Chen Ying-Jun, Yan Xiu-Ping
Research Center for Analytical Sciences, College of Chemistry, Nankai University, Tianjin, P.R. China.
Small. 2009 Sep;5(17):2012-8. doi: 10.1002/smll.200900291.
Most of the fluorescence resonance energy transfer (FRET)-based sensors employing quantum dots (QDs) usually use organic fluorophores and gold nanoparticles as the quenchers. However, complex processes for the modification/immobilization of the QDs are always necessary, as the generation of FRET requires strict distance between the donor and acceptor. Herein, a simple chemical redox strategy for modulating the surface chemistry of the QDs to develop a QD-based turn-on fluorescent probe is reported. The principle of the strategy is demonstrated by employing CdTe QDs with KMnO(4) as the quencher and ascorbic acid as the target analyte. The fluorescence of CdTe QDs is quenched with a blue-shift upon addition of KMnO(4) due to the oxidation of the Te atoms on the surface of the QDs. The quenched fluorescence of the QDs is then recovered upon addition of ascorbic acid due to the reduction of CdTeO(3)/TeO(2) on the surface of the QDs to CdTe. The recovered fluorescence of the QDs increases linearly with the concentration of ascorbic acid from 0.3 to 10 microM. Thus, a novel QD-based turn-on fluorescent probe with a detection limit as low as 74 nM is developed for the sensitive and selective detection of ascorbic acid in biological fluids. The present approach avoids the complex modification/immobilization of the QDs involved in FRET-based sensors, and opens a simple pathway to developing cost-effective, sensitive, and selective QD-based fluorescence turn-on sensors/probes for biologically significant antioxidants.
大多数基于荧光共振能量转移（FRET）的量子点（QD）传感器通常使用有机荧光团和金纳米颗粒作为猝灭剂。然而，由于FRET的产生需要供体和受体之间严格的距离，因此量子点的修饰/固定化过程总是很复杂。在此，报道了一种简单的化学氧化还原策略，用于调节量子点的表面化学性质，以开发基于量子点的开启式荧光探针。以CdTe量子点与KMnO₄作为猝灭剂、抗坏血酸作为目标分析物，证明了该策略的原理。加入KMnO₄后，由于量子点表面的Te原子被氧化，CdTe量子点的荧光发生猝灭并蓝移。加入抗坏血酸后，由于量子点表面的CdTeO₃/TeO₂还原为CdTe，量子点猝灭的荧光得以恢复。量子点恢复后的荧光随抗坏血酸浓度从0.3到10 microM线性增加。因此，开发了一种新型的基于量子点的开启式荧光探针，其检测限低至74 nM，用于生物流体中抗坏血酸的灵敏和选择性检测。本方法避免了基于FRET的传感器中涉及的量子点复杂修饰/固定化过程，为开发具有成本效益、灵敏且选择性的基于量子点的生物重要抗氧化剂荧光开启传感器/探针开辟了一条简单途径。
