Aqueous Cdte Quantum Dots Photoluminescence In The Cell Behavioral Research

The applications of nanomaterials and nanotechnology in biomedical field have attracted great attention in recent years.Water-soluble semiconductor fluorescent quantum dots(QDs) are considered as a very important bio-labeling material owing to their outstanding optical properties such as size-tunable emission,broad absorption and narrow symmetric emission,high photo-stability,large 2-photon absorption cross section,and etc.Recently,QDs have been widely studied in cell imaging,protein tracing,DNA assay detection,immunofluorescence assays,in vivo deep tissue and animal imaging,and so on.Combined with techniques of fluorescence resonance energy transfer(FRET),fluorescence recovery after photobleaching(FRAP), fluorescence lifetime imaging microscopy(FLIM),and etc,QDs have begun to be applied in cell biology,biochemistry and biomedicine.In fact,the technological innovations activated by QDs are far from the end.This thesis focused on the intracellular behavior of thiol-capped CdTe QDs.We have studied the dynamic distribution of subcellular QDs in living cells,the photoluminescence(PL) spectra of and PL lifetimes of intracellular QDs.The origins of the intracellular behaviors of QDs have been discussed.The main results are listed as follows:1.We studied the dynamic distribution of subcellular QDs with a laser scanning confocal microscope.By means of multiplex fluorescent labeling,we have found the co-localization of QDs with endsome/lysosomes,and more importantly,we have observed the dynamic transport process of QDs to the Golgi apparatus for the first time,which provides evidence that Golgi apparatus is also one of the main destinations of the intracellular QDs.These findings not only reveal the delivery mechanism of intracellular QDs,but may also provide a new modality to monitor the Golgi bodies with the thiol-capped QDs.2.The fluorescence quantum efficiency(QE) of intracellular QDs is a very important factor.However,it is difficult to study the QE of intracellular QDs quantitatively, because of the complicated cellular environment and non-uniform QD distribution. An alternative way is to study the PL lifetime of cellular QDs,which is not influenced by those factors and can provide information of the nonradiative decay rate,namely the QE,exactly.Besides,it is also an important parameter for other applications such as fluorescence lifetime imaging microscopy(FLIM).Based on the subcellular localization of QDs in living cells,PL lifetimes of QDs in some cell organelles were measured.It was found that the PL lifetime of intracellular QDs varied greatly depending on the complex intracellular environment.The lifetime of QDs in lysosomes was much shorter than that far away from any lysosomes.On the other hand,the PL lifetimes of QDs in living cells were generally shorter than that in the aqueous solutions with similar pH.Further investigation found that the acidic environment and the interactions between QDs and cellular biomolecules are two of the possible reasons for the shortening of PL lifetimes of intracellular QDs.