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Online ISSN: 2159-2535


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Table 1 . the sample codes and the initial measured values for oriented and sterilized rods 
Figure 1. In vitro occurring strength retention of Ø1.1-1.2 mm oriented pLLA, 96L/4D pLA, and 80L/20D,L pLA samples plotted against determined inherent viscosity value measured from the same specimens; shear strength (A) and bending strength (B). Values are averages of the mentioned parallel samples and error bars indicate standard deviations for the measurements.
Figure 2. effect of the polymers initial iv on shear strength retention of Ø4.0 mm oriented 96L/4D pLA and 80L/20D,L pLA samples. Shear strength as a function of degradation time (A) and inherent viscosity (B). Values are averages of the mentioned parallel samples and error bars indicate standard deviations for the measurements.
Figure 3. effect of the sample diameter on shear strength retention of oriented 96L/4D pLA and 80L/20D,L pLA samples. Shear strength as a function of degradation time (A) and inherent viscosity (B). Values are averages of the mentioned parallel samples and error bars indicate standard deviations for the measurements.
Figure 5. Summary graph of strength and inherent viscosity correlation of all samples analyzed in this study. Regardless from the variables affecting on the rate of iv decay, the strength loss occurs on similar iv range.
Strength retention behavior of oriented PLLA, 96L/4D PLA, and 80L/20D,L PLA
ArticleFull-text available

September 2013


212 Reads


The strength retention characteristics of oriented semicrystalline polylactides were monitored during hydrolytic degradation in vitro. The effects of the polymer type, the material's initial inherent viscosity (iv), the sample diameter and the residual monomer content on strength retention were analyzed. The analyzed polylactides had similar, but not identical, strength retention characteristics. It was concluded that a higher degree of initial crystallinity was a major variable determining the earlier and more profound strength loss of PLLA than 96L/4D PLA and 80L/20 D,L PLA. Samples with a higher initial iv were found to have a longer strength retention time than lower iv samples. Size-dependency was observed, as the strength retention time was shorter for the smaller diameter samples. This size-dependency was caused by faster iv decay. The amount of residual monomer content had a remarkable impact on strength retention. Neither the sample diameter, initial iv or residual monomer content were found to have an effect on the iv range in which there was a rapid decline in strength properties. Therefore, it was concluded that the inherent viscosity and/or molecular weight of oriented PLLA, 96L/4D PLA and 80L/20 D,L PLA is a major variable determining the strength retention of these materials.

Table 1. Results of the potentiodynamic tests 
Table 3. Results of the eIS test 
Table 5. Chemical composition of artificial plasma 
The effects of a SiO 2 coating on the corrosion parameters cpTi and Ti-6Al-7Nb alloy

March 2014


1,210 Reads






The aim of this paper was to evaluate the usefulness of the sol-gel method application, to modificate the surface of the Ti6Al7Nb alloy and the cpTi titanium (Grade 4) with SiO 2 oxide, applied on the vascular implants to improve their hemocompatibility. Mechanical treatment was followed by film deposition on surface of the titanium samples. An appropriate selection of the process parameters was verified in the studies of corrosion, using potentiodynamic and impedance method. A test was conducted in the solution simulating blood vessels environment, in simulated body fluid at t = 37.0 ± 1 °C and pH = 7.0 ± 0.2. Results showed varied electrochemical properties of the SiO 2 film, depending on its deposition parameters. Correlations between corrosion resistance and layer adhesion to the substrate were observed, depending on annealing temperature.

Knitted polylactide 96/4 L/D structures and scaffolds for tissue engineering: Shelf life, in vitro and in vivo studies

July 2011


160 Reads

This study covers the whole production cycle, from biodegradable polymer processing to an in vivo tissue engineered construct. Six different biodegradable polylactide 96/4 L/D single jersey knits were manufactured using either four or eight multifilament fiber batches. The properties of those were studied in vitro for 42 weeks and in 0- to 3-year shelf life studies. Three types (Ø 12, 15 and 19 mm) of cylindrical scaffolds were manufactured from the knit, and the properties of those were studied in vitro for 48 weeks. For the Ø 15 mm scaffold type, mechanical properties were also studied in a one-year in vivo experiment. The scaffolds were implanted in the rat subcutis. All the scaffolds were g-irradiated prior to the studies. In vitro, all the knits lost 99% of their mechanical strength in 30 weeks. In the three-year follow up of shelf life properties, there was no decrease in the mechanical properties due to the storage time and only a 12% decrease in molecular weight. The in vitro and in vivo scaffolds lost their mechanical properties after 1 week. In the case of the in vivo samples, the mechanical properties were restored again, stepwise, by the presence of growing/maturing tissue between weeks 3 and 12. Faster degradation was observed with in vitro scaffolds compared to in vivo scaffolds during the one-year follow up.

