A Storable Mediatorless Electrochemical Biosensor for Herbicide Detection.

Area of Science:

• Electrochemistry
• Environmental Science
• Biotechnology

Background:

• Development of sensitive and stable biosensors for environmental monitoring is crucial.
• Mediatorless electrochemical sensors offer advantages in simplicity and reduced environmental impact.
• Cyanobacteria biofilms present a promising platform for bioelectrochemical sensing due to their photosynthetic activity.

Purpose of the Study:

• To develop and test a novel mediatorless photo-bioelectrochemical sensor for herbicide detection.
• To evaluate the long-term stability and performance of the developed biosensor.
• To assess the potential of the biosensor for environmental analysis.

Main Methods:

• Utilized a biofilm of the cyanobacterium *Synechocystis* PCC6803 *wt* on an anode for photocurrent generation.
• Measured the inhibitory effect of herbicides (atrazine, diuron, paraquat) on photocurrent.
• Assessed sensor stability by storing the biofilm at 4 °C for 22 days and measuring chlorophyll content.

Main Results:

• Successfully generated photoanodic current without artificial mediators.
• Detected atrazine and diuron through immediate photocurrent drops, correlating with inhibition of photosynthetic electron transport.
• Observed an initial photocurrent increase with paraquat due to its redox mediator properties.
• Demonstrated long-term stability (>20 days) with preserved cyanobacterial biofilm performance after cold storage.

Conclusions:

• The developed mediatorless photo-bioelectrochemical sensor is stable and effective for detecting common herbicides.
• The sensor's performance is suitable for environmental analysis, aligning with US EPA benchmarks.
• The biosensor's storability and recovery capacity are key advantages for field applications in water bodies and agriculture.