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Gure 4Developing phosphonic acid bearing polyelectrolytes for their biocidal activity on surfaces, thermal properties, nanofiber and nano particle formation
Abstract
Bacteria infection is a growing problem all over the world. Within this contribution, phosphonium-phosphonic acid or hexyl pyridinium-phosphonic acid bearing copolymer series derived via ring opening metathesis polymerization (ROMP) method are synthesized to investigate their biocidal activity on the glass surface. The presence of phosphonic acid moieties enhanced the coating capability on the iron oxide nanoparticles and the thermal properties of the copolymers. Biocidal activities of the polymers and iron oxide bearing polymers were tested against E.coli and S.aureus. Polymers possessing higher activity was then blended with commercial polyacrylonitrile for the nanofiber formation via electrospinning methods.
... Apart from cancer treatment, IoNPs also showed antimicrobial and antibacterial properties [200] . Antibacterial action in food packaging of sulphar is stagnant due to hydrophobic nature. ...
The current scenario has seen many transformative changes in target-based drug delivery system. In this direction, encapsulation of medicines in nanoparticles has almost revolutionized the whole scenario where not only the effective, efficient, and precise delivery of drugs to the targeted tissues and cells is possible but also the adverse profile of drugs has also seen a decline. Nanotechnology and nanoscience have also spurred the target-based drug delivery for complicated illnesses including cancer, diabetes, atherosclerosis, antioxidants, microbial infections, and neurodegenerative complications. The major advantages of the technology involve enhanced permeation/retention and precise targeting of sensitive and delicate tissues including rectum, lung, rectum, or bladder which may enhance the local drug concentration avoiding targeting of other cells. The employment of nanotechnology to explore therapeutic avenues as well as their utilization as research tools in imaging, sensing and artificial implants have been further proven as the biggest assets. The new era includes nanoparticles of polymers (polysaccharides) and green synthesis which has shown multi-fold increase in the use of nanotechnology in the ever-emerging research era focused to target complicated illnesses. The present review describes the types of nanoparticles especially polymeric nanoparticles as well as metal-green synthesis approaches, their advantages, and the possible therapeutic prospects in several complicated pathologies.
In many developing countries, aquaculture is key to ensuring food security for millions of people. It is thus important to measure the full implications of environmental changes on the sustainability of aquaculture. We conduct a double meta-analysis (460 articles) to explore how global warming and antimicrobial resistance (AMR) impact aquaculture. We calculate a Multi-Antibiotic Resistance index (MAR) of aquaculture-related bacteria (11,274 isolates) for 40 countries, of which mostly low- and middle-income countries present high AMR levels. Here we show that aquaculture MAR indices correlate with MAR indices from human clinical bacteria, temperature and countries’ climate vulnerability. We also find that infected aquatic
animals present higher mortalities at warmer temperatures. Countries most vulnerable to climate change will probably face the highest AMR risks, impacting human health beyond the aquaculture sector, highlighting the need for urgent action. Sustainable solutions to minimise antibiotic use and increase system resilience are therefore needed.
In recent years, we have seen antimicrobial resistance rapidly emerge at a global scale and spread from one country to the other faster than previously thought. Superbugs and multidrug-resistant bacteria are endemic in many parts of the world. There is no question that the widespread use, overuse, and misuse of antimicrobials during the last 80 years have been associated with the explosion of antimicrobial resistance. On the other hand, the molecular pathways behind the emergence of antimicrobial resistance in bacteria were present since ancient times. Some of these mechanisms are the ancestors of current resistance determinants. Evidently, there are plenty of putative resistance genes in the environment, however, we cannot yet predict which ones would be able to be expressed as phenotypes in pathogenic bacteria and cause clinical disease. In addition, in the presence of inhibitory and sub-inhibitory concentrations of antibiotics in natural habitats, one could assume that novel resistance mechanisms will arise against antimicrobial compounds. This review presents an overview of antimicrobial resistance mechanisms, and describes how these have evolved and how they continue to emerge. As antimicrobial strategies able to bypass the development of resistance are urgently needed, a better understanding of the critical factors that contribute to the persistence and spread of antimicrobial resistance may yield innovative perspectives on the design of such new therapeutic targets.
In this study, it was aimed to prepare silver nanoparticles by reduction of silver salt (AgNO 3 ) in situ by means of only synthesized polyacrylonitrile (PAN) and poly(acrylonitrile-co-itaconic acid) (P(AN-co-IA)) polymers, and N,N dimethylformamide (DMF). Thereafter, PAN/Ag and P(AN-co-IA)/Ag nanofibers were prepared via electrospinning. Spectroscopic and morphologic characterizations, electrical and thermal features, and antimicrobial activities of the prepared nanofibers against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans were carried out in detail. It was observed that P(AN-co-IA) was much more effective than PAN on the reduction of AgNO 3 and formation of silver nanoparticles. Silver nanoparticles and also itaconic acid contributed to decrease the cyclization temperature of PAN by generating sharp exothermic peaks. In addition, electrical conductivity of the nanofibers increased dramatically from E ⁻¹³ to E ⁻⁴ related to the presence of silver nanoparticles. Furthermore, incorporation of silver nanoparticles to the nanofiber membranes let bactericidal/fungicidal activities, which started at 6–24 h and continued for up to 168 h, against S. aureus, E. coli, P. aeruginosa, and C. albicans. The prepared silver containing nanofibers can be regarded as good candidates for potential use in the biomedical and pharmaceutical applications.
Electrospinning technology is useful for making ultrafine drug-eluting fibers for the clinical treatment of wounds. We show the incorporation of an antimicrobial LfcinB-derived peptide into Pullulan nanofibers. The palindromic peptide LfcinB (21-25)Pal: RWQWRWQWR was synthesized, purified, and characterized by means of the RP-HPLC and MALDI-TOF MS methods. The peptide's antibacterial activity against the E. coli ATCC 25922 strain was evaluated, and the peptide LfcinB (20-25)Pal exhibited significant antibacterial activity. Nanofibers were obtained by electrospinning a Pullulan or Pullulan-LfcinB (21-25)Pal solution. The obtained nanofibers were characterized via microscopy (AFM and SEM) and RP-HPLC chromatography. The peptide incorporation efficiency was 31%. The Pullulan-LfcinB (21-25)Pal nanofibers were soluble in water, and the peptide was liberated immediately. The Pullulan-LfcinB (21-25)Pal nanofibers exhibited the same antibacterial activity against E. coli strain as the free peptide LfcinB (21-25)Pal. The results suggest that Pullulan-LfcinB (21-25)Pal nanofibers could be considered for designing and developing antibacterial wound dressings.
