A sensitive colorimetric probe for detection of 6-thioguanine based on its protective effect on the silver nanoprisms

In this work a non-aggregated colorimetric probe for detection of chemotherapeutic drug, 6-thioguanine (6-TG), is introduced. It is based on the protective effect of 6-TG on silver nanoprisms (AgNPRs) against the iodide-induced etching reaction. Iodide ions can attack the corners of AgNPRs and etch them, leading to the morphological transition from nanoprisms to nanodiscs. As a consequence, the solution color changes from blue to pink. However, in the presence of 6-TG, due to its protective effect on the corners of AgNPRs, I^- ions cannot etch the prisms and the blue color of solution remains unchanged. Using this effect, selective sensor was designed for detection of 6-TG in the range of 2.5-500 μg L^-1, with a detection limit of 0.95 μg L^-1. Since with varying the concentration of 6-TG in this range, the color variation from pink to blue can be easily observed, the designed sensing scheme can be used as a colorimetric probe. The method was used for analysis of human plasma samples.