Sensitive detection of dopamine with ultrasound cavitation-enhanced fluorescence method

摘要

Detection of dopamine (DA) is critical to medical diagnosis, and most of existing methods require sophisticated instruments and long processing time. Although fluorimetric methods show high sensitivity and selectivity, fluorescent probes are complicated. Ultrasound cavitation occurs when liquids are irradiated with ultrasound and comprises the formation, growth, and explosive collapse of microbubbles. In this study, we found that ultrasound cavitation accelerated the formation of polyethyleneimine-polydopamine fluorescent nanoparticles (PEI-PDA NPs), thereby enhancing the sensitivity and reducing the reaction time of DA detection. Perfluorohexane nanodroplets served as exogenous cavitation nuclei and were added into the reaction system to enhance the cavitation effect. During cavitation, water molecular was split into hydroxyl and hydrogen free radicals because of the high temperature. Hydroxyl free radicals accelerated the oxidation of DA, which polymerized into PDA. PDA then reacted with PEI and formed PEI-PDA NPs. The fluorescence intensity of PEI-PDA NPs made with ultrasound cavitation was higher than that of samples treated without ultrasound. The enhanced fluorescent intensity resulted in increased sensitivity of DA detection and less time due to accelerated reaction. Under the optimized conditions, the fluorescence intensity at 525 nm and DA concentrations exhibited good linear relationship within 0.1-100 mu M. The detection limit was 25 nM. The method also showed excellent selectivity when 10 times interfering chemicals were mixed with DA. Further experiments carried out in cerebrospinal fluid indicated acceptable accuracy and reproducibility.