title: Design of poly(ethylene glycol)/streptavidin coimmobilized upconversion nanophosphors and their application to fluorescence biolabeling.
abstract: Infrared-to-visible upconversion phosphors (i.e., rare earth ion-doped Y2O3 nanoparticles (UNPs)) were synthesized by the homogeneous precipitation method. Because the charge on the erbium (Er) ion-doped Y2O3 (Y2O3:Er) NP (UNP1) surface is positive under neutral conditions, the UNP1 surface was electrostatically PEGylated using negatively charged poly(ethylene glycol)- b-poly(acrylic acid) (PEG- b-PAAc). The adsorption of PEG- b-PAAc was confirmed by Fourier transform infrared (FT-IR) measurements and thermal gravimetric analysis (TGA). The surface charge of the PEGylated UNP1s (PEG-UNP1s) was effectively shielded by the PEGylation. The dispersion stability of the UNP1s was also significantly improved by the PEGylation. The PEG-UNP1s were dispersed over 1 week under physiological conditions as a result of the steric repulsion between the PEG chains on the UNP1 surface. The upconversion emission spectrum of PEG-UNP1s was observed under physiological conditions and was confirmed by near-infrared excited fluorescence microscope observation. Streptavidin (SA)-installed ytterbium (Yb) and Er ion-codoped Y2O3 (Y2O3:Yb,Er) NPs (UNP2s) were prepared by the coimmobilization of PEG- b-PAAc and streptavidin. The PEG/SA coimmobilized UNP2s (PEG/SA-UNP2s) specifically recognized biotinylated antibodies and emitted strong upconversion luminescence upon near-infrared excitation. The obtained PEG/streptavidin coimmobilized UNPs are promising as high-performance near-infrared biolabeling materials.
authors.affiliation: Graduate School of Pure and Applied Sciences, University of Tsukuba, Tennoudai, Tsukuba, Ibaraki, Japan.
authors.forename: Masao
authors.initials: M
authors.lastname: Kamimura
authors.forename: Daisuke
authors.initials: D
authors.lastname: Miyamoto
authors.forename: Yu
authors.initials: Y
authors.lastname: Saito
authors.forename: Kohei
authors.initials: K
authors.lastname: Soga
authors.forename: Yukio
authors.initials: Y
authors.lastname: Nagasaki
mesh_terms: D004871:Erbium / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D010087:Oxides / Q000737:chemistry; D010316:Particle Size; D010758:Phosphorus / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D019809:Streptavidin / Q000737:chemistry*; D013499:Surface Properties; D015018:Ytterbium / Q000737:chemistry
chemical_list: D005456:Fluorescent Dyes; D010087:Oxides; C093389:erbium oxide; D010758:Phosphorus; D011092:Polyethylene Glycols; D004871:Erbium; D019809:Streptavidin; D015018:Ytterbium