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

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).

Automated summary

In this study, fluorescent sensors with high stability and sensitivity were synthesized, and fluorescence enhancement was observed through interaction with specific biomolecules, facilitating the detection of dopamine. The sensors demonstrated good performance in detecting dopamine in neuronal cells and human samples.