IN-VIVO BIOCOMPATIBILITY STUDY OF ABA TRIBLOCK COPOLYMERS CONSISTING OF POLY(L-LACTIC-CO-GLYCOLIC ACID) A-BLOCK ATTACHED TO CENTRAL POLY(OXYETHYLENE) B-BLOCK

Films of three ABA-block copolymers composed of lactic-co-glycolic aci d A blocks and poly(oxyethylene) (PEG) B blocks and one random lactic- co-glycolic acid copolymer (PLG) were studied to investigate the influ ence of different polymer compositions and molecular weights on the ti ssue reaction, appearance of toxic degradation products, and swelling behavior in the cage implant system in rats. The inflammatory tissue r eaction was followed over a 21-day implantation period by monitoring t he leukocyte concentration, the extracellular acid, and alkaline phosp hatase activities in a quantitative manner. Size and density of adhere nt macrophages and foreign body giant cells on the film surfaces were determined. The ABA and PLG implants caused only a minimal inflammator y reaction, as characterized by a low concentration of leukocytes duri ng the implantation period when compared to empty cage controls. The c ontent of PEO had an influence on the density of the adherent cells on the surface of the polymer film. An increase in PEO content and molec ular weight decreased the cellular density during the implantation per iod. As demonstrated by scanning electron microscopy, no degradation w as observed for all polymers during the implantation period. Our resul ts demonstrate that the ABA block copolymers and PLG copolymer are equ ally well tolerated in the cage implant test system. (C) 1996 John Wil ey & Sons, Inc.