydroxybenzaldehyde hydrogel was successfully prepared using the sodium periodate...
Chitosan is known to possess excellent properties such as biodegradability, biocompatibility, antimicrobial activity and less toxicity due to which it has applications in various fields. Another important benefit of chitosan is that it can be processed into different forms like membranes, sponges, gels, scaffolds, microparticles, nanoparticles, nanofibers and 3D printed constructs. For these reasons, chitosan has found to be highly advantageous in biomedical field. The reactive amino and hydroxyl groups in its chemical structure make it an ideal candidate for a wide range of applications. However, the compromising mechanical strength of chitosan limits its applications, which can be improved using nanotechnology. Chitosan based nanocomposites have gained significant attention in the last two decades. In the present review, we discuss the advantages of chitosan based nanocomposites for biomedical applications majorly tissue engineering, wound dressing and drug delivery. This review emphasizes on recent findings concerning the use of innovative chitosan based nanocomposites in biomedical applications. It also covers brief overview of chitosan, its extraction, structure and modifications and its in vitro and in vivo efficacy. Then, a detailed summary of recent progress in biomedical applications are presented. Current chitosan based nanocomposite as product in market, future perspectives and challenges are also discussed.
We developed novel composite films based on biocompatible components, such as halloysite clay nanotubes and sulphated galactan (Funori) from red seaweed Gloiopeltis. The filling of the nanotubes within the sulphated galactan matrix was carried out by a green protocol (aqueous casting method) assuring that Funori/halloysite nanocomposites can be totally considered as sustainable materials. The amount of halloysite in the composites was systematically changed to explore the effects of the nanofiller concentration on the mesoscopic properties of the films. We observed that the halloysite content significantly affects the initial water contact angle and the light attenuation coefficient of the Funori based films. These results were interpreted according to SEM images, which showed that the surface morphologies of the nanocomposites depend on the halloysite amounts filled within the polymeric matrix. The mechanical characterization of the nanocomposites was conducted by tensile experiments performed using a linear stress ramp. Moreover, tensile tests were conducted in oscillatory regime at variable temperature to investigate the viscoelastic properties of the nanocomposites. Finally, we filled the biopolymeric matrix with halloysite nanotubes containing sodium diclofenac. The drug release kinetics from the nanocomposites at variable halloysite contents were studied to evaluate their suitability as oral dissolving films for pharmaceutical applications.
Chitosan, as a bionanocomposite has been garnering immense attention and become a center of comprehensive research, owing to its vast structural possibilities for physiochemical alterations to produce novel characteristics, functions, and utilizations, especially in the biomedical field. Chitosan is endowed with numerous properties such as biocompatibility, biodegradability, non-toxicity, antimicrobial activity, low immunogenicity, stimuli sensitivity, adjustable physical strength, and water solubility. This ideal biopolymer can be transformed into nanoparticles, nanocapsules, nano-vehicles, fiber meshes, scaffolds, and 3D printed scaffolds. The last decade is a testimony to the enormous potential of chitosan and chitosan-based nanocomposites, as showcased by the legion of research reports displaying many new applications in the field of targeted drug delivery, modern biomedical instruments, and bioimaging sensors. This chapter unfolds different aspects of chitosan, including its properties and mutations, and focuses on chitosan-based nanocomposites. Emphasis has been laid on the salient biomedical applications of chitosan-based nanocomposites including drug delivery, gene therapy, tissue engineering and regeneration, cancer diagnosis and treatment, and bioimaging among various others.
Metal-organic frameworks (MOFs) have a high specific surface area and inherent biodegradability due to their unique structure and composition. As well, owing to the properties of nanomaterials and especially their magnetic features, Fe3O4 nanoparticles and MOFs composite materials have great potential in the design and application of drug release. The present work: firstly, investigated norfloxacin loading in magnetic metal organic framework (Fe3O4@ZIF-8); and secondly, studied the release of norfloxacin and its antibacterial activity. Results showed the release efficiencies reached 97 % at 310 K after 84 h (pH 7.4). Drug release behavior was tested at various pH levels and it was found that Fe3O4@ZIF-8 has pH-sensitive properties. Furthermore, the release model calculation illustrated that the release process fitted well to the Bhaskar model. The magnetic properties of Fe3O4@ZIF-8 confirmed that the composite has potential application for a targeted drug delivery system. The mechanism of pH-responsive norfloxacin release was combined with diffusion, ion exchange and electrostatic repulsion. Furthermore, the antibacterial activities of Fe3O4@ZIF-8 and NOR-Fe3O4@ZIF-8 were tested against Escherichia coli. Results showed that Fe3O4@ZIF-8 had good biocompatibility while NOR-Fe3O4@ZIF-8 can deter or inhibit the actions of microorganisms.
This study aimed to investigate the effect of halloysite nanotubes (HNTs) on the physicochemical characteristics of the soy protein isolated/basil seed gum (SPI/BSG) film activated with propolis (PP). The obtained results of scanning electron microscope (SEM), thermal gravimetric analysis (TGA), and tensile investigations illustrated that the addition of HNTs as nanofiller led to positive changes in the morphology, thermal stability, and mechanical characteristics of SPI/BSG films. The barrier properties of films considerably decreased with incorporation of HNTs. Furthermore, the encapsulation of PP as bioactive agent into the produced films significantly increased (P < 0.05) the antioxidant potential of the samples in DPPH radical-scavenging activity assays. The antibacterial effects of film also significantly increased (P < 0.05) after the encapsulation of PP. In conclusion, the produced films illustrated acceptable efficiency for usage in food packaging system.
