Synthesis, Characterization And Biocompatibility Of Novel Biodegradable Block Copolymers Base On Polyhydroxyalkanoate

Biodegradable block copolymers have attracted special attention in both fundamental and applied research for materials science, pharmacological, biomedical, and environmental purposes because of their unique chain architecture, biodegradability and biocompatibility. Hence, for the first time, two series of biodegradable triblock copolymers poly[((R)-3-hydroxybutyrate)- block-(D,L-lactide)-block(-ε-caprolactone)] (PHB-PLA-PCL) and star-branched copolymers SPHBCLs based on poly[(R)-3-hydroxybutyrate] (PHB) were synthesized via ring opening polymerization (ROP) (eg. D, L-lactide,ε-caprolactone) in the presence of Sn(Oct)2 as the catalyst, respectively. The block copolymers overcome PHB drawbacks and obtain some new useful property based on blocking new segment. Two series of copolymers were characterized for their molecular structure, physical chemistry properties and in vitro biocompatibility. Block copolymers possess block architectural variations on segment lengths and arm numbers that were confirmed by nuclear magnetic resonance spectra (NMR) and gel permeation chromatography (GPC) as well as thermogravimetric analysys (TGA). Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) showed that the crystalline degree of block copolymers decreased with decreasing PHB content in copolymers. Films made from various block copolymers had different leaf-shape, porous or networking surface morphology by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Specially, the 4SPHBCLs-5 showed regular nano-ravine structures unique surface properties. Also the block copolymers were investigated for biocompatibility including blood-compatibility and cell-compatibility, and this article discussed the factors of surface morphology and surface hydrophilicity which influence material biocompatibility. With decreasing PHB content in the triblock copolymer, the blood coagulation time became longer accompanied by a reduced number of platelets adhered, and the murine osteoblasts MC3T3-E1 cells cultured on films spread and proliferated significantly better. SPHBCLs copolymers had porous or networking surface morphology, and all possessed improved biocompatibility in terms of less number of platelets adhered and more osteoblast cell growth compared with homopolymers PHB and PCL.