Semiconductor quantum dots bioconjugation

Scope and method of study. The goal of this study was the development of novel bioconjugation approaches using different semiconductor materials: cadmium telluride (CdTe) and core/shell cadmium selenide/cadmium sulfide (CdSe/CdS) quantum dots (QDs). This dissertation addresses the following concerns: (1) designing hydrophilic QDs that are luminescent, with surface chemistry adaptable to varied biological applications; (2) developing versatile techniques for selectively and specifically labeling cells and biomolecules; and (3) demonstrating that quantum dots do not interfere with normal physiology.; Finding and conclusions. Different QD-biomolecule conjugation approaches have been developed. Conjugates of bovine serum albumin (BSA) and CdTe QDs capped with L-cysteine have been synthesized via a one-pot glutaric dialdehyde cross-linking procedure. Also, complementary bioconjugates based on antibody-antigen interactions were synthesized from luminescent CdTe QDs. Antigen (BSA) was conjugated to red-emitting CdTe QDs, while green-emitting QDs were attached to the corresponding anti-BSA antibody (IgG). The formation of BSA-IgG immunocomplex resulted in the Forster resonance energy transfer (FRET) between the two different QDs: the luminescence of green-emitting QDs was quenched whereas the emission of the red-emitting QDs was enhanced. The immunocomplexes can be considered as a prototype of QD superstructures based on biospecific ligands, while the competitive FRET inhibition can be used in an immunoassay protocol. The developed bioconjugation procedures were combined in order to design new conjugates for cell targeting that are photo stable, water soluble and biocompatible. Obtained bioconjugates were applied for cell labeling by our collaborators at University of Texas Medical Branch (Galveston, TX).