We propose a novel keratin treatment of human hair by its aqueous mixtures with natural halloysite clay nanotubes. The loaded clay nanotubes together with free keratin produce micrometer thick protective coating on hair. First, colloidal and structural properties of halloysite/keratin dispersions and the nanotube loaded with this protein were investigated. Above the keratin isoelectric point (pH = 4), the protein adsorption into the positive halloysite lumen is favored due to the electrostatic attractions. The zeta-potential magnitude of these core-shell particles increased from -35 (in pristine form) to -43 mV allowing for an enhanced colloidal stability (15 hours at pH = 6). This keratin-clay tubule nanocomposite was used for the immersion treatment of hair. 3D measuring laser scanning microscopy demonstrated that 50-60 % of the hair surface coverage can be achieved with 1 wt. % suspension application. Hair samples have been exposed to UV irradiation for times up to 72 hours to explore the protection capacity of this coating by monitoring the cysteine oxidation products. The nanocomposites of halloysite and keratin prevent the deterioration of the human hair as evident by significant inhibition of cysteic acid. The successful hair structure protection was also visually confirmed by AFM and dark-field hyperspectral microscopy. The proposed formulation represents a promising strategy for a sustainable medical coating on the hair, which remediate UV irradiation stress.
Cell responses and mechanical properties are vital for scaffold in bone regeneration. Fe3O4 nanoparticles with excellent magnetism can provide magnetic stimulation for cell growth, while graphene oxide (GO) nanosheets are commonly used as reinforcement phases due to their high strength. However, Fe3O4 or GO is tended to agglomerate in matrix. In present study, a novel co-dispersed Fe3O4-GO nanosystem was constructed through electrostatic self-assembly of positively charged Fe3O4 (pFe3O4) on negatively charged GO nanosheets. In the nanosystem, pFe3O4 nanoparticles and GO nanosheets support each other, which effectively alleviates the π-π stacking between GO nanosheets and magnetic attraction between pFe3O4 nanoparticles. Subsequently, the nanosystem was incorporated into poly L-lactic acid (PLLA) scaffolds fabricated using selective laser sintering. The results confirmed that the pFe3O4-GO nanosystem exhibited a synergistic enhancement effect on stimulating cell responses by integrating the capturing effect of GO and the magnetic simulation effect of pFe3O4. The activity, proliferation and differentiation of cells grown on scaffolds were significantly enhanced. Moreover, the nanosystem also exhibited a synergistic enhancement effect on mechanical properties of scaffolds, since the pFe3O4 loaded on GO improved the efficiency of stress transfer in matrix. The tensile stress and compressive strength of scaffolds were increased by 67.1% and 132%, respectively. In addition, the nanosystem improved the degradation capability and hydrophilicity of scaffolds.
Magnesium (Mg) alloy shows great potential as bone implant owing to its favourable biocompatibility and degradability. In the present work, bioglass-reinforced Mg-based composite was manufactured via laser additive manufacturing. The results showed that too low a volumetric energy density (Ev) resulted in the appearance of open pores on the surface, which significantly deteriorated the densification behaviour. In contrast, too high an Ev caused the occurrence of the‘balling phenomenon’ with discontinuous surface, because of the excessive liquid formation and extended pool lifetime. Under a proper Ev of 185.19 J/mm³, favourable part with high densification rate was obtained. Meanwhile, the refined grains together with orderly dispersed reinforcing particles contributed to the enhanced mechanical properties. Significantly, the incorporated bioglass promoted the apatite deposition on Mg matrix, which served as an effective protection layer and reduced the degradation rate. Furthermore, it also improved the cell growth and differentiation, showing great potential in clinical bone repair.
The peculiar surfaces of halloysite nanotubes and their biocompatibility are attracting the interest of researchers based on the wide range of attainable applications. The large aspect ratio of this nanotubular material ensures promising properties as reinforcing agent in polymeric matrices, such as cellulose and its derivatives, that entail strengthening due for instance to ageing-induced degradation. The halloysite cavity has a suitable size to host a large variety of active species such as deacidifying (calcium hydroxide) and flame retardant agents (fluorinated surfactants) for a controlled and sustained release relevant in conservation of Cultural Heritage. Additionally, anionic surfactants can be selectively adsorbed at the inner surface generating inorganic micelles able to solubilize hydrophobic species in a controlled cleaning protocol. We briefly discuss how the natural halloysite nanotubes can be supportive in various conservation process of Cultural Heritage and present an outlook for future perspectives.
The emergence of antibiotic resistance of pathogenic bacteria has led to renewed interest in exploring the potential of plant-derived antimicrobials e.g., essential oils (EOs), as an alternative strategy to reduce microbial contamination. However, the volatile nature of EOs presents a major challenge in their incorporation into polymers by conventional high-temperature processing techniques. Herein, we employ halloysite nanotubes (HNTs) as efficient nano-carriers for carvacrol (a model EO). This pre-compounding encapsulation step imparts enhanced thermal stability to the carvacrol, allowing for its subsequent melt compounding with low-density polyethylene (LDPE). The resulting polymer nanocomposites exhibit outstanding antimicrobial properties with a broad spectrum of inhibitory activity against Escherichia coli, Listeria innocua in biofilms, and Alternaria alternata. Their antimicrobial effectiveness is also successfully demonstrated in complex model food systems (soft cheese and bread). This superior
A novel fluorescence probe based on modified halloysite nanotubes (HNTs) by using 1-pyrenylboronic acid selectively grafted onto the inner surface of lumen was successfully achieved. The solid-state nuclear magnetic resonance (13C and 11B), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) confirmed that the boronic acid group only binds to alumina at the tube lumen and does not bind the tube's outer siloxane surface. The modified HNTs (HNTs-PY) inherit the spectroscopic properties relating to the pyrene units. Interestingly, the established Al-O-B linkage gives the H2O2-sensitivity to pyrene grafted tubes. HNTs-PY exhibits a highly specific "turn-off" response for hyperoxide over other reactive oxygen species (ROS) and oxidative ions owing to their chemoselective boronate-to-phenol switch. The "turn-off" response can be even tracked when the addition amount of H2O2 was limited to 1×10-6 mol. Thus, the selective modification method under mild conditions for the design of novel organic-inorganic hybrid fluorescence probe may open up a broader application as well as for identification and diagnosis.
