Ultrasensitive SERS detection of antitumor drug methotrexate based on modified Ag substrate.

Methotrexate (MTX) is a drug with broad-spectrum antitumor activity that is of great importance in therapeutic drug monitoring applications. In this essay, the two-step modified concentrated Ag colloid with the assistance of KF and MgSO was used as the SERS active substrate for the ultrasensitive detection of MTX and its commercial formulations (tablets). It can be found that the two-step modification of the samples is a crucial procedure to remove the by-products in the synthesis of Ag colloid and further concentrate the Ag colloid. Under the optimal detection conditions, the minimum detection concentration of MTX is 1 × 10 mol/L. And, there is a good linear relationship over a wide concentration range of 1 × 10-1 × 10 mol/L. The labelled amounts of the two manufacturers of MTX commercial tablets are in the range of 96.4-104.3% with the RSDs between 1.8% and 3.5% by this method, which are in accordance with the methodological requirements. These results prove that the proposed SERS method exhibits a good reproducibility and ultra-high sensitivity for the detection of the antitumor drug MTX.