SciCombinator

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Journal: Journal of biomaterials science. Polymer edition

27

The barrier membranes maintain a secluded space to prevent the ingrowth of connective tissue and direct the growth of new bone into a desired site; however, they do not stimulate or induce bone regeneration. To enhance the bone bioactivities of membranes, we developed chitosan electret membranes with bioelectricity by grid-controlled constant voltage corona charging. The electret membranes charged with heat treatment (HT electret membranes) exhibited superior electret charge storage stability than the ones charged without heat treatment (RT electret membranes). Human bone marrow stromal cells (hBMSCs) demonstrated better growth on HT electrets membrane. Moreover, hBMSCs osteoblastic differentiation was enhanced on HT electret membranes, as evidenced by osteocalcin and osteopontin expression as assessed by immunocytochemistry, quantitative RT-PCR and western blot analysis. The rabbit calvarial defect model demonstrated that HT electret membranes induced a significantly enhanced bone regeneration compared with RT electret membranes. New bone formation was found at both the periphery and in the center of the defects four weeks after implantation. These results indicated that the chitosan electret membrane has osteogenic potential and could be applied as a novel barrier membrane.

Concepts: Bone, Blood, Bone marrow, Western blot, Cellular differentiation, Cartilage, Tissues, Stromal cell

27

Purpose: To alter the composition and structure of silicone hydrogel contact lenses to achieve controlled release of dexamethasone and evaluate the lens optical and mechanical properties compared to commercial lenses. There is a tremendous need for controlled release of drugs from ocular biomaterials as the majority of ophthalmic drugs are delivered via topical eye drops, which have low bioavailability and patient compliance. Methods: Poly(PDMS-co-TRIS-co-DMA) contact lenses were synthesized with varying PDMS/TRIS:DMA ratios (0.25:1, 0.67:1, 1.5:1) as well as with additional crosslinking monomers. Lenses were characterized via in vitro release studies in a microfluidic device at ocular flowrates and in large well-mixed volumes, optical quality studies over visible wavelengths, mechanical analysis, and determination of polymer volume fraction in the swollen state. Results: Extended and controlled release of therapeutically relevant concentrations of dexamethasone was achieved for multiple day, continuous wear up to 60 days at in vitro ocular flowrates. Release was delayed due to a combination of increased hydrophobic to hydrophilic composition and the inclusion of additional structural constraints, both of which decreased the polymer volume fraction in the swollen state. However, decreased mass release rates were at the expense of increased modulus and decreased lens flexibility. All lenses had high optical clarity (∼90% transmittance) and contained highly oxygen permeable siloxane composition similar to those found in commercial silicone hydrogel lenses, but they had poor flexibility for use as soft contact lenses. Conclusions: Based on our results, the lenses described herein likely have too high of a modulus for use as extended-wear, soft contact lenses with drug release. Therefore, other controlled release methods would be better suited for maintaining adequate mechanical properties and achieving controlled and extended release for the duration of wear in soft, silicone hydrogel contact lens biomaterials. However, these biomaterials may find clinical use as more rigid gas permeable contact lenses or inserts.

Concepts: Polymer, Cornea, Lens, Contact lens, Contact lenses, Corrective lens, Visible spectrum, Rigid gas permeable

27

Concerns about health issues and environmental pollution stimulate research to find new health and hygiene related products with healing properties and minimum negative effect on the environment. Development of new, natural antibacterial agents has become one of the most important research areas to combat some pathogens such as Gram- positive and Gram-negative bacteria, fungi, algae, yeast, and some microorganisms which cause serious human infections. Lawsonia Inermis (henna) leaf extracts for preparation of antibacterial poly(ethylene oxide) (PEO) and poly(vinyl alcohol) (PVA) nanofibers via electrospinning technique were investigated. PEO and PVA based electrospun fibers containing henna extract were verified by the appearance of FTIR peaks corresponding to the pure extract. Our study demonstrates that 2.793 wt.% Li in PVA and PEO based solutions showed bactericidal effects against Staphylococcus aureus and bacteriostatic action to Escherichia coli. Concentrations of henna leaf extract strongly impacted antibacterial activities against both bacteria. Henna leaves have a great potential to be used as a source of a potent eco-friendly antimicrobial agent.

