Optimization of dye-doped silica nanoparticles prepared using a reverse microemulsion method
TL;DR: A fundamental knowledge of the synthesis and optical properties of Ru(bpy) dye-doped silica nanoparticles is provided, which can be easily manipulated, with regard to particle size and size distribution, and bioconjugated as needed for bioanalysis and bioseparation applications.
Abstract: Fluorescent labeling based on silica nanoparticles facilitates unique applications in bioanalysis and bioseparation. Dye-doped silica nanoparticles have significant advantages over single-dye labeling in signal amplification, photostability and surface modification for various biological applications. We have studied the formation of tris(2,2'-bipyridyl)dichlororuthenium(II) (Ru(bpy)) dye-doped silica nanoparticles by ammonia-catalyzed hydrolysis of tetraethyl orthosilicate (TEOS) in water-in-oil microemulsion. The fluorescence spectra, particle size, and size distribution of Ru(bpy) dye-doped silica nanoparticles were examined as a function of reactant concentrations (TEOS and ammonium hydroxide), nature of surfactant molecules, and molar ratios of water to surfactant (R) and cosurfactant to surfactant (p). The particle size and fluorescence spectra were dependent upon the type of microemulsion system chosen. The particle size was found to decrease with an increase in concentration of ammonium hydroxide and increase in water to surfactant molar ratio (R) and cosurfactant to surfactant molar ratio (p). This optimization study of the preparation of dye-doped silica nanoparticles provides a fundamental knowledge of the synthesis and optical properties of Ru(bpy) dye-doped silica nanoparticles. With this information, these nanoparticles can be easily manipulated, with regard to particle size and size distribution, and bioconjugated as needed for bioanalysis and bioseparation applications.
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TL;DR: This Review provides an introduction to nanoparticle–biomolecular interactions as well as recent applications of nanoparticles in biological sensing, delivery, and imaging of live cells and tissues.
Abstract: The wide variety of core materials available, coupled with tunable surface properties, make nanoparticles an excellent platform for a broad range of biological and biomedical applications. This Review provides an introduction to nanoparticle–biomolecular interactions as well as recent applications of nanoparticles in biological sensing, delivery, and imaging of live cells and tissues.
1,399 citations
TL;DR: The incorporation of luminescent lanthanide complexes in solid matrices with controlled structural organization is of widespread interest in materials science and has witnessed important improvements with the development of low-temperature soft chemistry solution processes, such as solgel.
817 citations
TL;DR: The evaluation of targeted nanoparticles in the treatment of cancers and diseases of the central nervous system, such as glioblastoma multiforme, neurovascular disorders, and neurodegenerative diseases, is discussed.
816 citations
TL;DR: Using these surface-modification schemes, fluorescent dye-doped silica nanoparticles can be more readily conjugated with biomolecules and used as highly fluorescent, sensitive, and reproducible labels in bioanalytical applications.
Abstract: In this article, a systematic study of the design and development of surface-modification schemes for silica nanoparticles is presented. The nanoparticle surface design involves an optimum balance of the use of inert and active surface functional groups to achieve minimal nanoparticle aggregation and reduce nanoparticle nonspecific binding. Silica nanoparticles were prepared in a water-in-oil microemulsion and subsequently surface modified via cohydrolysis with tetraethyl orthosilicate (TEOS) and various organosilane reagents. Nanoparticles with different functional groups, including carboxylate, amine, amine/phosphonate, poly(ethylene glycol), octadecyl, and carboxylate/octadecyl groups, were produced. Aggregation studies using SEM, dynamic light scattering, and zeta potential analysis indicate that severe aggregation among amine-modified silica nanoparticles can be reduced by adding inert functional groups, such as methyl phosphonate, to the surface. To determine the effect of various surface-modificati...
792 citations
TL;DR: An overview of properties and design of contrast agents such as dye-doped silica nanoparticles, quantum dots and gold nanoparticles for non-invasive bioimaging is provided.
700 citations
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TL;DR: A new molecular conjugation method has been developed to label biomolecules with optically stable metalorganic luminophores, such as tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate (Rubpy), which are otherwise not possible for direct linking with the biomolecule.
