Practical considerations for DNA sensing using Faradaic electrochemical impedance spectroscopy on ENIG PCB electrodes

• Published in: Biosensors and bioelectronics. X Vol. 22; p. 100569
• Main Authors: Ahuja, Shruti, Kulkarni, Avani, Pandey, Richa, Kondabagil, Kiran, Tallur, Siddharth
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2025; Elsevier
• Subjects: Constant phase element (CPE); DNA sensing; Electrochemical impedance spectroscopy (EIS); Electroless nickel immersion gold (ENIG) PCB electrode; Wastewater epidemiology; Wastewater epidemiology; Electroless nickel immersion gold (ENIG) PCB electrode; Electrochemical impedance spectroscopy (EIS); Constant phase element (CPE); DNA sensing
• ISSN: 2590-1370; 2590-1370
• DOI: 10.1016/j.biosx.2024.100569

Electroless nickel immersion gold (ENIG) finish printed circuit board (PCB) substrates offer a cost-effective solution for electrochemical sensing of biomolecules. Electrochemical impedance spectroscopy (EIS) is highly sensitive and can differentiate between bioelectrochemical circuit elements over a wide frequency range. Traditional Faradaic EIS measurements often focus on charge transfer resistance (Rct) to determine analyte concentration. However, the long measurement time required to perform such EIS measurements down to very low frequencies (typically 0.1Hz) can adversely affect the ENIG PCB due to gold layer degradation and copper corrosion. To overcome these issues, we propose using the constant phase element (CPE) in the electrical equivalent circuit in EIS measurements for DNA sensing. Our approach employs ENIG PCB electrodes functionalized with thiolated single-stranded DNA probes targeting the uidA gene of E. coli. We evaluate the specificity of this sensing scheme to a 166bp complementary amplicon from E. coli against non-complementary amplicons of different lengths from E. coli and bacteriophage Phi6. By operating at higher frequencies (>10Hz), CPE analysis reduces measurement times and minimizes the risk of PCB degradation. Preliminary findings indicate that the CPE impedance exhibits concentration-dependent changes with increasing target DNA concentrations. We also present preliminary results for utilizing this sensing mechanism to detect E. coli from wastewater samples. •Faradaic EIS analysis on ENIG PCB substrates for electrochemical DNA sensors.•CPE-based rapid measurement safeguards PCB integrity against corrosion.•CPE impedance changes with target DNA concentration, effective for complex samples.•CPE shows reversal in trend with increasing DNA concentration.