title: Stable non-covalent labeling of layered silicate nanoparticles for biological imaging.
abstract: Layered silicate nanoparticles (LSN) are widely used in industrial applications and consumer products. They also have potential benefits in biomedical applications such as implantable devices and for drug delivery. To study how nanomaterials interact with cells and tissues, techniques to track and quantify their movement through different biological compartments are essential. While radiolabels can be very sensitive, particularly for in vivo studies, fluorescent labeling has been preferred in recent years because of the array of methods available to image and quantify fluorescent nanoparticles. However, labeling can be problematic, especially if it alters the physical properties of the nanomaterial. Herein is described a novel non-covalent labeling technique for LSN using readily available fluorescent dimeric cyanine dyes without the need to use excess amounts of dye to achieve labeling, or the need for removal of unbound dye. The approach utilizes the cationic binding properties of layered silicate clays and the multiple quaternary nitrogens associated with the dyes. Preparation of YOYO-1 labeled LSN with optimal dispersion in aqueous media is presented. The utilization of the labeled particles is then demonstrated in cell binding and uptake studies using flow cytometry and confocal microscopy. The labeled LSN are highly fluorescent, stable and exhibit identical physical properties with respect to the unlabeled nanoparticles. The general approach described here is applicable to other cyanine dyes and may be utilized more widely for labeling nanoparticles that comprise a crystalline plate structure with a high binding capacity.
authors.affiliation: School of Biomedical Sciences, University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia.
authors.forename: Gysell M
authors.initials: GM
authors.lastname: Mortimer
authors.affiliation: Centre for Microscopy and Microanalysis, University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia.
authors.forename: Kevin S
authors.initials: KS
authors.lastname: Jack
authors.affiliation: Australian Institute for Bioengineering and Nanotechnology, University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia.
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Musumeci
authors.affiliation: Australian Institute for Bioengineering and Nanotechnology, University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia.
authors.forename: Darren J
authors.initials: DJ
authors.lastname: Martin
authors.affiliation: School of Biomedical Sciences, University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia.
authors.forename: Rodney F
authors.initials: RF
authors.lastname: Minchin
mesh_terms: D001583:Benzoxazoles / Q000737:chemistry; D002460:Cell Line; D005456:Fluorescent Dyes / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D018613:Microscopy, Confocal; D053758:Nanoparticles / Q000737:chemistry* / Q000378:metabolism; D011806:Quinolinium Compounds / Q000737:chemistry; D017640:Silicates
chemical_list: D001583:Benzoxazoles; D005456:Fluorescent Dyes; D011806:Quinolinium Compounds; D017640:Silicates; C075296:1,1'-((4,4,7,7-tetramethyl)-4,7-diazaundecamethylene)bis-4-(3-methyl-2,3-dihydro(benzo-1,3-oxazole)-2-methylidene)quinolinium
keywords: Fluorescence; Layered silicate nanoparticle non-covalent labeling