Reusable biosensor-based polymer dot-coated electrode surface for wireless detection of bacterial contamination

Biosensor development for bacterial detection is critical to preventing infectious disease outbreaks caused by bacterial contamination. Recent studies have focused on colorimetric sensors, but high limit of detection (LOD) has restricted their application for sensitive bacterial detection. Here, we designed a reusable, sensitive smartphone-based electrochemical biosensor which uses electroconductive boronic acid-modified polymer dot (B-PD)-coated electrode to detect bacterial contamination. The pH-selective boronic acid in B-PD promotes binding between sensor and bacteria via increased diol-diol kinetics of boronic acid at pH 7.4. B-PD-coated electrodes can detect both gram-negative (E. coli) and gram-positive (S. aureus) bacteria by observing the conductivity change after attachment (10¹-10⁷ CFU/mL), with high sensitivity, as indicated by low LOD (E. coli=10^0.8 CFU/mL, S. aureus=10¹ CFU/mL). The electronic signal from bacterial detection is transmitted to smartphone by connecting B-PD-coated electrode with wireless microcontroller, which allows for simple in-line monitoring. This biosensor demonstrated excellent performance in detecting bacteria in real environmental samples, along with good selectivity towards bacteria, even in the presence of interfering compounds. Moreover, by maintaining boronic acid-diol interaction, B-PD-coated electrode can be reused after applying pH shock (pH < 6) up to four cycles. Thus, this system offers simple approach for bacteria monitoring with high sensitivity and reusability.