Development of portable whole-cell biosensing platform with lyophilized bacteria and its application for rapid on-site detection of heavy metal toxicity without pre-resuscitation.

The high toxicity of heavy metals necessitates monitoring technology that allows rapid adaptation and deployment. Microbial whole-cell biosensors have become a priority because of their excellent performance. However, traditional methods have several limitations, including long assay time, poor portability, and the lack of ready-to-use on-site devices. In this study, a novel portable whole-cell biosensing platform was developed by integrating a simple handheld fiber-optic dissolve oxygen sensor and bacterial culture or lyophilized bacteria. Based on the oxygen consumption inhibition mechanism, this platform achieved rapid acute toxicity measurement of heavy metal ions through inhibit Escherichia coli (E.coli) respiration. Under the optimal conditions, the limit of detection and IC50 of Hg2+ using E. coli culture were 5.62 μM and 11.64 μM, respectively. Interestingly, the lyophilized E. coli could be directly applied for Hg2+ toxicity detection without pre-resuscitation, where an IC50 of 31.28 μM was obtained, and the whole detection process was only 18 min. The lyophilized E. coli could be stored long-term at -80 °C without significant loss of activity and detection performance. The portable whole-cell biosensing platform demonstrated a high potential for rapid on-demand toxicity detection in real water samples. The developed strategy is not only fast, portable, and easily storable, but also highly suited for on-site ready-to-use, and high-frequency toxicity detection of heavy metal ions in the field.