A recognition-enhanced colorimetric sensor based on molecularly imprinted CoFe LDH nanozymes for detection of enrofloxacin in real water samples
This study presents a selective colorimetric sensor utilizing molecularly imprinted CoFe LDH nanozymes to detect enrofloxacin in water samples by inhibiting ROS-mediated TMB oxidation upon target binding, achieving a detection limit of 0.03 µM.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Water is the lifeblood of our planet, but it is also a place where the chemicals we use every day can accumulate. One such chemical is enrofloxacin, a powerful antibiotic used to treat infections in livestock and aquaculture. While it helps animals stay healthy, the drug often ends up in rivers and lakes through manure and wastewater. Because it breaks down very slowly, it can build up in the environment, potentially harming ecosystems and entering the food chain. Detecting these traces is crucial for protecting water quality, but the current methods are often slow, expensive, and require complex laboratory equipment. Scientists have long sought a simpler way to spot these contaminants quickly, ideally using a method that changes color to show what is present, much like a litmus test, but with the ability to distinguish one specific chemical from thousands of others.
To solve this, researchers have turned to a clever combination of two scientific ideas: nanozymes and molecular imprinting. A nanozyme is a tiny, man-made particle that acts like a natural enzyme, speeding up chemical reactions. In this case, the scientists used a material made of cobalt and iron that behaves like a natural catalyst, turning a clear liquid blue when mixed with hydrogen peroxide. However, these nanozymes are usually too eager to react; they cannot tell the difference between the target pollutant and other similar-looking chemicals. This is where molecular imprinting comes in. Imagine taking a mold of a specific object, removing the object, and leaving behind a cavity that fits that object perfectly. By creating these microscopic, shape-specific holes in a polymer coating, scientists can build a sensor that grabs only the target molecule and ignores everything else.
In a recent study, a team of researchers from Henan Polytechnic University and Jiangsu University of Science and Technology combined these concepts to create a new sensor for enrofloxacin. They started by growing tiny, spherical particles of cobalt-iron layered double hydroxide, a material known for its ability to catalyze reactions. They then coated these particles with a thin layer of chitosan, a natural polymer derived from shellfish, and cross-linked it with glutaraldehyde. Crucially, they added enrofloxacin to the mixture during this coating process. As the polymer formed around the particles, the enrofloxacin molecules acted as a template, creating specific pockets or cavities in the coating that matched the size and shape of the drug. Once the coating was solid, the researchers washed away the enrofloxacin, leaving behind empty, perfectly shaped holes on the surface of the nanozyme.
The mechanism of detection relies on a physical blockage. In the absence of enrofloxacin, the empty cavities on the sensor act as open doorways, allowing hydrogen peroxide to flow through the coating and reach the active cobalt-iron core. Once there, the core triggers a reaction that turns a clear chemical called TMB a vivid blue. However, when enrofloxacin is present in the water, it slides back into those specific cavities, fitting snugly like a key in a lock. This action physically blocks the doorway, preventing the hydrogen peroxide from reaching the core. As a result, the blue color does not develop, or it develops much more faintly. The more enrofloxacin is in the water, the more cavities get filled, and the less blue color appears. This change in color intensity provides a direct, visual measure of how much drug is in the sample.
The researchers tested this sensor with rigorous precision. They found that it could detect enrofloxacin in concentrations as low as 0.03 micromoles, with a linear response ranging from 0.19 to 50 micromoles. This means the sensor is sensitive enough to spot very small amounts of the drug while still working accurately when the concentration is higher. To ensure the sensor was not just reacting to any chemical, they tested it against other antibiotics and similar molecules. The sensor remained unresponsive to these look-alikes, proving that the molecular imprinting successfully taught the material to recognize only enrofloxacin. The study also confirmed that the sensor works by physically blocking the reaction pathway, rather than by chemically destroying the catalyst or changing its nature.
Finally, the team took the sensor out of the lab and into the real world. They collected water samples from the Yangtze and Yellow River systems, as well as from livestock farms and hospitals. In every case, the sensor accurately measured the amount of enrofloxacin, with recovery rates between 98.6% and 104%. This high level of accuracy in complex, dirty water samples suggests that the method is robust enough for field use. The sensor is also reusable; the enrofloxacin can be washed out of the cavities, allowing the material to be used again without losing its ability to detect the drug. This work offers a promising, cost-effective tool for monitoring water quality, providing a way to keep a close watch on antibiotic pollution without the need for expensive machinery or highly specialized training.
Drowning in papers in your field?
Get daily digests of the most novel papers matching your research keywords — with technical summaries, in your language.