Abstract
The early detection of HER2 (human epidermal growth factor receptor 2) status in breast cancer patients is very important for the effective implementation of anti-HER2 antibody therapy. Recently, HER2 detections using antibody conjugated quantum dots (QDs) have attracted much attention. QDs are a new class of fluorescent materials that have superior properties such as high brightness, high resistance to photo-bleaching, and multi-colored emission by a single-light source excitation. In this study, we synthesized three types of anti-HER2 antibody conjugated QDs (HER2Ab-QDs) using different coupling agents (EDC/sulfo-NHS, iminothiolane/sulfo-SMCC, and sulfo-SMCC). As water-soluble QDs for the conjugation of antibody, we used glutathione coated CdSe/CdZnS QDs (GSH-QDs) with fluorescence quantum yields of 0.23∼0.39 in aqueous solution. Dispersibility, hydrodynamic size, and apparent molecular weights of the GSH-QDs and HER2Ab-QDs were characterized by using dynamic light scattering, fluorescence correlation spectroscopy, atomic force microscope, and size-exclusion HPLC. Fluorescence imaging of HER2 overexpressing cells (KPL-4 human breast cancer cell line) was performed by using HER2Ab-QDs as fluorescent probes. We found that the HER2Ab-QD prepared by using SMCC coupling with partially reduced antibody is a most effective probe for the detection of HER2 expression in KPL-4 cells. We have also studied the size dependency of HER2Ab-QDs (with green, orange, and red emission) on the fluorescence image of KPL-4 cells.
Highlights
Tumor cells show overexpression of HER2 in approximately 20%−30% of breast cancer patients [1,2]
We have synthesized three types of HER2Ab-quantum dots (QDs) based on Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC)/sulfo-NHS, iminothiolane/sulfoSMCC, and sulfo-SMCC coupling reactions for fluorescence imaging of HER2 overexpressing cancer cells
atomic force microscopy (AFM) images of the HER2Ab-QDs indicate that the number of antibody molecules conjugating to the QD surface is limited by the steric hindrance between antibody molecules
Summary
Tumor cells show overexpression of HER2 (human epidermal growth factor receptor 2) in approximately 20%−30% of breast cancer patients [1,2]. Anti-HER2 antibodies inhibit the growth of HER2-overexpressing breast cancer cells, and the anti-HER2 antibody therapy is most effective in HER2-positive breast cancer patients [3,4,5]. The early detection of HER2 status in breast cancer patients is crucial for the effective implementation of anti-HER2 antibody therapy. Immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) are the most widely used methods for determining HER2 status in breast cancer patients [6]. FISH analysis is more sensitive and quantitative than IHC in determining HER2 status, this method is complicated, expensive and time-consuming [9,10]
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