Lactose tailored boronic acid conjugated fluorescent gold nanoclusters for turn-on sensing of dopamine

Dopamine being a neurotransmitter and chemical messenger plays a vivacious role in a number of significant medical conditions like Parkinson's disease, Attention Deficit Hyperactivity Disorder, Schizophrenia, and drug addiction. As turn-on sensors have a superior level of selectivity than fluorescence quenching based sensors, we developed a fluorescence retrieval strategy for dopamine sensing. Here, highly fluorescent amino phenyl boronic acid (APBA)aEuro'conjugated gold nanocluster (AuaEuro'BSAaEuro'APBA probe) has been synthesised from bovine serum albuminaEuro'protected gold nanocluster (AuaEuro'BSA NCs). Boronic acid forms boronate ester with disaccharides such as lactose due to its affinity to polyols. Hence fluorescence of AuaEuro'BSAaEuro'APBA probe is quenched when it binds with lactose molecules through boronate ester formation. The fluorescence of AuaEuro'BSAaEuro'APBAaEuro'lactose system can be retrieved (turn-on) with dopamine by the competitive displacement of lactose from the probe surface which suggests the higher affinity of boronic acid to the catechol group of dopamine. Furthermore, real samples spiked with dopamine including human serum and urine were analysed using this turn-on sensor and showed excellent recovery percentage. The developed fluorescent sensor offered high selectivity for dopamine over other catecholamines and aminoacids with detection limit as low as 0.7 mu M.