Application of EQCN for quantitative analysis of alkanethiol adsorbed on modified Ti surfaces

Self-assembled monolayers (SAMs) have become a basic modification technique for immobilization of peptides and specific proteins on a biomaterial surface. Little attempt has been made in investigating the relation between protein adsorption behavior and the surface chemistry of metallic implant materials. In this study, we examined the alkanethiol adsorption behavior on the modified titanium surfaces by using an electrochemical quartz crystal nanobalance (EQCN) developed in our laboratory. The resolution limit of the constructed EQCN was about 0.1 ng. Using the EQCN, we were able to precisely investigate the mass change ratio on the surfaces versus immersion time. We examined the formation of SAMs by alkanethiol on three working electrode surfaces (Au-coated Ti, pure Ti and TiO2). The mass changes on the Au/Ti and pure Ti surfaces were about 11.5 ng/cm2 for 450 s reaction time and 7.7 ng/cm2 for 400 s, respectively. The frequency variation on the TiO2 surface with less than ±1 Hz for 400 s reaction time indicated a negligible formation of SAMs. Results obtained from this study have shown that by altering titanium surface chemistry, titanium surface may be modified into a functional bioactive surface by introducing alkanethiol and can be used in the same way as Au substrate.