Abstract It is important to establish an efficient vascularization for the long-term acceptance of bioengineered skin equivalents treating the cutaneous wounds diabetic rats with hindlimb ischemia. This study investigates the possible use of a collagen/chitosan sponge scaffold encapsulated with Tβ4 (CCSS-eTβ4), an angiogenic factor, to accelerate cutaneous wound healing in streptozotocin (STZ)-induced diabetic rats with hindlimb ischemia. CCSSs-eTβ4 were fabricated using a freeze-drying method. The scaffolds were analyzed by scanning electron microscopy (SEM), swelling and degradation assays, mechanical properties, and scaffolds of 50:50 collagen-chitosan were selected and applied. The controlled release of Tβ4 from the scaffolds elicited localized and prolonged effects over 12 days, as shown by an enzyme-linked immunosorbent assay (ELISA). In vivo, CCSSs-eTβ4 improved diabetic cutaneous wound healing, with faster wound re-epithelialization, better dermal reorganization and higher wound vascularization. Furthermore CCSSs-eTβ4 down-regulated inflammatory genes and up-regulated angiogenic genes in the wound tissue. Significant increases in CD31-positive endothelial cells and new vessel density were also observed. In vitro, Tβ4 increased the migratory and proliferative activity of high glucose (HG)-treated human umbilical vein endothelial cells (HUVECs). Meanwhile we found that Tβ4 could promote HG-treated HUVECs migration and improve angiogenesis by activation of the VEGF/AKT pathway. Overall, these findings demonstrated the promising potential of CCSSs-eTβ4 to promote more effective wound healing and suggest its possible application for diabetic cutaneous wound treatment.
OBJECTIVES: The aim of the present investigation was to form matrix patches with ethyl cellulose (EC) as the base polymer, polyvinyl pyrrolidone (PVP) as the copolymer, plasticizer with dibutyl phthalate (DBP) or acetyl tributyl citrate (ATBC) and the drug glipizide (gz) by the solvent casting method. Physicochemical properties of the patches and in vitro drug release were determined in a modified Keshary-chien diffusion cell to optimize the patch formulations with the help of experimental data and figures for further studies. TECHNIQUES: EC and PVP of different proportions with different weight percentages of either DBP or ATBC and a fixed amount of glipizide were taken for matrix patch formations. The dried patches were used for measuring their drug contents as well as their thicknesses, tensile strengths, moisture contents and water absorption amounts in percentage. In vitro release amounts at different intervals were measured by UV-spectrophotometer. RESULTS: Drug contents varied from 96 - 99%. Thickness and tensile strength varied due to weight variation of the ingredients in the matrix patches. Moisture content and water absorption in wt % were greater for the patches containing higher amount of PVP due to its hydrophilic nature. Variations in drug release were observed among various formulations. It was found that all of the releases followed diffusion controlled zero order kinetics. Two DBP patches yielded better and more adequate release. CONCLUSIONS: The two formulations with DBP were the preferred choice for making matrix patches for further studies.
This work developed novel chitosan–halloysite nanotubes (HNTs) nanocomposite (NC) scaffolds by combining solution-mixing and freeze-drying techniques, and aimed to show the potential application of the scaffolds in tissue-engineering. The hydrogen bonding and electrostatic attraction between chitosan and HNTs were confirmed by spectroscopy and morphology analysis. The interfacial interactions resulted in a layer of chitosan absorbed on the surfaces of HNTs. The determination of mechanical and thermal properties demonstrated that the NC scaffolds exhibited significant enhancement in compressive strength, compressive modulus, and thermal stability compared with the pure chitosan scaffold. But the NC scaffolds showed reduced water uptake and increased density by the incorporation of HNTs. All the scaffolds exhibited a highly porous structure and HNTs had nearly no effect on the pore structure and porosity of the scaffolds. In order to assess cell attachment and viability on the materials, NIH3T3-E1 mouse fibroblasts were cultured on the materials. Results showed that chitosan–HNTs nanocomposites were cytocompatible even when the loading of HNTs was 80%. All these results suggested that chitosan–HNTs NC scaffolds exhibited great potential for applications in tissue engineering or as drug/gene carriers.
Chitosan–silver (CS–Ag) nanocomposite materials were synthesized by a simple chemical method. The synthesized CS–Ag nanocomposite contains 20 wt% silver. Silver nanoparticles were synthesized by chemical reduction method as well. The CS–Ag nanocomposite was characterized using Field emission scanning electronic microscope (FESEM), X-ray diffraction (XRD) and Fou-rier transform infrared spectroscopy (FTIR). The XRD pattern indicated the presence of both silver and chitosan in the nanocomposite. It is observed from the XRD pattern of silver that it is of cubic structure. The spherical morphol-ogy of silver nanoparticles was confirmed from the FESEM image. FTIR spectroscopy was used for the structural elucidation. CS–Ag nanocomposite exhibits good antimi-crobial and antitumor properties.
Surface modification of natural halloysite clay nanotubes with γ-aminopropyltriethoxysilane (APTES) was investigated. Untreated and modified samples were characterized by nitrogen adsorption, X-ray diffraction, elemental analysis, thermogravimetry, transmission electron microscopy, atomic force microscopy, MAS nuclear magnetic resonance (29Si, 13C, 29Al), and Fourier transform infrared spectroscopy. The modification mechanism was found to include not only the direct grafting of APTES onto the hydroxyl groups of the internal walls, edges and external surfaces of the nanotubes but other processes in which oligomerized APTES condensed with the directly grafted APTES to form a cross-linked structure. The thermal and evacuation pretreatment conditions were found to play an important role in controlling the extent and mechanism of the modification. The extent of modification is also strongly affected by the morphological parameters of the original clay samples. This study demonstrates that the surface chemistry of halloysite nanotubes is readily modified, enabling applications in nanocomposites, enzyme immobilization and controlled release.
