A Long-term and Stable Surface Modification Method for Lanthanide Doped Upconversion Nanoparticles by Oxidized Alginate

Lanthanide doped upconversion luminescent nanoparticles (UCNPs) have drawn widely attention in biomedical research. The generally synthesized oleate capped UCNPs have no aqueous dispersibility so that surface modification is required to be water dispersible. Herein, we developed an easy-going but effective approach to prepare hydrophilic UCNPs based on oxidized alginate molecule (OAlg). After surface modification treatment, the OAlg modified UCNPs (UCNPs-OAlg) shows excellent dispersibility and longer stability in aqueous solution even after 180 days. After incubation with UCNPs-OAlg, the upconversion luminescent images of living Hela cells were clearly obtained. It indicated that oxidized alginate modified UCNPs can be candidate for excellent imaging probes in future.