Chemometrically assisted nanosensor for methotrexate determination in the presence of its molecular analog folic acid.

Background: Methotrexate (MTX) is an antineoplastic drug used in high doses to treat different types of cancer. Its mechanism of action relies on the structural similarities to folic acid (FA), interfering in the metabolic pathway of FA. Due to the narrow therapeutic window and high cytotoxicity, MTX therapeutic drug monitoring is mandatory in high-dose administration schemes.

Results: A new nanosensor (NS) based on luminescent silver nanoclusters (AgNC) and metallic ions was developed to selectively determine MTX in samples containing its molecular analog FA. Notably, changes in the AgNC fluorescence signal are induced in the presence of MTX and FA, and this phenomenon was exploited to develop a sensing platform for quantitating non-fluorescent MTX in the presence of FA. The selectivity and sensitivity of the NS were improved by including Al and Mg, and their concentrations were optimized by design-of-experiment and response surface methodology tools. Analysis of excitation-emission fluorescence matrices by Multivariate curve resolution-alternating least squares allowed exploiting the advantages of the analyte-induced fluorescence changes since it can cope with deviations from multilinearity occurring upon NS interaction with MTX. The sensing strategy reached limits of detection and quantitation of 0.3 μmol L and 0.9 μmol L, respectively.

Significance: These findings support the method's applicability for quantitating MTX at clinically relevant concentrations in the presence of its molecular analog, without requiring exhaustive sample pretreatment. The developed sensing platform represents a simple, selective, sensitive, and cost-effective approach for quantitating non-fluorescent MTX in the presence of FA.