Ultra-sensitive turn-on fluorescent sensor based on β-cyclodextrin-stabilized melamine-derived carbon dots for the highly selective dual-detection of dopamine

Abstract

Dopamine (DA) is a critical catecholamine biomolecule with distinct roles, including regulation of learning and memory, in the human brain. The cost-effective, enzyme-free, and highly stabilized fluorescent sensors for neurotransmitters (e.g., DA) are in high demand. In this regard, the development of turn-on fluorescent sensors has gained significant attention in the research field because of their high signal-to-noise ratio, in contrast to turn-off sensors. In this study, we synthesized blue-fluorescent carbon dots (CDs) from melamine and 3-carbox-yphenylboronic acid (3-CPBA) using a solid-state hydrothermal method (MPBCDs) and again modified with beta-cyclodextrin (beta-CD) by simple magnetic stirring (beta-MPBCDs). beta-MPBCDs were characterized by UV-Vis, FT-IR, XPS, HRTEM, SEM, XRD, TGA, Raman, and fluorescence measurements. In contrast to the fluorescence of beta-MPBCDs alone, the fluorescence of beta-MPBCDs combined with guest biomolecule (i.e., pyridoxal: PYL) (beta-MPBCDs-PYL), delivered better fluorescence. The host-guest interaction between beta-CD and PYL biomolecules within the beta-MPBCDs-PYL probe can induce fluorescence sensitivity against DA, which showed a good fluores-cence enhancement against DA at different concentrations (0-320 nM) with a lower detection limit of 56 pM. The intracellular sensing and practicality of the probe for DA was investigated in neuroblastoma (SH-SY5Y) cells and biological samples like human serum and cerebrospinal fluid (CSF).