TITLE: Development of Highly Sensitive Bulk Acoustic Wave Device Biosensor Arrays for Screening and Early Detection of Prostate Cancer

A26 Advances in the proteomics of cancer proliferation are yielding many new potential targets, or biomarkers, for identifying a malignancy at the earliest stages of development. These markers have been difficult to find as they exist in extremely low concentrations in circulating blood. In order to make use of these discoveries at a clinical level, ultra-sensitive biosensors exhibiting high degrees of specificity will be required to identify these proteins in clinical samples, such as patient blood plasma or serum. Further, a sensing technology that identifies a multi-protein signature is most likely to minimize false positives and false negatives. A sensor array incorporating these aspects could have an impact at multiple levels including early detection screening, post-therapy monitoring, as well as on the proteomic discovery process. The research presented here involves the development of such a tool and its application towards detecting mesothelin, a cell-surface protein that is highly expressed in mesothelioma, ovarian cancer, pancreatic cancer, and some other malignancies. The acoustic resonator array design consists of electrodes fabricated on the surface of a piezoelectric ZnO thin-film. To functionalize the resonators for mesothelin detection, MB Mabs were immobilized on the surface, which have an affinity for mesothelin at 0.6 nmol/L. The Mabs were bound to the surface using a thiol-terminated silane surface chemistry. Reference device arrays coated with anti-FITC antibodies, specific to a molecule not present in the analyte, were also prepared. The goal of the investigation was therefore to gauge the sensitivity of the sensors to the molecular binding of mesothelin. A total of n=16 mesothelin-targeted devices and n=16 reference devices were tested by exposing them to a 10 μg/ml solution of purified mesothelin-rfc protein in PBS buffer for 25 minutes. The devices were washed and the final operating frequencies were measured. The frequency shifts were then compared with the initial "unloaded" operating frequencies. The reference sensors showed a mean shift of 540 kHz while the mesothelin-coated sensors showed a mean shift of 1.25 MHz. ANOVA was performed on the results which indicate a statistically significant difference (p < 0.001) in the overall frequency shifts associated with the mesothelin-target sensors and the reference sensors. The magnitude of these preliminary results promises a detection limit at much lower target concentrations than those tested; potentially well below the ng/ml threshold upheld in the literature as the necessary sensitivity level. An important feature of these devices is that the sensitivity of the sensor platform is scaleable by a simple adjustment of the fabrication parameters. The device design also incorporates standard fabrication practices from the microelectronic device industry, allowing for mass production of extremely low-cost sensors. Work is on-going to demonstrate the efficacy of these devices under realistic physiological conditions and for lower concentrations of target.