title: Fluorescence labeling of colloidal core-shell particles with defined isoelectric points for in vitro studies.
abstract: In the light of in vitro nanotoxicological studies fluorescence labeling has become standard for particle localization within the cell environment. However, fluorescent labeling is also known to significantly alter the particle surface chemistry and therefore potentially affect the outcome of cell studies. Hence, fluorescent labeling is ideally carried out without changing, for example, the isoelectric point. A simple and straightforward method for obtaining fluorescently labeled spherical metal oxide particles with well-defined isoelectric points and a narrow size distribution is presented in this study. Spherical amorphous silica (SiO2, 161 nm diameter) particles were used as the substrate material and were coated with silica, alumina (Al2O3), titania (TiO2), or zirconia (ZrO2) using sol-gel chemistry. Fluorescent labeling was achieved by directly embedding rhodamine 6G dye in the coating matrix without affecting the isoelectric point of the metal oxide coatings. The coating quality was confirmed by high resolution transmission electron microscopy, energy filtered transmission electron microscopy and electrochemical characterization. The coatings were proven to be stable for at least 240 h under different pH conditions. The well-defined fluorescent particles can be directly used for biomedical investigations, e.g. elucidation of particle-cell interactions in vitro.
authors.affiliation: Advanced Ceramics, University of Bremen, Am Biologischen Garten 2, 28359 Bremen, Germany.
authors.forename: Timo
authors.initials: T
authors.lastname: Daberkow
authors.forename: Fabian
authors.initials: F
authors.lastname: Meder
authors.forename: Laura
authors.initials: L
authors.lastname: Treccani
authors.forename: Marco
authors.initials: M
authors.lastname: Schowalter
authors.forename: Andreas
authors.initials: A
authors.lastname: Rosenauer
authors.forename: Kurosch
authors.initials: K
authors.lastname: Rezwan
mesh_terms: D003102:Colloids / Q000737:chemistry*; D006801:Humans; D007526:Isoelectric Point; D008027:Light; D008856:Microscopy, Fluorescence; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D010316:Particle Size; D012235:Rhodamines / Q000378:metabolism; D012542:Scattering, Radiation; D012822:Silicon Dioxide / Q000737:chemistry; D013194:Staining and Labeling / Q000379:methods*
chemical_list: D003102:Colloids; D012235:Rhodamines; C026188:rhodamine 6G; D012822:Silicon Dioxide