Fluorescence and UV-vis spectrophotometry: a dual-mode competitive approach for selective sensing of dopamine

The quantification of dopamine (DA) is essential due its vital role as a neurotransmitter. Here, we used a sensing strategy, which is based on competition between the DA-resorcinol (RA) reaction and resorcinol-stabilized silver nanoparticle (AgNP) formation in slightly alkaline medium. The AgNP and DA-RA reaction product formation were well characterized, specifically by transmission electron microscopy (TEM) and mass spectrometry, respectively, and also by other well-known techniques. The beauty of this sensing strategy is that the quantification of dopamine using both UV-visible and fluorescence spectrophotometry employing simple chemistry, where the RA molecule itself acts as a reducing agent and stabilizing agent for the formation of AgNPs and also selectively reacts with DA to produce fluorescent entities under alkaline conditions. A dual approach with naked-eye recognition of dopamine with an ambient light source was developed using the well-known chemistry between DA-RA and RA-AgNPs. The interference study was performed using both methods, and almost no interference observed in the fluorescence method. The strategy exhibits high selectivity and sensitivity toward DA with a wide linear range of 0.25 μM to 30 μM and a limit of quantification (LOQ) of 0.25 μM. Additionally, the assay was performed using a human urine sample. The initial assessment of dopamine by the fast colorimetric method, followed by the confirmation with a fluorescence technique, makes this strategy highly promising and thereby attracting much attention for applications.