A self-priming mediated chain extension cysteine catalytic oxidation-based colorimetric method for sensitive <i>Pseudomonas aeruginosa</i> detection

Nursing hospital infections with <i>Pseudomonas aeruginosa</i> (<i>P. aeruginosa</i>) pose a significant risk to human health, especially to those immunosuppressed patients receiving surgical therapy. Consequently, it is imperative to create a novel and portable <i>P. aeruginosa</i> analysis method for the early diagnosis of <i>P. aeruginosa</i> infections. For sensitive and reliable <i>P. aeruginosa</i> analysis, we depict here a novel colorimetric approach based on rolling circle amplification (RCA) based construction of a detection scaffold and self-priming mediated signal recycling. In this method, the RCA product is attached to a plate surface to recognize <i>P. aeruginosa</i> targets and initiate the chain extension mediated cysteine catalytic oxidation based colorimetric reaction. This method involves activating RCA to generate several RCA products with repetitive functional portions by cyclizing the padlock sequence using primer sequences. To facilitate the color reaction based on gold nanoparticles, the produced G-rich sequences during the self-priming mediated signal recycling process can fold to G-quadruplex DNAzyme, which can catalyze the conversion of cysteine to cystine and produce color changes that can be observed directly with the naked eye. Based on this elegant design, the method has a broad detection range and a low limit of detection of 3.6 cfu mL^-1. In addition, this colorimetric approach showed good selectivity to target bacteria. This technology has great potential for use in biomedical diagnostics and bio-sensing of pathogenic bacteria.