On-chip electrochemical detection of cholera using a polypyrrole functionalized dendritic gold sensor.

Rapid diagnosis of infectious disease at the site of the patient is critical for preventing the escalation of an outbreak into an epidemic. Devices suited to point-of-care (POC) diagnosis of cholera must not only demonstrate clinical laboratory levels of sensitivity and specificity, but must do so in a portable and low-cost manner, with a simplistic readout. We report work towards an on-chip electrochemical immunosensor for the detection of cholera toxin subunit B (CTX), based on a dendritic gold architecture biofunctionalized via poly-(2-cyano-ethyl)pyrrole (PCEPy). The dendritic electrode has an ∼18x greater surface area than a planar gold counterpart, per electrochemical measurements, allowing for a higher level of diagnostic sensitivity. A layer of PCEPy polymer generated on the dendritic surface facilitated the performance of an electrochemical enzyme-linked immunosorbant assay (ELISA) for CTX on-chip, which demonstrated a detection limit of 1 ng mL-1 , per a signal-to-noise ratio of 2.6. This was more sensitive than detection using a simple planar gold electrode (100 ng mL-1 ), and also matched the diagnostic standard optical ELISA, but on a miniaturized platform with electrical readout. The ability to meet POC demands makes biofunctionalized gold dendrites a promising architecture for on-chip detection of cholera.