Silica-Coated CdTe Quantum Dots Functionalized with Thiols for Bioconjugation to IgG Proteins

• Published in: The journal of physical chemistry. B Vol. 110; no. 11; pp. 5779 - 5789
• Main Authors: Wolcott, Abraham, Gerion, Daniele, Visconte, Micah, Sun, Jia, Schwartzberg, Adam, Chen, Shaowei, Zhang, Jin Z
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 23.03.2006
• Subjects: Biotinylation; Boric Acids - chemistry; Cadmium Compounds - chemical synthesis; Cadmium Compounds - chemistry; Edetic Acid - chemistry; Electrophoresis, Agar Gel; Immunoglobulin G - chemistry; Immunoglobulin G - metabolism; Maleimides - chemistry; Microscopy, Atomic Force; Microscopy, Electron, Transmission; Nanotechnology - methods; Polyethylene Glycols - chemistry; Polystyrenes - chemistry; Quantum Dots; Silicon Dioxide - chemistry; Sodium Chloride - chemistry; Solubility; Streptavidin - chemistry; Sulfhydryl Compounds - chemistry; Surface Properties; Tellurium - chemistry; Tromethamine - chemistry; Water - chemistry
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp057435z

Quantum dots (QDs) have been increasingly used in biolabeling recently as their advantages over molecular fluorophores have become clear. For bioapplications QDs must be water-soluble and buffer stable, making their synthesis challenging and time-consuming. A simple aqueous synthesis of silica-capped, highly fluorescent CdTe quantum dots has been developed. CdTe QDs are advantageous as the emission can be tuned to the near-infrared where tissue absorption is at a minimum, while the silica shell can prevent the leakage of toxic Cd2+ and provide a surface for easy conjugation to biomolecules such as proteins. The presence of a silica shell of 2−5 nm in thickness has been confirmed by transmission electron microscopy and atomic force microscopy measurements. Photoluminescence studies show that the silica shell results in greatly increased photostability in Tris−borate−ethylenediaminetetraacetate and phosphate-buffered saline buffers. To further improve their biocompatibility, the silica-capped QDs have been functionalized with poly(ethylene glycol) and thiol-terminated biolinkers. Through the use of these linkers, antibody proteins were successfully conjugated as confirmed by agarose gel electrophoresis. Streptavidin−maleimide and biotinylated polystyrene microbeads confirmed the bioactivity and conjugation specificity of the thiolated QDs. These functionalized, silica-capped QDs are ideal labels, easily synthesized, robust, safe, and readily conjugated to biomolecules while maintaining bioactivity. They are potentially useful for a number of applications in biolabeling and imaging.