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A ratiometric fluorescence sensor for ultra-sensitive detection of trypsin inhibitor in soybean flour using gold nanocluster@carbon nitride quantum dots

Hu, Xuetao, Shi, Jiyong, Shi, Yongqiang, Li, Wenting, Arslan, Muhammad, Zhang, Wen, Huang, Xiaowei, Li, Zhihua, Xu, Yiwei, Li, Yanxiao, Zou, Xiaobo
Analytical and bioanalytical chemistry 2019 v.411 no.15 pp. 3341-3351
bovine serum albumin, carbon nitride, detection limit, fluorescence, gold, heat treatment, hydrolysis, nanocomposites, nanogold, quantum dots, sensors (equipment), soy flour, trypsin, trypsin inhibitors
Gold nanocluster@carbon nitride quantum dot nanocomposites protected by bovine serum albumin (BSA-AuNC@CNQDs) were designed as a ratiometric fluorescence nanosensor for ultra-sensitive detection of trypsin inhibitor (TI). CNQDs were prepared via thermal treatment of carbon nitride powder. BSA-CNQDs acted as templates to synthesize BSA-AuNC@CNQDs with dual-emission peaks at 450 and 650 nm. Trypsin can catalyze the hydrolysis of BSA and decompose BSA-AuNC@CNQDs resulting in fluorescence quenching. The fluorescence quenching at 650 nm was prevented by the addition of TI to inhibit the activity of trypsin. The nanosensor-trypsin system showed a satisfactory ability toward TI detection. The ratiometric responses (the ratio of intensity at 650 to 450 nm, I₆₅₀/I₄₅₀) had an excellent linearity (R² = 0.981) with logarithmic values of TI concentrations in the broad range of 1–10,000 ng/mL. The limit of detection (LOD, 0.089 ng/mL) indicates ultra-sensitive detection of TI can be achieved. Additionally, TI in soybean flour was detected by the proposed ratiometric method with satisfactory recoveries (98.15–105.52%) and less than 6% of coefficient of variation. This study reveals that BSA-AuNC@CNQDs have potential applications in detection of TI in real samples.