In the present study, phosphonate ester, phosphonic acid, and aromatic (phenyl, naphthalene, anthracene) groups containing polymers were synthesized by the ROMP method to analyze thermal properties of these polymers. Thermal stability of the synthesized polymers is tested by thermal gravimetric analysis under nitrogen, air, and microscale combustion calorimetry analysis. Analysis shows that thermal behavior is directly related to the phosphorus level in the copolymer series. All the polymers are thermally stable under nitrogen and air up to 900 °C. Synergistic charring effect under air was observed between aromatic groups and phosphonic acid functionality in the copolymer series. Anthracene units have a greater potential to form carbonaceous char than the naphthalene and phenyl units. Phosphonate ester and naphthalene units bearing copolymers (P3A) gave 8.13% char yield at 900 °C under air. Phosphonic acid derivatives of this polymer, P3D, gave a highest char residue of 17.15% under the same condition. The introduction of phosphonate and phosphonic acid in each copolymer series is also beneficial in reducing the peak heat release rate (PHRR). Cleavage of the phosphonate ester bearing homopolymer (P4) to phosphonic acid (P4A) causes a sharp decrease in the PHRR ratio from 274 to 28.2 W/g. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47085.
The antimicrobial polypeptide ε-poly(l-lysine) (ε-PL) was electrostatically incorporated to poly(acrylic acid) (PAA)/poly(vinyl alcohol) (PVA) electrospun nanofibers. ε-PL loading and distribution was assessed by infrared spectra, ζ-potential measurements and the primary amino reactive dye fluorescamine. Functionalized fibers with 485 ± 140 nm diameter, could be loaded with 0.57–0.74 g ε-PL (g dressing)−1 that released at a constant rate of 5.4 ± 2.8 mg ε-PL (g dressing day)−1. Such a dressings resulted in two orders of magnitude lower bacterial colonization than non-functionalized PAA-PVA after 14 days of incubation. Bacterial impairment was attributed to the damage of cell membranes and the formation of intracellular reactive oxygen species. ε-PL functionalized nanofibers did not display cytotoxicity to human corneal epithelial cells, HCEpC, in 24 h MTT assays. However, the viability of rapidly growing tumoral HeLa cells decreased >50% under the same conditions. The prepared biocompatible nanofibrous dressings with durable antibacterial activity show potential application as wound dressings and other biomedical uses.
Electrospinning is a versatile, simple, and low cost process for the controlled production of fibers. In recent years, its application to the development of multifunctional materials has encountered increasing success. In this paper, we briefly overview the general aspects of electrospinning and then we focus on the implementation of inorganic nanoantimicrobials, e.g., nanosized antimicrobial agents in electrospun fibers. The most relevant characteristics sought in nanoantimicrobials supported on (or dispersed into) polymeric materials are concisely discussed as well. The interesting literature issued in the last decade in the field of antimicrobial electrospun nanomaterials is critically described. A classification of the most relevant studies as a function of the different approaches chosen for incorporating nanoantimicrobials in the final material is also provided.
Size, shape and surface characteristics strongly affect interfacial interactions, as the presented among iron oxide nanoparticles (NPs) aqueous colloids and bacteria. In other to find the forces among this interaction, we compare three types of surface modified NPs (exposing oxalate, arginine or cysteine residues), based on a simple synthesis and derivation procedure, that allows us to obtain very similar NPs (size and shape of the magnetic core). In this way, we assure that the main difference in the synthesized NPs are the oxalate or amino acid residue exposed, an ideal situation to compare their bacterial capture performance, and so too the interactions among them. Field emission scanning electron microscopy showed homogeneous distribution of particle sizes for all systems synthesized, close to 10 nm. Magnetization, zeta potential, Fourier transformed infrared spectrometry and other studies allow us further characterization. Capture experiments of Pseudomonas putida bacterial strain showed a high level of efficiency, independently of the amino acid used to wrap the NP, when compared with oxalate. We show that bacterial capture efficiency cannot be related mostly to the bacterial and NP superficial charge relationship (as determined by z potential), but instead capture can be correlated with hydrophobic and hydrophilic forces among them.
Medical applications and biotechnological advances, including magnetic resonance imaging, cell separation and detection, tissue repair, magnetic hyperthermia and drug delivery, have strongly benefited from employing iron oxide nanoparticles (IONPs) due to their remarkable properties, such as superparamagnetism, size and possibility of receiving a biocompatible coating. Ongoing research efforts focus on reducing drug concentration, toxicity, and other side effects, while increasing efficacy of IONPs-based treatments. This review highlights the methods of synthesis and presents the most recent reports in the literature regarding advances in drug delivery using IONPs-based systems, as well as their antimicrobial activity against different microorganisms. Furthermore, the toxicity of IONPs alone and constituting nanosystems is also addressed.
The phosphonic acid functional group, which is characterized by a phosphorus atom bonded to three oxygen atoms (two hydroxy groups and one P=O double bond) and one carbon atom, is employed for many applications due to its structural analogy with the phosphate moiety or to its coordination or supramolecular properties. Phosphonic acids were used for their bioactive properties (drug, pro-drug), for bone targeting, for the design of supramolecular or hybrid materials, for the functionalization of surfaces, for analytical purposes, for medical imaging or as phosphoantigen. These applications are covering a large panel of research fields including chemistry, biology and physics thus making the synthesis of phosphonic acids a determinant question for numerous research projects. This review gives, first, an overview of the different fields of application of phosphonic acids that are illustrated with studies mainly selected over the last 20 years. Further, this review reports the different methods that can be used for the synthesis of phosphonic acids from dialkyl or diaryl phosphonate, from dichlorophosphine or dichlorophosphine oxide, from phosphonodiamide, or by oxidation of phosphinic acid. Direct methods that make use of phosphorous acid (H3PO3) and that produce a phosphonic acid functional group simultaneously to the formation of the P–C bond, are also surveyed. Among all these methods, the dealkylation of dialkyl phosphonates under either acidic conditions (HCl) or using the McKenna procedure (a two-step reaction that makes use of bromotrimethylsilane followed by methanolysis) constitute the best methods to prepare phosphonic acids.
Contact-active antimicrobial polymer surfaces bear cationic charges and kill or deactivate bacteria by interaction with the negatively charged parts of their cell envelope (lipopolysaccharides, peptidoglycan, and membrane lipids). The exact mechanism of this interaction is still under debate. While cationic antimicrobial polymer surfaces can be very useful for short-term applications, they lose their activity once they are contaminated by a sufficiently thick layer of adhering biomolecules or bacterial cell debris. This layer shields incoming bacteria from the antimicrobially active cationic surface moieties. Besides discussing antimicrobial surfaces, this feature article focuses on recent strategies that were developed to overcome the contamination problem. This includes bifunctional materials with simultaneously presented antimicrobial and protein-repellent moieties; polymer surfaces that can be switched from an antimicrobial, cell-attractive to a cell-repellent state; polymer surfaces that can be regenerated by enzyme action; degradable antimicrobial polymers; and antimicrobial polymer surfaces with removable top layers.
