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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)-conjugated gold nanocluster ( Au-BSA-APBA probe) has been synthesised from bovine serum albumin-protected gold nanocluster ( Au-BSA NCs). Boronic acid forms boronate ester with disaccharides such as lactose due to its affinity to polyols. Hence fluorescence of Au-BSA-APBA probe is quenched when it binds with lactose molecules through boronate ester formation. The fluorescence of Au-BSA-APBA-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 μM. [ABSTRACT FROM AUTHOR]

Schematic Representation of developed fluorescent "Turn-off" sensor for the detection of bilirubin. [Display omitted] • Bright green Tb-DPA luminescent complex was designed. • Tb-DPA act as a luminescent probe for the detection of bilirubin. • Selectivity and sensitivity with other coexisting biomolecules were evaluated. • Real sample analysis is performed in human serum and urine samples and obtained satisfactory result. The sensitive and selective fluorescent probes for biomolecule detection have significant application in clinical diagnosis and bioanalysis. Hyperbilirubinemia is a disease condition in which the excessive or less production of bilirubin in blood resulting in jaundice. In this work, we have synthesised Terbium based bright green, fluorescent lanthanide complex (Tb-DPA) with emission at λ em = 544 nm for the detection of Bilirubin. A one-step synthesis approach was adopted with 2,6-pyridine dicarboxylic acid (DPA) as ligand and Sodium dodecyl sulphate (SDS) as surfactant. The green fluorescence of Tb-DPA was quenched with the addition of bilirubin due to the inner filter effect mechanism. The fluorescence intensity of Tb-DPA decreases as bilirubin concentration increases and a linear " turn-off " response is obtained. Even in presence of other coexisting biomolecules and ions, the Tb-DPA probe exhibited good selectivity and sensitivity for the detection of bilirubin. The limit of detection (LOD) of 2.6 mg/dL was obtained. Furthermore, the proposed fluorescent probe was applied in Human serum and urine samples with satisfactory recoveries in the range of 92–122 %. Based on the result obtained, it has probability to be used as a rapid detection method for bilirubin in biological samples at bedside. [ABSTRACT FROM AUTHOR]