Selective Functionalization of Micromachined Quartz Resonator Arrays Using Electrochemical Techniques for Biosensing Applications

An 8-pixel micromachined quartz crystal resonator array with fundamental resonance frequency of 73 MHz has been designed, fabricated and tested for detecting respiratory syncytial virus (RSV) G-gene. We established a protocol for selectively functionalizing the surface of resonator array using electrochemical desorption. The selective functionalization of hydrophobic and hydrophilic surfaces with methyl-and carboxylate-terminated alkanethiols is characterized by Fourier transform infrared spectroscopy and contact angle measurements. Quartz crystal microbalance (QCMs) functionalized with hydrophobic and hydrophilic terminations also showed a clearly distinguishable response to ionic (buffer) solution. Thiol modified single-stranded DNA (oligonucleotide probes) were designed for functionalization of the QCM pixel surfaces. Selective desorption of the pixels was achieved via electrochemical methods and was characterized by cyclic voltammogram. The specific detection of RSV G-gene is successfully demonstrated by the frequency response of the QCM pixels and was verified by fluorescence images after hybridization using fluorescently labeled probes. We demonstrate that micromachined quartz crystal resonator arrays could potentially become a convenient DNA array technology that can be used for label-free, quantitative gene assays using extremely small volumes of analytes.