Synthesis and characterization of different generations (G 0 –G 5) of polyamidoamine (PAMAM) dendrimer – coated Fe 3 O 4 nanoparticles using ethyl acrylate and 1,3-propane diamine have been reported in this study. Superparamagnetic iron oxide Fe 3 O 4 nanoparticles were synthesized by co-precipitation method and modified with tris(hydroxymethylamino) methane hydrochloride for dendrimer coating. Physical characterization of the newly prepared PAMAM dendirmer-coated Fe 3 O 4 nanocomposite have been carried out by using infrared spectrophotometer (IR), Transmission electron microscope (TEM), steady-state spectrophotomer (UV–Vis), thermogravimetric analysis (TGA), and X–ray diffraction. TEM images demonstrated that the PAMAM dendirmer-coated nanocomposite have monodisperse of 7.3–6.3 nm. The antimicrobial activity of the PAMAM dendirmer-coated Fe 3 O 4 nanoparticles and Fe 3 O 4 nanoparticles were tested against various microorganisms Staphylococcus aureus (+ve) Gram and (-ve) Escherichia coli bacteria. In general, the PAMAMdendirmer-coated Fe 3 O 4 nanoparticles showed good antimicrobial activity.
In this study, silver nitrate was added to polyacrylonitrile filament structure and chemical reduction was applied to composite filaments in order to develop multifunctional polyacrylonitrile filaments with electrostatic dissipative and antibacterial properties. Composite filaments of polyacrylonitrile and silver nitrate were characterized and evaluated in terms of morphology, chemical structure, tensile properties, crystallinity, conductivity, thermal properties, silver ion release behaviour and antibacterial activity. Additionally, ultraviolet-visible spectroscopy was used to confirm the formation of nanoparticles and the variation in the concentration of the nanoparticles with the application of the chemical reduction process. Scanning electron microscope images and ultraviolet-visible spectroscopy results confirmed the formation of nanoparticles in the filament structure. Breaking strength and breaking elongation increased at silver nitrate content of 1%. Composite filaments displayed improved thermal stability and their conductivities were in the semiconductive range. Atomic absorption spectroscopy confirmed that necessary amounts of silver release for antibacterial activity occurred, while the antibacterial activity analysis showed that the composite filaments have excellent antibacterial activity. The results obtained were promising and showed that the composite filaments could be used in electrostatic dissipative and antibacterial applications.
Electrospun nanofibers based antimicrobial filter were examined for their capability to build conductive environment. An
antimicrobial agent, silver nitrate (AgNO3), was added to the nanofibers membrane for its ability to prevent growth of
microorganisms over the filter media. In this direction in the present investigation the different fractions of silver nanoparticles
were in-situ synthesized in PAN solution and then polyacrylonitrile (PAN)-silver composite nanofibers membrane filter was
prepared by electrospinning technique. The resultant solution and PAN-silver composite nanofibers was characterized by UV–
visible spectroscopy, scanning electron microscope, atomic force microscope and X-ray diffraction. Antibacterial property of
PAN silver composite nanofibers were investigated against gram positive Staphylococcus aureus and gram negative
Escherichia coli microorganisms. The formation of clear zone suggests that composite nanofibers containing silver
nanoparticles show strong antibacterial activity and it increases with increasing silver content in the composite nanofibers. The
PAN-silver composite nanofibers sheet was also examined for filtration of microorganisms and dust particles. It was observed
that PAN-silver composite nanofibers filter proven to be an excellent filter for creating microorganism and dust free hygienic
environment. Thus electrospun PAN nanofibers filters containing an antibacterial agent can be a promising solution for effective
microorganism filtration from indoor air in hospitals or other places which are more prone to bacterial infections. Copyright ©
2014 VBRI press.
The control of microbial infections is a very important issue in modern society. In general there are two ways to stop microbes from infecting humans or deteriorating materials—disinfection and antimicrobial surfaces. The first is usually realized by disinfectants, which are a considerable environmental pollution problem and also support the development of resistant microbial strains. Antimicrobial surfaces are usually designed by impregnation of materials with biocides that are released into the surroundings whereupon microbes are killed. Antimicrobial polymers are the up and coming new class of disinfectants, which can be used even as an alternative to antibiotics in some cases. Interestingly, antimicrobial polymers can be tethered to surfaces without losing their biological activity, which enables the design of surfaces that kill microbes without releasing biocides. The present review considers the working mechanisms of antimicrobial polymers and of contact-active antimicrobial surfaces based on examples of recent research as well as on multifunctional antimicrobial materials.
The objective of this paper is to present a new class of polylactic acid (PLA) fibers containing cobalt-based metal organic frameworks (MOF). The material used was Co-SIM-1, a cobalt-based substituted imidazolate. Composite mats were prepared by electrospinning PLA with a suspension of polyvinylpyrrolidone-stabilized Co-SIM-1. MOF particles formed aggregate of a small number of primary particles that, after electrospun, became completely embedded inside polymeric fibers. The dispersion of particles was better for lower loadings, for which the relative amount of metal released to culture media was also higher. The antimicrobial activity of composite mats was assessed using SEM images, fluorescence microscopy, direct plate reading of fluorescent stains and plate count of colony forming units among other. The microorganisms used in this study were Pseudomonas putida and Staphylococcus aureus. Fluorescence techniques allowed recording viable and damaged cells directly on mat surface and in the culture media embedding the fibers. The results showed higher sensitivity of S. aureus to cobalt-containing fibers, with a reduction in colony forming units of up to 60% with respect to PLA mats. The results also showed the presence of viable but non-culturable microorganisms, which fail to form colonies but yield a positive signal to viable cell staining. Cobalt-based MOF included in electrospun mats provide antibacterial activity suitable to be used to prepare membranes for various biomedical applications.
Nystatin is a tetraene diene polyene antibiotic showing a broad spectrum of antifungal activity. In the present study, we prepared
a nystatin nanocomposite (Nyst-CS-MNP) by loading nystatin (Nyst) on chitosan (CS) coated magnetic nanoparticles (MNPs).
The magnetic nanocomposites were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy
(FT-IR), thermogravimetry analysis (TGA), vibrating sample magnetometer (VSM), and scanning electron microscopy (SEM).
