Subject Number : S-16-NM-0054
Support Type : 機器利用
Proposal Title (English) : Quantum dots for biological applications
Username (English) : CHINNATHAMBI SHANMUGAVEL
Affiliation (English) : JSPS

1. Summary
As light emitting quantum dots (QDs) have been a noteworthy center of innovative work amid the previous decades. In the present study, water dispersion of the CdSe/ZnS quantum dots were accomplished by their encapsulation within polyethyleneglycol (PEG)-grafted phospholipid micelles with biotin as a free end. The prepared near infra-red (NIR) QDs micelle permit photon infiltration through tissue and minimize the impacts of tissue auto fluorescence. In addition, the micelle formation reduces the cell cytotoxicity and increases the fluorescence signal in the cell. For the separation purpose we added iron oxide nanoparticle in the micelle core. This type of micelle easily uptake cancer cells without further modification, because it will enter the cancer tissue through blood vessel holes. The photo stability of micelle under ultraviolet irradiation is stronger than free CdSe/ZnS quantum dots. The interaction of micelle with human serum albumin was studied using steady state and excited state fluorescence spectroscopy and the binding parameter was obtained with various temperature. Hydrophobic force and hydrogen bond stabilized the interaction between albumin and micelle. Furthermore, we checked cell viability and cellular uptake of prepared micelles using the following cell lines HeLa, RAW 267.4 and A549. There is no notable cytotoxicity observed micelle concentration up to 25μg/mL. We observed fluorescence images of micelle using confocal laser scanning microscope. The observed fluorescence images clearly shows the high intensity of micelles after 24h incubation. This methodology demonstrates the huge guarantee of quantum dots as a part of tests for multimodal imaging and therapy.I offen used confocal microscopy for cell imaging.

2. Experimental
Confocal Microscopy, Cell Culture clean room facility and Fluorescence photometer
HeLa and A549 cells (8000 cells per cm2) were cultured in a 35 mm dish for 24 h for micelle uptake and fluorescence imaging, for which 20 mg/ml of micelle were used. Control experiments were performed under identical conditions but without adding micelles to the cultures. Cells were washed three times with phosphate-buffered saline and fixed with 3.7% paraformaldehyde for 10 min. Differential interference contrast and fluorescence images were obtained with an SP5 confocal laser scanning microscope (Leica Microsystems, Wetzlar, Germany).

3. Results and Discussion
The present study described the properties and demonstrated the application of fluorescent CdSe/ZnS QD micelles for in vitro imaging. Even at a high concentration (25 mg/mL), micelles of various surface

modification were non-toxic to HeLa and A549 cells. We used ~ 115 nm-sized micelles for in vitro imaging, since smaller particles are more readily taken up by cancer cells via blood vessels near the tumor site. Our findings indicate that CdSe/ZnS QD micelles can be useful for long-term imaging of biological samples.

4. Others
I received training from technical staff of this platform.

5. Publication/Presentation
N/A

6. Patent
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