Biocompatibility testing of ABA triblock copolymers consisting of poly(L-lactic-co-glycolic acid) A blocks attached to a central poly(ethylene oxide) B block under in vitro conditions using different L929 mouse fibroblasts cell culture models

The biocompatibility of ABA triblock copolymers consisting of poly(L-lactide-co-glycolide) A blocks attached to a central poly(ethylene oxide), (PEO), B block was investigated under in vitro conditions. The ABA triblock copolymer was compared to commercially available Poly(D,L-lactide-co-glycolide) (PLGA) and reference materials in different L929 cell culture models according to the procedure recommended by the international Standard Organization (ISO). Different preparation methods: namely extraction, indirect contact and direct contact with polymer samples were compared. The extraction method seems to be the most sensitive assay, allowing estimates of IC50 values. ABA and PLGA polymers showed excellent compatibility with L929 fibroblasts with all preparation techniques used. The influence of polymer composition and molecular weight on degradation rate as well as in vitro biocompatibility was then investigated. Changes in pH and osmolarity as well as lactic acid content of the extracts were determined and compared to in vitro degradation data of polymer films in phosphate buffered saline at 37 degrees C evaluating molecular weight (GPC) and massloss (gravimetry). An acceleration of the degradation rate of the ABA triblock copolymers with increasing PEO content was observed. The in vitro cytotoxicity studies demonstrated that the three ABA polymers were well tolerated by fibroblasts in cell culture. One ABA polymer batch ABA2 showed unusual in vitro cytotoxicity in L929 fibroblasts, possibly related to the molecular weight of the PEO used for this particular batch or residual glycolic acid. Cell culture models for biocompatibility testing of polymers according to ISO are useful as screening models in characterizing biodegradable polymers, but they cannot replace animal testing. The extraction method in combination with the MTT assay allows quantitative ranking of cytotoxic properties with high sensitivity. (C) 1998 Elsevier Science B.V. All rights reserved.