Incorporation of carbon nanotubes into the biomedical polymer poly(styrene-β-isobutylene-β-styrene)

Poly(styrene-β-isobutylene-β-styrene) (SIBS) is a block copolymer that has been used extensively as a coating for medical devices in which it acts as a carrier for therapeutics. In this study the incorporation of carbon nanotubes (CNTs) into SIBS coatings was investigated as a means of modifying both the electrical conductivity and the surface characteristics of the SIBS coatings in order to affect the cell adhesion and proliferation characteristics of the coatings. SIBS was found to aid in the dispersion of CNTs in toluene. The conductivity of films cast from these dispersions increased with increased single wall carbon nanotube (SWNT) content in the range 0.05% to 0.30% (w/v). The surface morphology of these cast films was found to depend on the concentration of incorporated SWNTs. Growth of L-929 (mouse fibroblast) cells on the coatings was visualised by light microscopy and by calcein staining and fluorescence microscopy. The cytotoxicity of the coatings was assessed by quantitation of growth of L-929 cells on the coatings over 72 h using lactate dehydrogenase assay (LDH). L-929 cells were found to grow logarithmically on SIBS coatings and on SIBS incorporating SWNTs. SWNT/SIBS dispersions may therefore be used to form suitable coating materials for biomedical applications, and are worthy of further investigation.