A dual enzyme-mimicking nanoplatform based on CoMn-LDHs for ultrasensitive detection of L-cysteine: Toward environmental and food safety monitoring

• CoMn-LDHs with dual oxidase and peroxidase mimic activity were synthesized at room temperature • A facile colorimetric sensing platform for cysteine has been successfully developed • The colorimetric sensing platform shows high sensitivity for the detection of cysteine down to 0.024 μM • The developed method was applied for the detection of cysteine in milk and water, with good recovery • The method's sustainability was thoroughly evaluated, verifying its highly sustainable and innovative nature L-Cysteine (CYS) is a pivotal biomolecule involved in both biological and environmental processes, yet conventional detection methods suffer from low sensitivity, complex procedures, and interference issues. In this study, we report the development of cobalt-manganese layered double hydroxides (CoMn-LDHs) as a novel nanomaterial-based sensing platform with dual oxidase/peroxidase mimicry for label-free CYS detection. The synthesized CoMn-LDHs exhibit exceptional catalytic activity, efficiently oxidizing the chromogenic substrate TMB through the generation of reactive species such as superoxide anion (O₂•⁻) and hydroxyl radicals (•OH), which significantly enhance sensitivity and selectivity. This dual-enzyme mimic mechanism enables a rapid, colorimetric detection method with ultra-low detection limits of 0.024 μM and 0.12 μM for oxidase and peroxidase modes, respectively, outperforming traditional techniques. The sensor demonstrates excellent performance in real samples, including mineral water, tap water, and milk, with high recovery rates (> 98%) and low relative standard deviation (%RSD < 5%), showcasing its robust stability and reproducibility in complex matrices. This work presents a cost-effective, highly sensitive, and selective platform for CYS detection, offering significant advancements in environmental monitoring and food safety applications through the innovative use of nanomaterial-based enzyme mimics.