Table 1 . application of biopolymers in neural stem/progenitor cell therapy of focal brain ischemic lesion 
Figure 1. Scanning electron micrograph of Ha hydrogel at (A) lower or (B) higher magnification. Reproduced with permission from reference 77. Scale bar = (A) 50 μm and (B) 20 μm.
Figure 3. an illustrative model on how changes in Ha regulate NSpcs in normal state and in response to injury. (1) cNS insults activate NSpcs in the subventricular zone (SvZ); (2) Ha in the niche is degraded due to increased hyaluronidase activity of NSpcs and other cell types and therefore (3) NSpcs proliferate, migrate toward the lesion and differentiate to opcs. (4) However, their maturation is inhibited if they encounter HMw Ha-rich chronic lesions. Reproduced with permission from reference 26.
Hyaluronan, neural stem cells and tissue reconstruction after acute ischemic stroke
Focal stroke is a disabling disease with lifelong sensory, motor and cognitive impairments. Given the paucity of effective clinical treatments, basic scientists are developing novel options for protection of the affected brain and regeneration of lost tissue. Tissue bioengineering and stem/progenitor cell treatments have both been individually pursued for stroke neural repair therapies, with some benefit in tissue recovery. Emerging directions in stroke neural repair approaches combine these two therapies to use biopolymers with stem/progenitor transplants to promote greater cell survival in the transplant and directed delivery of bioactive molecules to the transplanted cells and the adjacent injured tissue. In this review the background literature on a combined use of neural stem/progenitor cells encapsulated in hyaluronan gels is discussed and the way this therapeutic approach can affect the important processes involved in brain tissue reconstruction, such as angiogenesis, axon regeneration, neural differentiation and inflammation is clarified. The glycosaminoglycan hyaluronan can optimize those processes and be employed in a successful neural tissue engineering approach.

Figure 1. Schematic of the implantation of Ha-hydrogels and subsequent release and mobilization of embedded epc for treatment of aKi in a mouse model. (1) Ha-hydrogels with embedded epc are implanted either superficially into ears or subcapsularly into kidneys. (2) induction of aKi (cyto-/endotoxins). (3a) Kidney implants are digested by endogenous release of hyaluronidase from the kidneys during aKi and embedded epc are mobilized into the kidney, or (3b) ear implants are digested by direct injection of hydrogel-digesting enzymes and embedded epc are mobilized into the circulation. (4) Released epc generate therapeutic effects (see Tables 1 and 2).
Delivery of EPC embedded in HA-hydrogels for treatment of acute kidney injury
Adoptive transfer of stem cells has shown potential as an effective treatment for acute kidney injury (AKI). The current strategy for adoptive transfer of stem cells is by intravenous injection. However, this conventional method of stem cell delivery is riddled with problems causing reduced efficacy of the therapeutic potential of delivered stem cells. This review summarizes the recent advancements in an alternative method of stem cell delivery for treatment of AKI, embedding stem cells in hyaluronic acid (HA-) based hydrogels followed by their implantation. Furthermore, one stem cell type in particular, endothelial progenitor cells (EPC), have shown remarkable therapeutic benefits for treatment of AKI when delivered by HA-hydrogels. The review also summarizes the delivery of EPC by HA-hydrogels in the setting of AKI.

Infection of orthopedic implants with emphasis on bacterial adhesion process and techniques used in studying bacterial-material interactions
Staphylococcus comprises up to two-thirds of all pathogens in orthopedic implant infections and they are the principal causative agents of two major types of infection affecting bone: septic arthritis and osteomyelitis, which involve the inflammatory destruction of joint and bone. Bacterial adhesion is the first and most important step in implant infection. It is a complex process influenced by environmental factors, bacterial properties, material surface properties and by the presence of serum or tissue proteins. Properties of the substrate, such as chemical composition of the material, surface charge, hydrophobicity, surface roughness and the presence of specific proteins at the surface, are all thought to be important in the initial cell attachment process. The biofilm mode of growth of infecting bacteria on an implant surface protects the organisms from the host immune system and antibiotic therapy. The research for novel therapeutic strategies is incited by the emergence of antibiotic-resistant bacteria. This work will provide an overview of the mechanisms and factors involved in bacterial adhesion, the techniques that are currently being used studying bacterial-material interactions as well as provide insight into future directions in the field.

Figure 1. Xps high resolution spectra of N1s and c1s before and after plasma treatment. 
Figure 2. FtIR spectra of pVa films before (A) and after plasma treatment (B). New peaks and bands appeared at 1654 cm −1 , 1705 cm −1 and 3200-3400 cm −1 , associated to amide, carboxylic acid and Oh/Nh functionalities, respectively. a.u., arbitrary units. 
Figure 3. surface morphology of untreated and plasma-treated pVa films observed by aFM. Roughness was calculated by the root mean square roughness (Rrms). 
Figure 5. (A) endothelial cells were stained with phalloidin/DapI and observed on (left) untreated pVa and (right) plasma-treated pVa substrates with fluorescence microscopy at day 3. scale bar: 50 μm. cell area (B) and shape factor (C) were calculated from digital images (n = 15). significant difference from untreated pVa: *p < 0.05 and **p < 0.01. (D) cells eventually reached confluence on a treated pVa surface, forming an endothelium-like monolayer. 
Plasma functionalization of poly(vinyl alcohol) hydrogel for cell adhesion enhancement

