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Protein-Driven Synthesis of Transition Metal-Doped ZnS Immuno-Quantum Dots

semiconductor nanocrystals with transition
metals is an efficient route to tune emission color over a broad range of
wavelengths. We have developed a simple and environmentally friendly process
for protein-aided mineralization of transition metal doped ZnS nanocrystals. Biofabricated ZnS:Mn quantum dots (QDs)
hold particular promise for bioimaging and biosensing applications because: (1) they emit bright
yellow-orange light upon excitation with standard UV sources; (2) their core
does not incorporate cadmium ions that persist for long times in tissues; (3)
the capping protein shell incorporates an antibody-binding domain and is stably
tethered to the crystalline core through a mineralizing ZnS binding peptide; and
(4) the antigen-binding valency of the resulting nanoparticles can be controlled by
varying  the molar ratio of antibodies to
fusion protein.

ZnS Immuno-QD Highlight(A)
Schematic illustration of the QD biomineralization process mediated by the BB-TrxA::CT43 fusion
protein. Antibody-binding BB domain (red), ZnS-binding loop (green) and TrxA framework (blue) are shown. (B) Influence of Mn2+ concentration
on fluorescence. Emission (C) and absorption (D) spectra . The inset shows a
HRTEM image of a ZnS:Mn  nanocrystal. (E) Schematic illustration of the antibody conjugation
process through the BB domain (red). (F) Agarose gel analysis of immuno-complexes (a and b) at various IgG to QD ratios.


* Supported by NSF via GEMSEC, MRSEC at UW (DMR-0520567)