Monitoring electrochemical impedance changes due to aptamer and target binding inside nanochannels is becoming an attractive sensing mechanism for chemical and biological species. This method, without requiring external labels, can cause a change in impedance based on the charge variation during aptamer- targets recognition. Electrochemical impedance spectroscopy (EIS) can be performed across the nanochannels and transduce the recognition signal to an electrical signal for detection. A potentiostat is usually required for performing EIS with its stability and versatility. However, for point-of-care purposes, the potentiostat has disadvantages such as its high cost, unwieldy size and training requirements for its proper use.

As a replacement for a potentiostat, our group reports a microcontroller-based impedance reader – ADuCM350. With a powerful processor and FFT core, this microcontroller can perform impedance scans at frequencies between 80Hz – 80kHz with a noise level maximum of 3%. To test this impedance reader, our group compared EIS detection with the ADuCM350 and a potentiostat (Gamry Reference 600+) against the cocaine aptamer immobilized on nanoporous alumina membranes. With amodiaquine at different concentrations in an electrochemical cell, membrane impedances were monitored and recorded. To calculate the binding affinity K_D, resistance variation ratios (∆R/R) were calculated from data acquired by both devices. Our group reports comparable K_Ds for amodiaquine of 2nM and 4nM from the potentiostat and ADuCM350 impedance reader, respectively. To further verify the ADuCM350 device abilities, the limit of detection (LOD) for amodiaquine was calculated from multiple experiments. The impedance reader exhibited a higher LOD (~25nM) compared to the potentiostat (~8nM) which could be due to lower accuracy and resolution of the former. In summary, the ADuCM350 impedance reader has strong potential for future point-of-care purpose with its low cost, tiny size, and automation advantages.