Preliminaryin vivo report on the osteocompatibility of poly(anhydride-co-imides) evaluated in a tibial model

Abstract

A novel class of polymers with mechanical properties similar to cancellous bone are being investigated for their ability to be used in weight-bearing areas for orthopedic applications. The poly(anhydride-co-imide) polymers based on poly[trimellitylimidoglycine-co-1,6-bis(carboxyphenoxy)hexan e] (TMA-Gly:CPH) and poly[pyromellitylimidoalanine-co-1,6-bis(carboxyphenoxy)hexa ne] (PMA-Ala:CPH) in molar ratios of 30:70 were investigated for osteocompatibility, with effects on the healing of unicortical 3-mm defects in rat tibias examined over a 30-day period. Defects were made with surgical drill bits (3-mm diameter) and sites were filled with poly(anhydride-co-imide) matrices and compared to the control poly(lactic acid-glycolic acid) (PLAGA) (50:50), a well-characterized matrix frequently used in bone regeneration studies, and defects without polymeric implants. At predetermined time intervals (3, 6, 9, 12, 20, and 30 days), animals were sacrificed and tissue histology was examined for bone formation, polymer-tissue interaction, and local tissue response by light microscopy. The studies revealed that matrices of TMA-Gly:CPH and PMA-Ala:CPH produced responses similar to the control PLAGA with tissue compatibility characterized by a mild response involving neutrophils, macrophages, and giant cells throughout the experiment for all matrices studied. Matrices of PLAGA were nearly completely degraded by 21 days in contrast to matrices of TMA-Gly:CPH and PMA-Ala:CPH that displayed slow erosion characteristics and maintenance of shape. Defects in control rats without polymer healed by day 12, defects containing PLAGA healed after 20 days, and defects containing poly(anhydride-co-imide) matrices produced endosteal bone growth as early as day 3 and formed bridges of cortical bone around matrices by 30 days. In addition, there was marrow reconstitution at the defect site for all matrices studied along with matured bone-forming cells. This study suggests that novel poly(anhydride-co-imides) are promising polymers that may be suitable for use as implants in bone surgery, especially in weight-bearing areas.

Shape Memory Materials for Biomedical Applications

“…[174,180,181] Many other polymeric scaffolds have been developed for tissue engineering applications such as breast reconstruction, [182] as well as the replacement and regeneration of damaged bone [183] and cartilage. [184,185] For example, polyanhydrides have been used as successful scaffolds for orthopaedic implants [186,187] and tyrosine-derived polycarbonates have produced interesting results when used as scaffolds in tissue engineering. As shown by Choueka et al, [188] these polymers exhibited an intimate contact with bone.…”

Vascularized Bone Tissue Engineering: Approaches for Potential Improvement

“…Among synthetic polymers, poly (a-hydroxy) esters, such as poly (lactic acid), 74 poly (glycolic acid), 75 PLGA, 76 and polyurethanes, 77,78 have been widely utilized for bone regeneration. Other synthetic polymers that are of interest for bone repair are poly (propylene fumarate) (PPF), [79][80][81][82] polyanhydride, 83,84 and poly (ethylene oxide)/poly (butylene terephthalate) copolymers. 85,86 Synthetic biodegradable polymers have higher mechanical properties than natural polymers and can be easily processed.…”

Effect of RGD coating on osteocompatibility of PLGA-polymer disks in a rat tibial wound

“…These untreated porous PLGA disks were a physical barrier that somewhat delayed healing of tibial wounds, demonstrated by the lack of complete bridging after 3 weeks. This can be explained as a 35 The discrepancies may be due to the different composition of the copolymers, to the various sizes of the defects, to differences in pore size and structure among the devices, or to the animal model used.…”