July 2013


1,168 Reads

Tailoring the interface interactions between a biomaterial and the surrounding tissue is a capital aspect to consider for the design of medical devices. Poly(vinyl alcohol) (PVA) hydrogels present suitable mechanical properties for various biological substitutes, however the lack of cell adhesion on their surface is often a problem. The common approach is to incorporate biomolecules, either by blending or coupling. But these modifications disrupt PVA intra- and intermolecular interactions leading therefore to a loss of its original mechanical properties. In this work, surface modification by glow discharge plasma, technique known to modify only the surface without altering the bulk properties, has been investigated to promote cell attachment on PVA substrates. N2/H2 microwave plasma treatment has been performed, and the chemical composition of PVA surface has been investigated. X-ray photoelectron and Fourier transform infrared analyses on the plasma-treated films revealed the presence of carbonyl and nitrogen species, including amine and amide groups, while the main structure of PVA was unchanged. Plasma modification induced an increase in the PVA surface wettability with no significant change in surface roughness. In contrast to untreated PVA, plasma-modified films allowed successful culture of mouse fibroblasts and human endothelial cells. These results evidenced that the grafting was stable after rehydration and that it displayed cell adhesive properties. Thus plasma amination of PVA is a promising approach to improve cell behavior on contact with synthetic hydrogels for tissue engineering.

On the potential for fibronectin/phosphorylcholine coatings on PTFE substrates to jointly modulate endothelial cell adhesion and hemocompatibility properties

March 2015


387 Reads

The use of biomolecules as coatings on biomaterials is recognized to constitute a promising approach to modulate the biological response of the host. In this work, we propose a coating composed by two biomolecules susceptible to provide complementary properties for cardiovascular applications: fibronectin (FN) to enhance endothelialization, and phosphorylcholine (PRC) for its non thrombogenic properties. Polytetrafluoroethylene (PTFE) was selected as model substrate mainly because it is largely used in cardiovascular applications. Two approaches were investigated: 1) a sequential adsorption of the two biomolecules and 2) an adsorption of the protein followed by the grafting of phosphorylcholine via chemical activation. All coatings were characterized by immunofluorescence staining, X-Photoelectron Spectroscopy and Scanning Electronic Microscopy analyses. Assays with endothelial cells showed improvement on cell adhesion, spreading and metabolic activity on FN-PRC coatings compared with the uncoated PTFE. Platelets adhesion and activation were both reduced on the coated surfaces when compared with uncoated PTFE. Moreover, clotting time tests exhibited better hemocompatibility properties of the surfaces after a sequential adsorption of FN and PRC. In conclusion, FN-PRC coating improves cell adhesion and non-thrombogenic properties, thus revealing a certain potential for the development of this combined deposition strategy in cardiovascular applications.

Adipose and mammary epithelial tissue engineering

April 2013


50 Reads

Breast reconstruction is a type of surgery for women who have had a mastectomy, and involves using autologous tissue or prosthetic material to construct a natural-looking breast. Adipose tissue is the major contributor to the volume of the breast, whereas epithelial cells comprise the functional unit of the mammary gland. Adipose-derived stem cells (ASCs) can differentiate into both adipocytes and epithelial cells and can be acquired from autologous sources. ASCs are therefore an attractive candidate for clinical applications to repair or regenerate the breast. Here we review the current state of adipose tissue engineering methods, including the biomaterials used for adipose tissue engineering and the application of these techniques for mammary epithelial tissue engineering. Adipose tissue engineering combined with microfabrication approaches to engineer the epithelium represents a promising avenue to replicate the native structure of the breast.

Figure 1. CDC surface markers compatible with hydrogel. Representative flow cytometry histograms showing expression of CD49a (A), CD49b (B), CD49c (C) and CD44 (D) in CDCs (in blue). Isotype controls are shown in red.
Figure 2. CDC survival in the hydrogel. (A and B) Representative fluorescent micrographs showing live (Calcien-AM: green) and dead (EthD: red) staining of CDCs cultured in Hystem™ and Hystem-CTM for 7 d. (C) CCK-8 assay quantifying cell survival rates in HystemTM (black bars) or Hystem-CTM (green bars) (n = 3). * indicates p < 0.05 when compared with HystemTM.
Figure 3. Enhanced cell engraftment by delivering CDCs in Hystem-CTM. (A and B) Representative confocal images showing engraftment of DiI-labeled human CDCs (red) 24 h after injection into post-MI mouse hearts. (C) Quantitative PCR analysis of cell engraftment rates in the mouse hearts 3 weeks post injection (n = 3). * indicates p < 0.05 when compared with “CDC in PBS.”
Figure 4. Cardiac function and heart morphometry. (A) Changes of left ventricular ejection fraction (LVEF) measured by echocardiography from baseline to 3 weeks in each group. (B) Quantitative analysis and LV morphometric parameters of Masson’s trichrome images (n = 3–5 mice per group). * indicates p < 0.05 when compared with Control. ** indicates p < 0.05 when compared with any other group.
Figure 5. Promotion of angiogenesis by CDC/hydrogel transplantation. (A) Representative confocal images showing α smooth muscle actin-positive vasculature in the hearts receiving various treatment products. (B) Quantitation of α smooth muscle actin-positive vasculature in various groups (n = 5 mice per group). * indicates p < 0.05 when compared with Control. ** indicates p < 0.05 when compared with any other group. Bar = 200 µm.
Enhancing retention and efficacy of cardiosphere-derived cells administered after myocardial infarction using a hyaluronan-gelatin hydrogel
Cardiosphere-derived cells (CDCs) are under clinical development and are currently being tested in a clinical trial enrolling patients who have undergone a myocardial infarction. CDCs are presently administered via infusion into the infarct-related artery and have been shown in early clinical trials to be effective agents of myocardial regeneration. This review describes the administration of CDCs in a hyaluronan-gelatin hydrogel via myocardial injection and the subsequent improvements in therapeutic benefit seen in animal models. Development of a next generation therapy involving the combination of CDCs and hydrogel is discussed.