The XRD results showed that the MNPs and nanocomposite are pure magnetite. The FTIR analysis confirmed the binding of CS
on the surface of theMNPs and also the loading of Nyst in the nanocomposite. The Nyst drug loading was estimated using UV-Vis
instrumentation and showing a 14.9% loading in the nanocomposite. The TEM size image of the MNPs, CS-MNP, and Nyst-CSMNPwas
13, 11, and 8 nm, respectively.The release profile of theNyst drug fromthe nanocomposite followed a pseudo-second-order
kineticmodel.The antimicrobial activity of the as-synthesizedNyst andNyst-CS-MNP nanocomposite was evaluated using an agar
diffusion method and showed enhanced antifungal activity against Candida albicans. In this manner, this study introduces a novel
nanocomposite that can decrease fungus activity on-demand for numerous medical applications.
The main objective of the present paper is to represent a new class of Poly Lactic-co-Glycolic Acid (PLGA) nanofibers containing silver (Ag) nanoparticles (NPs) by electrospinning process. Silver nanoparticles were well loaded without any chemical and structural modifications into PLGA polymer matrix to form an organic-inorganic nanocomposite. Syntheses of silver NPs was carried out by exploiting reduction ability of N, N-dimethylformamide (DMF) solvent which is mainly utilized in decomposition of silver nitrate precursor into silver NPs. Typsically, a sol-gel consisting of different concentration of AgNO3 in PLGA has been electrospun, so, silver NPs have been created in the nanofibers. Observable beads can be noticed with high silver nitrate contents. TEM image of one of the modified nanofiber confirmed that NPs are present in/on the nanofiber. Overall, the size of the nanofibers was within the range of 50 to 100 nm, while the size of silver nanoparticles was within range 5 to 10 nm. The said realized results strongly recommend the use of obtained nanofiber mats as antimicrobial agents in biomaterials or water purifying systems.
Iron oxide nanoparticles (IONPs) were synthesized by coprecipitation of iron salts in alkali media followed by coating with glycol chitosan (GC-coated IONPs). Both bare and GC-coated IONPs were subsequently characterized and evaluated for their antibacterial activity. Comparison of Fourier transform infrared spectra and thermogravimetric data of bare and GC-coated IONPs confirmed the presence of GC coating on IONPs. Magnetization curves showed that both bare and GC-coated IONPs are superparamagnetic and have saturation magnetizations of 70.3 and 59.8 emu g−1, respectively. The IONP size was measured as ~8–9 nm by transmission electron microscopy, and their crystal structure was assigned to magnetite from x-ray diffraction patterns. Both bare and GC-coated IONPs inhibited the growths of Escherichia coli ATCC 8739 and Salmonella enteritidis SE 01 bacteria better than the antibiotics linezolid and cefaclor, as evaluated by the agar dilution assay. GC-coated IONPs showed higher potency against E. coli O157:H7 and Staphylococcus aureus ATCC 10832 than bare IONPs. Given their biocompatibility and antibacterial properties, GC-coated IONPs are a potential nanomaterial for in vivo applications.
This review article presents important and recent progress in the manufacture and application of antimicrobial macromolecules. Microbial infections continue to endanger human health and pose a great economic burden to society. To resolve this crisis, huge efforts to improve or develop macromolecules that can inhibit pathogens without incurring pathogen resistance are required and actively ongoing. Synthetic antimicrobial macromolecules which include antimicrobial peptides (AMPs), polymers and peptide-polymer hybrids represent a huge class of molecules which can incur effective antimicrobial therapy due to their unique biochemical properties. The use of these antimicrobial macromolecules which target the cytoplasmic membrane of microbes, is a promising approach to lower the propensity of pathogen resistance development. Therefore, huge efforts to synthesize these molecules at scales and purities that enable their structure-function and clinical studies are actively underway. Due to the high cost involved in extracting AMPs from natural sources, biological processes are being developed to economically manufacture AMPs at large scale. Synthetic AMP analogs are also being engineered to further improve antimicrobial potency and lower synthesis cost. Synthetic polymers have also been found to exhibit excellent antimicrobial properties which are comparable to those of natural AMPs. Various antimicrobial polymers have been synthesized based on the amphiphilicity of natural AMPs. Although the facile synthesis of polymers poses no cost problems, numerous synthetic antimicrobial polymers are disadvantaged by high toxicity to mammalian cells due to their non-selectivity. To combine the advantages of AMPs and antimicrobial polymers, peptide-polymer hybrid macromolecules are actively being developed, with a few effective and strongly microbicidal models recently demonstrated. With the advancement of biochemical engineering tools and chemical synthesis methods, these antimicrobial macromolecules can be specifically designed to be highly selective, broad spectrum and biocompatible. In this review, we summarize the recent advances and challenges in the manufacture of these antimicrobial macromolecules. Based on their antimicrobial mechanisms, their applications in addressing challenges associated with infectious disease and antibiotic-resistance are also discussed.
Magnetic nanoparticles exhibit many interesting properties that can be exploited in a variety of applications such as catalysis and in biomedicine. This review discusses the properties, applications, and syntheses of three magnetic iron oxides - hematite, magnetite, and maghemite - and outlines methods of preparation that allow control over the size, morphology, surface treatment and magnetic properties of their nanoparticles. Some challenges to further development of these materials and methods are also presented. (C) 2008 Elsevier Ltd. All rights reserved.
We prepared non-woven electrospun polylactic acid (PLA) membranes containing functionalized sepiolite fibrillar particles (5 wt. %). Biocidal activity was achieved by functionalizing sepiolite fibers with Ag (26 wt. %) and Cu (26 wt. %), which were embedded in the fiber surface. Sepiolite particles were negatively charged in all cases, with zeta potential in the range of (-15)-(-37) mV, increasing their negative charge with pH. The membranes were biofouled in a cross-flow filtration device using model biofoulants, cultures of Saccharomyces cerevisiae (pH 4.5) and Pseudomonas putida (pH 7.5), which were pumped across the membrane for 24/48 h. The assessment of active biomass was performed by measuring the concentration of adenosine-5’-triphosphate (ATP) in used membranes. The results showed a significant decrease in the amount of surface ATP for PLA loaded with Ag and Cu functionalized sepiolite. The effect was particularly intense for Ag-sepiolite in contact with Saccharomyces cerevisiae, where the reduction amounted to 85% compared to neat PLA (control). This was attributed to the differences in ion availability as a function of pH and to the presence of chloride ions in solution. Pristine sepiolite (without functionalization) did not show any noticeable effect.