Abstract: A new molecular conjugation method has been developed to label biomolecules with optically stable metalorganic luminophores, such as tris(2,2‘-bipyridyl)dichlororuthenium(II) hexahydrate (Rubpy), which are otherwise not possible for direct linking with the biomolecules. Unique biochemical properties of the biomolecule can, thus, be associated with photostable luminophores. This opens a general way to conjugate desired biomolecules using a sensitive signal transduction method. It also promotes the application of excellent luminescent materials, especially those based on photostable metalorganic luminophores, in biochemical analysis and biomolecular interaction studies. The conjugation method is based on uniform luminophore-doped silica (LDS) nanoparticles (63 ± 4 nm). These nanoparticles have been prepared using a water-in-oil (W/O) microemulsion method. The controlled hydrolysis of tetraethyl orthosilicate (TEOS) in W/O microemulsion leads to the formation of monodisperse LDS nanoparticles. The luminophor...
758 citations
TL;DR: In this article, stable dispersions of colloidal colloidal silica spheres containing a dye or fluorophore have been synthesized according to a general procedure and dispersed in polar and apolar liquids.
Abstract: Stable dispersions of monodisperse colloidal silica spheres containing a dye or fluorophore have been synthesized according to a general procedure and dispersed in polar and apolar liquids. The procedure consists of the coupling of the dye to a silane coupling agent, (3++minopropyl)triethoxysilane, and the controllable incorporation of the reaction product into the silica sphere. The silica spheres are prepared from tetraethoxysilane in mixtures of ammonia, water, and ethanol. The composition of the silica spheres can be controlled in such a way that the organic groups can be placed on the surface, in a thin shell inside the particle or distributed through the volume of an inner core. Fluorescein isothiocyanate was used to make easily bleachable, fluorescent silica spheres. Hydrophilic charge stabilized and organophilic sterically stabilized 1-octadecanol-coated dyed silica systems were synthesized and dispersed in several solvents. All the particles were characterized after the several reaction steps by static and dynamic light scattering and transmission electron microscopy. The fluorescent spheres were further characterized by fluorescence spectroscopy and confocal scanning laser fluorescence microscopy. Great effort was taken to prepare monodisperse dispersions free of clusters of particles. Such model dispersions are required for (scattering) studies of interparticle interactions in (concentrated) systems. Therefore, the several steps of the synthesis and optical characterization are described in detail.
707 citations
TL;DR: Exchange rates of aqueous solubilisates between water droplets in a water-in-oil microemulsion stabilised by sodium bis(2-ethyl-hexyl) sulphosuccinate (AOT) have been measured as a function of droplet size, temperature and the chain length of the oil as mentioned in this paper.
Abstract: Exchange rates of aqueous solubilisates between water droplets in a water-in-oil microemulsion stabilised by sodium bis(2-ethyl-hexyl) sulphosuccinate (AOT) have been measured as a function of droplet size, temperature and the chain length of the oil The effects of additives (eg alcohols) on the exchange kinetics have also been investigated Exchange rates were measured using very fast chemical reactions as indicators for exchange Three types of reaction were investigated: proton transfer, metal–ligand complexation and electron transfer Similar exchange rates were found for all three reactions The indicator reactions involve the exchange of reactant ions of differing size and charge type; exchange rates were, however, independent of the ion transferred, but dependent on droplet size and temperature For AOT as dispersant, exchange occurs with a second-order rate constant of 106–108 dm3 mol–1 s–1, two to four orders of magnitude slower than the droplet encounter rate as predicted from simple diffusion theory The apparent activation enthalpy is high (and increases with droplet size) but is largely compensated by a positive activation entropy Exchange, on balance, is a relatively facile process which typically takes place on a millisecond timescale (depending on the droplet concentration)The exchange mechanism involves transient water droplet coalescence and separation This is the dynamic process whereby the equilibrium properties of the microemulsion, eg droplet size and polydispersity, are maintained There is a correlation between the exchange rate constants and the stability of the single-phase microemulsion This relationship between the kinetic and equilibrium properties is discussed in terms of the ‘natural curvature’ of the surfactant interface and inter-droplet interactions
435 citations
TL;DR: In this article, the authors revised the microemulsion technique with special emphasis in the mechanisms of control of particle size, namely the proper microemulsions and the control by the surfactant adsorption (capping).
Abstract: The evolution of the microemulsion technique in the last years is revised with special emphasis in the mechanisms of control of particle size, namely the control by the proper microemulsions and the control by the surfactant adsorption (capping). The kinetics of the particle formation; the possibility of the preparation of coatings, core-shell and ‘onion-like’ structures with a very precise size control; the use of microemulsions to produce fine ceramics and finally their use in the preparation of superlattices is addressed.
426 citations
402 citations