Controllable detection threshold achieved through the toehold switch system in a mercury ion whole-cell biosensor.

Area of Science:

• Environmental Science
• Biotechnology
• Analytical Chemistry

Background:

• Mercury's toxicity necessitates sensitive, specific, and cost-effective water monitoring methods.
• Existing methods often lack a wide detection range or simple visual output.
• Whole-cell biosensors offer a promising platform for environmental sensing.

Purpose of the Study:

• To develop a whole-cell biosensor for mercury ion detection with adjustable detection limits and an expanded range.
• To engineer a gene circuit for controllable mercury detection with a visual readout.
• To assess the biosensor's specificity and interference resistance.

Main Methods:

• Construction of a gene circuit combining toehold switch, lactose operon, mercury-ion-specific operon, and red fluorescent protein.
• Design and selection of dual-input single-output sensing logic circuits using MATLAB.
• Evaluation of biosensor DTS-3 performance, including fluorescence response, specificity, and interference resistance in spiked samples.

Main Results:

• Biosensor DTS-3 demonstrated controllable threshold detection across various mercury ion concentrations (0.005-6 μM) by adjusting isopropyl β-D-Thiogalactoside (IPTG) levels.
• High specificity was observed, with no significant fluorescence changes in the presence of other metal ions.
• The biosensor detected mercury ions down to 7.5 nM visually and 5 nM with a microplate reader, showing good interference resistance.

Conclusions:

• The developed whole-cell biosensor provides a feasible, sensitive, and specific method for mercury ion detection.
• The controllable detection threshold and expanded range offer a significant advantage for environmental monitoring.
• This approach presents a new strategy for enhancing biosensor capabilities for rapid and convenient measurements.