Expanding luminol activity: UV-enhanced peroxidase-like activity for dual-mode wide-pH biosensing

While luminol is typically employed for its chemiluminescence in basic media, this report uncovers a previously unrecognized function: a strong peroxidase-like activity in acidic environments, enabling a colorimetric sensing modality that complements its well-established chemiluminescence under basic conditions. By integrating these dual functionalities, luminol can serve as a broad-pH, dual-mode sensing reagent, laying the groundwork for microfluidic systems that provide colorimetric detection when the sample is acidic and chemiluminescent detection when the sample is basic. Specifically, the peroxidase-like activity of luminol was leveraged in this study to establish a colorimetric assay for the detection of H₂O₂ and dopamine. Under optimized conditions, the proposed detection method enabled reliable monitoring of H₂O₂ and dopamine with limit of detection (LOD) values of 0.0149 mM and 0.52 µM, respectively. This study also reveals that UV activation substantially enhances luminol's peroxidase-like activity, decreasing the detection time from 35 to 4.5 min and improving the sensitivity by lowering the LOD from 0.0149 to 0.0085 mM. Kinetic studies using Michaelis-Menten and Lineweaver-Burk analyses demonstrate that luminol exhibits high peroxidase-like catalytic competency compared with other reported nanozymes. Moreover, the method was successfully applied for the determination of dopamine in a simulated blood sample, achieving an LOD value of 1.5089 µM, thereby demonstrating its excellent performance and suitability for dopamine analysis in complex biological environments. These findings highlight the use of luminol as an efficient, UV-enhanced peroxidase mimic with strong potential as a rapid and sensitive platform for next-generation colorimetric biosensors in clinical applications.