Hydrophilic modification of Au Nanoparticles on the gold electrode of QCM by plasma deposition for biomedical applications

In this study, we proposed a method of surface modification for gold nanoparticles (AuNPs) for biomedical research and applications. 11-Mercaptoundecanoic acid (MUA) is a hydrophilic material and was used to modify the surface on AuNPs by self-assembly mechanism to promote the hydrophilic property and decrease water contact angle (WCA) by 3.2°. To measure the mass of modified AuNPs, the surface of gold electrodes of QCM (quartz crystal microbalance) was plasma-deposed with Hexamethyldisilazane (HMDSZ) and O2 by the plasma deposition method at the condition of low temperature. The content of AuNPs was determined by the relation between frequency shift and concentration of AuNPs. This study showed that the gold electrode surface became hydrophobic after HMDSZ deposition treatment. Also the WCA of the surface of gold electrode decreased to less than 10° and hydrophilic property after O2 treatments were detected, compared to the HMDSZ treatment alone. The surface of gold electrode was treated by both HMDSZ and O2 procedures. The sensitivity of QCM measurement for the AuNPs could be improved and have a good linear relationship (R²:0.9722). In vitro study, there was no cytotoxicity of MUA-AuNPs in the MTT assay and cell uptake was quantified by the micro CT imaging. Our proposed method offered a new method for immobilized biomolecular coating for AuNPs and biosensor.