Applications Of Graphene/Polymer Composites In Tissue Engineering Scaffold And Drug Carrier

Graphene (GNS) is a new carbon material which is closely stacking of carbon atoms to form monolayer two-dimensional honeycomb structure. Since it was found by Geim et al. from Manchester University in2004, GNS and its derivative graphene oxide (GO) has sparked a boom in science and industry circles by virtue of its unique structure and excellent mechanical, electrical, thermal and chemical properties. GNS as a filler material to reinforce mechanical strength of polymer and polymer as the modified materials to functionalize GNS may be the most promising research in composite material field. But the application of GNS in biological medicine is still at the stage of exploration, it will be a challenge to conduct research of GNS/polymer composites for tissue engineering scaffolds and drug carrier to give full play to its excellent properties. In the reseach, we prepared and characterized GO/polyvinyl alcohol (PVA), GO/chitosan (CS) and GNS/polyacrylic acid (PAA) composites around the excellent properties of GNS and its derivative, and studied their applications in tissue engineering scaffolds and drug carrier. The main contents and results are summarized as follows:1. GO/PVA nanofibrous scaffold was fabricated by electrospinning technology. The conditions of the PVA electrospinning and the influence of GO on the morphology, microstructure, mechanical properties and biocompatibility of PVA nanofiber were investigated. As the content of GO increased, the diameter of GO/P VA nanofibers turned to be thinner and appearing beaded structure. Increasing the content of GO up to1wt%increased the mechanical strength, but further increasing GO up to3-5%caused the decrease of mechanical strength. When GO content was1wt%, the tensile strength and elastic modulus of GO/PVA were22%and57%higher than pure PVA scaffold. On GO/PVA composite scaffold, the attachment and growth of osteoblasts were good, and the viability and morphology of cells were better than pure PVA scaffold which indicated the composite scaffolds have potential application in tissue engineering field.2. GO/chitosan(CS) composite porous xerogels were prepared by a freeze-drying method. The influence of GO content on the morphology, microstructures, mechanical property of CS xerogel and its ability for adsorption and release of doxorubicin hydrochloride (DOX) were investigated. The adding of GO dereased the pore size of the xerogels, but increased the compressive strength. The porous structure of the composites as well as large surface of GO enhanced the drug adsorption ability. When the content of GO was5wt%, the DOX loading ability of GO/CS composites could reach96mg/g, which was240%higher than that of pure CS. The in vitro drug release showed there was only17.4%of DOX release after35d. It indicated good drug adsorption and slow release performance of GO/CS composite porous xerogels, which can be used for drug carrier.3. Large quantities of small size GNS sheets with diameters of50-200nm were prepared by arc discharge technology. PAA functionalized GNS (PAA-GNS) was prepared by in-situ polymerization of acrylic monomers. By functionalization, the surfaces of GNS sheets were grafted with-COOH groups which improved the solubility and stability of GNS. This also facilitated chemical binding of DOX to the GNS and realized efficient loading and pH controlled release. With the increase of the initial DOX concentration, the loading capacity of DOX increased and reached2.183mg/mg when the DOX concentration was0.35mg/ml, and the release ratio of DOX in pH2was about twice that of pH7and about seven times of pH10, which indicated that PAA-GNS was the ideal nano carrier.