Reduction of nonspecific protein adsorption on cantilever biosensors caused by transverse resonant mode vibration†
We examine if vibration of millimeter-sized cantilever sensors can release nonspecifically adsorbed proteins. Integrated electrochemical and mass-change measurement as well as fluorescence assays showed transverse surface vibration released nonspecifically bound proteins in samples prepared at 0.2–3.6 mg bovine serum albumin (BSA) per mL. Extent of release was directly related to magnitude of excitation voltage (Vex) applied to the self-actuating lead zirconate titanate (PZT) cantilever over three log units (0, 10 mV, 100 mV, and 1 V). Vibration-induced release was not instantaneous, but had an apparent first-order rate constant (kapp) which ranged from 0.02–0.1 min−1. Results suggest significant serum albumin protein release could be achieved using excitation voltages of 1 V in millimeter-sized cantilever sensors. Complementary experiments with thiolated DNA, which binds to surface gold 〈111〉 sites with ∼ four times higher binding energy than BSA, showed negligible release under the same vibration magnitude. The results of the study suggest a direct correlation between surface-adsorbate binding energy and the effectiveness of vibration-induced release. We suggest that the release mechanism includes contributions from surface strain energy, body force, and acoustic streaming-associated hydrodynamic effects. The primary contribution of this study suggests that surface vibration of cantilever sensors may be useful in reducing nonspecific adsorption, especially for biosensing of analytes present in a complex background.