Poly(ethylene glycol) (PEG) is partially furanylated with different feed ratios of furfuryl isocyanate and used as the macro initiator of ring‐opening polymerization of l ‐ and d ‐lactides to synthesize copolymer mixtures of furan‐terminated AB diblock and ABA triblock copolymers (poly(oxyethylene)–poly(l ‐lactide)/poly(l ‐lactide)–poly(oxyethylene)–poly(l ‐lactide) and poly(oxyethylene–poly(d ‐lactide)/poly(d ‐lactide)–poly(oxyethylene)–poly‐(d ‐lactide)) having different diblock/triblock ratios. The mixed micelle solutions of these enantiomeric copolymer mixtures undergo sol‐to‐gel or gel‐to‐sol transition depending on the diblock/triblock ratio of the copolymer mixtures. The rheological properties of the mixed micelle solutions could also be controlled by changing the diblock/triblock ratios or the initial furanylation ratio of PEG.
PLLA-TMC-GA terpolymer was prepared by ring-opening polymerization of l-lactide, 1, 3-trimethylene carbonate (TMC), and glycolide (GA). The biocompatibility of terpolymer was evaluated in comparison with PLLA and PLLA-TMC with the aim of assessing their potential in the development of bioresorbable cardiovascular stents. Various aspects of in vitro biocompatibility were considered, including MTT assay, hemolytic test, dynamic clotting time, platelet adhesion, platelet activation, protein adsorption, plasma recalcification time and release of cytokines. The results revealed that the terpolymer presents good cytocompatibility and hemocompatibility. Moreover, no significant increase in the release of cytokines was detected. It is thus concluded that these polymers, in particular PLLA-TMC-GA terpolymer present good biocompatibility for cardiovascular applications. 相似文献
Novel lactide-based poly(ethylene glycol) (PEG) polymer networks (GL9-PEGs) were prepared by UV copolymerization of a glycerol-lactide triacrylate (GL9-Ac) with PEG monoacrylate (PEG-Ac) to use as scaffolds in tissue engineering, and the surface properties and biocompatibility of these networks were investigated as a function of PEG molecular weight and content. Analysis by ATR-FTIR and ESCA reveled that PEG was incorporated well within the GL9-PEG polymer networks and was enriched at the surfaces. From the results of SEM, AFM, and contact angle analyses, GL9-PEG networks showed relatively rough and irregular surfaces compared to GL9 network, but the mobile PEG chains coupled at their termini were readily exposed toward the aqueous environment when contacting water such that the surfaces became smoother and more hydrophilic. This reorientation and increase in hydrophilicity were more extensive with increasing PEG molecular weight and content. As compared to GL9 network lacking PEG, protein adsorption as well as platelet and S. epidermidis adhesion to GL9-PEG networks were significantly reduced as the molecular weight and content of PEG was increased, indicating that GL9-PEG networks are more biocompatible than the GL9 network due to PEG's passivity. Based on the physical and biological characterization reported, the GL9-PEG materials would appear to be interesting candidates as matrices for tissue engineering. 相似文献
A comprehensive investigation of in situ aggregation of structurally well‐defined enantiomeric poly(styrene)‐block‐poly(lactide) (PS‐b‐PLLA and PS‐b‐PDLA) in a non‐selective solvent, tetrahydrofuran (THF), is presented. The isolated aggregates are found to form poly(L ‐lactide) (PLLA)/poly(D ‐lactide) (PDLA) racemic crystals by differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), and Fourier transform infrared (FTIR) spectroscopy. The kinetic study reveals that the growth rate of the aggregates depends on the molecular weight of the enantiomeric PLA blocks, as well as the preparation conditions. The proposed mechanism demonstrates a new PS (shell)–PLA (core) structural hierarchy solely driven by stereocomplexation between enantiomeric PLLA and PDLA blocks.
In bone tissue regeneration, certain polymer and calcium-phosphate-based composites have been reported to enhance some biological surface phenomena, facilitating osteoinduction. Although the crucial role of inorganic fillers in heterotopic bone formation by such materials has been shown, no reports have been published on the potential effects the polymer phase may have. The present work starts from the assumption that the polymer molecular weight regulates the fluid uptake, which determines the hydrolysis rate and the occurrence of biological surface processes. Here, two composites were prepared by extruding two different molecular weight l/d,l-lactide copolymers with calcium phosphate apatite. The lower molecular weight copolymer allowed larger fluid uptake in the composite thereof, which was correlated with a higher capacity to adsorb proteins in vitro. Further, the large fluid absorption led to a quicker composite degradation that generated rougher surfaces and enhanced ion release. Following intramuscular implantation in sheep, only the composite with the lower molecular weight polymer could induce heterotopic bone formation. Besides influencing the biological potential of composites, the molecular weight also regulated their viscoelastic behaviour under cyclic stresses. The results lead to the conclusion that designing biomaterials with appropriate physico-chemical characteristics is crucial for bone tissue regeneration in mechanical load-bearing sites. 相似文献
Summary When there is significant loss of spinal dura mater, dural substitution with synthetic or allogenic materials is essential.
In the case of laminectomy, mechanical protection and reformation of the dorsal spinal canal may be useful.
This is a report on a patient with total dura loss through tumour atrophy of the dura and laminae. In order to reconstruct
the dorsal face of the spinal canal a polylactide sheet was cut and shaped to fit the physiological contour. A bovine dura
substitute was firmly attached and sutured to the inner surface of the polylactide shield. The implant was wedged in between
the pedicles and the facet joints and resulted in a water-tight dura substitute maintaining the shape of the spinal canal
and protecting it against mechanical forces and intradural scar formation. 相似文献