Design of a Fluorescent Sensor Based on the Polydopamine Nanoparticles for Detection of Gallic Acid

Gallic acid (GA) is one of the polyphenolic compounds with antioxidant, antimicrobial and radical scavenging activities, which plays a main role in human health against cancer and cardiovascular diseases. GA concentration can be quantitatively measured in food, medicinal plants and body fluids.

In this study, MnO2 nanosheets were prepared by reducing potassium permanganate in the presence of Gum Arabic. MnO2 nanosheets rapidly oxidized dopamine substrate and produced fluorescent polydopamine nanoparticles. GA could reduce MnO2 nanosheets to Mn2+, thus, the amount of MnO2 nanoparticles for the formation of polydopamine nanoparticles decreased and the
fluorescent intensity of the mixture decreased.

GA concentration depended on the reduction of fluorescence intensity of the prepared polydopamine nanoparticles. The effects of different experimental parameters such as pH, time and excitation wavelength on the designed sensor were also examined. Under optimized conditions, a good linear relationship was observed between the fluorescence intensity of the system and the concentration of GA in the range of 1.0–100 μmol L−1 with a detection limit of 0.5 μmol L−1. In addition, the developed sensor has a good selectivity on the GA detection.

Furthermore, as a sensitive and selective fluorescent probe, the polydopamine nanoparticles sensor was successfully employed for the detection of GA in real samples.