Dimeric-serotonin bivalent ligands induced gold nanoparticle aggregation for highly sensitive and selective serotonin biosensor.

Chemically modulating monoamine neurotransmitter serotonin undergoes a physiological reaction of enzyme intermediated peroxidation to reconstruct dimeric self-assembled complex. A standard bivalent ligand approach dimeric serotonin increases structural and functional scaffolding with recognition-binding sites that are fundamentally more friendly than monovalent binding sites. Dimerization reaction accelerates the catalytic activity of one-electron oxidation at the C(4) position of serotonin to generate dual phenolic radicals in the presence of horseradish (HRP) and hydrogen peroxide (H2O2). Herein, we suggest the dimeric serotonin-based colorimetric assay, which presents a new rapid, sensitive, selective, and quantitative visualization. The dimeric serotonin possesses the capability to recognize intermolecular interaction units that cause aggregation scaffold of gold nanoparticles (GNPs), providing inexpensive and straightforward analytical needs. As a proof of visual and spectral analysis, peroxidative dimeric serotonin demonstrated sensitive and robust results. The calorimetric method enables highly sensitive detection of serotonin in phosphate buffer, and in human serum samples at nanomolar levels with a LOD of 2.6 nM and 2.81 nM, respectively, and the sensor possesses a dynamic range of 100-300 nM in buffer condition. Also, as proof of concept, visible color imaging of immunosensors which is appropriate for fast visible testing at detection limits as low as 2.90 nM concentration.