Abstract
Being a powerful technique of modifying the surface property, Self-assembled monolayers (SAMs) has been employed for academia research and industrial application. The substrate can be bulk or nanoparticles; the SAMs composition provides wild selection for specific requirement. For biological application, the SAM system of thiols on Au susbtrate is of great interest on the development of biochip, biosensor, gene carriers, etc. Studying the interaction between cells and SAM-modified Au substrate with specific surface property has gained attention. With the development of binary SAM-modified Au substrates, the interaction between cell and SAM-modified Au substrates could be studied. In this work, binary SAM-modified Au substrates with a series of surface potential were made, including Au nanoparticles and bulks with Au surface. It was found that binary SAM-modified AuNPs have low cytotoxicity and can be internalized by cells that confirmed by STEM images, and the internalized AuNPs increased with increasing surface potential of AuNPs. The cellular distribution would be further studied using time-of-flight secondary ion mass spectroscopy (ToF-SIMS). For the capability of binary SAM–modified AuNPs as carriers to deliver DNA for expression, it was found to be relevant to the surface potential of AuNPs with respect to the change of pH value during delivery process. The highest delivery happened when AuNPs with moderate surface potential that can adsorb and protect DNA in endosome and release DNA in cytoplasm. Moreover, cell behavior of fibroblasts and epithelial cells on binary SAM-modified Au surfaces were examined, including adhesion, proliferation and morphology. The results showed that the adhesion density of epithelial cells increased with increasing surface potential, which is similar to but varied more significantly compared with fibroblasts. The proliferation rate is found to be independent of surface potential in both cell types. Furthermore, epithelial cells show no morphological change with respect to surface potential, whereas the morphology of the fibroblasts clearly changed with the surface potential. These differences between the cell types were rationalized by considering the difference in ECM composition. Laminin-dominant epithelial cells showed higher adhesion density and less morphological change than did fibronectin-dominant fibroblasts because the more significant adsorption of positively charged laminin on the surface enhanced the adhesion of epithelial cells. In contrast, due to the dominance of negatively charged fibronectin that adsorbed weakly on the surface, fibroblasts had to change their morphology to fit the inhomogeneous fibronectin-adsorbed area.