We have developed nanoparticle coatings that are water dispersible, have a strong affinity for binding to magnetic nanoparticles, and can be easily modified for attaching the coating to biological materials. The nanoparticle coatings comprise a polyacrylic acid based backbone onto which PEG-based oligomers are appended by modifying the native carboxyl groups of the PAA backbone. The PEG-based oligomers include functional groups on their terminal ends, which are chosen to provide a certain function. Some of the terminal functional groups bind the coatings to the nanoparticle's surface, while others provide reactive sites for binding other compounds to the coating. The method we developed for making these coatings allows one to tune the number and type of PEG-based oligomers appended to the PAA backbone based on the desired properties of the coating.

In accordance with a composition aspect of the invention, the nanoparticle coatings comprise repeating polyacrylic acid monomers covalently bound together in an aliphatic chain having a plurality of carboxylic acid functional groups and modified carboxylic acid functional groups extending there from. A first portion of the modified carboxylic acid functional groups are modified by a PEG oligomer having a terminal methoxy functional group and a second portion of the modified carboxylic acid functional groups are modified by a PEG oligomer having at least one terminal catechol group.

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

Polymer Ligands for Nanoparticles Conjugation with Biomolecules

Professor Mattoussi developed polymer ligands that are optimally suited for surface-functionalizing magnetic nanoparticles. The amphiphilic polymers are prepared by coupling several amine-terminated anchoring groups, polyethylene glycol moieties, and reactive groups onto a poly(isobutylene-alt-maleic anhydride) (PIMA) chain. The reaction of maleic anhydride groups with amine-containing molecules is highly-efficient and occurs in one-step. The availability of several dopamine groups in the same ligand greatly enhances the ligand affinity, via multiple-coordination, to the magnetic NPs, while the hydrophilic and reactive groups promote colloidal stability in buffer media and allow subsequent conjugation with target biomolecules. Nanoparticles ligated with terminally reactive polymers have been easily coupled to target dyes and tested in live cell imaging with no measurable cytotoxicity.

Photo-Induced Phase Transfer of Luminescent Quantum Dots

A method for the photo-mediated phase transfer of inorganic nanocrystals, such as luminescent quantum dots, QDs, is provided. Irradiation, specifically UV excitation (?_ex<400 nm), promotes the in-situ ligand exchange of hydrophobic quantum dots with hydrophilic ligands and their facile transfer to polar solvents and buffer media. The technique enables transfer of quantum dots and other nanocrystal materials from hydrophobic to polar and hydrophilic solutions.