High radio frequency biosensor for a nano-concentration detection of the label free prostate specific antigen cancerous cells

Abstract

This research presents an original and novel biosensor based on the transmission line geometry of a high radio frequency microstrip filter which aims to achieve rapid diagnostics of cancer. The analytical design of the biosensor has been computationally verified. The biosensor was fabricated by patterning a 10 μm nickel/gold metal layer on a 1.6 mm FR-4 dielectric base with a continuous metal back plane. Subsequently, the microstrip was integrated with a microfluidic channel. Characterization of scattering parameters was performed by a vector network analyzer (VNA), with results showing good agreement with the modelling. To assess functionality, sensitivity to prostate specific antigens (PSA) was quantified. Initially, the biosensor was functionalized by coating it with antibody receptors (Ab) to capture PSA. Thereafter, sensitivity and repeatability towards the detection of captured PSA was assessed by immobilization of PSA onto the treated golden surface. Measurements were taken directly after each stage of coating and capturing. A nano-concentrations (2000-20ng/ml) of PSA were sensed. The characteristic dips in the reflection signal parameter (S11) all showed both an amplitude and frequency shift, most notably at 0.6, 1.08 and 1.32 GHz respectively. This therefore revealed the ability of this biosensor to immobilize and detect nano-concentrations of PSA analyte by measuring the signal changes due to the presence of PSA, with variability in results being attributed to the surface quality of the biosensor. Mostly, electrical biosensor research is focusing on low frequency (<1MHz), on the other hand, the work reported here proves the achievability of this new high frequency approach.