Hydroxypropyl methylcellulose (HPMC) is now available in modified hydrophobic forms (Sangelose). In this paper, the effect of viscosity grade and HPMC concentration on in vitro release kinetics of a topically applied drug were studied using gel formulations of a nonsteroidal anti-inflammatory drug (NSAID), diclofenac potassium (DP), with different viscosity grades of the polymer (60L, 60 M, 90 M for hydrophobic HPMC and 50 cPs for conventional hydrophilic HPMC) in different proportions. It was found that hydrophobic HPMC-based gels having a higher viscosity and lower polymer concentration release a notably higher amount of drug compared with hydrophilic HPMC-based gels containing a higher concentration of polymer but with lower viscosity. For gels, the suitability of different common empirical (zero-order, first-order, and Higuchi), and semi-empirical (Ritger-Peppas and Peppas-Sahlin) models, and some new statistical (logistic, log-logistic, Weibull, Gumbel, and generalized extreme value distribution) models to describe the drug release profile were tested through non-linear least-square curve fitting. A general purpose mathematical analysis tool MATLAB was used. Further, instead of the widely used transformed linear fit method, direct fitting was used in the paper to avoid any form of truncation and transformation errors. The results revealed that the log-logistic distribution, amongst all the models investigated, was the best fit for hydrophobic formulations. For hydrophilic ones, the semi-empirical models and Weibull distribution worked best, although log-logistic also showed a close fit. The shape parameter for the log-logistic and Weibull distribution conveys vital information about the rate of release and helps improve understanding of drug release profiles.
The use of tubular halloysite clay as a nanotemplate for layer‐by‐layer (LbL) shell assembly and its utilization for controlled release of drug macromolecules are studied. The LbL nanoshell allowed additional control for the sustained release of drug loaded halloysite tubes. The number of polymeric layers in the shell and molecular weight of the assembled polymers influences the drug release rate. Three bilayer shells of chitosan and gelatin of 15 nm thicknesses gave the best encapsulation and retardation in the release rate of dexamethasone. An encapsulation of the macromolecules inside the lumen of the biocompatible clay nanotubes coupled with the polyelectrolyte shell formation provides a novel formulation for the controlled release of bioactive agents.
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Chitosan is reported as an accelerator of wound healing. Histological findings of previous reports indicate that chitosan accelerates the reformation of connective tissue, however the details of the mechanism are not clear. In this study, firstly L929 mouse fibroblasts were cultured with chitosan and the production of extracellular matrix (ECM) was evaluated in vitro. Type I and III collagens and fibronectin were secreted by L929 with or without chitosan; however there was no significant difference in the amount of ECM between the control and the chitosan groups. Secondly, macrophages were stimulated with chitosan, and then transforming growth factor-beta 1 (TGF-beta1) and platelet-derived growth factor (PDGF) messenger ribonucleic acid (mRNA) expressions and production of their proteins were assayed in vitro. As a result, chitosan promoted the production of TGF-beta1 and PDGF. These results indicate that chitosan does not directly accelerate ECM production by fibroblast and the ECM production may increase by the growth factors.
The use of halloysite clay as a low cost alternative to more traditional microencapsulation systems is reported. Halloysite is an alumino-silicate clay which demonstrates a predominately cylindrical geometry, uniquely characterized by a hollow core or series of voids with diameters ranging from 16-50 nm. These nanoscale-to-mesoscale microcylinders are capable of entrapping active agents within the core lumen as well as within any void spaces contained in the multilayered walls of the cylinder. Some of the active agents associated with the clay are also bound to the external surfaces of the clay. Delivery of the active agent is first by desorption of the active agent from the exterior surfaces and exposed ends of the microcylinders, and is followed by a second more prolonged phase dominated by pore diffusion from the ends of the cylinders. Halloysite is capable of retaining and releasing a range of active ingredients. Both hydrophilic and hydrophobic agents may be entrapped following appropriate pre-treatment of the clay to render it lipophilic. Here, a unique low cost alternative microcylindrical delivery system: the clay mineral halloysite, is investigated.
The interfacial bonding between inorganic clay and organic polymer is weak although clay is usually used as a reinforcement phase in polymer. In this study, montmorillonite (MMT) was organic modified by (3-aminopropyl) triethoxysilane (KH550) and incorporated into poly (ε-caprolactone) (PCL) to enhance the interfacial bonding in bone scaffold. In detail, KH550 intercalated into the interlayer of MMT through cation exchange. And then one end of KH550 with NH3+ was adsorbed onto the negatively charged surface of MMT while the other end with long alkylammonium carbon chain extended outward in the opposite direction, stretching the interlayer spacing of MMT for the easy intercalation of PCL molecular chains. More importantly, interfacial bonding between PCL and MMT was enhanced since Si-OH from KH550 hydrolysis formed siloxane linkages with -OH of MMT firstly, and then formed hydrogen bonding with C=O of PCL. Consequently, the movement of PCL molecular chains was restricted in MMT galleries due to the interlayer locking effect. The results showed that the interlayer spacing of MMT after modifying was extended from 1.23 to 1.77 nm and homogeneous dispersion of MMT in the PCL matrix was obtained. Besides, the tensile strength of PCL+10% modified MMT scaffold increased to 3.46 times compared with the PCL scaffold. In addition, the scaffold fabricated via selective laser sintering possessed good biodegradability and cytocompatibility, which may be attributed to that the presence of hydroxyl groups increased adsorbed water and the release of Ca and Si ions contributed to cell growth, respectively.
Polyvinylidene fluoride (PVDF)/barium titanate (BaTiO3) composites are becoming increasingly attractive in bone repair since it combines the advantage of polymer flexibility and ceramic piezoelectric constant. Herein, silver (Ag) nanoparticles were decorated on polydopamine functioned BaTiO3 (Ag-pBT) by in situ growth. Then the strawberry-like structured Ag-pBT nanoparticles were introduced into PVDF scaffold fabricated by selective laser sintering. On one hand, Ag nanoparticles would act as a conductive phase to enhance the strength of the polarized electric field on BaTiO3, thereby forcing more domains to be aligned in the direction of the electric field and make piezoelectric effect of BaTiO3 fully play in composite scaffold. On the other hand, Ag nanoparticles would attack multiple targets in bacteria by release of Ag⁺ and production of reactive oxygen species. In fact, the antibacterial activity is highly desirable for bone repair. Results demonstrated that the PVDF/4Ag-pBT scaffold exhibited enhanced piezoelectric properties with output current and voltage increased by 50% and 40% than that of PVDF/pBT, respectively. In vitro cell culture confirmed that the enhanced electric output further promoted cell proliferation and differentiation. Meanwhile, the scaffold presented robust antibacterial activity against E.coli.