Antimicrobial polymers have emerged as a potential solution to the growing problem of antimicrobial resistance. Although several studies have examined the effects of various parameters on the antimicrobial and hemolytic activity of statistical copolymers, there are still numerous parameters to be explored. Therefore, in this study, we developed a library of 36 statistical amphiphilic ternary copolymers prepared via photoinduced electron transfer-reversible addition-fragmentation chain transfer polymerization to systematically evaluate the influence of hydrophobic groups [number of carbons (5, 7, and 9)] and chain type of the hydrophobic monomer (cyclic, aromatic, linear, or branched), monomer ratio, and degree of polymerization (DPn) on antimicrobial and hemolytic activity. To guide our synthetic strategy, we developed a pre-experimental screening approach using C log P values of oligomer models, which correspond to the logarithm of the partition coefficient of compounds between n-octanol and water. This method enabled correlation of polymer hydrophobicity with antimicrobial and hemolytic activity. In addition, this study revealed that minimizing hydrophobicity and hydrophobic content were key factors in controlling hemolysis, whereas optimizing antimicrobial activity was more complex. High antimicrobial activity required hydrophobicity (i.e., C log P, hydrophobicity index) that was neither too high nor too low, an appropriate cationic/hydrophobic balance, and structural compatibility between the chosen monomers. Furthermore, these findings could guide the design of future antimicrobial ternary copolymers and suggest that C log P values between 0 and 2 have the best balance of high antimicrobial activity and low hemolytic activity.
In this study, synthetic mimics of antimicrobial peptides based on poly(oxanorbornene) molecules (or PONs) were used to coat CdTe quantum dots (QDs). These PONs-CdTe QDs conjugates were investigated for their activity against Escherichia coli, a bacterium with antibiotic resistant strains. At the same time, the antibacterial activity of the PONs-CdTe QDs was compared to the antibacterial activity of free PONs and free CdTe QDs. The observed antibacterial activity of the PONs-CdTe QDs was additive and concentration dependent. The conjugates had a significantly lower minimum inhibitory concentration (MIC) than the free PONs and QDs, particularly for PONs-CdTe QDs which contained PONs of high amine density. The maximum activity of PONs-CdTe QDs was not realized by conjugating PONs with the highest intrinsic antibacterial activity (i.e. the lowest MIC in solution as free PONs), indicating that the mechanism of action for free PONs and PONs-CdTe QDs is different. Equally important, conjugating PONs to CdTe QDs decreased their hemolytic activity against red blood cells compared to free PONs, lending to higher therapeutic indices against E. coli. This could potentially enable the use of higher and therefore more effective PONs-QDs concentrations when addressing bacterial contamination, without concerns of adverse impacts on mammalian cells and organisms.
Novel nanomaterials have been developed for antimicrobial and wound healing applications. Here, we report the preparation of a polyvinyl alcohol/chitosan (PVA/CS) nanofiber with carboxymethyl chitosan nanoparticles (CMCS-OH30 NPs) encapsulating the antibacterial peptide OH-CATH30 (OH-30). The PVA/CS nanofibers containing OH-30 NPs (NP-30-NFs) obtained via electrospinning could achieve a secondary embedded OH-30. The effect of NP-30-NFs on the release of OH-30 was investigated through high-performance liquid chromatography. The antibacterial activities of NP-30-NFs against Escherichia coli and Staphylococcus aureus were studied by bacterial plate counting. NP-30-NFs containing different concentrations of NPs were applied to mouse skin wounds to determine their effectiveness in promoting wound healing. Results showed that NP-30-NFs exhibited antibacterial properties and promoted skin wound healing.
Nearly monodispersed superparamagnetic maghemite nanoparticles (15-20 nm) were prepared by a one-step thermal decomposition of iron(II) acetate in air at 400 C. The presented synthetic route is simple, cost effective and allows to prepare the high-quality superparamagnetic particles in a large scale. The as-prepared particles were exploited for the development of magnetic nanocomposites with the possible applicability in medicine and biochemistry. For the purposes of the MRI diagnostics, the maghemite particles were simply dispersed in the bentonite matrix. The resulting nanocomposite represents very effective and cheap oral negative contrast agent for MRI of the gastrointestinal tract and reveals excellent contrast properties, fully comparable with those obtained for commercial contrast material. The results of the clinical research of this maghemite-bentonite contrast agent for imaging of the small bowel are discussed. For biochemical applications, the primary functionalization of the prepared maghemite nanoparticles with chitosan was performed. In this way, a highly efficient magnetic carrier for protein immobilization was obtained as demonstrated by conjugating thermostable raffinose-modified trypsin (RMT) using glutaraldehyde. The covalent conjugation resulted in a further increase in trypsin thermostability (T 50 ¼ 61 C) and elimination of its autolysis. Consequently, the immobilization of RMT allowed fast in-solution digestion of proteins and their identification by MALDI-TOF mass spectrometry.
The aim of this study was to fabricate a novel bilayered wound dressing with excellent antibacterial performance through electrospinning and in-situ cross-linking polymerization. Quaternary ammonium salts ([2-(methacryloyloxy)ethyl] trimethylammonium, MTA) were first polymerized and cross-linked in the presence of polycaprolactone (PCL) to form PCL/PMTA composites. Then, PCL was electrospun as the cytocompatible inner layer that directly contact the wound, and the PCL/PMTA layer was placed as the outer layer as a defense against bacteria. The PCL/PMTA layer exhibited a hydrophilic surface and showed a strong antibacterial effect on E. coli. and S. aureus. All bilayered antimicrobial nanofiber membranes did not release any toxic agents to cells, and the PCL layer exhibited better effects on cell growth. The electrospun bilayered nanofiber membranes are promising candidates for antimicrobial wound dressings.
Nanofiber membranes for biomedical filtration devices require antibacterial activity to prevent bacterial contamination under moisture conditions while exhibiting biocompatibility. Here, we propose an antibacterial membrane filter composed of electrospun polyacrylonitrile (PAN) nanofibers with a surface functionalized with silver nanoparticles (AgNPs) by a facile wetting process for in situ silver reduction under physiologically mild conditions. Sequential wetting of thermally stabilized PAN nanofibers in silver nitrate (AgNO 3) and sodium hydroxide (NaOH) solutions enabled direct control of the amount of synthesized AgNPs and their release behaviors in an aqueous environment. The fabricated AgNPs-functionalized PAN nanofibers (PAN-AgNPs) exhibit the appreciable antibacterial efficiency against Escherichia coli and Staphylococcus aureus bacteria with considerable sustainability for repetitive use. In addition, the generated AgNPs on PAN nanofiber membranes in an adequate loading range also revealed good biocompatibility with mammalian cells. Thus, PAN-AgNPs nanofibers can be practically applied as a promising disinfecting membrane filter for biomedical and hygienic applications.
