PSA detection using label free graphene FET with coplanar electrodes based microfluidic point of care diagnostic device.

Affordable point-of-care (PoC) diagnostic devices enable detection of prostate specific antigen (PSA) in resource limited settings. Despite the advancements in PoC systems, most of the reported methods for PSA detection have unsatisfactory detection limits and are based on labelled assays, requiring multiple reagent flow steps which increases both expenses and inconvenience. Circumventing these constraints, we report here the development and validation of a label free, affordable dielectrophoresis (DEP) based graphene field effect transistor (FET) sensor implemented using coplanar electrodes and integrated uniquely with a compact disc based microfluidic platform along with electronics readout for the estimation of PSA at the point of care. Design of coplanar gate electrode which has not been explored earlier is not a straightforward approach. In fact, it has been observed that there is a non-monotonic dependence of the capture of PSA molecules in the channel region of the FET with varying widths and spacings of the gate electrode. The graphene FET based PoC device with optimized coplanar gate electrode is the only label free analytical system for PSA detection requiring simple operation and achieving a detection limit of 1 pg/ml in serum with a wide dynamic range upto 4 ng/ml and appreciable selectivity against potential interferents like bovine serum albumin (BSA) and human immunoglobulin G (IgG). Further, it has been validated satisfactorily with commercially available existing systems using human serum samples. Moreover, the proposed sensing system lowers the detection limit by three orders of magnitude compared to a recent study on label free PoC device on other cancer biomarkers.