A well-designed drug delivery platform improves the pharmacological properties of therapeutics. Here, we report a biodegradable interpenetrating polymer network (IPN) microbeads delivery technology developed by crosslinking a polymer blend of poly(vinyl alcohol), xanthan gum, and sodium alginate to enhance the solubility of poorly soluble drugs. The microbeads effectively improve the solubility of a model BCS Class IV drug, norfloxacin, known for its low solubility and low permeability. Differential scanning calorimetry, powdered X-ray diffractometry, and FT-IR data showed that the IPN microbeads solubilised and encapsulated the drug within the network. We found over 83% encapsulation efficiency for norfloxacin and this efficiency increases with the concentration of polymer. Ex vivo experiments using caprine intestine revealed that the IPN microbeads adhered to the intestinal epithelium, a mucoadhesive behaviour that could be beneficial to the drug pharmacokinetics while in vitro experiments in phosphate buffer show that the IPN enables significant drug release. We believe that these IPN microbeadsare an excellent drug delivery system to solubilise norfloxacin, ensure adhesion to the intestinal wall, thereby localising the drug release to enhance bioavailability of poorly soluble drugs.
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Most of the existing scaffolds do not provide physical stimulation to cells in scaffold-guided bone regeneration. In this work, a superparamagnetic scaffold was fabricated using selective laser sintering with polyglycolic acid as matrix and Fe3O4 nanoparticles as internal magnetic source. Additionally, a self-developed external static magnetic field (SMF) was used to provide external magnetic source. In this case, the magnetic moment of the Fe3O4 nanoparticles rearranged along the direction of SMF, thereby generating a locally enhanced magnetic field. The enhanced magnetic field might directly stimulate cell surface receptors and activate downstream signaling pathways. As a consequence, the human umbilical cord-derived mesenchymal stem cells cultivated in the scaffold exhibited significantly enhanced gene expression of alkaline phosphatase, osteocalcin, type I collagen and runt-related transcription factor-2. In vivo tests revealed that the bone regeneration was accelerated with bone mineral density (with SMF: 515 ± 50 mg/cc, without SMF: 326 ± 15 mg/cc), percentage of bone volume/tissue volume (with SMF: 92 ± 3.5%, without SMF: 73 ± 5.2%) and new bone area fraction (with SMF: 86 ± 2.2%, without SMF: 70 ± 1.6%) after 8 weeks' implantation. The biodistribution and serum biochemistry analysis demonstrated that superparamagnetic scaffold possessed favorable biosafety.
This research was based on the preparation and treatment of raw cotton fabrics with nanoparticles and date seed extract/chitosan at the same time and in a single treatment bath in an easy and modern manner. The date seed extract and chitosan were used in the treatment bath to increase the functional properties of these fabrics. Tests were performed for the resulting fabrics such as air permeability, water absorbance, tensile strength, Scanning electron microscope (SEM), X-ray Diffraction (XRD) and antimicrobial activity for four types of microbes such as gram negative (Pseudomonas aerugenosa), gram positive (S. aureus), fungi (A. niger) and yeast (C. albicans). The results showed that raw fabrics treated with silver nitrate in the presence of chitosan and date seed extract gave the best result for resistance to microbes and this led to increased air permeability and water absorbance. From the above, these fabrics can be used in the various packaging process such as packaging of seeds and powder materials.
We have prepared new biohybrid materials based on halloysite nanotubes and natural polymers (alginate and chitosan) for the controlled and sustained release of bioactive species. A functional nanoarchitecture has been designed allowing to generate a layered tablet with a chitosan/halloysite nanocomposite film sandwiched between two alginate layers. The assembly of the raw components and the final structure of the hybrid tablet have been highlighted by the morphological and wettability properties of the prepared materials. Being that the biohybrid has been designed as a smart carrier, halloysite nanotubes have been firstly loaded with a model drug (sodium diclofenac). The effect of the tablet thickness on the drug release kinetics has been investigated confirming that the delivery capacity can be controlled by modifying the alginate amounts of the external layers. A simulation of the typical pH conditions along the human gastro-intestinal path has been carried out. Strong acidic conditions (pH = 3, typical in the stomach) prevent the drug release. In contrast, the drug has been released under pH = 5.7 and 7.8, which simulate duodenum/ileum and colon paths, respectively. These results demonstrate that the proposed nanoarchitecture is suitable as functional material with tunable delivery capacity.
The filling of halloysite nanotubes with active compounds solubilized in aqueous solvent was investigated theoretically and experimentally. Based on Knudsen thermogravimetric data, we demonstrated the water confinement within the cavity of halloysite. This process is crucial to properly describe the driving mechanism of halloysite loading. In addition, Knudsen thermogravimetric experiments were conducted on kaolinite nanoplates as well as on halloysite nanotubes modified with an anionic surfactant (sodium dodecanoate) in order to explore the influence of both the nanoparticle morphology and the hydrophobic/hydrophilic character of the lumen on the confinement phenomenon. The analysis of the desorption isotherms allowed us to determine the water adsorption properties of the investigated nanoclays. The pore sizes of the nanotubes’ lumen was determined by combining the vapor pressure of the confined water with the nanoparticles wettability, which was studied through contact angle measurements. The thermodynamic description of the water confinement inside the lumen was correlated to the influence of the vacuum pumping in the experimental loading of halloysite. Metoprolol tartrate, salicylic acid and malonic acid were selected as anionic guest molecules for the experimental filling of the positively charged halloysite lumen. According to the filling mechanism induced by the water confinement, the vacuum operation and the reduced pressure enhanced the loading of halloysite nanotubes for all the investigated bioactive compounds. This work represents a further and crucial step for the development of halloysite based nanocarriers being that the filling mechanism of the nanotube's cavity from aqueous dispersions was described according to the water confinement process.
