Laccase-manganese dioxide nanoflowers with enhanced catalytic activity: colorimetric analysis platform for...

Neurotransmitters (NTs) play crucial roles in brain function by mediating communication between neurons at synaptic junctions and are considered an indicator for determining neurological diseases. Therefore, early and sensitive detection and monitoring are critical for maximizing the effectiveness of treatment. For this purpose, a highly active nanoflower (NF)-based colorimetric sensor system was developed for the determination of neurotransmitters. Herein, laccase@manganese dioxide NFs (lac@MnO₂ NFs) were successfully synthesized via an in situ approach by the incorporation of manganese dioxide nanoparticles (MnO₂ NPs) into laccase nanoflowers (lac NFs). The lac@MnO₂ NFs retained 100% relative activity at pH 7, while lac NFs showed negligible activity (below 1%) under identical conditions, which is attributed to the synergistic integration of MnO₂ NPs that exhibit laccase-like activity and facilitate rapid electron transport. Lac@MnO₂ NFs were applied for the colorimetric detection of various neurotransmitters (NTs) including epinephrine (EP), dopamine (DA), and levodopa (L-DOPA). The analytical performance of the developed colorimetric sensor was evaluated, demonstrating a limit of detection (LOD) of 1.376 μM for EP, 0.891 μM for DA, and 0.825 μM for L-DOPA, with relative standard deviation values less than 7%. In addition, to broaden the application of NFs in colorimetric sensors, a lac@MnO₂ NF-based portable agarose gel kit was designed. The developed sensing platform can be utilized for on-site detection of DA, demonstrating a low LOD of 3.33 μM and a wide detection range of 5-400 μM. These findings suggest that lac@MnO₂ NF-based colorimetric sensors hold substantial potential for future clinical and biomedical applications.