Self-immolative polymers (SIMPs) are macromolecules that spontaneously undergo depolymerization into small molecules when triggered by specific external stimuli. We report here the first examples of antimicrobial SIMPs with potent, rapid, broad-spectrum bactericidal activity. Their antibacterial and hemolytic activities are examined as a function of cationic functionality. Polymers bearing primary ammonium cationic groups showed more potent bactericidal activity against E. coli, relative to tertiary and quaternary ammonium counterparts, whereas the quaternary ammonium polymers showed the lowest hemolytic toxicity. These antibacterial polycations undergo end-to-end depolymerization when triggered by an externally applied stimulus. Specifically, poly(benzyl ether)s end-capped with a silyl ether group and bearing pendant allyl side chains were converted to polycations by photo-initiated thiol-ene radical addition using cysteamine HCl. The intact polycations are stable in solution, but they spontaneously unzip into their component monomers upon exposure to fluoride ions, with excellent sensitivity and selectivity. Upon triggered depolymerization, the antibacterial potency is largely retained but the hemolytic toxicity is substantially reduced. Thus, we reveal the first example of a self-immolative antibacterial polymer platform that will enable antibacterial materials to spontaneously unzip into biologically active small molecules upon the introduction of a specifically designed stimulus.
New approaches to treat bacterial infections are badly needed to address the increasing problem of antibiotic-resistance. This study explores phosphonium-functionalized block copolymer micelles as intrinsically antibacterial polymer assemblies. Phosphonium cations with varying alkyl lengths were conjugated to the terminus of a poly(ethylene oxide)-polycaprolactone block copolymer and the phosphonium-functionalized block copolymers were self-assembled to form micelles in aqueous solution. The size, morphology, and ζ-potential of the assemblies were studied and their abilities to kill Escherichia coli and Staphylococcus aureus were evaluated. It was found that the minimum bactericidal concentration depended on the phosphonium alkyl chain length and different trends were observed for Gram-negative and Gram-positive bacteria. The most active assemblies exhibited no hemolysis of red blood cells above the bactericidal concentrations, indicating that they can selectively disrupt the membranes of bacteria. Furthermore, it was possible to encapsulate and release the antibiotic tetracycline using the assemblies, providing a potential multi-mechanistic approach to bacterial killing.
Electrospun nanofibers incorporated with antimicrobial agents have been produced with antimicrobial capability against a wide range of microorganisms. These nanofibers show promising applications in filtration, wound-dressing materials, protective textiles, tissue scaffolds, and biomedical devices. A comprehensive review is presented on current research and development activities of electrospun nanofibers incorporated with different antimicrobial agents. The effects of loading antimicrobial agents on the characteristics of precursor solutions with different polymer systems and properties of resultant electrospun nanofibers are summarized. The antimicrobial mechanism of selected antimicrobial agents and different methods on maximizing antimicrobial performance of electrospun nanofibers are also discussed.
Keywords
Electrospinning; Antimicrobial; Metallic nanoparticles; Carbon nanomaterials; Antibiotics; Biopolymers; ɛ-Poly-lysine
Acknowledgment
The authors would like to acknowledge the financial support from the Economic Development Assistantship Program of Louisiana State University, the USDA National Institute of Food and Agriculture McIntire Stennis project [1000017], and USDA-NIFA (Grant No. 2008-38814-04771).
Poly(ethylene glycol)-poly(vinylphosphonic acid) block copolymers (PEG-b-PVPA) of low average molar mass were synthesized by RAFT/MADIX polymerization. Their intrinsic properties (i.e. anionic-neutral character which brings both ability to strongly interact with cations and steric stabilization) allow the one-step in situ synthesis of water dispersible iron oxide nanoparticles with controlled size and high colloidal stability. The effect of structural properties of the polymer (chain length of PEG and PVPA blocks) on the formation and/or stabilization of nanoparticles has been evaluated. Additionally, PVPA and PAA block complexing abilities were compared and the advantage of phosphonic acid groups over carboxylic acid groups was proven. Hemocompatibility tests carried out with the DHBCs alone and DHBC / iron oxide hybrid nanoparticles revealed that the hemolysis rates observed with phosphonated copolymers were much lower than for their carboxylated analogs.
Magnetite nanoparticles due to the special specifications have been widely used in medical as well as industrial applications. In such applications, it is important to control morphology and size of the nanoparticles. In this work, magnetite nanoparticles were synthesized via the co-precipitation method. For investigating the effect of various precursors on mean size and morphology of synthesized nanoparticles, six groups of magnetite precursors were arranged. The magnetite product of each group was characterized by using XRD, SEM, TEM, VSM and the analytical methods. The results have shown the kind of precursors influence on the mean size of the synthesized nanoparticles. The reason for this behavior was explained by the double layer theory. However, kind of precursors did not have a sensible effect on the morphology of the synthesized nanoparticles.
In this study, amphiphilic polyoxanorbornene with different alkyl and aromatic phosphonium side chains was synthesized. The biological activities of these polymers were determined by the minimal inhibitory concentration (MIC) against E. coli, S. aureus, M. tuberculosis and the yeast C. albicans, and cytotoxicity studies on red blood cells were performed. A series of polymers with different alkyl and aromatic substituents (methyl, ethyl, tripropyl, tert-butyl, phenyl, and tris 4-methoxyphenyl) and two types different molecular weight, 3000 g mol−1 and 10000 g mol−1, were prepared. It was observed that the biological activity of the polymers with aromatic group substituents had an MIC of 16, 8, 64 and 128 μg mL−1 against E. coli, S. aureus, M. tuberculosis and C. albicans, respectively, while those with non-aromatic carbons had a higher MIC compared to those with aromatic carbons. The aromaticity of the repeat unit had impressive effects on hemolytic activities as well. Zeta potential measurements of E. coli incubated with active and inactive polymer concentration revealed a relationship between the MIC and membrane surface charge density. Polymers bearing aromatic groups killed the bacteria with widespread damage after the polymers, holding the threshold concentration, were added to the bacteria.
An antimicrobial peptide (AMP), Magainin II (Mag II) was covalently immobilized on poly(lactide-co-glycolide) (PLGA) and PLGA/gelatin electrospun fibrous membranes. The surface immobilization was characterized by X-ray Photoelectron Spectroscopy (XPS). Scanning Electron Microscopy (SEM) and Atomic Force Microscopy studies showed that the surface morphology of the fibers at micron scale was not affected by the immobilization process. The antibacterial activity of the bound Mag II was tested against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Bacterial adhesion tests, SEM and confocal analyses revealed that the attachment and survival of bacteria were inhibited on Mag II functionalized membranes. AMP immobilization strategy was introduced as a new perspective for the modulation of antibacterial properties on PLGA based materials prepared by electrospinning.
