Surface ligand effects on metal-affinity coordination to quantum dots: implications for nanoprobe self-assembly.

The conjugation of biomolecules such as proteins and peptides to semiconductor quantum dots (QD) is a critical step in the development of QD-based imaging probes and nanocarriers. Such protein-QD assemblies can have a wide range of biological applications including in vitro protein assays and live-cell fluorescence imaging. One conjugation scheme that has a number of advantages is the self-assembly of biomolecules on a QD surface via polyhistidine coordination. This approach has been demonstrated using QDs that have different coating types, resulting in different interactions between the biomolecule and QD surface. Here, we report the use of a fluorescence resonance energy transfer (FRET) assay to evaluate the self-assembly of fluorescent proteins on the surface of QDs with eight distinct coatings, including several used in commercial preparations. The results of this systematic comparison can provide a basis for rational design of self-assembled biomolecule-QD complexes for biomedical applications.