Preparation And Biocompatibility Of PHBV Composite Scaffolds Modified With β-Ca₂SiO₄

Tissue engineering mainly aims at fabricating a cell/scaffold complex using theprinciple and method of engineering and life science, so as to repair or replace thedamaged organism tissue and organs. Among which, acting as the basic tissueengineering framework, scaffold plays a key role in the construction of engineeredtissue, which provides abundant space for cell adhesion, proliferation anddifferentiation. In addition, the physical and chemical properties of scaffold such assurface morphology and hydrophilicity have vital influence on the cells’ biologicalcharacteristics.PHBV which is the second generation of polyhydroxyalkanoates （PHAs） hasexcellent properties such as plastic processing, biocompatibility and biodegradation.In recent years, PHBV exhibits a good application prospect, and has become theresearch focus of tissue engineering materials. However, PHBV shows obvioushydrophobic property which is not benifit for the cell adhesion and growth. Therefore,measures should be taken to modify the PHBV hydrophilicity. In this study, physicalblend were applied to improve the hydrophilicity and biocompatibility of PHBV usingβ-Ca₂SiO₄bioactive nanoparticles.In order to comprehensively evaluate the influence of β-Ca₂SiO₄nanopaticles onthe biocompatibility of PHBV polymer,2-D PHBV composite membranes and3-Dporous PHBV composite scaffolds were fabricated respectively. First of all,2-Dβ-Ca₂SiO₄/PHBV composite membranes were prepared by solvent casting. The ESEMand XRD results showed that β-Ca₂SiO₄nanopaticles evenly dispersed in the PHBVmatrix. The contact angle measurement indicated the obvious improvement in thehydrophilicity of β-Ca₂SiO₄/PHBV composite membranes. Compared with purePHBV membrane, MG-63cells adhered earlier and better on the β-Ca₂SiO₄/PHBVcomposite membranes. The Alamar Blue assay showed that a moderate amount ofβ-Ca₂SiO₄nanopaticles in the PHBV polymer could promote the MG-63cellproliferation. Furthermore, RT-PCR was used to verify the modification of β-Ca₂SiO₄nanopaticles to the PHBV polymer from molecular biology level. The results ofRT-PCR suggested that β-Ca₂SiO₄nanopaticles promoted the adhesion andproliferation of MG-63cells through increasing the genes transcriptional level ofintegrin and ECM proteins. Secondly,3-D β-Ca₂SiO₄/PHBV composite scaffolds with interconnected porous structure and high porosity were fabricated using solventcasting-particulate leaching method. The measurement of water swelling percentage（WSP） indicated that the wettability of scaffolds was significantly improved aftercompositing β-Ca₂SiO₄nanopaticles with PHBV polymer. When culturing MG-63cells on the β-Ca₂SiO₄/PHBV composite scaffolds, ESEM showed that the cells couldadhere and proliferate better on2.5%and10%β-Ca₂SiO₄/PHBV composite scaffoldsthan the cells on the pure PHBV scaffold. The Alamar Blue assay manifested that amoderate amount of β-Ca₂SiO₄nanopaticles in the PHBV polymer could significantlypromote the MG-63cell proliferation. RT-PCR test suggested that β-Ca₂SiO₄nanopaticles could enhance the transcriptional level of transcriptional growth factorssuch as TGF-β1and BMP-7, so as to improve the proliferation of MG-63cells.Moreover, the RNA level of alkaline phosphates （ALP） was significantly increased onβ-Ca₂SiO₄/PHBV composite scaffolds, which indicated that β-Ca₂SiO₄nanopaticlescould also enhance the early differentiation of MG-63cells. The above results showedthat physically blending β-Ca₂SiO₄nanopaticles with PHBV could improve the matrixphysical and chemical properties, thus improved its biocompatibility. And theβ-Ca₂SiO₄/PHBV composite scaffolds would have a good prospect for development asbone or cartilage tissue engineering scaffolds.