Design of a Blood Serum Acoustic Biosensor for Inferring Prostate Cancer Recurrence
Giardina, Christopher K.
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Biomarkers and the methods which are utilized to detect them are at the forefront of disease prevention, detection, and prognosis. To further the prostate cancer clinical detection modalities, quartz crystal microbalances with dissipation (QCM-D) were inoculated with a functional layer of antibodies to afford an immuno-specific biosensor capable of reporting frequency, dissipation, and viscoelasticity shifts indicative of changes in surface chemistry. Because serum protein binding occurs selectively at the antibody’s paratope and non-selectively at the QCM-D surface, multiple sensors were used simultaneously to isolate the frequency and dissipation shifts due exclusively to the antigen-antibody binding event. Early studies with fluorescein isothiocyanate (FITC) indicated that binding to its respective antibody yielded significantly positive frequency shifts in a dose-dependent fashion, contrary to the Sauerbrey model. The data, however, fits a time-dependent perturbation theory in which surface frequency changes during adsorption are due to both mass and stiffness changes. FITC was further used as a reference sensor to account for the non-specific binding of Bovine Serum Albumin (BSA) in a recombinant BSA solution and several solutions of fetal bovine serum (FBS). FBS was diluted to the same BSA concentration as a recombinant solution and experimentation showed no significant difference in detected frequency shift, despite a large difference in viscosity. These findings indicate that only recombinant protein is necessary when creating dose-response curves for calibrating an assay from this technique. Pure samples of FBS were also studied, and exhibited frequency shifts similar to a multiple of the prior FBS dilution factor. These proof of concept studies allowed for the simultaneous detection of PSA, alkaline phosphatase, and Simple-minded homolog 2 (SIM2) in human serum from patients with either recurrent or non-recurrent prostate cancer. Repeated trials will allow for robust comparison between cohorts.