Facile and sensitive detection of dopamine based on in situ formation of fluorescent polydopamine nanoparticles catalyzed by peroxidase-like ficin

Polydopamine nanoparticles (pDA NPs), a kind of popular polymer material, have been broadly applied to various areas owing to its excellent physicochemical properties. In this work, we employed ficin as a peroxidase-mimic to in situ synthesize intrinsic fluorescent pDA NPs and developed a fluorescence turn-on method for rapid dopamine (DA) sensing which is based on monitoring the intrinsic fluorescence of pDA NPs. Ficin possesses intrinsic peroxidase-like activity that could catalyze the oxidization of dopamine to its quinone derivative and autopolymerize into fluorescent pDA NPs by H2O2. Thus, the fluorescence intensity of pDA NPs gradually enhanced with increasing concentration of DA. Under the optimum conditions, the strategy showed a good linear relationship from 10 nM to 5.0 μM (R2 = 0.996) and provided an exciting detection limit of 5.5 nM. More importantly, the presented sensing approach has high sensitivity, good selectivity and has been successfully applied to DA sensing in human serum samples. With its good analytical figures of merit, our proposed analytical method is promising for the detection of DA-related diseases.