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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

With a new non-destructive and solvent-free photografting technique, N-vinylpyrrolidone was covalently grafted onto the surfaces of degradable polymers; poly(l-lactide), poly(epsilon-caprolactone), poly(lactide-co-glycolide), and poly(trimethylene carbonate). The modified surfaces were characterized by XPS, ATR-FTIR, SEM, and cell growth tests. The wettability was markedly improved, as static contact angles changed from about 80 degrees for the pristine substrates to around 30 degrees after 30min of grafting. Well-defined surface topographies, such as micro-patterns, are preserved in the process since the graft layers are thin. The biological response, measured as cytotoxicity, showed that the modified films provide good substrates, comparable with optimized cell culture plastics, for the adhesion and proliferation of normal human keratinocytes and skin fibroblasts.
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PMID:Surface functionalization of degradable polymers by covalent grafting. 1625 44

This study compared the effect of an antioxidant on the in vivo biodegradation of a poly(carbonate urethane) (PCU) and a poly(ether urethane) (PEU). Unstrained PEU and PCU films with and without Santowhite were implanted subcutaneously into 3-month-old Sprague-Dawley rats for 3, 6, and 12 months. Characterization of unstabilized PEU and PCU with ATR-FTIR and SEM showed soft-segment and hard-segment degradation consistent with previous studies. In particular, evidence of chain scission and crosslinking of the surface was present in the ATR-FTIR spectra of explanted specimens. Addition of 2.2 wt % antioxidant inhibited the in vivo degradation of both PCU and PEU. Although the antioxidant probably improved polyurethane biostability by decreasing the susceptibility of the polymer to degradation, modulation of the cellular response to prevent the release of degradative agents was also possible. To differentiate the effects, the foreign-body response was investigated with the use of a standard cage implant protocol. Polyurethane films were implanted in wire mesh cages subcutaneously in rats for 4, 7, and 21 days. There were no statistical differences among materials in the inflammatory exudate cell counts, adherent cell densities, or percent fusion of macrophages into foreign-body giant cells (FBGCs). Therefore, it was concluded that the antioxidant inhibited degradation by capturing oxygen radicals that would otherwise cause polyurethane chain scission and crosslinking.
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PMID:Antioxidant inhibition of poly(carbonate urethane) in vivo biodegradation. 1627 58

A series of polyurethane polymers was synthesized with increasing proportions of silicone in the form of polydimethylsiloxane (PDMS) utilised as a cross-linking agent, based on an aromatic, non-biostable polyetherurethane (PEtU). Eight formulations ranging from 0-50% PDMS were constructed into porous and non-porous films. These were implanted subcutaneously in rats, both unstrained and 100% strained, for 3 and 6 months. Degradation was determined by FTIR-ATR. Porous films were implanted for 6 and 12 months intramuscularly in both rats and rabbits. These were explanted and examined for inflammatory cell markers by immunohistochemistry. Both low and high percentages of siloxane gave rise to increased degradation, with 20-40% PDMS resulting in the least degradation. Infrared spectral changes correlated well with both visual examination and observation by SEM. Changes to the concentration of siloxane gave rise to differences in the thickness of fibroblastic capsule and infiltration of inflammatory cells in both films & scaffolds. Cellular infiltration was greatest in the films with lower siloxane concentrations. Macrophage activation (MHC-I & MHC-II expression) was least in the higher siloxane variants. It is concluded that by varying the siloxane content in the PEtU matrix we can obtain an acceptable inflammatory response with a relatively short degradation time.
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PMID:Inflammatory response to a novel series of siloxane-crosslinked polyurethane elastomers having controlled biodegradation. 1636 23

In the present work, the surface of chitosan membranes was modified using a phosphorylation method carried out at room temperature. Phosphorylation may be of particular interest in materials for orthopaedic applications, due to the cation-exchange properties of phosphate functionalities. Phosphate groups chelate calcium ions, thus inducing the deposition of an apatite-like layer known to improve the osteoconduction of polymer-based implants. Additionally, the negatively charged phosphate functionalities, together with the positively charged amine groups from chitosan, are expected to provide chitosan with an amphoteric character, which may be useful as a combinatorial therapeutic strategy, by simultaneously allowing the immobilization of signalling molecules like growth factors. Phosphorylation was carried out at room temperature using the H3PO4/Et3PO4/P2O5/butanol method. Surface characterization was performed by XPS, ATR-FT-IR, and SEM. Cross-sections were analyzed by SEM fitted with EDS. The phosphate content increased with the reaction time, as shown by XPS and ATR-FT-IR, a P/N atomic ratio of 0.73 being obtained after 48 h of treatment. High-resolution XPS spectra regarding C1s, O1s, N1s and P2p are discussed. The introduction of a neutralization step led to a reduction of P content, which pointed out to the presence of phosphates ionically bound to protonated amines, in addition to phosphate esters. EDS analysis of cross-sections revealed a gradual P reduction up to 50% towards the inner part of the membrane.
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PMID:Chemical modification of chitosan by phosphorylation: an XPS, FT-IR and SEM study. 1636 38

An end-to-end assembly of spherical Ag nanoparticles takes place in the presence of biotin to form long fiberlike microstructures. These microstructures are about 4 mum long with a thickness of 1 mum, obtained from SEM studies. TEM studies showed the presence of spherical silver nanoparticles having an average size of 20 nm. ATR-FTIR studies revealed that silver ions interact with biotin involving the carboxylate group. A weak binding of the silver particles with the thioether and ureido groups helps in connecting the Ag nanoparticles to form long fiberlike structures. Elucidation of the mechanism of formation of the spherical Ag clusters was done by pulse radiolysis.
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PMID:Self-assembly of Ag nanoparticle-biotin composites into long fiberlike microstructures. 1637 26

