Osteocompatibility of Photopolymerizable Anhydride Networks

Abstract

A new family of polyanhydrides has been developed which can be cured photochemically to produce degradable networks. These degradable polyanhydride networks can be useful in orthopedics as bone cements and for drug delivery. This system, which is a semi-interpenetrating network (semi-IPN), has been evaluated for tissue compatibility in subcutaneous sites in rats and shown to undergo degradation by surface erosion. It was observed that the inflammatory response to the semi-IPN implants was minimal at both short (3, 6 weeks) and long (28 weeks) time points and the fibrotic response was largely absent throughout the duration of this study. Furthermore, excellent tissue infiltration and integration with good neovascularization was observed around the semi-IPN implants. The osteocompatibility and osteoconductive properties of this system have been evaluated in a longitudinal defect model in the articular surface of the distal femur in adult rabbits. This study compared the semi-IPN implants to control groups consisting of unfilled defects and PLA implants. Histological evaluation (H&E and Trichrome Masson staining) of the implant site revealed that the semi-IPN implant is osteocompatible and well tolerated by the surrounding cancellous bone and marrow constituents. The tissue reaction to the implant is characterized by an ingrowth of vascularized connective tissue and a mild fibrous capsule. Furthermore, partial to complete closure of the articular surface with fibrocartilage and fibrous tissue was observed in all experimental animals containing the semi-IPN polymer implants.