Copyright © 2014 Elsevier B.V. All rights reserved.
Surface modification which creates surfaces capable of killing adherent bacteria and simply repelling dead bacteria was performed on electrospun polyacrylonitrile (PAN) nanofibrous membranes. Briefly, nitrile groups on the PAN nanofiber surfaces were reduced into amino groups, extended tethers by coupling of hydrophilic flexible spacers, followed by reaction with polyhexamethylene guanidine hydrochloride (PHGH) to provide antibacterial properties. The surface morphology and chemical composition of the functionalized nanofibrous membrane were characterized by scanning electron microscopy (SEM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FT-IR) and energy-dispersive spectroscopy (EDS). Furthermore, the antibacterial activities of the PHGH-immobilized nanofibrous membranes were assayed with Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli). It was found that these PHGH-immobilized nanofibrous membranes possessed highly effective antibacterial activities which were highly retained even after three cycles of antibacterial assays. The functionalized membranes also exhibited significantly enhanced easy-cleaning performance due to the incorporation of hydrophilic spacers. Water permeance results illustrated that the novel modified PAN nanofibrous membranes showed potential in the applications of water filtration.
We report a new procedure, exploiting “green” chemistry, resulting in biocompatible magnetically-driven nanocomposites with high antibacterial and antifungal activities against ten tested bacterial strains and four Candida species. The nanocomposites consist of silver nanoparticles (NPs), biogenic magnetite NPs isolated from magnetotactic bacteria, and an environmentally friendly polymer – chitosan. These hybrids were prepared using an acidified chitosan suspension to cover biogenic magnetite NPs by a cross-linking method, followed by employing the NH2 groups of chitosan for the reduction of silver salt in an alkaline medium. Thus, in the procedure, chitosan acts as (i) a biocompatible matrix surrounding the magnetite NPs, (ii) a reducing agent for the silver ions, and (iii) a linker between magnetic and silver NPs. The size of the resulting silver NPs and the total amount of silver involved in the nanocomposites can be simply controlled by the initial concentration of the silver salt used in the reaction mixture. The as-prepared nanocomposites reveal increased bactericidal and antifungal activity when compared to previously reported magnetic silver NPs systems which were not prepared by green synthetic routes. The use of biogenic magnetite with an uniform shape and size, the absence of any other reducing agent during synthesis, the simple control of silver NPs size and loading, the biocompatible character of chitosan matrix, and a high antimicrobial effect predetermine the developed nanocomposites for targeted applications in biomedicine.
The present study describes the preparation and characterization of poly(N-pyrrole phosphonic acid)–Fe3O4 (PPP/Fe3O4-NPs) nanocomposite. Structural characterizations and some physical properties such as magnetism, ac–dc conductivity performance and dielectric permittivity of the nanocomposite were performed by FT-IR, XRD, TGA, TEM and VSM (vibrating sample magnetometer). FT-IR measurements of the nanocomposite showed that the Fe3O4-NPs bound to the polymer chains via phosphonic acid moieties. From the XRD powder pattern, the crystallite size was estimated as 11±4nm which is consistent with the TEM micrographs and magnetic core size from VSM measurements. Analysis of conductivity and permittivity meausurements revealed the magnetic transition above 60 which gives rise to the maximum conductivity of 1.7×10−6Scm−1 at 100°C.
We have developed a two-step synthetic sequence for our introductory
organic laboratory that demonstrates key reactions that the students
learn concurrently in the lecture portion of their organic chemistry
course. It represents the Diels-Alder reaction and solvolysis of an
anhydride accompanied by Fischer esterification. Both of these steps
produce crystals in a dramatic manner that catches the students'
attention. This sequence can stand on its own as part of an organic
laboratory, or the product can be utilized as a monomer for ring-opening
metathesis polymerization (ROMP) studies.
Iron oxide nanoparticles (IONPs) are important tools for nanobiotechnology applications. However, aqueous instability and non-specific biodistribution problems limit the applications of IONPs. Considering this, alpha-phosphonic acid, omega-dithiopyridine functionalized polymers were synthesized via the reversible addition-fragmentation chain transfer (RAFT) polymerization and used for stabilizing and biofunctionalizing IONPs. A new trithiocarbonate RAFT agent bearing dimethyl phosphonate group was utilized in the synthesis of well-defined telechelic polymers of styrene, oligoethylene glycol acrylate (OEG-A) and N-isopropylacrylamide (NIPAAm). IONPs were grafted with alpha-phosphonic acid, omega-dithiopyridine functionalized poly(OEG-A) through the alpha-chain end of the polymer, as evidenced by FTIR-ATR, XPS and zeta potential measurements. Using TGA results, the grafting density of the polymer chains was calculated between 0.12 and 0.23 chains/nm(2) particle depending on the molecular weight of the polymer. DLS measurements indicated that the particles grafted with poly(OEG-A) larger than 10 000 g/mol were stable in water for several days and the mean diameter of the particles was between 40 and 130nm depending on the molecular weight of the polymer. Moreover, particles stabilized with poly(OEG-A) with a M(n) = 62 000 g/mol were stable in phosphate buffer (pH 6.5, 0.1 M) containing varying concentrations of BSA. Polymer-stabilized IONPs were successfully functionalized with two different peptides, i. e. reduced glutathione as a model peptide and NGR motif as a tumor-targeting peptide through the omega-dithiopyridine functionality of the polymer, as measured by XPS and zeta potential analysis. Poly(OEG-A)-stabilized IONPs were also found to be resistant to protein adsorption.
The first synthesis of adenine-containing polymers and block copolymers using the ring-opening metathesis polymerization of non-covalently protected monomers are shown. Studies of the copolymer 9 reveal an unexpected cylindrical morphology, which can be interpreted as arising from the hydrogen-bonding self-complementarity of the adenine units in the micellar core. Thus, further studies are currently conducted to fully characterize this morphogenesis mechanism as well as to study the effect of hydrogen-bonding guests on the polymer morphologies.