This study aimed to develop and characterize the calcium alginate films loaded with diclofenac sodium and other hydrophilic polymers with different degrees of cross-linking obtained by external gelation process. To the formed films different physicochemical evaluation were performed which showed an initial character of the films. The films produced by this external gelation process were found thicker (0.031–0.038 mm) and stronger (51.9–52.9 MPa) but less elastic (2.3%) than those non-cross-linked films (0.029 mm; 39.7 MPa; 4.4%). The lower water vapor permeability (WVP) values of the films were obtained where maximum level of crosslinking occurs. Composite films can be cross-linked in presence of external crosslinking agent to improve the quality of the produced matrices for various uses. The characterization of the film was performed using Differential Scanning Calorimetry (DSC) and Fourier-Transform Infrared Spectroscopy (FT-IR) analysis. The Scanning Electron Microscopy (SEM) study showed the morphology of treated composite films. The kinetic release studies showed a sustained release of the drug from the formulated films as it can be prolonged in composite film. The prepared biodegradable Ca-Alginate bio-composite film may be of clinical importance for its therapeutic benefit.
Natural halloysite nanotubes (HNTs) show a unique hollow structure, high aspect ratio, and adsorption ability, good biocompatibility, and low toxicity, which allow for various biomedical applications in diagnosis and treatment of diseases. Here, we summarized advances in self-assembly of halloysite for cell capturing and bacterial proliferation, coating on biological surfaces, and related drug delivery, bone regeneration, bioscaffolds and cell labeling. The in vivo toxicity of these clay nanotubes is discussed. Halloysite allows for 10-20 % drug loading and can extend the delivery time to 10-100 hrs. These drug-loaded nanotubes can be doped into the polymer scaffolds to release the loaded drugs. The rough surfaces fabricated by self-assembly of the clay nanotubes enhance the interactions with tumor cells, and the cell capture efficacy is significantly improved. Since halloysite has no toxicity toward microorganisms, the bacteria composed within these nanotubes can be explored in oil/water emulsion for petroleum spilling bioremediation. Coating of living cells with halloysite can control the cell growth and is not harmful to their viability. Quantum dots immobilized on halloysite were employed for cell labeling and imaging. The concluding academic results combined with the abundant availability of these natural nanotubes promise halloysite applications in personal healthcare and environmental remediation.
Bacterial infection is a major problem world-wide, especially in wound treatment where it can severely prolong the healing process. In this study, a double drug co-delivery elastic antibacterial nanocomposite was developed by combining ciprofloxacin (CPX) and polymyxin B sulfate-loaded halloysite clay nanotubes (HNTs-B) into a gelatin elastomer. CPX nanoparticles which act against both gram positive and gram-negative bacterium were dispersed directly in the matrix, and polymyxin B sulfate was loaded in HNTs and then distributed into the matrix. The effect of CPX and HNTs-B content on the physical properties, cytotoxicity, fibroblast adhesion and proliferation, in vitro drug release behavior and anti-bacterial properties were systematically investigated. The ciprofloxacin crystals and HNT-B were distributed in the matrix uniformly. The HNTs in the drug loading system not only enhanced the matrix’ tensile strength but also slowed down the release rate of the high dissoluble polymyxin B sulfate. When the amount of HNT in the matrix increased, the thermal stability and tensile strength also increased but the polymyxin B sulfate release rate decreased because the HNTs prevented the drug release inside. All the nanocomposites exhibited antimicrobial activity against both gram-negative and gram-positive bacteria with the dual combination of drugs released from the nanocomposites. Furthermore, this kind of gelatin-based nanocomposites possesses higher water-absorbing quality, low cytotoxicity, adaptable biodegradability and good elasticity which can satisfy the requirements for an ideal biomaterial for use in wound healing applications.
The structure of halloysite nanotubes (Hal) from different mines was investigated by Small-Angle Neutron Scattering (SANS) and Electric Birefringence (EBR) experiments. The analysis of the SANS curves allowed us to correlate the sizes and polydispersity and the specific surfaces (obtained by a Porod analysis of the SANS data) of the nanotubes with their specific geological setting. Contrast matching measurements were performed on patch Hal (from Western Australia) in order to determine their experimental scattering length density for a more precise analysis. Further characterization of the mesoscopic structure of Hal was carried out by Electric Birefringence (EBR), which allowed to study the rotational mobility of Hal. From the obtained rotational diffusion coefficients of the different Hal we deduced their length via the Broersma theory, which compares well to TEM data. The analysis of both SANS and EBR data provided a bulk average information on the Hal structure in water, which, for instance, documented the markedly higher degree of well-definedness of the PT-Hal and the thinner tube walls present here. The attained systematic structural knowledge represents a step forward for the robust structural description of halloysites selected from four geological deposits and shows that Hal of different origin differ very markedly with respect to their mesoscopic structure.
Naturally formed halloysite tubules have a length of 1 μm length and lumens with a diameter of 12-15 nm which can be loaded with drugs. Halloysite’s biocompatibility allows for its safe delivering to cells at a concentration of up to 0.5 mg/mL. We encapsulated the anti-cancer drug paclitaxel in halloysite and evaluated the drug release kinetics in simulated gastric and intestinal conditions. To facilitate maximum drug release in intestinal tract, halloysite tubes were coated with the pH-responsive polymer poly(methacrylic acid-co-methyl methacrylate). Release kinetics indicated a triggered drug release pattern at higher pH, corresponding to digestive tract environment. Tablets containing halloysite, loaded with paclitaxel, as a compression excipient were formulated with drug release occurring at a sustained rate. In vitro anticancer effects of paclitaxel-loaded halloysite nanotubes were evaluated on human cancer cells. In all the treated cell samples, polyploid nuclei of different sizes and fragmented chromatin were observed, indicating a high therapeutic effect of halloysite formulated paclitaxel.
Halloysite is an alumosilicate tubular clay with a diameter of 50 nm, an inner lumen of 15 nm and a length of 600-900 nm. It is a natural biocompatible nanomaterial available in thousands of tons at low price, which makes it a good candidate for nanoarchitectural composites. The inner lumen of halloysite may be adjusted by etching to 20-30% of the tube volume and loading with functional agents (antioxidants, anticorrosion agents, flame-retardant agents, drugs, or proteins) allowing for formulations with sustained release tuned by the tube end-stoppers for hours and days. Clogging the tube ends in polymeric composites allows further extension of the release time. Thus, antioxidant-loaded halloysite doped into rubber enhances anti-aging properties for at least 12 months. The addition of 3-5 wt% of halloysite increases the strength of polymeric materials, and the possibility of the tube's orientation promises a gradient of properties. Halloysite nanotubes are a promising mesoporous media for catalytic nanoparticles that may be seeded on the tube surface or synthesized exclusively in the lumens, providing enhanced catalytic properties, especially at high temperatures. In vitro and in vivo studies on biological cells and worms indicate the safety of halloysite, and tests for efficient adsorption of mycotoxins in animals' stomachs are also carried out.
