Dopamine sensing by fluorescent carbon nanoparticles synthetized by artichoke extract

Abstract

The practical and easy detection of Dopamine levels in human fluids, such as urine and saliva, is of great interest due to the correlation of Dopamine concentration with several diseases. In this work, the one-step synthesis of water-soluble carbon nanoparticles (CNPs), starting from an artichoke extract, containing catechol groups, for the fluorescent sensing of Dopamine is reported. Size, morphology, chemical composition and electronic structure of CNPs were elucidated by DLS, AFM, XPS, FT-IR, EDX and TEM microscopy. The optical properties were then explored by UV-Vis and fluorescence measurements in water. The dopamine recognition properties of these CNPs were investigated in water trough fluorescence measurements and we observed the progressive enhancement of the CNPs emission intensity upon the progressive addition of dopamine, with a binding affinity value of logK= 5.76, and a detection limit of 0.81 nM. Selectivity towards dopamine was tested over other interfering analytes commonly present in human saliva. Finally, in order to obtain a solid point of care test, CNPs were adsorbed on a solid support and exposed to different concentrations of dopamine, thus observing a pseudo linear response, using a smartphone as detector. Therefore, the detection of Dopamine in simulated human saliva was performed with excellent results, in terms of selectivity and a detection limit of 100 pM.