Application of sulfur and nitrogen doped carbon quantum dots as sensitive fluorescent nanosensors for the determination of saxagliptin and gliclazide

In this study, highly fluorescent sulfur and nitrogen doped carbon quantum dots (S,N-CQDs) were used as fluorescent nanosensors for direct spectrofluorimetric estimation of each of gliclazide and saxagliptin without any pre-derivatization steps for the first time. S,N-CQDs were synthesized employing a simple hydrothermal technique using citric acid and thiosemicarbazide. The produced S,N-CQDs were characterized using different techniques including fluorescence emission spectroscopy, UV spectrophotometry, high resolution transmission electron microscopy, and FT-IR spectroscopy. Following excitation at 360 nm, S,N-CQDs exhibited a strong emission peak at 430 nm. The native fluorescence of S,N-CQDs was quantitatively enhanced by addition of increased concentrations of the studied drugs. The fluorescence enhancement of S,N-CQDs and the concentrations of the studied drugs revealed a wide linear relationship in the range of 30.0-500.0 μM and 75.0-600.0 µM with limits of detection of 5.0 μM and 10.15 µM for gliclazide and saxagliptin, respectively. The proposed method was efficiently utilized for determination of cited drugs in their commercial tablets with % recoveries ranging from 98.6 to 101.2% and low % RSD values (less than 2%). The mechanism of interaction between S,N-CQDs and the two drugs was studied. Validation of the proposed method was carried out in accordance with ICH guidelines.

本研究首次采用高荧光硫氮掺杂碳量子点(S,N-CQDs)作为荧光纳米传感器，无需任何预衍生步骤，即可直接通过荧光分光光度法分别测定格列齐特(gliclazide)与沙格列汀(saxagliptin)的含量。硫氮掺杂碳量子点以柠檬酸和氨基硫脲为原料，通过简便的水热法合成。所制备的硫氮掺杂碳量子点采用多种技术进行表征，包括荧光发射光谱、紫外分光光度法、高分辨透射电子显微镜以及傅里叶变换红外光谱(FT-IR)。在360 nm波长激发下，硫氮掺杂碳量子点在430 nm处呈现出强发射峰。随着所考察药物浓度的升高，硫氮掺杂碳量子点的本征荧光被定量增强。硫氮掺杂碳量子点的荧光增强强度与所考察药物的浓度呈现出良好的线性关系：格列齐特的线性范围为30.0~500.0 μM，检出限为5.0 μM；沙格列汀的线性范围为75.0~600.0 μM，检出限为10.15 μM。所建立的方法可有效用于市售片剂中上述两种药物的含量测定，回收率为98.6%~101.2%，相对标准偏差(RSD)低于2%。本研究还探讨了硫氮掺杂碳量子点与两种药物之间的相互作用机制。本方法按照人用药品注册技术要求国际协调会(ICH)指南完成了方法学验证。