Concepts: Photosynthesis, Bacteria, Microbiology, Staphylococcus aureus, Escherichia coli, Tea tree oil, Henna, Chloramphenicol

25

Hydrogels were prepared using polyvinyl pyrrolidone (PVP) blended with carrageenan by gamma irradiation at different doses of 25 and 40 kGy. Gel fraction of hydrogels prepared using 10 and 15% PVP in combination with 0.25 and 0.5% carrageenan was evaluated. Based on gel fraction, 15% PVP in combination with 0.25% carrageenan and radiation dose of 25 kGy was selected for the preparation of hydrogels with nanosilver. Radiolytic synthesis of silver nanoparticles within the PVP hydrogel was carried out. The hydrogels with silver nanoparticles were assessed for antimicrobial effectiveness and physical properties of relevance to clinical performance. Fluid handling capacity (FHC) for PVP/carrageenan was 2.35 ± 0.39-6.63 ± 0.63 g/10 cm(2) in 2-24 h. No counts for Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, and Candida albicans were observed in the presence of hydrogels containing 100 ppm nanosilver after 3-6 h. The release of silver from hydrogels containing 100 ppm nanosilver was 20.42 ± 1.98 ppm/100 cm(2) in 24 h. Hydrogels containing 100 ppm nanosilver with efficient FHC demonstrated potential microbicidal activity (≥3 log10 decrease in CFU/ml) against wound pathogens, P. aeruginosa, S. aureus, E. coli, and C. albicans. PVP/carrageenan hydrogels containing silver nanoparticles can be used as wound dressings to control infection and facilitate the healing process for burns and other skin injuries.

Concepts: Bacteria, Opportunistic infection, Staphylococcus aureus, Antibiotic resistance, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, Skin flora

25

Porous poly(glycerol sebacate) (PGS) scaffolds were prepared using a salt leaching technique and subsequently surface modified by a low oxygen plasma treatment prior to the use in the in vitro culture of human chondrocytes. Condensation polymerization of glycerol and sebacic acid used at various mole ratios, i.e., 1:1, 1:1.25, and 1:1.5, was initially conducted to prepare PGS prepolymers. Porous elastomeric PGS scaffolds were directly fabricated from the mixtures of each prepolymer and 90% (w/w) NaCl particles and then subjected to the plasma treatment to enhance the surface hydrophilicity of the materials. The properties of both untreated and plasma-treated PGS scaffolds were comparatively evaluated, in terms of surface morphology, surface chemical composition, porosity, and storage modulus using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), micro-computed tomography (μCT), and dynamic mechanical analysis (DMA), respectively. The responses of chondrocytes cultured on individual PGS scaffolds were assessed, in terms of cell proliferation and ECM production. The results revealed that average pore sizes and porosity of the scaffolds were increased with an increasing sebacic acid concentration used. The storage moduli of the scaffolds were raised after the plasma treatment, possibly due to the further crosslinking of PGS upon treatment. Moreover, the scaffold prepared with a higher sebacic acid content demonstrated a greater capability of promoting cell infiltration, proliferation, and ECM production, especially when it was plasma-treated; the greatest HA, sGAG, uronic acid, and collagen contents were detected in matrix of this scaffold. The H&E and safranin O staining results also strongly supported this finding. The storage modulus of the scaffold was intensified after being incubated with the chondrocytes for 21 days, indicating the accretion and retention of matrix ECM on the cell-cultured scaffold.

Concepts: Electron, Polymer chemistry, Transmission electron microscopy, X-ray photoelectron spectroscopy, Scanning electron microscope, Castor oil, Dicarboxylic acid, Sebacic acid

25

Polylysine is an important class of polyamino acids with a broad spectrum of applications in biomedical research and development. It can be divided into two classes, α-polylysine and ε-polylysine, the former is synthesized by artificial chemical synthesis and has limited applications due to its high toxicity, and the latter is produced by microbial synthesis as a class of natural polymers and is widely used in various food, medicinal, and electronics products. Another major class of synthetic polymers is dendrimers (after linear, cross-linked, and branched polymers). Dendrigraft poly-L-lysine (DGL) has the favorable properties of polylysine and dendrimers, with a broad spectrum of applications in drug discovery and development, including drug delivery, gene carriers, diagnostic imaging, diagnostics, biosensors, and special cancer therapies (such as boron neutron capture therapy and photodynamic therapy). As there are still some problems with the development of DGL, further research is warranted for its broad applications.

Concepts: Medicine, Chemical reaction, Biotechnology, Polymer, Chemical synthesis, Medical physics, Boron, Boron neutron capture therapy