Figure 1. Morphological analysis of CH porous scaffolds with DA 4% and 15%. (A) SeM micrographs of transversal cross-sections of the dehydrated scaffolds, showing a highly porous and interconnected structure, with macropores (arrow) and interconnecting pores (*). (B) CLSM imaging of 100 μm thick cryosections of hydrated CH scaffolds. the polymeric structure is shown in blue due to CH autofluorescence upon excitation by the 405 nm laser. the pore diameter distribution resultant from image analysis is shown in the box plot chart, and depicts the following statistics: minimum, first quartile, median, third quartile, and maximum. pinpoints represent outliers. Values reported correspond to 120 measurements made in CLSM images of cryosections obtained from four different CH scaffolds. 
Figure 2. Kinetics and isotherms of FN adsorption to CH scaffolds, as determined using 125 I-labeled FN. (A) FN adsorption to CH (DA 4%) from a 20 μg/ mL FN solution, as a function of incubation time (mean ± SD; n = 8). (B) FN adsorption to CH scaffolds (DA 4 and 15%; 15-h incubation period), as a function of FN solution concentration (mean ± SD; n = 6). All the FN levels shown were determined after subsequent incubation of the porous scaffolds in complete culture medium for 24 h. 
Figure 3. Fibronectin adsorption to CH scaffolds (DA 4 and 15%) from a 20 μg/mL FN solution, as well as elution and exchangeability of pre-adsorbed FN in the presence of serum proteins. FN adsorption levels were determined by gamma counting after a 15-h incubation period in a 20 μg/mL 125 I-labeled FN solution. to estimate the elution of pre-adsorbed FN in the presence of serum proteins, samples were further immersed in complete culture medium (CCM) for 24 h, and the levels of remaining FN quantified by gamma counting. the exchangeability of pre-adsorbed FN by new FN molecules from serum was investigated incubating samples pre-adsorbed with unlabelled FN (20 μg/mL) in CCM containing 125 I-FN. Results presented are the mean ± SD (n = 6). 
Figure 4. Distribution and conformation of FN upon adsorption to CH scaffolds with DA 4% (A) and 15% (B), as probed by immunofluorescent staining of the integrin-binding RGD site of FN. Scaffolds were incubated in a 20 μg/mL FN solution for 15 h, cryosectioned, processed for immunofluorescence, and imaged by CLSM. the scale bar for the low-and high-magnification images corresponds to 300 μm and 75 μm, respectively. (C) Quantitative analysis of exposed cell-binding domains, as determined by fluorimetry. Results reported are the mean ± SD of fluorescence intensity (FI) values correspondent to 8 cryosections. 
Kinetics and isotherm of fibronectin adsorption to three-dimensional porous chitosan scaffolds explored by I-radiolabelling

April 2013


142 Reads

In this study, ( 125) I-radiolabelling was explored to follow the kinetics and isotherm of fibronectin (FN) adsorption to porous polymeric scaffolds, as well as to assess the elution and exchangeability of pre-adsorbed FN following incubation in serum-containing culture medium. Chitosan (CH) porous scaffolds with two different degrees of acetylation (DA 4% and 15%) were incubated in FN solutions with concentrations ranging from 5 to 50 µg/mL. The kinetic and isotherm of FN adsorption to CH were successfully followed using ( 125) I-FN as a tracer molecule. While on DA 4% the levels of adsorbed FN increased linearly with FN solution concentration, on DA 15% a saturation plateau was attained, and FN adsorbed amounts were significantly lower. These findings were supported by immunofluorescent studies that revealed, for the same FN solution concentration, higher levels of exposed cell-binding domains on DA 4% as compared with DA 15%. Following incubation in serum containing medium, DA 4% also revealed higher ability to exchange pre-adsorbed FN by new FN molecules from serum than DA 15%. In accordance, when assessing the efficacy of passively adsorbed FN to promote endothelial cell (EC) adhesion to CH, ECs were found to adhere at higher levels to DA 4% as compared with DA 15%, 5 µg/mL of FN being already efficient in promoting cell adhesion and cytoskeletal organization on CH with DA 4%. Taken together the results show that protein radiolabelling can be used as an effective tool to study protein adsorption to porous polymeric scaffolds, both from single and complex protein solutions.

