Microfluidic colorimetric biosensor for rapid and sensitive detection of Shewanella oneidensis MR‑1

Extracellular respiratory bacteria (ERB) assume a significant role in biological and environmental remediation, so the rapid detection of ERB is essential to monitor its biological repair process. This study developed a microfluidic colorimetric biosensor for rapid and sensitive detection of ERB model strain Shewanella oneidensis MR-1. In the process of separation and enrichment of bacteria based on immune magnetic nanoparticles (MNPs), the biological signal is significantly amplified by the excellent peroxidase activity of flower-like CoOOH (FL-CoOOH). Firstly, immune MNPs, samples and immune FL-CoOOH were mixed and incubated within the microfluidic chip’s channel. Magnetic capture in the separation chamber yielded MNP-bacteria-CoOOH complex. Then, 3, 3′, 5, 5′-tetramethylbenzidine (TMB) substrate was added to make the FL-CoOOH nanozyme catalyze the formation of yellow product. Finally, the target bacteria in the microplate were quantitatively detected. Based on the excellent simulated enzyme activity and stability of FL-CoOOH, the detection can be completed within 45 min after the introduction of the microfluidic chip. The detection was 5×10 1 ∼5×10 6 CFU/mL. Compared with the previously reported colorimetric sensors for MR-1, the sensitivity was increased by 99.54 % to 23 CFU/mL. This study uniquely integrates optical sensors and microfluidic technology for rapid ERB detection with enhanced portability. The design of biosensor can facilitate further investigations into extracellular respiration mechanisms and rapid ecological environment restoration applications.