The influence of copolymer ratio and drug loading level on the biocompatibility of P(3HB-co-4HB) synthesized by Cupriavidus sp. (USMAA2-4)

Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] belongs to the members of polyhydroxyalkanoates (PHA) family with better degradation and biocompatibility properties. The biocompatibility of P(3HB-co-4HB) polyesters was evaluated in vitro. Mouse fibroblast cell line (L929) was inoculated on films made of P(3HB-co-4HB) of various compositions, various drug loading levels and poly(dl-lactide-co-glycolide) (50:50) (positive control). The effect of P(3HB-co-4HB) composition and surface morphology for both loaded and unloaded films was investigated. The low crystallinity degree of P(4HB) provided fairly regular and smooth surface in P(3HB-co-4HB) with higher 4HB composition. It was found that the cell growth was poor on PHB. As 4HB content increased, the surface morphology changed from a coralloid surface to a smoother one, leading to increasing cell viability from 2.7 × 105 to 12.2 × 105 cells/ml. The surface morphology for P(3HB-co-4HB) loaded with Mitragyna speciosa crude extract also changed from smoother to a coralloid one, and even rougher when the drug loading level increased. MTS assay showed the cell growth on loaded films decreased with an increase in drug loading. This is due to the surface morphological changes as cells preferred smoother surfaces. Therefore, this demonstrated that the biocompatibility of P(3HB-co-4HB) was contributed by 4HB fraction as well as the drug loading level. The results also illustrated that the biocompatibility of P(3HB-co-4HB) was comparable with the positive control (PLGA), and thus can possibly be used as a matrix for drug carrier and tissue engineering applications.