Ultrasensitive multicolor electrochromic sensor built on closed bipolar electrode: Application in the visual...

Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic infection-causing pathogen that threatens human health. Accordingly, a rapid and ultrasensitive analytical method is required urgently. Herein, an ultrasensitive multicolor electrochromic sensing platform was established on the basis of a closed bipolar electrode (BPE). Prussian blue (PB), the blue spot that can be easily electrodeposited, was selected as an electrochromic indicator at the closed BPE cathode. Integrating with the anodic emitter, Ru(bpy)₃²⁺, which emitted optical red light, visualized multicolor electrochromism was achieved on closed BPE. Particularly, physical separation between the positive and negative poles of the closed BPE greatly prevented mutual interference between Ru(bpy)₃²⁺ and PB. Consequently, the sensitivity and accuracy of the proposed biosensor considerably improved. Notably, owing to magnetic-separation technology, the closed BPE surface required no modification. Without any complex pretreatment, the entire experiment time could be greatly shortened because the PA@MBs completely captured P. aeruginosa in food matrix within only 20 min. By comparing the visual electrochromic colors, ultrasensitive screening of P. aeruginosa was accomplished within 1-10⁸ CFU mL^-1. Combining the merits of closed BPE, electrochemiluminescence (ECL), and electrochromic, this strategy provided an accurate and intrinsic way for visual detection of P. aeruginosa, as well as great potential in measuring other pathogens.