A dual-function nanoreactor detects and degrades chloramphenicol with high sensitivity and speed, offering a promising tool for food safety and water purification.
(Nanowerk Spotlight) The contamination of food and water by residual antibiotics poses a persistent threat to public health. One such antibiotic is chloramphenicol, a broad-spectrum agent once used to treat serious infections in humans and livestock. Although effective, its severe side effects—including bone marrow suppression and neurological damage—have led to its restriction or ban in many countries. Yet residues continue to be detected in food products and water systems. The challenge lies not only in detecting such trace levels quickly and accurately, but also in removing them safely and efficiently.
Standard methods for detecting chloramphenicol include chromatography-based systems, which are highly accurate but require expensive instruments, skilled personnel, and lengthy procedures. Enzyme-linked immunosorbent assays (ELISA) are faster but limited in sensitivity and vulnerable to enzyme degradation.
Meanwhile, strategies for removing chloramphenicol from water or food matrices range from physical adsorption to chemical breakdown. Among these, photocatalysis has emerged as a promising tool. It relies on light-activated catalysts to generate reactive molecules capable of degrading pollutants. However, few materials can both detect and degrade contaminants in a single integrated system.
A recent study published in Advanced Science (Advanced Science, “Rational Design of MOF‐Based Multifunctional Bio‐Nanoreactor for Efficient Detection and Photo‐Degradation of Chloramphenicol”) addresses this challenge directly. Researchers from Huazhong Agricultural University and collaborating institutions developed a hybrid nanoreactor capable of performing both tasks with high efficiency. Their design integrates a metal–organic framework (MOF) known as NU-1003 with two key active components: the enzyme horseradish peroxidase (HRP) and iron ions. The resulting composite, termed HRP@Fe-NU-1003, functions as both a biosensor and a photocatalyst.
The MOF provides a porous, stable scaffold that supports and protects the enzyme while allowing small molecules to access active sites. It also contributes to light absorption, facilitating the catalytic breakdown of pollutants. Iron ions are embedded into the MOF’s framework to enhance electron transfer processes and enable the generation of reactive oxygen species under light exposure. Together, these components allow the material to bind, detect, and degrade chloramphenicol in complex environments such as wastewater and food samples.
Schematic diagram of HRP@Fe-NU-1003. (Image: Reprinted form DOI:10.1002/advs.202414866, CC BY) (click on image to enlarge)
The researchers first confirmed the structural integrity of the modified MOF through electron microscopy and spectroscopic techniques. Iron ions were uniformly distributed without forming particles, and the MOF maintained its crystal structure after the incorporation of both enzyme and metal components. Further imaging showed that HRP molecules were well-dispersed within the pores of the framework, indicating successful immobilization without compromising enzyme activity.
To assess its sensing capability, the team combined HRP@Fe-NU-1003 with magnetic nanoparticles functionalized with antibodies. These acted as capture agents, while the MOF composite served as the detection probe. In this competitive binding format, the presence of chloramphenicol reduced the formation of signal-generating complexes. The strength of the signal inversely correlated with the chloramphenicol concentration, enabling precise quantification.
This biosensor achieved a detection limit of 15.38 picograms per milliliter, a level more than sixty times lower than that of conventional ELISA. It also reduced detection time by 63 percent. Tests showed high specificity, with minimal cross-reactivity to other antibiotics like tetracycline and kanamycin.
In real-world samples—including fish tissue, urine, and wastewater—the biosensor consistently detected trace levels of chloramphenicol with high accuracy. Its results aligned closely with those from high-performance liquid chromatography–mass spectrometry, a laboratory gold standard, and outperformed ELISA in low-concentration detection.
The material’s second function—photocatalytic degradation—was also evaluated. Under visible light, HRP@Fe-NU-1003 rapidly broke down chloramphenicol. Within 30 minutes, it achieved nearly complete removal of the antibiotic at a concentration of 50 micrograms per milliliter. This performance was superior to that of other materials tested, including unmodified MOFs and MOFs without iron or enzyme components.
The nanoreactor operates through a dual degradation mechanism. Iron ions promote the Fenton reaction, which produces hydroxyl radicals from hydrogen peroxide. Simultaneously, HRP catalyzes additional reactions that generate reactive species. These radicals attack chloramphenicol molecules, breaking them down into simpler compounds such as carbon dioxide and water. The mineralization rate reached 61 percent, indicating not just adsorption but chemical transformation of the pollutant.
Importantly, the material was reusable. After five cycles of adsorption and light exposure, it retained high degradation efficiency with minimal structural change and only 0.05 percent iron leaching. It also proved effective against a range of other antibiotics, including fluoroquinolones and tetracyclines, suggesting broader applicability.
To understand the basis of its enhanced performance, the team investigated its electronic and photochemical properties. Spectroscopy revealed that iron doping narrowed the material’s bandgap and shifted its light absorption toward longer wavelengths. Electrochemical tests showed improved electron transport and lower resistance. These properties facilitate charge separation—keeping photo-induced electrons and holes apart long enough to drive catalytic reactions.
Photoluminescence measurements and excited-state lifetime analysis confirmed that Fe-NU-1003 suppressed recombination of electron-hole pairs and extended the duration of their reactive state. Density functional theory calculations supported these observations. They showed that the spatial separation of electrons and holes increased after iron modification, improving the material’s ability to generate reactive species under light.
Further analysis pinpointed the main reactive molecules involved. Chemical quenching experiments and electron paramagnetic resonance spectroscopy identified superoxide and hydroxyl radicals as the dominant agents in chloramphenicol breakdown. These findings were consistent with the observed degradation performance and confirmed the critical role of both iron and HRP in the process.
This study demonstrates a practical strategy for integrating molecular recognition and photocatalysis into a single, recyclable material. By combining enzyme stability, MOF versatility, and iron’s catalytic properties, the authors created a platform that addresses both detection and degradation of contaminants in complex samples. The design principles used here could be adapted to other pollutants, making this a modular approach with potential in environmental monitoring, food safety, and water treatment.
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