Upconversion phosphor nanoparticles (UCNP) have recently regained copious interests due to their favorable optical characteristics. UCPs absorb multiple near-infrared (NIR) photons (980nm) and emits in visible. And because NIR is very transparent in biological samples, UCPs provide high-contrast images with deep penetration depth. Furthermore, there is no blinking or photobleaching because UCNPs rely on energy transfer between real states between two rare-earth ions. UCNP nanoparticles are, however, commonly synthesized in organic solvents and in order to use UCNPs as bioimaging agent, further surface modification is necessary to make them water-soluble. Here we report a new, efficient, and cost-effective UCNP surface modification using poly(maleic anhydride-alt-1-octadecene) (PMAO) and methoxy ethyl amine (EtOMe). In the presence of amine group on EtOMe, PMAO undergoes ring opening and creates an acyl bond. PMAO-EtOMe, an amphiphilic polymer, then goes through hydrophobic interaction with oleic acid on the surface of UCNP. We report successful conjugation, surface modification, and chemical as well as optical characterization of water-soluble UCPs through electron microscopy, Fourier transform infrared spectroscopy (FTIR), photoluminescence spectroscopy, and dynamic light scattering (DLS). PMAO-EtOMe amphiphilic polymer reaction results in an additional carboxylic group. This carboxylic group can have two functions. First, it can provide net negative charge on PMAO-EtOMe coated UCPs and second, it can be used in reaction with additional amine group. Using the first characteristic, we report a successful layer-by-layer deposition of UCPs on charged substrates. These layer-by-layer assembled UCPs can then be used to convert NIR light into visible light for the application of organic photovoltaics. With second characteristic, we conjugate PMAO-EtOMe coated UCNPs with C-225 antibody, a complement of epidermal growth factor receptor (EGFR) overly expressed on HTB9 bladder cancer cells. We provide evidence of specific binding of PMAO-EtOMe coated UCPs with HTB9 bladder cancer cells and show UCPs capability as targeted bioimaging agent.

New and efficient surface modification of NaYF4: Yb3+, Er3+ upconversion phosphor nanoparticles (UCNP) for biomedical imaging and organic photovoltaic applications

249th National Meeting (2015)

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