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

In recent years, quantum dots (QDs) and the design of probe devices based on QDs have attracted much attention in the scientific community [1]. Because QDs have poor selectivity, these should be modified with appropriate materials. Molecular imprinting is an easy and inexpensive method for modification of QDs [2]. In this work, molecularly imprinted polymers (MIPs) on the surface of cadmium telluride quantum dots (CdTe QDs) was used for simultaneous detection of folic acid (FA) and methotrexate (MTX). First, two different sizes of CdTe QDs with emission peaks in yellow (QDY) and orange (QDO) spectral regions were synthesized [3] and then capped with MIPs [4]. FA and MTX were used as templates for synthesis of QDY-MIPs and QDO-MIPs, respectively. For characterization of QDY-MIPs and QDO-MIPs, Fourier transform infrared spectroscopy, transmission electron microscopy and fluorescence spectroscopy were employed. The mixture of QDY-MIPs and QDO-MIPs (QDs-MIPs) were excited in the identical excitation wavelength and showed two different emission wavelengths without spectral overlap. The fluorescence intensity of QDY-MIPs and QDO-MIPs diminished linearly with increasing the concentration of the corresponding template molecules. Under the optimal conditions, the dynamic range was 0.5-20 μmol L-1 for FA and MTX and the limit of detection 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 μmol L-1 of FA and MTX, and the results showed RSD% as 4.2 and 6.3, respectively. Finally, the applicability of the method was checked using human blood plasma samples. The results showed that the method could be used as a fluorescent probe to detect FA and MTX rapidly in real samples.