Fast, Simple Electrochromic Biosensors for Point-of-Use Infectious Disease Diagnosis.

Rapid and accurate diagnostics are essential for controlling infectious diseases, especially in low-resource settings. To enable broad implementation, there is a pressing need for point-of-use sensors that offer high sensitivity, portability, and user-friendliness. Electrochemical technologies, namely bipolar electrode (BPE) sensors, are promising because of their sensitivity and simplicity. However, traditional BPE sensors require complex equipment, hindering portability. Here, we present an electrochromic, BPE-based nucleic acid sensor that enables detection without additional equipment, making it ideal for point-of-care (POC) testing. Low cost, easily fabricated gold leaf electrodes are used as the substrate for electrochromic sensing. Through a nanostructuring step, the surface area of the gold is significantly increased, boosting the surface area for DNA probe immobilization and producing detectable color signals. These electrodes are integrated with microfluidics and a lithium-ion battery to yield an integrated system, which enables on-site, real-time viral detection with simplified preparation and detection on a single chip. We demonstrate sequence specific detection of SARS-CoV-2 RNA using loop-mediated isothermal amplification (LAMP) followed by Cas12a-mediated cleavage of ferrocene-tagged probes, offering a low-cost, equipment-free, and accurate diagnostic tool for infectious disease detection in resource-limited settings.