A highly selective and sensitive fluorescence probe for dopamine determination based on a bisquinoline-substituted calix[4]arene carboxylic acid derivative

Dopamine (DA) at normal levels in the human body exhibits a high potential for maintaining a proper neuron network. However, their abnormalities in humans can bring out aggressive disorders such as Schizophrenia, hypertension, Tourette's syndrome, Alzheimer's disease, bipolar depression, Parkinson's disease, drug addiction and attention-deficit hyperactivity diseases. Hence, in this study, a bis-quinoline-substituted calix[4] arene carboxylic acid derivative (Quin-Calix-CO₂H) at cone conformation was developed as an effective fluorescent sensor for the detection of a catecholamine neurotransmitter (dopamine). The structure of Quin-Calix-CO₂H was confirmed using ¹H-NMR, ¹³C-NMR, ESI-MS and elemental analysis techniques. The calixarene-based fluorescent sensor (Quin-Calix-CO₂H) has shown fluorescence emission at 404 nm under the excitation of 270 nm. Further, biomolecules binding property of Quin-Calix-CO₂H against various biomolecules such as L-cysteine (L-Cys), α-D-glucose (D-Glu), (+)-sodium-L-ascorbate (SAA), urea (UR), L-alanine (L-Ala) and dopamine (DA) exhibited that the fluorescent sensor enables selectively and sensitively detection for DA with a remarkable affinity. The probe Quin-Calix-CO₂H has shown fluorescence quenching towards DA concentration ranging from 0 to 4.0 µM with a very low limit of detection (LOD) of 88.5 nmol L^-1. In addition, the binding constant and stoichiometry as well as the mechanism of quenching have been also determined from the fluorescence data.Communicated by Ramaswamy H. Sarma.