Shen Jiang-Shan, Yu Tao, Xie Jian-Wei, Jiang Yun-Bao
Department of Chemistry, Xiamen University, China.
Phys Chem Chem Phys. 2009 Jul 7;11(25):5062-9. doi: 10.1039/b900053d. Epub 2009 Mar 26.
A nanohybrid consisting of water-soluble thioglycolic acid (TGA)-capped CdTe nanocrystals (NCs) and methylene blue (MB) was designed as a label-free luminescent signaling platform for DNA. This sensing system was identified to operate under the photoinduced electron transfer (PET) mechanism in which MB is the electron acceptor and the binding site for the designated target molecule DNA. We showed that MB bound with TGA-capped CdTe NCs via strong electrostatic interactions resulted in an efficient quenching of the photoluminescence (PL) of NCs. Steady-state and time-resolved PL, and electron paramagnetic resonance (EPR) experiments established the quenching pathway of PET from the conduction band (CB) of NCs to the ground state of MB. In the presence of the target molecule DNA, the MB-quenched PL of NCs could be reversibly restored by double-stranded DNA as the PET pathway is blocked when MB is taken away from the NCs surface due to its intercalation into, and electrostatic interaction with, DNA. The platform was successfully applied for sensing DNA and signaling DNA hybridization by switching the PET process. Such a nanohybrid represents a robust PET luminescent nanosensor that is, in principle, applicable for other species by employing suitable electron acceptors as binding sites.
一种由水溶性巯基乙酸（TGA）包覆的碲化镉纳米晶体（NCs）和亚甲基蓝（MB）组成的纳米杂化物被设计为一种用于DNA的无标记发光信号平台。该传感系统被确定在光诱导电子转移（PET）机制下运行，其中MB是电子受体以及指定目标分子DNA的结合位点。我们表明，通过强静电相互作用与TGA包覆的CdTe NCs结合的MB导致了NCs光致发光（PL）的有效猝灭。稳态和时间分辨PL以及电子顺磁共振（EPR）实验确定了从NCs的导带（CB）到MB基态的PET猝灭途径。在目标分子DNA存在的情况下，由于MB通过插入DNA并与之发生静电相互作用而从NCs表面被带走，PET途径被阻断，因此双链DNA可以使MB猝灭的NCs的PL可逆地恢复。该平台通过切换PET过程成功地应用于检测DNA和指示DNA杂交。这种纳米杂化物代表了一种强大的PET发光纳米传感器，原则上通过使用合适的电子受体作为结合位点可应用于其他物种。