In this study, a series of alginate/halloysite nanotube (HNTs) composite scaffolds were prepared by solution-mixing and freeze-drying method. HNTs are incorporated into alginate to improve both the mechanical and cell-attachment properties of the scaffolds. The interfacial interactions between alginate and HNTs were confirmed by the atomic force microscope (AFM), transmission electron microscope (TEM) and FTIR spectroscopy. The mechanical, morphological, and physico-chemical properties of the composite scaffolds were investigated. The composite scaffolds exhibit significant enhancement in compressive strength and compressive modulus compared with pure alginate scaffold both in dry and wet states. A well-interconnected porous structure with size in the range of 100-200μm and over 96% porosity is found in the composite scaffolds. X-ray diffraction (XRD) result shows that HNTs are uniformly dispersed and partly oriented in the composite scaffolds. The incorporation of HNTs leads to increase in the scaffold density and decrease in the water swelling ratio of alginate. HNTs improve the stability of alginate scaffolds against enzymatic degradation in PBS solution. Thermogravimetrica analysis (TGA) shows that HNTs can improve the thermal stability of the alginate. The mouse fibroblast cells display better attachment to the alginate/HNT composite than those to the pure alginate, suggesting the good cytocompatibility of the composite scaffolds. Alginate/HNT composite scaffolds exhibit great potential for applications in tissue engineering.
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The effect of hydroxypropyl methylcellulose (HPMC) concentration on β-cyclodextrin (β-CD) solubilization of norfloxacin was examined. The solubility and dissolution of norfloxacin/β-CD and norfloxacin/β-CD/HPMC inclusion complexes were studied. The presence of β-CD increased significantly the solubility and dissolution of norfloxacin. The addition of HPMC until 5% (w/w) improved the solubilization of norfloxacin but further addition above 5% (w/w), decreased norfloxacin solubilization. Fourier transformed Infra-red (FTIR) showed that norfloxacin was successfully included into β-CD. Differential scanning calorimetry (DSC) showed that the norfloxacin endothermic peak shifted to a lower temperature with reduced intensity indicating the formation of inclusion complex. The addition of HPMC reduced further the intensity of norfloxacin endothermic peak. Most of the sharp and intense peaks of norfloxacin disappeared with the addition of HPMC. In conclusion, the concentration of hydrophilic polymer used to enhance β-CD solubilization of poorly soluble drugs is very critical.
We report a novel electrospun composite nanofiber-based drug delivery system. In this study, halloysite nanotubes (HNTs) were first used to encapsulate a model drug, tetracycline hydrochloride. Then, the drug-loaded HNTs with an optimized encapsulation efficiency were mixed with poly(lactic-co-glycolic acid) (PLGA) polymer for subsequent electrospinning to form drug-loaded composite nanofibrous mats. The structure, morphology, and mechanical properties of the formed electrospun composite nanofibrous mats were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and tensile testing. In vitro drug release behavior was examined using UV-vis spectroscopy. The biocompatibility of HNT-containing PLGA fibers was evaluated through cell culture and MTT assay. We show that the incorporation of HNTs within the nanofibrous mats does not significantly change the morphology of the mats. In addition, our results indicate that this double-container drug delivery system (both PLGApolymer and HNTs are drug carriers) is beneficial to reduce the burst release of the drug and the introduction of HNTs can significantly improve the tensile strength of the polymer nanofibrous mats. Given the proved biocompatibility of the HNT-containing PLGA nanofibers via MTT assay of cell viability and SEM observation of cell morphology, the drug loaded electrospun composite nanofibrous mats developed in this study may find various applications in tissue engineering and pharmaceutical sciences.
A beneficial effect of chitin-chitosan as a food supplement is the reduction of plasma cholesterol and triglycerides due to its ability to bind dietary lipids, thereby reducing intestinal lipid absorption. The hypolipidemic influence of chitosan may also be due to interruption of the enterohepatic bile acid circulation. Plasma cholesterol in animals on cholesterol-free diet, however, is not affected, indicating that endogenous biosynthesis of cholesterol remains intact. Chitosan acts by forming gels in the intestinal tract which entrap lipids and other nutrients, including fat soluble vitamins and minerals, thus interfering with their absorption. Dietary chitosan may influence calcium metabolism by accelerating its urinary excretion. The reported undesirable effects are a marked decrease in plasma vitamin E level, reduction in bone mineral content and growth retardation. Ascorbic acid enhances gel formation of chitosan, thereby potentiating the plasma cholesterol lowering activity. Bile acid composition and short-chained fatty acid content in the cecum are altered by chitosan which impedes lipid emulsification and absorption. Although the increase in lipid content of feces does not appear to alter gastrointestinal functions, it may potentially aggravate the symptoms of mild steatorrhea. Chitin-chitosan inhibits in vitro growth of microorganisms including Candida and in vivo has a protective effect on Candida infection. The antibacterial and antiyeast activities of chitosan are desirable properties and may be useful in preventing infection of wounds by direct application. On prolonged ingestion, however, it may alter the normal flora of the intestinal tract which may result in the growth of resistant pathogens. Although studies with cells, on tissues and animals indicate that chitin-chitosan promotes wound healing, increases immune response, and possesses antitumor activity, these claims need to be further validated in human subjects by clinical trials. Chitin-chitosan, when used as a food supplement, does lower plasma cholesterol and triglycerides and improves the HDL-cholesterol/total cholesterol ratio. Certain medical precautions, however, should be observed with long-term ingestion of high doses of chitosan to avoid potential adverse metabolic consequences.
