Controlled membrane interactions by lipid coated quantum dots

Quantum Dots (QDs) are being employed in a wide range of biological application due to their superior fluorescence characteristics. Biocompatibility of QDs is usually achieved by exchange of as-synthesized surface ligands with ligands that impart the particle with water solubility properties. An alternative approach for surface functionalization is ligand adsorption. This approach is based on weak interactions between the alkane chains of the as-synthesized surface ligands and a hydrophobic element of an adsorbed ligand with a functional head group/s. There are several advantages for this approach. (i) The photophysical properties stay intact and (ii) the weak association allows for potential adaptive re-distribution of the ligands in response to environment changes. Membrane targeting introduces another layer of complexity and requires precise control of QD’ surface properties to control the mode of interaction with the membrane (adsorption, insertion and uptake). The interplay between the hydrophobic, hydrophilic and electrostatic properties of a particle surface is crucial for controlling the mode of membrane interaction. Here we demonstrate that precise control of lipid mixture composition can modulate QDs mode of interaction with the membrane. We show compositions that favor membrane insertion and compositions that favor surface-charge dependent adsorption. We also show that the latter could be used to detect suspended malignant cells (that have different surface charge than healthy cells).