Abstract：
Ratiometric fluorescence and colorimetric strategies for detecting activity of butyrylcholinesterase (BChE) in human serum were developed by using g-C3N4 nanosheets, silver ion (Ag+) and o-phenylenediamine (OPD) as chromogenic agents. The oxidation-reduction reaction of OPD and Ag+ generates 2,3-diaminophenazine (oxOPD). Under exciation at 370 nm, g-C3N4 nanosheets and oxOPD emit fluorescence at 440 nm (F440) and 560 nm (F560), respectively. Additionally, oxOPD exhibits quenching ability towards g-C3N4 nanosheets via photoinduced electron transfer (PET) process. Thiocholine (TCh), as a product of BChE-catalyzed hydrolysis reaction of butylthiocholine iodide (BTCh), can coordinate with Ag+ intensively, and consequently diminish the amount of free Ag+ in the testing system. Less amount of free Ag+ leads to less production of oxOPD, resulting in less fluorescence quenching towards g-C3N4 nanosheets as well as less fluorescence emission of oxOPD. Therefore, by using g-C3N4 nanosheets and oxOPD as fluorescence indicators, the intensity ratio of their fluorescence (F440/F560) was calculated and employed to evaluate the activity of BChE. Similarly, the color variation of oxOPD indicated by the absorbance at 420 nm (ΔA420) was monitored for the same purpose. These strategies were validated to be sensitive and selective for detecting BChE activity in human serum, with limits of detection (LODs) of 0.1 U L-1 for ratiometric fluorescence mode and 0.7 U L-1 for colorimetric mode.
摘要：
通过使用g-C3N4纳米片开发了用于检测人血清中丁酰胆碱酯酶（BChE）活性的比率荧光和比色策略，银离子(Ag+)和邻苯二胺(OPD)作为显色剂。OPD和Ag的氧化还原反应生成2,3-二氨基吩嗪(oxOPD)。在370nm的激发下，g-C3N4纳米片和oxOPD在440nm（F440）和560nm（F560）发射荧光，分别。此外,oxOPD通过光诱导电子转移（PET）过程对g-C3N4纳米片具有猝灭能力。硫胆碱(TCh),作为BChE催化的丁基硫代胆碱碘化物（BTCh）水解反应的产物，可以与Ag+强烈协调，并因此减少测试系统中游离Ag+的量。较少的游离Ag+导致较少的oxOPD产生，导致较少的荧光猝灭对g-C3N4纳米片以及较少的荧光发射的oxOPD。因此,通过使用g-C3N4纳米片和oxOPD作为荧光指示剂，计算它们的荧光强度比(F440/F560)并用于评估BChE的活性。同样，出于相同的目的,监测由420nm处的吸光度(ΔA420)指示的oxOPD的颜色变化。这些策略被证实对检测人血清中的BChE活性是敏感和选择性的。比率荧光模式的检出限（LOD）为0.1UL-1，比色模式的检出限为0.7UL-1。
