Investigating of stain's adsorption on PMMA QCM Sensors

Objectives: A quartz crystal microbalance (QCM) is a highly sensitive and practical device for in situ monitoring of protein adsorption. A QCM-based sensor consists of a quartz crystal and sensing material. A 27-MHz QCM is capable of measuring mass in aqueous solutions with extremely high sensitivity, and its resonance frequency has been shown to decrease linearly with increasing mass on the QCM electrode at the nanogram level. In this study, polymethyl methacrylate (PMMA) sensors that imitate the denture surface were prepared by a thin film magnetron that spin-coated PMMA onto gold-plated quartz.
Methods: We discuss the quality of the PMMA sensor and evaluate the potential of the high-frequency PMMA QCM sensor by investigating the binding between the PMMA QCM sensor and albumin (a salivary-related protein) and beef tallow imitating psedofood debris (teeth stains). To prepare PMMA-coated sensors, bare QCM sensors were cleaned with piranha solution. PMMA (0.1 g/ml in ethyl acetate) was coated onto the gold electrode of the quartz crystal at 3000 rpm for 15 s in a spin coater. The PMMA QCM sensors were put on for a day at room temperature. The surface topology and roughness of the PMMA-coated (test) and bare (control) QCM sensors were evaluated over a surface area of 10 × 1.0 μm by scanning probe microscopy. Test QCM sensors were characterized by Fourier transform infrared (FTIR) spectroscopy, and the coating composition was analyzed by X-ray photoelectron spectroscopy (XPS). QCM measurements were used to quantify the albumin and beef tallow.
Results: SPM showed a slight change in the surface morphology of test QCM sensors. FTIR showed that test QCM sensors and the PMMA block had similar absorbance spectra. XPS of control QCM sensors showed a gold peak and test QCM sensors had oxygen and carbon peaks, but no significant gold peak. Test QCM sensors showed significantly more adherence of albumin and beef tallow than control QCM sensors. Moreover, beef tallow adhered more than albumin on control and test QCM sensors. SPM, FTIR and XPS analyses revealed that thin PMMA films with their original composition were coated onto QCM sensors.
Conclusions: This study presents the technical basis to observe protein adsorption on denture surfaces and may contribute to the development of denture cleaners that prevent biofilm formation.