Feasibility investigation and development of microbial electrochemical biosensors for marine pollution monitoring

Electrochemical biosensor, as a real-time and rapid detection method, has rarely been explored in marine monitoring. In present work, microbial electrochemical biosensors based on two design strategies: disperse system and integrated microbial electrode, were systematically discussed and their feasibility in marine biotoxicity assessment were investigated. An isolation method was initially investigated to eliminate the potential interference and detect the biological response accurately. The influence of water salinity on the current response was eliminated by adopting the salt-tolerant bacteria Staphylococcus aureus as test microorganism and buffer solution with sufficient ionic strength. The biotoxicity of heavy metal ions and pesticides were sensitively determined. Furthermore, a novel integrated microbial biosensor was designed by immobilizing S. aureus with a redox-active gel that consists of chitosan and poly (diallyl dimethyl ammonium chloride) mixture and confined potassium ferricyanide via electrostatic interaction. The IC₅₀ values for Cu²⁺, Zn²⁺, Cr₂O₇²⁻ and Ni²⁺ were 3.01 mg/L, 1.34 mg/L, 7.64 mg/L and 9.41 mg/L, respectively. This work not only verified the feasibility of electrochemical biosensor in marine pollution monitoring, but also compared the pros and cons of two biosensor design strategies, which provide a guidance for the future development and application of marine monitoring devices based on electrochemical method.