Towards smartphone-aided electrochemical detection for point-of-care diagnostics

A novel portable amperometric bio-instrumentation platform that utilises the processing power of a smartphone is developed. The system rapidly reports the results of electrochemical measurement and requires small sample volumes (<15 µl). This diagnostic platform can be beneficial in developing countries, where there is limited access to medical centres. This lab-on-PCB system exploits commercial PCB manufacturing processes to make the system inexpensive. The electronic readout board connects to an Android-based smartphone for data processing and acts as a power source for the instrumentation. The results of the electrochemical reactions are reported through a simple to use, custom designed App. The electronic instrumentation platform has a wide dynamic range, measuring currents with a range of few nA to +2.5mA, allowing it to be able to reliably measure a wide range of electrochemical reactions. An automatic range-adjustment system is also implemented to adjust the input signal range maintain a high resolution in the system (122 pA resolution for input current range +/- 2.5 µA). This automatic algorithm provides better results in comparison to the constant range measurements. Furthermore, different sensing designs are performed investigating the effect of electrode’s design and size on the system’s sensitivity and accuracy. Finally, the system is evaluated using NaCl, H2O2 and an enzymatic assay: horseradish peroxidase acting on the substrate TMB (a common reporter for ELISA colorimetric detection) in the presence of H2O2. Results show that the amperometric data correlate well with the colorimetric for the above reaction. The promising results encourage further development of the system by adding a more complicated microfluidic design and detecting the concentration of the IFN-γ into solution