A pluronic F127 coating strategy to produce stable up-conversion NaYF4:Yb,Er(Tm) nanoparticles in culture media for bioimaging

Abstract

Up-conversion nanoparticles (UCNPs) have exhibited great potential in biological imaging and labeling. The further development of the correlated techniques strongly depends on the stability of UCNPs in buffers and biological growth media. In this paper, Pluronic F127, a nonionic triblock copolymer of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-b-PPO-b-PEO), is applied to coat the originally hydrophobic NaYF₄:Yb,Er(Tm) UCNPs, leading to an oil-to-water phase transfer. After the phase transfer, F127-coated UCNPs are well dispersed in water with more than 43% UC luminescence preserved. Because of the nonionic nature of F127, the F127-coated UCNPs are quite stable in culture media, and exhibit excellent biocompatibility and low toxicity. The biocompatible decoration using F127 is facile and repeatable, thus facilitating the biological applications of UCNPs. As an example, the bioimaging of caenorhabditis elegans is demonstrated.