(747e) Tailoring Surface Charge and Hydrophicity In Colloidal Quantum Dot Biosensors

Broad and improved use of quantum dots as biosensors requires precise control over the surface chemistry to improve colloidal stability, retain desirable optical properties, and target extra- and sub-celluar structures.  We have explored a facile procedure for producing water-soluble CdSe-ZnS quantum dots having a tunable mixture of ligands bound to their surface.  This biphasic synthetic route results in quantum dots with compact hydrodynamic size which is critical for many biosensing applications.  The affinity of quantum dots for live cells and fixed tissues was investigated using fluorescence microscopy and flow cytometry.  We found that the addition of lipid molecules to the quantum dot surface resulted improved partitioning in the lipid bilayer as well as lipid-rich or hydrophobic sections of tissue. Additionally, the net charge was seen to strongly influence the binding characteristics of quantum dots.  Overall, the interplay between these characteristics results in a complex interaction mechanism suggesting that quantum dots can be engineered to target specific regions of cells and tissues by varying fundamental surface parameters.