SURFACE MODIFICATION USING AMPHIPHILIC DIBLOCK COPOLYMERS FOR TISSUE ENGINEERING APPLICATIONS

Surface modification of biomaterials is becoming an increasingly popular method to improve device biocompatibility, functionality and mechanical properties. Amphiphilic block copolymers have been utilized for many applications based principally on their ability to self assemble within the bulk and at interfaces into regular nano-meter scale patterns. The self-assembled patterns of the block copolymers at surfaces are thus seen as ideal surface modifiers for tissue engineering applications. In this project, a model diblock copolymer system, polystyrene-polyacrylic acid (PS339- PAA84), was prepared using the reversible addition-fragmentation chain transfer (RAFT) polymerization technique. The behaviour of PSAA was studied in dioxane-water mixtures. The morphologies changed with increasing water content from sphere to rods and to vesicles. The spinodal and binodal phase diagrams of PSAA in a dioxane-water system were thereafter determined. The self-assembly of these amphiphilic diblock copolymers at the surface of a twodimensional (2D) polystyrene film was then characterised as a function of concentration and block composition. The size of the self assembled aggregates at the PS surface was shown to vary from 10 to 30 nm by changes in the block copolymer concentration. Fibroblast cells cultured on these films demonstrated a strong dependency on PAA aggregate size and number density with regards to their attachment on the modified PS thin films. Two primary morphologies of the attached cells were observed: radial spread and axial polarised. Interestingly the number of cells attached at a period of 24h was similar for all films investigated. This study has shown the significant potential of block copolymers as surface modifying additives for use in tissue engineering applications