Self-assembly of CdSe-ZnS quantum dot bioconjugates using an engineered recombinant protein

A novel and direct method is described for conjugating protein molecules to luminescent CdSe-ZnS core-shell nanocrystals (Quantum Dots) for use as bio active fluorescent probes in sensing, imaging, immunoassay, and other diagn ostics applications. The approach makes use of a chimeric fusion protein de signed to electrostatically bind to the oppositely charged surface of cappe d colloidal quantum dots (QDs). Preparation of protein-modified QD dispersi ons with high quantum yield, little or no particle aggregation, and retenti on of biological activity was achieved. Combining the advantages of lipoic acid capped CdSe-ZnS quantum dots (photochemical stability, a wide range of size-dependent emission wavelengths, and aqueous compatibility) with facil e electrostatic conjugation of bioactive proteins, this type of hybrid bioi norganic conjugate represents a powerful fluorescent tracking tool for dive rse applications. The design and preparation of a model QD/ protein conjuga te based on E. coli Maltose Binding Protein is described, together with fun ctional characterization of this new type of nanoassembly using Luminescenc e, laser scanning microscopy, and bioassay.