25

Scaffold design is an important aspect of in vitro model development. In this study, nanoscaffold surface modification, namely UV-radiation and genipin cross-linking to immobilize collagen on the surface of electrospun Poly (methylmethacrylate) (PMMA) nanofibers sheet was investigated. Samples were divided into 4 groups; PMMA nanofibers (PMMA), collagen-coated PMMA nanofibers (PMMACOL), Genipin-crosslinked-collagen coated PMMA nanofibers (PMMAGEN), and UV-irradiated collagen-coated PMMA nanofibers (PMMAUV). 6 hours of UV radiation significantly reduced the hydrophobicity of PMMA nanofibers from (131.88°±1.33°) to (110.04°±0.27°) (p<0.05). The amount of collagen immobilized was significantly higher in PMMAGEN group (239.36±16.63 µg collagen/mg nanofibers) (p<0.05) compared to the other groups. RECs on all scaffold expressed epithelial cell specific markers (CK18 and CK14), mucin producing cell marker (MUC5Ac) and were actively proliferating, based on the positive expression of Ki67. Total number of attached cells was significantly highest in PMMAUV group on day 9 (6.44x10(4)±2.77x10(4) cells/cm(2)) and it has the highest proliferation rate from day 4 to 9 (0.005±0.003 h(-1)) compared to the other groups. Eventhough PMMAGEN group showed highest collagen adsorption, in terms of cells attachment and proliferation, PMMAUV group showed a better outcome compared to the other groups. Thus, PMMAUV scaffold is more suitable to be used in construction of in vitro respiratory epithelial model.

Concepts: DNA, Gene expression, Ultraviolet, Epithelium, Cornea, Respiratory epithelium, Connective tissue

25

A negatively charged copolymer poly (MPC-co-AMPS) of 2-methacryloyloxyethyl phosphorylcholine (MPC) and 2-acrylamide-2-methyl propane sulfonic acid (AMPS) was designed and synthesized. Chitosan nanoparticles with cell outer membrane mimetic structure were prepared by electrostatic interaction between the sulfonic acid groups of poly (MPC-co-AMPS) and the protonated amino groups of chitosan. Effects of factors on influencing the particle size, distribution and stability were investigated.The experimental results showed that cell membrane mimetic chitosan nanoparticles with controllable and homogeneous size ranged from 100 to 300 nm were prepared at the concentration of 0.1~2.0 mg/mL and the charge ratio of 0.5~1.1. Chitosan nanoparticles prepared can exist stably for more than 45 days placed at 4℃ and pH < 7.5. The cytotoxicity of chitosan nanoparticles reduced significantly after surface modification with cell membrane mimetic structure, meeting the basic requirements of biomedical materials. The results suggest cell membrane mimetic chitosan nanoparticles prepared with polyanion and polycation obtain good biological compatibility and immune stealth ability, which has important academic significance and great application prospect.

Concepts: Protein, Cell, Electric charge, Amino acid, Amine, Cell membrane, Electrostatics, Sulfonic acid

25

The water structure and platelet compatibility of poly(methyl methacrylate (MMA)-block-2-hydroxyethyl methacrylate (HEMA)) were investigated. The molecular weight (Mn) of the polyHEMA segment was kept constant (average: 9600), while the Mn of the polyMMA segment was varied from 1340 to 7390. The equilibrium water content of the copolymers was found to be mainly governed by the HEMA content. The water structure in the copolymers was characterized in terms of the amounts of non-freezing and freezing water (abbreviated as Wnf and Wfz, respectively) using differential scanning calorimetry. It was found that the Wnf for the copolymers were higher than those estimated from the Wnf for the HEMA and MMA homopolymers and that the amount of excess non-freezing water depended on the polyMMA segment length. In addition, X-ray diffraction analysis revealed that some of the copolymers had cold-crystallizable water. These facts suggested that the polyMMA segments were involved in determining the water structures in the copolymers. Furthermore, the platelet compatibility of the copolymers was improved as compared to that of the HEMA homopolymer. It was therefore concluded that the platelet compatibility of the copolymer was related to the amount of excess non-freezing water.

Concepts: Diffraction, X-ray, Water, Molecule, Polymer, Copolymer, X-ray crystallography, Differential scanning calorimetry

24

About 50% N-acetylation-thiolated chitosan possessing good water solubility was modified from commercial low-molecular-weight chitosan. Chitosan performed obvious target toward renal tubular epithelial cells, and bivalent cobalt ions improved the renal fibrosis inflammation significantly. There were many complexation sites on chitosan after being modified with sulfydryl. So sulfydryl played a role of connecting bridge between chitosan and cobalt ions. Then, this N-acetylation-thiolated chitosan cobalt (NTCC) nanocomplex was designed. The nanocomplex showed excellent stability under normal physiological conditions, and cobalt would be released from the biomaterials in acidic environment. As it was affected by inflammation, the pH in renal fibrosis lesion region was acidic. So there was a specific drug release process happening in lesion region. And drug release efficiency was determined by acidity, which demonstrated that lower the acidity, the faster and more the cobalt ion release. When this nanocomplex was intraperitoneally injected into ureter-obstructed mice, obvious attenuation of fibrotic progression was shown. It was demonstrated that NTCC exhibited special renal-targeting capacity and could be chosen as drug for treating renal fibrosis.

Concepts: Acid, Ammonia, Water, Hydrogen, Endothelium, PH, Ion, Base