Table 3 . peptide summary 
Figure 2 of 2
Development of affinity-based delivery of NGF from a chondroitin sulfate biomaterial

October 2011


67 Reads

Chondroitin sulfate is a major component of the extracellular matrix in both the central and peripheral nervous systems. Chondroitin sulfate is upregulated at injury, thus methods to promote neurite extension through chondroitin sulfate-rich matrices and synthetic scaffolds are needed. We describe the use of both chondroitin sulfate and a novel chondroitin sulfate-binding peptide to control the release of nerve growth factor. Interestingly, the novel chondroitin sulfate-binding peptide enhances the controlled release properties of the chondroitin sulfate gels. While introduction of chondroitin sulfate into a scaffold inhibits primary cortical outgrowth, the combination of chondroitin sulfate, chondroitin sulfate-binding peptide and nerve growth factor promotes primary cortical neurite outgrowth in chondroitin sulfate gels.

Figure 2. IR spectra of (A) raw bioactive glass, (B) BG-e and (C) BG-C.
Figure 3. tGA thermo gram for bioactive glass stabilized by ethanol washing and calcination.
Figure 9. percentage viability of rBMSC cultured with the extract of bioactive glass samples, as assessed by Mtt assay.
A new synthesis route to high surface area sol gel bioactive glass through alcohol washing: A preliminary study

March 2013


462 Reads

Bioactive glass is one of the widely used bone repair material due to its unique properties like osteoconductivity, osteoinductivity and biodegradability. In this study bioactive glass is prepared by the sol gel process and stabilized by a novel method that involves a solvent instead of the conventional calcinations process. This study represents the first attempt to use this method for the stabilization of bioactive glass. The bioactive glass stabilized by this ethanol washing process was characterized for its physicochemical and biomimetic property in comparison with similar composition of calcined bioactive glass. The compositional similarity of the two stabilized glass powders was confirmed by spectroscopic and thermogravimetric analysis. Other physicochemical characterizations together with the cell culture studies with L929 fibroblast cells and bone marrow mesenchymal stem cells proved that the stabilization was achieved with the retention of its inherent bioactive potential. However an increase in the surface area of the glass powder was obtained as a result of this ethanol washing process and this add up to the success of the study. Hence the present study exhibits a promising route for high surface area bioactive glass for increasing biomimicity.

Table 3 . Biological effects associated with sulfated polysaccharides from green algae 
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Marine algae sulfated polysaccharides for tissue engineering and drug delivery approaches
Biomedical field is constantly requesting for new biomaterials, with innovative properties. Natural polymers appear as materials of election for this goal due to their biocompatibility and biodegradability. In particular, materials found in marine environment are of great interest since the chemical and biological diversity found in this environment is almost uncountable and continuously growing with the research in deeper waters. Moreover, there is also a slower risk of these materials to pose illnesses to humans. In particular, sulfated polysaccharides can be found in marine environment, in different algae species. These polysaccharides don’t have equivalent in the terrestrial plants and resembles the chemical and biological properties of mammalian glycosaminoglycans. In this perspective, are receiving growing interest for application on health-related fields. On this review, we will focus on the biomedical applications of marine algae sulfated polymers, in particular on the development of innovative systems for tissue engineering and drug delivery approaches.

The influence of operating parameters on the drug release and antibacterial performances of alginate fibrous dressings prepared by wet spinning

October 2012


561 Reads

Wet spinning was used to manufacture fibrous alginate hydrogel wound dressings. Samples manufactured using varied operating parameters (decreased air pressure and calcium concentration or increased nozzle diameter and alginate concentration) were compared with the control samples. The changes in the fiber size, Young's modulus, swelling ratio, fetal bovine serum (BSA) release efficacy, water vapor transmission rate (WVTR) and bacterial inhibition potential due to alterations of the operating parameters were measured. The samples manufactured using altered operating parameters had larger fiber sizes (p < 0.05) and lower Young's moduli (p < 0.05). The changes in swelling ratios, BSA release efficacies, WVTR and bacterial inhibition potential showed a significant dependence on the degree of calcium crosslinking of the hydrogel and on how tightly the fibers were bound with one another. By manipulating the operating parameters in the wet-spinning system, wound dressings with different properties were successfully made.

Table 1. Primer sequences for real-time PCR 
Figure 3. (A) The hydroxyl groups of a-CD present in PCL-a-CD IC fibers can be conjugated with several biological or chemical moieties, including a fluorescent molecule. Step 1: activation of a-CD with N,N'-carbonyldiimidazole (CDI) followed by its reaction with ethylenediamine. The hydroxyl groups are abundant and available for activation by N,N'-CDI in PCL-a-CD IC compared with only terminal hydroxyl groups of PCL. Step 2: fluorescamine was conjugated to amine groups. (B) Optical microscope images of electrospun fibers of PCL before (i) and after fluorescamine labeling (ii); PCL/a-CD fibers before (iii) and after fluorescamine labeling (iv).
Multifunctional aliphatic polyester nanofibers for tissue engineering