Bacitracin-conjugated superparamagnetic iron oxide (Fe(3) O(4) ) nanoparticles were prepared by click chemistry and their antibacterial activity was investigated. After functionalization with hydrophilic and biocompatible poly(acrylic acid), water-soluble Fe(3) O(4) nanoparticles were obtained. Propargylated Fe(3) O(4) nanoparticles were then synthesized by carbodiimide reaction of propargylamine with the carboxyl groups on the surface of the iron oxide nanoparticles. By further reaction with N(3) -bacitracin in a Cu(I) -catalyzed azide-alkyne cycloaddition, the magnetic Fe(3) O(4) nanoparticles were modified with the peptide bacitracin. The functionalized magnetic nanoparticles were characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, TEM, zeta-potential analysis, FTIR spectroscopy and vibrating-sample magnetometry. Cell cytotoxicity tests indicate that bacitracin-conjugated Fe(3) O(4) nanoparticles show very low cytotoxicity to human fibroblast cells, even at relatively high concentrations. In view of the antibacterial activity of bacitracin, the biofunctionalized Fe(3) O(4) nanoparticles exhibit an antibacterial effect against both Gram-positive and Gram-negative organisms, which is even higher than that of bacitracin itself. The enhanced antibacterial activity of the magnetic nanocomposites allows the dosage and the side effects of the antibiotic to be reduced. Due to the antibacterial effect and magnetism, the bacitracin-functionalized magnetic nanoparticles have potential application in magnetic-targeting biomedical applications.
In this study, amphiphilic polyoxanorbornene with different quaternary alkyl pyridinium side chains were synthesized. The biological efficiencies of these polymers, with various alkyl substituents, were determined by bacterial growth inhibition assays and hemolytic activity (HC 50 ) against human red blood cells (RBCs) to provide selectivity of these polymers for bacterial over mammalian cells. A series of polymers with different alkyl substituents (ethyl, butyl, hexyl, octyl, decyl and phenylethyl) and two different molecular weights (3 and 10 kDa) were prepared. The impact of alkyl chain length divided the biological activity into two different cases: those with an alkyl substituent containing four or fewer carbons had a minimum inhibitory concentration (MIC) of 200 µg · mL ⁻¹ and a HC 50 greater than 1 650 µg · mL ⁻¹ , while those with six or more carbons had lower MICs ≤ 12.5 µg · mL ⁻¹ and HC 50 ≤ 250 µg · mL ⁻¹ . Using MSI‐78, the potent Magainin derivative which has an MIC = 12.0 µg · mL ⁻¹ and HC 50 = 120 µg · mL ⁻¹ , as a comparison, the polymers with alkyl substituents ≤C 4 (four carbons) were not very potent, but did show selectivity values greater than or equal to MSI‐78. In contrast, those with alkyl substituents ≥C 6 were as potent, or more potent, than MSI‐78 and in three specific cases demonstrated selectivity values similar to, or better than, MSI‐78. To understand if these polymers were membrane active, polymer induced lipid membrane disruption activities were evaluated by dye leakage experiments. Lipid composition and polymer hydrophobicity were found to be important factors for dye release.
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An approach to synthesize phosphoric acid type block copolymers derived from ring-opening metathesis polymerization (ROMP) using Grubbs third generation catalyst was presented. Block copolymers were synthesized by a nucleophile exchange reaction and Mitsunobu coupling, using easily accessible starting material exo-oxabicyclo-[2.2.1]hept-5-ene-2,3-dicarboximide. It is found that the completion of polymerization is indicated by the total disappearance of the characteristic monomer olefin protons at 6.5 ppm and the appearance of the backbone double bond singles at 5.8-6.1. The results also show that the ratio of the methylene peaks and the phosphonate ester peaks of the polymer is 0.50 and 0.40, resulting in the block ratio of 0.8. A strong vibration band at 1241 cm -1, due to vibrations of phosphonate esters, disappears after cleavage.
The thermal degradation of poly(vinyl sulfonic acid) and its sodium salt, poly(4-styrenesulfonic acid) and its sodium salt, and poly(vinylphosphonic acid) was studied by a combination of techniques, including TGA/FTIR, to identify the volatile products which were evolved during the degradation as well as analysis of the residues which were obtained in order to propose a mechanism for the degradation. The motivation for the work was to attempt to identify new monomers which could be graft copolymerized onto a polymer in order to improve the thermal stability of that polymer.
A nanostructured iron oxide (NanoFe3O4, particle size ca. 25 nm and roughness ca. 21 nm) film deposited onto a
hydrolyzed indium-tin-oxide (ITO) coated glass plate has been used to immobilize cholesterol oxidase (ChOx) to
fabricate an impedimetric cholesterol sensor. Electrochemical studies reveal that surface charged Fe3O4 nanoparticles
provide better conformation for ChOx loading resulting in enhanced electron transfer between ChOx and the
electrode. Impedimetric response studies of the ChOx/NanoFe3O4/ITO bioelectrode exhibit improved linearity (2.5 –
400 mg/dL), low detection limit (0.25 mg/dL), fast response time (25 s), high sensitivity (86 W/mg dL�1/cm�2) and a low
value of the Michaelis-Menten constant (Km, 0.8 mg/dL) with a regression coefficient of 0.997.
Two types of magnetic binary nanocomposites, Ag@Fe(3)O(4) and γ-Fe(2)O(3)@Ag, were synthesized and characterized and their antibacterial activities were tested. As a magnetic component, Fe(3)O(4) (magnetite) nanoparticles with an average size of about 70 nm and monodisperse γ-Fe(2)O(3) (maghemite) nanoparticles with an average size of 5 nm were used. Nanocomposites were prepared via in situ chemical reduction of silver ions by maltose in the presence of particular magnetic phase and molecules of polyacrylate serving as a spacer among iron oxide and silver nanoparticles. In the case of the Ag@Fe(3)O(4) nanocomposite, silver nanoparticles, caught at the surfaces of Fe(3)O(4) nanocrystals, were around 5 nm in a size. On the contrary, in the case of the γ-Fe(2)O(3)@Ag nanocomposite, ultrafine γ-Fe(2)O(3) nanoparticles surrounded silver nanoparticles ranging in a size between 20 and 40 nm. In addition, the molecules of polyacrylate in this nanocomposite type suppress considerably interparticle magnetic interactions as proved by magnetization measurements. Both synthesized nanocomposites exhibited very significant antibacterial and antifungal activities against ten tested bacterial strains (minimum inhibition concentrations (MIC) from 15.6 mg/L to 125 mg/L) and four candida species (MIC from 1.9 mg/L to 31.3 mg/L). Moreover, acute nanocomposite cytotoxicity against mice embryonal fibroblasts was observed at concentrations of higher than 430 mg/L (Ag@Fe(3)O(4)) and 292 mg/L (γ-Fe(2)O(3)@Ag). With respect to the non-cytotoxic nature of the polyacrylate linker, both kinds of silver nanocomposites are well applicable for a targeted magnetic delivery of silver nanoparticles in medicinal and disinfection applications.