Spectrofluorimetric Method for Monitoring Methotrexate in Patients’ Plasma Samples and Cell Lysates Using Highly Fluorescent Carbon Dots

: For the first time, nitrogen, sulfur, phosphorus, and boron-doped carbon dots (N, S, P, B-codoped CDs) were synthesized through a hydrothermal reaction. The produced CDs were utilized to develop an optical sensor to determine methotrexate (MTX) in cell lysates and patients’ plasma samples. Basically, in the presence of MTX, the fluorescence emission of the CD-based probe was quenched. Under optimum conditions, a good proportional relationship was obtained between the quenched fluorescence signal and MTX concentrations from 74.9 ng/mL to 99.9 µg/mL with a limit of detection of 74.9 ng/mL. The developed nanoprobe provided a wide linear range and high accuracy and was successfully utilized in the routine therapeutic drug monitoring of MTX in plasma samples. The obtained results proposed the developed nanoprobe for the on-time and specific detection of MTX in blood samples. As another application, N, S, P, B-codoped CDs were utilized for bioimaging MCF-7 cancer cells and could be proposed as efficient bioimaging agents for tumor cells.