Biocompatibilities and biodegradation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)s produced by a model metabolic reaction-based system

Background: This study evaluated the biocompatibilities of random and putative block poly(3-hydroxybutyrate-co-3-hydroxyvalerate)s (PHBVs) produced by a metabolic reaction-based system. The produced PHBVs were fractionated, and the copolymer sequence distributions were analyzed using H-1 and C-13 NMR spectroscopy. The thermal properties were analyzed using differential scanning calorimetry (DSC). Mechanical tests were conducted using a universal testing machine. The in vitro cytotoxicities of films composed of random PHBVs and putative block PHBVs were investigated against three types of mammalian cells. The surfaces of the copolymer films and the morphologies of the cells were qualitatively monitored using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Results: Films composed of poly(3-hydroxybutyrate) (PHB), random PHBVs, putative block PHBVs, polystyrene and polyvinylchloride were prepared and characterized. The diad and triad sequence distributions indicated that the PHBVs produced via the fed-batch cultivation using two different feed systems resulted in two types of copolymers: random PHBVs and putative block PHBVs. The monomer compositions and sequence distributions strongly affected the thermal and mechanical properties. The mechanical integrity and characteristics of the film surfaces changed with the HV content. Notably, the random PHBVs possessed different mechanical properties than the putative block PHBVs. The biocompatibilities of these films were evaluated in vitro against three types of mammalian cells: L292 mouse connective tissue, human dermal fibroblast and Saos-2 human osteosarcoma cells. None of the PHBV films exhibited cytotoxic responses to the three types of mammalian cells. Erosion of the PHA film surfaces was observed by scanning electron microscopy and atomic force microscopy. The production of transforming growth factor-beta-1 and interleukin-8 was also examined with regards to the usefulness of PHB and PHBV as biomaterials for regenerative tissue. The production of IL-8, which is induced by PHB and PHBVs, may be used to improve and enhance the wound-healing process because of deficiencies of IL-8 in the wound area, particularly in problematic wounds. Conclusion: Taken together, the results support the use of PHB and the random and putative block PHBVs produced in this study as potential biomaterials in tissue engineering applications for connective tissue, bone and dermal fibroblast reconstruction.