Higher Educational Key Laboratory for Nano Biomedical Technology of Fujian Province, Department of Pharmaceutical Analysis , Fujian Medical University , Fuzhou , Fujian 350004 , China.
Fujian Key Laboratory of Drug Target Discovery and Structural and Functional Research, School of Pharmacy , Fujian Medical University , Fuzhou , Fujian 350004 , China.
Anal Chem. 2020 Jan 21;92(2):2019-2026. doi: 10.1021/acs.analchem.9b04434. Epub 2020 Jan 2.
Donor-linker-acceptor (D-L-A)-based photoinduced electron transfer (PET) has been frequently used for the construction of versatile fluorescent chemo/biosensors. However, sophisticated and tedious processes are generally required for the synthesis of these probes, which leads to poor design flexibility. In this work, by exploiting a Schiff base as a linker unit, a covalently bound D-L-A system was established and subsequently utilized for the development of a PET sensor. Cysteamine (Cys) and N-acetyl-l-cysteine (NAC) costabilized gold nanoclusters (Cys/NAC-AuNCs) were synthesized and adopted as an electron acceptor, and pyridoxal phosphate (PLP) was selected as an electron donor. PLP can form a Schiff base (an aldimine) with the primary amino group of Cys/NAC-AuNC through its aldehyde group and thereby suppresses the fluorescence of Cys/NAC-AuNC. The Rehm-Weller formula results and a HOMO-LUMO orbital study revealed that a reductive PET mechanism is responsible for the observed fluorescence quenching. Since the pyridoxal (PL) produced by the acid phosphatase (ACP)-catalyzed cleavage of PLP has a weak interaction with Cys/NAC-AuNC, a novel turn-on fluorescent method for selective detection of ACP was successfully realized. To the best of our knowledge, this is the first example of the development of a covalently bound D-L-A system for fluorescent PET sensing of enzyme activity based on AuNC nanoprobes using a Schiff base.
供体-连接体-受体（D-L-A）型光诱导电子转移（PET）已广泛用于构建多功能荧光化学/生物传感器。然而，这些探针的合成通常需要复杂和繁琐的过程，这导致设计灵活性较差。在这项工作中，通过利用席夫碱作为连接单元，建立了一个共价键合的 D-L-A 体系，并随后用于开发 PET 传感器。半胱氨酸（Cys）和 N-乙酰-L-半胱氨酸（NAC）稳定的金纳米簇（Cys/NAC-AuNC）被合成并用作电子受体，而吡哆醛磷酸（PLP）被选为电子供体。PLP 可以通过其醛基与 Cys/NAC-AuNC 的伯氨基形成席夫碱（亚胺），从而抑制 Cys/NAC-AuNC 的荧光。Rehm-Weller 公式结果和 HOMO-LUMO 轨道研究表明，观察到的荧光猝灭是由还原型 PET 机制引起的。由于酸性磷酸酶（ACP）催化 PLP 裂解产生的吡哆醛（PL）与 Cys/NAC-AuNC 相互作用较弱，因此成功实现了用于选择性检测 ACP 的新型开启型荧光方法。据我们所知，这是第一个使用席夫碱基于 AuNC 纳米探针开发用于荧光 PET 感测酶活性的共价键合 D-L-A 系统的例子。
