| Early detection, early diagnosis, early treatment is key to enable the cure rateincreased to83％in tumer research and clinical practice. At present, the mosteffective method of early diagnosis of cancer is to look for tumer markers throughblood tests. In this paper, photoelectrochemical biosensor and laser scanningconfocal fluorescence image were applied for the detection of thrombin and tumercells.1. Graphene should be a promising material to capture and transport electronsfrom excited QDs and serve as a potential optoelectronic scaffold in photovoltaicconversion.A novel photoelectrochemical biosensor for sensitive detection of thrombinwas developed based on amplification effect of graphene on photocurrent andphotoinduced electron transfer effect of viologen. The quantitative behavior of thephotoelectrochemical aptasensor was assessed by measuring the dependence of theincreased photocurrent intensity （I） before and after incubated with differentconcentration of thrombin. Photocurrent intensity increased as the concentration ofthrombin increased. The increase of photocurrent intensity was linearly related to theconcentration of thrombin in the range from1×10-12to4×10-11M. A detection limitof4.0×10-13M can be estimated using3σ.2. In this study, we report an efficient method to fabricate a signal-onphotoelectrochemical biosensor. Carboxyl group functionalized graphene wassynthesized to construct CdSe QDs sensitized sensing interface. Then dual-quenchedphotoelectrochemical film, achieved by electron transfer via bipyridinium relay andenergy transfer via AuNPs, largely lowered the initial signal. After removal ofbipyridinium relay and AuNPs through biorecognition event, significant signalrestore could be obtained. By integrating the signal amplifation effect of functionalized graphene and dual-quenched effect of bipyridinium relay and AuNPsin a conventional analytical strategy, thrombin could be detected sensitively, a linearrange was achieved from2.0×10-14to2.0×10-13M with a detection limit of5.9×10-15M. Furthermore, this work opens up the possibility for the design of moreefficient photoelectrochemical biosensors.3. Graphene sheets smaller than100nm, generally called graphene quantumdots（GQDs）. GQDs possess strong quantum confinement, edge effect andnon-toxicity, which make them excellent materials for the construction of nanoscaledoptical and electronic device. In this study, GQDs and folic acid are attached tomagnetic Fe3O4nanoparticle surface covalently. The multifunctional nanoparticalswere used as fluorescent probes in Hela cell imaging. The result of confocal laserscanning microscopy（LCSM） showed that composite nanoparticles could be used forintracellular delivery and fluorescence imaging successfully. This strategy can befurther used in the field of targeted drug delivery, magnetic separation of cells,analysis of cytotoxic. |
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