Image created by Dr. Michael J. Miller
The biosensor uses an enzyme-based biofuel cell, antibodies called aptamers and a bacterial elimination mechanism to make water decontamination faster and easier.
A team of researchers has developed a new self-powered biosensor that can detect Escherichia coli (E. coli) bacteria in drinking water and destroy them in situ (on site). This discovery could have enormous ramifications for providing safe drinking water worldwide.
Traditional methods, such as culturing or polymerase chain reaction (PCR), are time-consuming and labor-intensive. They also require specialized equipment and trained staff.
Biosensors (devices that use living organisms or biological molecules) are faster, but tend to need external power sources to function. They also have the irksome tendency to degrade over time. The new sensor, however, addresses many of these issues by deploying three main components to generate its own energy.
Three components
The first, an enzymatic biofuel cell (EBFC), provides power for the sensor by using enzymes to generate electricity from biochemical reactions. It uses glucose oxidase (GOx) to break down glucose, producing electrons (electricity) and hydrogen peroxide. However, this enzyme loses stability over time.
To solve this, the team encapsulated it in a hollow metal-organic framework (MOF) called ZIF-8, which protects from damage over time and maintains efficiency and stability under different conditions.
The second is the use of antibodies called aptamers in the biosensor. These short strands of DNA can specifically bind to parts of the E. coli‘s exterior. According to the team, aptamers are linked to silver nanoparticles (AgNPs) which block glucose from reaching the enzyme until E. coli is detected.
When E. coli is present, the aptamer binds to it, triggering a reaction to the silica barrier, allowing glucose to reach the enzyme. The oxidation reaction produces electrons, generating an electrical signal confirming bacteria’s presence.
The third component is a bacterial elimination mechanism that kills any E. coli cells the sensor finds. This is achieved using a targeted dose of hydrogen peroxide, a byproduct of the sensor’s biofuel cell. This oxidizes the silver nanoparticles, releasing silver ions (Ag+) renowned for their antibacterial properties. They are so effective that they can kill 99.9% of bacteria in just a few hours.
Efficient and stable
The researchers report that the new sensor is also very sensitive and is able to detect E. coli at extremely low concentrations (3 CFU/mL). It also comes with a catalytic hairpin assembly (CHA) mechanism which amplifies the signal by forming double-stranded DNA structures that enhance the electrical readout.
When tested, the new biosensor successfully differentiated E. coli from other bacteria like Staphylococcus aureus and Salmonella. It was also found to remain functional over multiple uses, even days after being stored. Upon being tested on actual seawater samples, it showed 91.06% to 101.9% detection accuracy while retaining 90% functionality after five use cycles.
It is important to note that while the results are promising, the study also raises questions about scalability and long-term usability. For example, silver ions, while effective at killing bacteria, can accumulate in the environment, potentially harming beneficial microbes. To this end, future research is necessary to explore controlled release mechanisms to minimize environmental impact while preserving antimicrobial efficiency.
The study has been published in the journal Advanced Functional Materials.
Reference
Y. Wang, X. Hai, Y. Yan, S. Zhi, S. Bi, Self-Powered Biosensor-Based Multifunctional Platform for Detection and In Situ Elimination of Bacteria. Adv. Funct. Mater. 2025, 2420480. https://doi.org/10.1002/adfm.202420480
Abstract
Enzymatic biofuel cells (EBFCs) have been widely applied in self-powered biosensing. However, the relatively low catalytic activity and poor stability of enzymes during immobilization limit their applications. Herein, hollow porous metal-organic frameworks (MOFs) are synthesized to encapsulate glucose oxidase (GOx), which is applied to modify the bioanode of an EBFC-based self-powered biosensor to reduce interfacial interactions and improve the enzyme catalytic activity and stability. Based on aptamer recognition of the target Escherichia coli (E. coli), a cascade reaction is triggered on the bioanode, followed by the catalytic hairpin assembly (CHA) on the biocathode for signal amplification. This self-powered biosensing platform exhibits high sensitivity and selectivity for E. coli detection in the range of 10 to 1.0 × 107 CFU mL−1 (S/N = 3) with a detection limit of 3 CFU mL−1. Moreover, owing to the generation of Ag+ during the cascade reaction, the in situ elimination of E. coli is realized. This study provides a new perspective for integrating the detection and in situ elimination of pathogenic environmental bacteria.