October 2012


228 Reads

Electrospun fibers based on aliphatic polyesters, such as poly(ε-caprolactone) (PCL), have been widely used in regenerative medicine and drug delivery applications due to their biocompatibility, low cost and ease of fabrication. However, these aliphatic polyester fibers are hydrophobic in nature, resulting in poor wettability, and they lack functional groups for decorating the scaffold with chemical and biological cues. Current strategies employed to overcome these challenges include coating and blending the fibers with bioactive components or chemically modifying the fibers with plasma treatment and reactants. In the present study, we report on designing multifunctional electrospun nanofibers based on the inclusion complex of PCL-α-cyclodextrin (PCL-α-CD), which provides both structural support and multiple functionalities for further conjugation of bioactive components. This strategy is independent of any chemical modification of the PCL main chain, and electrospinning of PCL-α-CD is as easy as electrospinning PCL. Here, we describe synthesis of the PCL-α-CD electrospun nanofibers, elucidate composition and structure, and demonstrate the utility of functional groups on the fibers by conjugating a fluorescent small molecule and a polymeric-nanobead to the nanofibers. Furthermore, we demonstrate the application of PCL-α-CD nanofibers for promoting osteogenic differentiation of human adipose-derived stem cells (hADSCs), which induced a higher level of expression of osteogenic markers and enhanced production of extracellular matrix (ECM) proteins or molecules compared with control PCL fibers.

Table 1 . Comparison of polarization resistance and corrosion current for the Untreated and Kolsterised ® samples. 
Biocompatibility and characterization of a Kolsterised ® medical grade cobalt-chromium-molybdenum alloy

January 2014


344 Reads

High failure rates of cobalt-chromium-molybdenum (Co-Cr-Mo) metal-on-metal hip prosthesis were reported by various authors, probably due to the alloy's limited hardness and tribological properties. This thus caused the popularity of the alloy in metal-on-metal hip replacements to decrease due to its poor wear properties when compared with other systems such as ceramic-on-ceramic. S-phase surface engineering has become an industry standard when citing surface hardening of austenitic stainless steels. This hardening process allows the austenitic stainless steel to retain its corrosion resistance, while at the same time also improving its hardness and wear resistance. By coupling S-phase surface engineering, using the proprietary Kolsterising(®) treatment from Bodycote Hardiff GmbH, that is currently being used mainly on stainless steel, with Co-Cr-Mo alloys, an improvement in hardness and tribological characteristics is predicted. The objective of this paper is to analyze the biocompatibility of a Kolsterised(®) Co-Cr-Mo alloy, and to characterize the material surface in order to show the advantages gained by using the Kolsterised(®) material relative to the original untreated alloy, and other materials. This work has been performed on 3 fronts including; Material characterization, "In-vitro" corrosion testing, and Biological testing conforming to BS EN ISO 10993-18:2009 - Biological evaluation of medical devices. Using these techniques, the Kolsterised(®) cobalt-chromium-molybdenum alloys were found to have good biocompatibility and an augmented corrosion resistance when compared with the untreated alloy. The Kolsterised(®) samples also showed a 150% increase in surface hardness over the untreated material thus predicting better wear properties.

Alternative technique for calcium phosphate coating on titanium alloy implants

March 2014


355 Reads

As an alternative technique for calcium phosphate coating on titanium alloys, we propose to functionalize the metal surface with anionic bath containing chlorides of palladium or silver as activators. This new deposition route has several advantages such as controlled conditions, applicability to complex shapes, no adverse effect of heating, and cost effectiveness. A mixture of hydroxyapatite and calcium phosphate hydrate coatings is deposited on the surfaces of Ti-6Al-4V. Ca-P coating is built faster compared with the one by Simulated Body Fluid. Cell morphology and density are comparable to the control one; and the results prove no toxic compound is released into the medium by the ACM1 and ACM2 specimens during the previous seven days of immersion. Moreover, the cell viability is comparable with cells cultivated with the virgin medium. These experimental treatments allowed producing cytocompatible materials potentially applicable to manufacture implantable devices for orthopedic and oral surgeries.

Influence of ECAP process on mechanical and corrosion properties of pure Mg and ZK60 magnesium alloy for biodegradable stent applications

February 2014


470 Reads

Equal channel angular pressing (ECAP) was performed on ZK60 alloy and pure Mg in the temperature range 150-250 °C. A significant grain refinement was detected after ECAP leading to an ultrafine grain size (UFG) and enhanced formability during extrusion process. Comparing to conventional coarse grained samples, fracture elongation of pure Mg and ZK60 alloy were significantly improved by 130% and 100%, respectively, while the tensile strength remained at high level. Extrusion was performed on ECAP processed billets to produce small tubes (with outer/inner diameter of 4/2.5 mm) as precursors for biodegradable stents. Studies on extruded tubes revealed that even after extrusion the microstructure and microhardness of the UFG ZK60 alloy were almost stable. Furthermore, pure Mg tubes showed an additional improvement in terms of grain refining and mechanical properties after extrusion. Electrochemical analyses and microstructural assessments after corrosion tests demonstrated two major influential factors in corrosion behavior of the investigated materials. The presence of Zn and Zr as alloying elements simultaneously increases the nobility by formation of a protective film and increase the local corrosion damage by amplifying the pitting development. ECAP treatment decreases the size of the second phase particles thus improving microstructure homogeneity, thereby decreasing the localized corrosion effects.

