Simultaneous detection of folic acid and methotrexate by an optical sensor based on molecularly imprinted polymers on dual-color CdTe quantum dots

In this work, molecularly imprinted polymers (MIPs) were used on the surface of cadmium telluride quantum dots (CdTe QDs) for the simultaneous determination of folic acid (FA) and methotrexate (MTX). For this purpose, two different sizes of CdTe QDs with emission peaks in the yellow (QD(Y)) and orange (QD(O)) spectral regions were initially synthesized and capped with MIPs. FA and MTX were used as templates for the synthesis of the two composites and designated as QD(Y)-MIPs and QD(O)-MIPs, respectively. Fourier transform infrared spectroscopy, transmission electron microscopy, and fluorescence spectroscopy were employed to characterize the composites. QD(Y)-MIPs and QD(O)-MIPs were then mixed (to form QDs-MIPs) and excited at identical excitation wavelengths; they emitted two different emission wavelengths without any spectral overlap. The fluorescence signals of QD(Y)-MIPs and QD(O)-MIPs diminished in intensity with increasing concentration of the corresponding template molecules. Under optimal conditions, the dynamic range was 0.5-20 mu mol L-1 for FA and MTX, and the detection limits for FA and MTX were 32.0 nmol L-1 and 34.0 nmol L-1, respectively. The reproducibility of the method was checked for 12.5 mu mol L-1 of FA and MTX to find RSD values of 4.2% and 6.3%, respectively. Finally, the applicability of the method was checked using human blood plasma samples. Results indicated the successful application of the method as a fluorescent probe for the rapid and simultaneous detection of FA and MTX in real samples. (C) 2017 Elsevier B.V. All rights reserved.