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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nowadays, many degradable polymers are being used under the form of interference screws to fix the bone-tendon-bone autograft in anterior cruciate ligament reconstruction. However, little is known about the post-implantation fate of these screws, especially about the formation of crystalline residues which seems to be a critical factor for the success of surgery with temporary implants based on lactic and glycolic acid derived polymers (PLAGA). In an attempt to bring in some new insights, various high molecular weight stereoregular poly(lactide)s (PLAX with X = percentage of L-lactyl units) obtained by ring-opening polymerization of lactides in the presence of zinc-metal (PLA98-Zn), zinc lactate (PLA98-Znlac) or stannous octoate (PLA100-Sn), were processed by injection-molding to make interference screws to be compared. In vivo data were collected from screws implanted in sheep knees with follow ups ranging from 6 months to 5 years. Histology confirmed the heterogeneous degradation mechanism introduced nearly 10 years ago from in vitro investigations of homemade implants having simpler geometry. The effects of the initiator system (zinc- or tin derivatives) used to polymerize the lactide monomer on the properties of injection molded interference screws was also investigated in vitro in a phosphate buffer solution at 37 degrees C. Major differences in terms of hydrophilicity, hydrolysis rate and loss of mechanical properties were observed between PLA-Zinc and PLA-Tin. Discussion of the behavior of interference screws of different compositions was made on the basis of the present understanding of PLAGA morphology and degradation characteristics.
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PMID:In vitro and in vivo degradation of lactic acid-based interference screws used in cruciate ligament reconstruction. 1041 76

Polylactic acid is a polymer of great technological interest, whose excellent mechanical properties, thermal plasticity, and bioresorbability render it potentially useful for environmental applications, as a biodegradable plastic and as a biocompatible material in biomedicine. This article discusses the synthesis and characterization of poly-L-lactic acid, obtained through two synthetic routes: direct polycondensation reactions without organic solvents, and in a supercritical medium. Tin complexes were used as catalysts in both polymerization reactions. The polymers were characterized by (1)HNMR, IR, GPC, DSC, and TGA techniques. In vitro biocompatibility tests were performed with human alveolar bone osteoblasts and there were assessed cell adhesion, proliferation and viability. The poly condensation reaction proved to be an excellent synthetic route to produce PLA polymers with different molar mass. The formation of polymers from lactic acid monomer was confirmed through techniques utilized. It was observed that cell adhesion and viability was not disturbed by the presence of the polymer, although the proliferation rate was decreased when compared to control.
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PMID:Chemical synthesis and in vitro biocompatibility tests of poly (L-lactic acid). 1743

Vascular structures in natural systems are able to provide high mass transport through high surface areas and optimized structure. Few synthetic material fabrication techniques are able to mimic the complexity of these structures while maintaining scalability. The Vaporization of a Sacrificial Component (VaSC) process is able to do so. This process uses sacrificial fibers as a template to form hollow, cylindrical microchannels embedded within a matrix. Tin (II) oxalate (SnOx) is embedded within poly(lactic) acid (PLA) fibers which facilitates the use of this process. The SnOx catalyzes the depolymerization of the PLA fibers at lower temperatures. The lactic acid monomers are gaseous at these temperatures and can be removed from the embedded matrix at temperatures that do not damage the matrix. Here we show a method for aligning these fibers using micromachined plates and a tensioning device to create complex patterns of three-dimensionally arrayed microchannels. The process allows the exploration of virtually any arrangement of fiber topologies and structures.
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PMID:Process of making three-dimensional microstructures using vaporization of a sacrificial component. 2430 Mar 42