Dye-doped silica nanoparticles

Dye doped silica nanoparticles are conventional biological dyes encapsulated in a ceramic matrix to protect them from oxygen, enhance chemical stability, and allows the surface of the nanoparticle to be modified to enhance the hydrophilic qualities and improve cell uptake [37],... 

Silica particles have been exploited in virtually every assay or detection strategy that polymer particles have been used in for bioapplication purposes. Recently, fluorescent dye-doped silica nanoparticles have been developed by a number of groups that have similar fluorescence characteristics to quantum dot nanocrystals (Chapter 9, Section 10). Fluorescent silica nanoparticles can be synthesized less expensively than quantum dots due to the fact that the silica particles incorporate standard organic dyes (Ow et al., 2005 Wang et al., 2006) and are not dependent on making reproducible populations of semiconductor particles with precise diameters to tune emission wavelengths. 

Santra, S., Wang, K., Tapec, R., and Tan, W. (2001) Development of novel dye-doped silica nanoparticles for biomarker application./. Biomed. Optics 6, 160-166. 

An overview on the synthesis and biomedical applications of dye-doped silica nanoparticles is given in recent review [79]. 

Dye-Doped Silica Nanoparticle Synthesis Using Nonionic Surfactant-Based... 

Traditionally, the sol-gel process has been used for the preparation of silica nanoparticles via the hydrolysis of alkoxides in organic solvents [52,53]. Similar hydrolysis and condensation carried out in w/o microemulsion offers robust control over the synthesis process. W/o emiflsion-mediated sol-gel synthesis is currently used for the fabrication of pure sihca, as well as inorganic and organic dye-doped silica nanoparticles. The synthesis of sihca and dye-doped nanoparticles is classified in the following sections on the basis of the classification of the head group fimctionahty of the major surfactant used. 

From our research group Santra et al. [11,41,42] reported the development of novel luminescent nanoparticles composed of inorganic luminescent dye RuBpy, doped inside a sihca network. These dye-doped silica nanoparticles were synthesized using a w/o microemulsion of Tx-lOO/cyclohexane/ n-hexanol/water in which controlled hydrolysis of the TEOS leads to the formation of mono dispersed nanoparticles ranging from 5-400 nm. This research illustrates the efficiency of the microemulsion technique for the synthesis of uniform nanoparticles. These nanoparticles are suitable for biomarker application since they are much smaller than the cellular dimension and they are highly photostable in comparison to most commonly used organic dyes. It was shown that maximum liuninescence intensity was achieved when the dye content was around 20%. Moreover, for demonstration... 

Santra S, Dutta D, Moudgil BM (2005) Functional dye-doped silica nanoparticles for bioimaging, diagnostics and therapeutics. Food Bioprod Process 83 136-140... 

He XX, Duan JH, Wang KM, Tan WH, Lin X, He CM (2004) A novel fluorescent label based on organic dye-doped silica nanoparticles for HepG liver cancer ceU recognition. J Nanosci Nanotechnol 4 585-589... 

Zhao XJ, Bagwe RP, Tan WH (2004) Development of organic-dye-doped silica nanoparticles in a reverse microemulsion. Adv Mater 16 173... 

Bagwe RP, Yang CY, Hilliard LR, Tan WH (2004) Optimization of dye-doped silica nanoparticles prepared using a reverse microemulsion method. Langmuir 20 8336-8342... 

The sensitivity of fluorescence-based assays can hence be greatly improved by the use of dye-doped silica nanoparticles and this approach has been pioneered and subsequently deeply investigated by Tan and coworkers.15 Their luminophore of choice was the water-soluble, positively charged tris(2,2 -bipyridyl)dichlororuthenium(II) [Ru(bpy)3]2+ hydrochloride that can be easily incorporated into silica nanoparticles prepared using the reverse microemulsion method. The charge complementarity between the dye and the silica matrix prevents leaching from the particles.15... 

Newer immunodetection applications, and particularly the so-called microarrays, employ new fluorescent probes such as europium chelates (Scorilas et al., 2000), lanthanide oxide nanoparticles (Dosev et al., 2005 Nichkova et al., 2006), fluoro-phore loaded latex beads (Orth et al., 2003), dye-doped silica nanoparticles (Zhou and Zhou, 2004 Yao et al., 2006), and inorganic nanocrystals (Gerion et al., 2003 Geho et al., 2005). 

There are many different synthetic methods to prepare silica nanoparticles and in particular dye doped silica nanoparticles (DDSNs), all characterized by simplicity, low costs, versatility and great control over the architecture of the resulting materials. We will discuss in detail the most common procedures in the next section, with some emphasis on a new synthetic strategy that we have developed and patented [64, 65] that affords monodisperse silica nanoparticles with a particularly versatile and readily obtained core-shell architecture. 

Fig. 9 Van Blaaderen modification of the Stober method for the synthesis of dye doped silica nanoparticles...

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