Design of a ratiometric fluorescence nanoprobe to detect plasma levels of levodopa

摘要

Simply obtained by the oxidation of levodopa in alkaline media, polylevodopa nanoparticles are able to quench the fluorescence emission of CdTe quantum dots (QDs) via energy transfer mechanism. The extent of this quenching can be exploited for the quantification of levodopa, as an important therapeutic agent in the treatment of Parkinson's disease. However, to effectively improve the detection performance, in this study, we have designed a ratiometric probe by making use of variations in both the emission of QDs and the intrinsic emission of polylevodopa nanoparticles. The enhanced sensitivity, in particular, arose from the measurement of the ratio of fluorescence intensities at two different wavelengths, by which the resulting signal was totally analyte-dependent and free from environmental effects. The built-in self-calibration in this ratiometric approach led to a remarkable detection limit of 18.3 nmol L-1, without interruption from possible interferences. The proposed ratiometric nanoprobe not only proved to be highly selective, but also showed to be capable of successively detecting levodopa in complex biological fluids such as plasma, in which possible interferences are usually likely to affect the detection results.