Improvement of a highly sensitive and specific whole-cell biosensor by adding a positive feedback amplifier

Area of Science:

• Synthetic Biology
• Environmental Monitoring
• Biosensor Technology

Background:

• Whole-cell biosensors are crucial for detecting environmental contaminants like cadmium (Cd²⁺).
• Previous biosensor designs utilizing negative feedback amplifiers (TCM) showed limitations in response range and signal output.
• Optimizing biosensor performance requires innovative amplification strategies.

Purpose of the Study:

• To design and evaluate a novel whole-cell Cd²⁺ biosensor (LTCM) incorporating both positive and negative feedback cascade amplifiers.
• To compare the performance of LTCM against a previously developed biosensor (TCM) with only negative feedback.
• To assess the potential of LTCM for enhanced practical applications in environmental monitoring.

Main Methods:

• Engineered *Pseudomonas putida* KT2440 with a dual-feedback (positive and negative) genetic circuit for Cd²⁺ detection.
• Comparative analysis of LTCM and TCM biosensors under identical culture conditions.
• Evaluation of key performance metrics including linear response range, fluorescence output, response time, sensitivity, and specificity.

Main Results:

• LTCM demonstrated an expanded linear response range for Cd²⁺, extending to 0.1 μM, a twofold increase from TCM.
• Fluorescence output signal intensity was enhanced 1.11-2.64 times in LTCM compared to TCM.
• Response time for practical sample detection was reduced from 6 hours (TCM) to 4 hours (LTCM), with maintained high sensitivity (0.1 nM Cd²⁺) and specificity (23.29).

Conclusions:

• The integration of positive and negative feedback cascade amplifiers significantly enhances whole-cell biosensor performance.
• LTCM exhibits superior characteristics including a broader linear response range, amplified signal output, and reduced response time.
• The improved performance of LTCM indicates its greater potential for sensitive, specific, and efficient practical applications in cadmium detection and environmental monitoring.