Implementation of quartz crystal microbalance with polystyrene layer modification for bovine serum albumin adsorption

Quartz crystal microbalance (QCM) sensor and bioactive-modified thin films of polystyrene (PS) have been successfully and respectively fabricated using resistance evaporation technique. The films' quality, bovine serum albumin (BSA) adsorption characteristic, and sensor performance were investigated. Firstly, the aluminum and silver layers were, respectively, sputtered on the At-cut quartz to form QCM sensors and characterized by atomic force microscopy. The aluminum layer exhibits much greater roughness than silver layer. The QCM sensor coated with silver electrode layer of 300 nm exhibits the resonance frequency around 10 MHz and more superior Q-factor around 8000. Then, the morphology of the deposited PS membranes were analyzed by positive fluorescence microscope, attenuated total reflectance Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and water contact angle methods. The island-like PS membranes were achieved and used as sensitive layer for BSA adsorption. A similar to 186 Hz drop in the PS-based QCM sensor resonance frequency was observed when the sensor exposed to the BSA solution that dissolved in pure phosphate buffer saline. Finally, the QCM sensor has good linear sensitivity of similar to 87 Hz/(100 mu g/mL) to different BSA concentrations from 50 mu g/mL to 500 mu g/mL.