A droplet array device for electrochemical detection of methylene blue based on local redox cycling

Methylene blue is widely utilized as an indicator and dye in bioassays. For the simultaneous detection of many samples in bioassays, a multiple assay device is desired. Here, we present an array device based on local redox cycling for the detection of small droplets of methylene blue. The device consists of 8 row, 8 column electrodes connected to interdigitated array (IDA) electrodes at individual crossing points to form 64 sensor points. By segmenting the sensor points with droplets, each point works as an electrochemical cell, thus allowing multipoint detection of the analyte. In this study, methylene blue was successfully detected using redox cycling. Also, multiple detection of methylene blue was achieved. Because methylene blue binds strongly to DNA via intercalation, this interaction will be detected as an electrochemical signal via redox cycling. In particular, the proposed method will be useful for the simultaneous detection of multiple samples in droplet digital PCR.