Progressive alterations in microstructural organization and biomechanical response in the ApoE mouse model of aneurysm

April 2013


115 Reads

AAA is a complex disease that leads to a localized dilation of the infrarenal aorta that develops over years. Longitudinal information in humans has been difficult to obtain for this disease, therefore mouse models have become increasingly used to study the development of AAAs. The objective of this study was to determine any changes that occur in the biomechanical response and fiber microstructure in the ApoE (-/-) AngII mouse model of aneurysm during disease progression. Adult ApoE (-/-) AngII infused mice along with wild-type controls were taken at 14 and 28 d. Aortas were excised and tested simultaneously for biaxial mechanical response and ECM organization. Data sets were fit to a Fung-type constitutive model to give peak strains and stiffness values. Images from two photon microscopy were quantified in order to assess the preferred fiber alignment and degree of fiber orientation. Biomechanical results found significant differences that were present at 14 d had returned to normal by 28 d along with significant changes in fiber orientation and dispersion indicating remodeling occurring within the aneurysmal wall. This return of some of the normal biomechanical function, in addition the continuing changes that occur in the microstructure suggest a restorative response that occurs in the ApoE (-/-) AngII infused model after the initial aneurysm formation.

Table 2 . Solubility test: number of samples per pH and time point 
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Evaluation of silicon nitride as a wear resistant and resorbable alternative for total hip joint replacement

April 2012


196 Reads

Many of the failures of total joint replacements are related to tribology, i.e., wear of the cup, head and liner. Accumulation of wear particles at the implants can be linked to osteolysis which leads to bone loss and in the end aseptic implant loosening. Therefore it is highly desirable to reduce the generation of wear particles from the implant surfaces. Silicon nitride (Si3N4) has shown to be biocompatible and have a low wear rate when sliding against itself and is therefore a good candidate as a hip joint material. Furthermore, wear particles of Si3N4 are predicted to slowly dissolve in polar liquids and they therefore have the potential to be resorbed in vivo, potentially reducing the risk for aseptic loosening. In this study, it was shown that α-Si3N4-powder dissolves in PBS. Adsorption of blood plasma indicated a good acceptance of Si3N4 in the body with relatively low immune response. Si3N4 sliding against Si3N4 showed low wear rates both in bovine serum and PBS compared with the other tested wear couples. Tribofilms were built up on the Si3N4 surfaces both in PBS and in bovine serum, controlling the friction and wear characteristics.

Figure 1. SeM images of both sides of a 100 nm anodized aluminum oxide membrane. (A) Side A of an uncoated anodized aluminum oxide membrane, showing 200 nm circular pores. (B) Side A of an 8 nm Zno-coated anodized aluminum oxide membrane, showing 200 nm circular pores. (C) Side B of an uncoated anodized aluminum oxide membrane, showing 100 nm branching pores. (D) Side B of an 8 nm Zno-coated anodized aluminum oxide membrane, showing 100 nm branching pores. 
Figure 2. cross-sectional SeM and elemental analysis of a 20 nm nanoporous anodized aluminum oxide with an 8 nm Zno coating. (A) cross-sectional view of the membrane, showing the crystals present on the surface. (B) eDX spectrum obtained from the 200 nm circular pore side, showing Al and Zn peaks (Side B). 
Figure 3. cell viability (Mtt assay) in macrophages cultured on nanoporous uncoated anodized aluminum oxide membranes and nanoporous Zn-coated anodized aluminum oxide membranes. No statistical differences are present at 24 h. After 48 h, cells cultured on both 20 and 100 nm Znocoated anodized aluminum oxide membranes showed a reduction in cell viability compared with cells cultured on corresponding uncoated anodized aluminum oxide membranes and cells grown on standard tissue culture wells. Statistical significance ***P < 0.001, **P < 0.01 from cell and media only control. 
Figure 4. RoS production in macrophages treated with 24-h extracts from Zno-coated anodized aluminum oxide membranes over 1 h, 3 h, 12 h, and 24 h. cells were treated with H 2 o 2 as a positive control. All experimental groups, including Zno-coated and uncoated anodized aluminum oxide, had similar responses to cells grown with fresh media, indicating no significant RoS generation for any surface extract. 
Cytotoxicity of cultured macrophages exposed to antimicrobial zinc oxide (ZnO) coatings on nanoporous aluminum oxide membranes

June 2013


1,372 Reads

Zinc oxide (ZnO) is a widely used commercial material that is finding use in wound healing applications due to its antimicrobial properties. Our study demonstrates a novel approach for coating ZnO with precise thickness control onto 20 nm and 100 nm pore diameter anodized aluminum oxide using atomic layer deposition (ALD). ZnO was deposited throughout the nanoporous structure of the anodized aluminum oxide membranes. An 8 nm-thick coating of ZnO, previously noted to have antimicrobial properties, was cytotoxic to cultured macrophages. After 48 h, ZnO-coated 20 nm and 100 nm pore anodized aluminum oxide significantly decreased cell viability by ≈65% and 54%, respectively, compared with cells grown on uncoated anodized aluminum oxide membranes and cells grown on tissue culture plates. Pore diameter (20-200 nm) did not influence cell viability.