Changes in the crystallinity and polymorphic nature of chitosan, as a function of N-deacetylation of chitin under different conditions were studied. Viscosity average molecular weight suggests a higher degree of polymerization (DP) for chitosan prepared in the presence of thiophenol, as an oxygen scavenger. FT-IR spectra exhibited a progressive weakening of the bands at 1655, 3265 and 3100 cm−1 during N-deacetylation and A1382/A2920 cm−1 ratios of 0.65, 0.56 and 0.46 indicated a higher order structure for chitosan prepared with thiophenol than those prepared under N2 atmosphere or otherwise. The differences in crystallinity indices of chitosans were further substantiated by X-ray diffraction data. Splitting of C1 and C4 signals in CP-MAS 13C NMR spectra suggested the possible occurrence of newer conformational polymorphs. DSC thermograms showed higher thermal stability for chitosan with higher DP.
The clinical features, microbiological characteristics, and outcomes of 163 episodes of bacteremia occurring at a long-term-care
facility were evaluated. The rate of nosocomial bacteremia increased from 0.20 to 0.36 cases/1,000 patient-days from 1985
to 1989; there was a parallel increase in the rate of all nosocomial infections combined. Bacteremia was documented in 6.5%
of all hospital-acquired infections. The majority of isolates were gram-negative, and Providencia stuartii was the most common gram-negative species. Staphylococcus aureus was the most frequent isolate; one-third of S. aureus strains were resistant to methicillin. Bacteremia was polymicrobial in 36 episodes (22%), 14 of which involved an enterococcal
species. Portals of entry included the urinary tract (55%), the respiratory tract (11%), and soft tissue (9%). Overall mortality
was 21.5%. Death was significantly associated with residence on the intermediate-care unit, the presence of a respiratory
infection, a change in mental status, and relatively recent admission. Optimal management of bacterial infection in a long-term-care
setting requires the availability of blood culture results. Initial decisions about antibiotic therapy should be made in light
of the likelihood of infection with multiresistant organisms and of polymicrobial infection.
Numbers of nursing home beds now exceed hospital beds in the United States and are usually occupied by women. Urinary incontinence
is very common and may be managed with long-term urethral catheters. Bacteriuria invariably results, yet its clinical consequences
are not well known. Westudied 47 catheterized and bacteriuric women for almost 25 patientyears. The incidence of febrile episodes
of possible urinary origin was 1.1 episodes/1OO patient-days. Because these were diagnoses of exclusion, even this low incidence
may be an overestimate. Most of these episodes were of ⩽38.3 C (101.0 F), lasted for less than one day, and resolved without
antibiotic therapy. Six deaths, half the total from all causes, occurred during these episodes, an incidence 60 times that
during afebrile periods. Deaths and bacteremias were significantly associated with episodes of ⩾38.8 C (102.0 F). In the individual
patient, these risks should be weighed against benefits of patient comfort, family satisfaction, and prevention and management
of decubitus ulcers.
In a prospective study carried out in June 1979-April 1981, 134 of 1,458 adult inpatients at New England Deaconess Hospital, Boston, Massachusetts, acquired 136 urinary tract infections during 1,474 indwelling bladder catheterizations. Multiple logistic regression analysis identified nine factors that were significantly associated with acquisition of infection: duration of catheterization, lack of systemic antibiotic during short catheter courses, lack of urinemeter drainage, female sex, diabetes mellitus, microbial colonization of the drainage bag, serum creatinine greater than 2 mg/dl at the time of catheterization, the reason for catheterization, and the use of catheters with sealed collection junctions when no antibiotic was administered. When potential risk factors were considered individually, without adjusting for the influence of other factors, infection was also significantly associated with 11 other factors, including several that have been previously reported as risk factors for catheter-associated urinary tract infections; however, these associations were no longer significant after adjustment for one or more of the nine factors noted above. These findings suggest approaches to surveillance, prevention, and research activities. They also strongly support the widely-held but poorly documented belief that persons with diabetes are more susceptible to urinary tract infection than are persons without diabetes.
Over recent years, drug release/dissolution from solid pharmaceutical dosage forms has been the subject of intense and profitable scientific developments. Whenever a new solid dosage form is developed or produced, it is necessary to ensure that drug dissolution occurs in an appropriate manner. The pharmaceutical industry and the registration authorities do focus, nowadays, on drug dissolution studies. The quantitative analysis of the values obtained in dissolution/release tests is easier when mathematical formulas that express the dissolution results as a function of some of the dosage forms characteristics are used. In some cases, these mathematic models are derived from the theoretical analysis of the occurring process. In most of the cases the theoretical concept does not exist and some empirical equations have proved to be more appropriate. Drug dissolution from solid dosage forms has been described by kinetic models in which the dissolved amount of drug (Q) is a function of the test time, t or Q=f(t). Some analytical definitions of the Q(t) function are commonly used, such as zero order, first order, Hixson-Crowell, Weibull, Higuchi, Baker-Lonsdale, Korsmeyer-Peppas and Hopfenberg models. Other release parameters, such as dissolution time (tx%), assay time (tx min), dissolution efficacy (ED), difference factor (f1), similarity factor (f2) and Rescigno index (xi1 and xi2) can be used to characterize drug dissolution/release profiles.
Halloysite supplied from New Zealand was shown by electron microscopy to be composed mainly of hollow microtubules having typical dimensions of 2-3 microm long and 0.3/0.1 microm outer/inner diameter. Aggregates of microtubules, double tubules and occasional split or partially unrolled tubules were observed. Energy dispersive analysis showed the mineral to be composed mainly of aluminium, oxygen and silicon, with a low content of iron. The dehydrated state of the mineral was confirmed by XRD analysis, which was partially reversible using a rehydration procedure with subsequent exchange of the intercalated water gained by glycerol, but larger molecules including the drug, diltiazem HCl, failed to exchange. The surface charge was predominantly negative over most of the physiologically relevant pH range (> 2) and the specific surface area of the material was very large (approximately 57 m(2)/g), indicating that the material has significant potential for extensive binding of cationic drugs. Removal of allophanc present by a hot alkali treatment had little effect on luminal porosity, which prior to treatment was estimated to be approximately 0.25 ml/g by a mercury intrusion technique and consequently should be the major site for drug loading. Halloysite also extruded and spheronised well to form smooth round pellets as an aid to further formulation development, which rapidly disintegrated in water unless prevented by sintering at 200 degrees C.