Fabrication and characterization of polymer-based composite materials for use in biomedical applications

In this thesis, electrospinning and spin coating techniques has been studied to develop interfaces for biomedical applications, particularly on invasive neural implants and prosthesis. Chitosan, a natural biopolymer that has wide application areas on biomedical sciences, polycaprolactone, a synthetic biopolymer that is usually used in long term invasive implant applications due to its slow degradation in the body and ease of production by electrospinning technique, and graphene, due to its high electrical conductivity, since neural cells are electro-active and can be electrically stimulated, were chosen for production of composites. Thin films were produced by graphene/chitosan composites, while nanofibers were produced using graphene/PCL composites. Characterization of composites were performed scanning electron microscopy (SEM), XRD analysis, Raman spectroscopy, FTIR spectroscopy, TG-DTG termogram analysis, four point probe method and electrochemical impedance spectroscopy. Proliferation of cells seeded on thin film and nanofiber surfaces were determined by MTT assay. The surfaces that had better proliferation values than control were investigated for neurite growth properties by fluorescence microscopy using actin-DAPI staining. The results showed that cell proliferation shows a parallel trend with electrical conductivity, and graphene reinforced nanofibers lead to higher neurite numbers, higher sprouting and longer neurite formation. Our results show that graphene loaded PCL nanofibers are suitable surfaces for invasive neural implants and interfaces. Another important scientific contribution of this thesis is the succesful production of graphene reinforced PCL nanofibers by electrospinning.