Biocompatible Surface Coated Quantum Dots For Live Cell Imaging and Early Cancer Detection, 10-9536

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Principal Investigators
Jian Ling
Hong Dixon

Inclusive Dates:  04/01/05 – 04/01/06

Background - Quantum dots (Qdots) are manmade semiconductor CdSe-ZnS fluorescence nanoparticles, which are currently being developed for live-cell and in vivo imaging. Qdots are brighter, more stable, and more spectrally distinct than traditional organic fluorescent dyes. These properties make Qdots especially suitable for long-term live-cell imaging. The critical problems that need to be solved before live-cell imaging will become practical are 1) the potential toxicity of CdSe, 2) the capability of live-cell internalization of Qdots, and 3) the feasibility of conjugating Qdots to antibodies for the labeling of intracellular biomarkers (proteins related to a specific disease). 

Approach - The objective of this project is to develop biocompatible surface-coated Qdots for live-cell imaging and for tumor cell detection. Commercially available water soluble and biocompatible Qdots will be modified to facilitate their internalization by cells. The method of conjugation between the Qdots and antibodies will be developed. These antibodies target the intracellular biomarkers, which are highly expressed in tumor cells but not in normal cells. The Qdot-conjugated antibodies will be tested on normal and tumor cell lines. Long-term time-lapse images will be recorded from the live cells after being exposed to the Qdot conjugated antibodies. It is expected that more Qdot-conjugated antibody will be internalized by tumor cells than by normal cells. In addition, the Qdots will be distributed specifically to the locations where the biomarkers are expressed. 

Accomplishments - A temperature-controlled chamber was integrated into the Nikon 2000E microscope system for long-term live cell imaging. The Qdots were successfully conjugated with antibodies. A live cell experiment was conducted. The tumor cell line called SiHa was used in the experiment. The cells were stained with the Qdot 655-conjugated antibody. The red fluorescence emitted from Qdots determines the antibody locations. The following figure illustrates the cells before, during, and after the staining of the Qdot conjugated antibody. Before the staining, the image shows no red fluorescence either inside or outside the cells. During the staining, the image shows that the Qdot 655-conjugated antibody is present in the solution outside the cells. After the staining, the Qdot solution outside the cells was washed out. Image "c" illustrates that the cells have internalized the Qdot-conjugated antibody. An AVI video following the link o:\Div10\J. Ling\QdotsImaging\LiveCellQdotsImaging.avi illustrates the cell staining process. In the images between 11:18 through 11:20, no Qdot solution was present. In the images between 11:21 through 12:03, the cells were stained with the Qdot-conjugated antibody. In the images between 12:06 through 14:03, the Qdot solution outside the cells were washed out, and the Qdot-conjugated antibody was internalized by the live cells. 

(a) Before Staining Process      (b) During Staining Process         (c) After Staining Process

The distribution of red fluorescence Qdot-conjugated antibody inside or outside the live SiHa cells before, during, and after the staining process. The Qdot-conjugated antibody was internalized by the live cancer cells.

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