Upconversion nanoparticles (UCNPs) have been widely used for drug delivery, analytical sensing, and theranostics. The properties of anti-Stokes optical upconversion and in-situ generation of ultraviolet (UV) light are particularly well suited for applications in nanomedicine. However, applications in such fields have been hindered by poor colloidal stability in physiologically relevant aqueous buffers, like phosphate buffered saline (1×PBS). Typically, the stability of UCNPs in 1×PBS has been on the order of a few days to weeks, and long-term stability (&gt; 3 months) has not been readily achieved. Motivated by this challenge, a systematic investigation was done to identify polymeric nanoparticle overcoating chemistries capable of imparting long-term colloidal stability. Co-polymers comprised a poly(isobutylene-alt-maleic anhydride) (PIMA) backbone functionalized with phosphonate-based anchoring groups and polyethylene glycol (PEG; MW of 750 g mol-1) moieties were prepared at various grafting ratios and with different anchoring group denticities. Of these co-polymers, two variants were identified that provided &gt; 3 months of colloidal stability to UCNPs (1 mg mL-1) in 1×PBS, and these were the formulations that contained the greatest number of surface anchoring groups. Incorporation of Cy3 dye molecules and folic acid by copper-free click chemistry was also investigated for imaging and controlling cellular uptake of UCNPs by U87-MG cells.

Upconversion nanoparticles coated with phosphonate-based polymers have long-term colloidal stability in aqueous buffers

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.