Multifunctional amino acids empowering bifunctional biosensing platform for depression study.

Poor availability of objective approaches hinders effective diagnosis and treatment for depression. Biosensors provide a promising platform for the development of quantitative and practical methods for disease detection, as well as for drug discovery. Here, we developed an electrochemical biosensor has been established with the ability to simply and accurately detect the trace glucocorticoid receptor alpha (GRα), as a key biomarker of depression, in both hippocampus and blood cells. The integration of amino-ion graphene oxide (IL-rGO) and amino acid-coated gold nanoparticles (AA-AuNPs) via green synthesis remarkably magnifies the electrochemical signals, where amino acids play multiple roles as reducing agents, stabilizers, and bridging agents. After the optimization among AA-AuNPs@IL-rGO nanocomposites based on five typical amino acids, a biosensing surface has been constructed to implement analysis in real samples as a bifunctional platform. The obtained biosensor exhibited a remarkably low limit of detection (0.283 pg mL-1) and could thus sensitively identify the GRα differences in healthy and depressive rats with and without fluoxetine. The electrochemical biosensor developed herein was not only outstandingly sensitive but also simple to use and labor-saving, making it a promising all-in-one platform for depression diagnosis and drug discovery.