Quantitative detection of 6-thioguanine in body fluids based on a free-standing liquid membrane SERS substrate

The adverse reactions caused by 6-thioguanine (6-TG) in anti-cancer treatment are closely related to the dose, leading to the urgent need for clinical monitoring of its concentration. In this work, a highly reproducible free-standing liquid membrane (FLM) surface-enhanced Raman spectroscopy (SERS) substrate was developed to detect 6-TG in human urine and serum quantitatively. Briefly, a prepared sample was adjusted to pH 2 and mixed with concentrated core–shell bimetallic nanoparticle (Ag core Au shell NP) suspension. The Au/Ag ratio of the Ag core Au shell NPs was optimized. Then the mixture was formed into an FLM using a custom mold. The relative standard deviation (RSD) of the experimental results can be stabilized below 10% ( n ≥ 10). The R 2 of the calibration curve in the range of 10 ~ 100 μg kg −1 was 0.988. In addition, the limit of detection (LOD) (3 σ / k ) of 6-TG was 5 μg kg −1 . The FLM SERS platform has been successfully applied to the rapid and reliable analysis of 6-TG spiked in body fluids. Graphical abstract