Controlling the Architecture, Coordination and Reactivity of Nanoparticle Coating Starting from an Aminoacid Precursor

We have developed a versatile strategy to prepare a series of multi-coordinating and multifunctional ligands optimized for the surface-functionalization of luminescent quantum dots (DGs) and gold nanoparticles (AuNPs) alike. Our two new sets of multi-dentate ligands can promote the dispersion of both QDs and gold nanoparticles in buffer media with colloidal stability over a broad range of conditions, while conferring compactness and biocompatibility.

The present synthetic scheme starts from L-aspartic acid to develop a versatile platform that allows the controllable coupling of one or more LA groups, one or more polyethylene glycol (PEG) moieties, along with terminal reactive groups, yielding a series of molecular-scale ligands with various architectures and selective reactivity. By attaching various combinations of lipoic acid and PEG chains on the aspartic acid, via peptide coupling chemistry, we have prepared a series of reactive ligands presenting either one PEG chain appended with multiple lipoic acid, or multiple PEG chains attached onto one lipoic acid.

Advantages:

• Offers a simpler version for preparing bis(LA-appended ligands compared to the Michael addition reaction we have previously employed
• Provides high reaction efficiency at each reaction step, the ligand synthesis can be easily scaled up and various functional groups can be attached easily
• Ligands are fully compatible with a mild photoligation strategy to promote the in-situ ligand exchange and phase transfer of hydrophobic QDs to buffer media