A novel technique to immobilize DNA on surface of a quartz crystal microbalance by plasma treatment and graft polymerization

A quartz crystal microbalance (QCM) is well known to provide mass-sensitive devices in nanogram levels, because of the resonance frequency changes upon the adsorption on the electrode. It offers the possibility of monitoring hybridization in real time and with high selectivity. In this study, a biosensor system was developed for the detection of Vibrio parahaemolyticus via its oligonucleotide probe immobilized on the gold electrodesʹ surface of QCM. However, because the surface of QCM was an inorganic substance, it was difficult to immobilize the oligonucleotide probe. In this study, the plasma surface modification of QCM through deposition of hexamethyldisilazane (HMDSZ) films as an interlayer was investigated. The interlayer provided good adhesion to the substrate and had a uniform structure. The result indicates that plasma deposition was a useful technique to immobilize the oligonucleotide probe on the gold electrodesʹ surface via glutaraldehyde (GA) coupling. To improve immobilization, post treatments by surface grafting of acrylamide (AAm) and polyethyleneimine (PEI) treatment onto the electrodes were also performed. The result demonstrates that the shift of resonance frequency of QCM was improved via subsequent graft polymerization of AAm and PEI treatment onto the electrodes. The QCM sensor after plasma deposition and surface modification could provide detection sensitivity up to 86 ng/ml and kept at 88% detecting sensitivity after 19 days of storage at 0 °C. After washing with 0.1 M NaOH solution and 7 times of repeated use in detecting, the regeneration rate of QCM could be up to 60%.