The objective of present investigation was the characterization of chitosan films after in vivo implantation. Chitosan films were prepared at three dose loadings of paclitaxel by classical casting method. They were implanted subcutaneously in Swiss mice in the neck region and were removed at 7, 15, 21 and 30 days post implantation for characterization. In vitro release studies on explanted films were done to observe the influence of the time of implantation and loading on paclitaxel release, which were correlated with amount of paclitaxel remaining in films. Residual amount of paclitaxel remaining in explanted films decreased with increase in loading i.e. after 30 days, the % residual content of drug at 25, 20 and 15 mg loadings (per film) were 13, 20 and 45 % of the initial loading. The in vivo release of paclitaxel from films with higher loadings was higher, indicating that paclitaxel, per se, altered biodegradation of chitosan. Light microscopy and SEM studies of films removed from mice provided qualitative information on the loss of integrity and biodegradation of films with time. Further, FTIR and ATR-FTIR spectra revealed the changes in the film matrix that occur after implantation.
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PMID:An ex vivo characterization of Paclitaxel loaded chitosan films after implantation in mice. 1684 30

The apatite forming ability of biopolymer bacterial cellulose (BC) has been investigated by soaking different BC specimens in a simulated body fluid (1.5 SBF) under physiological conditions, at 37 degrees C and pH 7.4, mimicking the natural process of apatite formation. From ATR-FTIR spectra and ICP-AES analysis, the crystalline phase nucleated on the BC microfibrils surface was calcium deficient carbonated apatite through initial formation of octacalcium phosphate (OCP) or OCP like calcium phosphate phase regardless of the substrates. Morphology of the deposits from SEM, FE-SEM, and TEM observations revealed the fine structure of thin film plates uniting together to form apatite globules of various size (from <1 mum to 3 mum) with respect to the substrates. Surface modification by TEMPO (2,2,6,6-tetramethylpyperidine-1-oxyl)-mediated oxidation, which can readily form active carboxyl functional groups upon selective oxidation of primary hydroxyl groups on the surface of BC microfibrils, enhanced the rate of apatite nucleation. Ion exchanged treatment with calcium chloride solution after TEMPO-mediated oxidation was found to be remarkably different from other BC substrates with the highest deposit weight and the smallest apatite globules size. The role of BC substrates to induce mineralization rate differs according to the nature of the BC substrates, which strongly influences the growth behavior of the apatite crystals.
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PMID:Surface functional group dependent apatite formation on bacterial cellulose microfibrils network in a simulated body fluid. 1711 6

Embryonic stem (ES) cells have a great interest for tissue engineering because of their pluripotent nature and proliferative capacity. The objective of this study is to constitute a synthetic microenvironment to support the in vitro propagation of murine ES cells in an undifferentiated state. That is why we used a three-dimensional matrix, nonwoven polyester fabric (NWPF), which was formed from poly(ethylene terephthalate) (PET) fibers. NWPF discs were partially hydrolyzed, and then the carboxyl groups were coupled with leukemia inhibitory factor (LIF) in the presence of water-soluble carbodiimide. The effectiveness of immobilization process was checked with ATR-FTIR spectroscopy, fluorimetry, and cell culture studies. ES cell colony morphology, alkaline phosphatase (AP) activity, stage-specific embryonic antigen-1 (SSEA-1) immunoreactivity, and SEM analysis following a 72 - 96-h culture period upon hydrolyzed and LIF-immobilized surfaces were assessed to determine the pluripotent status of ES cells. Results revealed that LIF was active in immobilized form; undifferentiated colonies had not only a significant AP and SSEA-1 immunoreactivity, but also a higher undifferentiated colony ratio on LIF-immobilized surfaces than that of hydrolyzed surfaces. The immobilized LIF protein might be a good model to provide a feeder-free system, but the physical properties of the scaffold is more convenient for differentiation studies.
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PMID:LIF-immobilized nonwoven polyester fabrics for cultivation of murine embryonic stem cells. 1724 52

The in vitro rate of degradation was purposely affected by covalently grafting the surface of poly(l-lactide) (PLLA). PLLA films were surface modified by our vapor-phase nondestructive photografting technique. Films were grafted for 20 min with one of the following monomers: acryl amide (AAm), N-vinyl pyrrolidone (VP), or acrylic acid (AA) and thereafter incubated in vitro in a phosphate-buffered saline solution at 37 degrees C for 154 days. The films were studied with contact angle measurements, SEM, ATR-FTIR, SEC, and DSC. The analyses verified that the in vitro rate of degradation was enhanced and that the grafted surface layer did remain covalently attached to the surface during the initial stages of incubation.
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PMID:Covalent grafting of poly(L-lactide) to tune the in vitro degradation rate. 1763 Jul 95

Paint cross-sections have been analysed using the attenuated total reflection technique combined with FTIR mapping microspectroscopy in order to characterise the nature of the compounds present and map their localisation in the stratigraphy. The study reveals the possibilities offered by micro-ATR devices for obtaining informations about the organic substances employed in painting techniques and in particular their distribution in the different layers, showing a real improvement over traditional analytical investigations in use for the detection of organic substances. Limitations, such as the contamination of the embedding resin and the typical spectral resolution (20 microm) are presented and alternative methods were proposed to obtain better results. In particular, the use of an infrared transparent salt (KBr) as embedding material for the cross-sections is evaluated and seems to be very promising. Furthermore, ATR mapping represent a useful non-destructive analytical technique complementary to others molecular and elemental analyses to be performed afterwards such as SEM-EDX.
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PMID:Attenuated Total Reflection-Fourier transform infrared microspectroscopic mapping for the characterisation of paint cross-sections. 1776 70


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