Figure 3. (a) effect of wt. fraction of pVa/ chitosan on swelling ratio of the cryogel. (B) effect of savlon variation on the swelling ratio of the cryogels.  
Figure 4. (a) effect of no. of freeze thaw cycles (Ftc) on swelling ratio of the cryogels. (B) effect of ph on swelling sorption capacity of the cryogels.  
Figure 5. effect of temperature on swelling ratio of the cryogels. Figure 6. effect of biological fluids on swelling ratio.  
Figure 7. (a) effect of wt. fraction of pVa/chitosan on deswelling behaviors of the cryogels. (B) Influence of amount of savlon (mL) on the deswelling of cryogel.  
Figure 10. Influence of Ftc on pore size of the cryogel (a) 3 Ftc, (B) 5 Ftc, (c) 7 Ftc and (D) 9 Ftc.  
Designing polysaccharide-based antibacterial biomaterials for wound healing applications

October 2011


441 Reads

In this study, the development and characterization of novel polymer blends based on chitosan-poly (vinyl alcohol) and physically cross-linked by freeze-thaw method for possible use in a variety of biomedical application is reported. The present investigation deals with designing savlon-loaded blend hydrogels (coined as cryogels) of poly (vinyl alcohol) (PVA) and chitosan by repeated freeze-thaw method and their characterization by SEM and FTIR techniques. The FTIR spectra clearly reveal that savlon-loaded chitosan and PVA blends are bonded together through hydrogen bonding. The SEM analysis suggests that cryogels show a well-defined porous morphology. The prepared cryogels were also investigated for swelling and deswelling behaviors. The results reveal that both the swelling and deswelling behaviors greatly depend on factors like chemical composition of the cryogels, number of freeze-thaw cycles, pH and temperature of the swelling bath. The savlon-loaded blends were also investigated for their in vitro blood compatibility and antibacterial activity.

Maintenance of α 1 -antitrypsin activity by means of co-application of hypochlorous acid-scavengers in vitro and in the supernatant of polymorphonuclear leukocytes: As a basis for a new drug delivery approach

January 2012


88 Reads

Tissue destruction, pain and loss of function in chronically inflamed tissues can result from noxious agents released from myeloperoxidase (MPO) and its highly reactive product hypochlorous acid (HOCl) or proteases such as neutrophil elastase (NE). Currently there exists a high demand for medications that provide gentle treatments, free from side effects inherent in those prescribed today. One method to circumvent side effects is through the use of locally applied drug delivery. In contrast to systemic therapy, the main advantages of transport systems are the low dosages of drug with a time-controlled delivery. The aim of this study was to ascertain interactions of NE and its inhibitor α 1-antitrypsin (AT), the influence of hypochlorous acid (HOCl), as well as its scavengers, in order to define an effective mixture of drugs acting in a synergistic way which can be applied by means of drug delivery systems. These investigations determine the effective amounts of AT/HOCl-scavengers that drug mixtures need for delivery under inflammatory conditions in order to prevent tissue damage. AT was shown to inhibit NE in a dose-dependent manner, whereas a physiological concentration of 1.14 µM AT caused a significant NE inhibition (78%, pH 7.5). The concomitant existence of MPO/HOCl inactivated AT in a dose-dependent manner as well. To regain AT efficacy, HOCl-scavengers, such as l-methionine, α-aminosalicylic acid and cefoperazone were additionally applied. Finally, AT was assembled as surface layer onto layer-by-layer biopolymer-coated microcarriers and carrier phagocytosis by polymorphonuclear leukocytes could be shown.

Table 1 . treatment effects of the MC group and the autograft group 
Figure 1. Ct imaging of the treatment site. (A) preoperative three-dimensional Ct imaging; (B) 6 mo postoperative Ct imaging.
The mineralized collagen for the reconstruction of intra-articular calcaneal fractures with trabecular defects

November 2013


62 Reads

Background: In cases of severe subversion of the morphology of calcaneal fractures with trabecular defects, bone graft is often necessary to provide a mechanical buttress. The mineralized collagen (MC) is a novel bone substitute that is developed by biomimetic synthesis strategy that mimics the extracellular matrix (ECM) of natural bone in structure and chemical composition. It can avoid donor site morbidity and complications associated with harvesting autologous bone graft. Objective: In this study, we conducted a retrospective matched-pair analysis to assess the clinical and radiological performances of MC as a bone graft substitute in intra-articular calcaneal fractures with trabecular defects. Methods: 24 pairs of intra-articular calcaneal fractures with trabecular defects were treated with open reduction, internal fixation, and grafting either with MC or autograft. Patient demographics, medical history, and CT fracture classification were matched. Fractures were monitored 6 weeks, 12 weeks, 6 months, and 1 year postoperatively for healing and postoperative complications and results were analyzed. Results: All patients had follow-up at a minimum of 12 months after surgery with a mean follow-up time of 17 months. All fractures were healed; there were no significant differences in the meantime to union and clinical between the two groups. The radiographic evaluation confirmed that a significant improvement in the mean Böhler's angle, Gissane's angle and the calcaneus height was observed in all patients in both treatment groups. A total of 29% (7/24) of patients suffered from harvest-site morbidity at 12 months in the autograft group. In contrast, all patients were free from postoperative local complications in the iliac region and no patient developed adverse reactions attributable to MC in the MC group. Conclusion: These results justify and favor the use of MC as a good autograft alternative in displaced intra-articular calcaneal fractures with trabecular defects.