title: Silica-coated Ln3+-Doped LaF3 nanoparticles as robust down- and upconverting biolabels.
abstract: The preparation of nearly monodisperse (40 nm), silica-coated LaF(3):Ln(3+) nanoparticles and their bioconjugation to FITC-avidin (FITC=fluorescein isothiocyanate) is described in this report. Doping of the LaF(3) core with selected luminescent Ln(3+) ions allows the particles to display a range of emission lines from the visible to the near-infrared region (lambda=450-1650 nm). First, the use of Tb(3+) and Eu(3+) ions resulted in green (lambda=541 nm) and red (lambda=591 and 612 nm) emissions, respectively, by energy downconversion processes. Second, the use of Nd(3+) gave emission lines at lambda=870, 1070 and 1350 nm and Er(3+) gave an emission line at lambda=1540 nm by energy downconversion processes. Additionally, the Er(3+) ions gave green and red emissions and Tm(3+) ions gave an emission at lambda=800 nm by upconversion processes when codoped with Yb(3+) (lambda(ex)=980 nm). Bioconjugation of avidin, which has a bound fluorophore (FITC) as the reporter, was carried out by means of surface modification of the silica particles with 3-aminopropyltrimethoxysilane, followed by reaction with the biotin-N-hydroxysuccinimide activated ester to form an amide bond, imparting biological activity to the particles. A 25-fold or better increase in the FITC signal relative to the non-biotinylated silica particles indicated that there is minimal nonspecific binding of FITC-avidin to the silica particles.
authors.affiliation: University of Victoria, Department of Chemistry, P.O. Box 3065, Victoria, British Columbia V8W 3V6, Canada.
authors.forename: Sri
authors.initials: S
authors.lastname: Sivakumar
authors.forename: Peter R
authors.initials: PR
authors.lastname: Diamente
authors.forename: Frank C J M
authors.initials: FC
authors.lastname: van Veggel
mesh_terms: D001360:Avidin / Q000737:chemistry; D005063:Europium / Q000737:chemistry; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives / Q000737:chemistry; D005459:Fluorides / Q000737:chemistry*; D007811:Lanthanum / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D013725:Terbium / Q000737:chemistry
chemical_list: C036963:fluorescein isothiocyante avidin; D013725:Terbium; C083668:lanthanum trifluoride; D001360:Avidin; D005063:Europium; D007811:Lanthanum; D012822:Silicon Dioxide; D016650:Fluorescein-5-isothiocyanate; D005459:Fluorides