Silica modified nanoparticles

Z. Li, B. Houa, Y. Xn, D. Wn, Y. Sun, Hydrothermal synthesis, characterization and photocatal3dic performance of silica-modified titaninm dioxide nanoparticles , Jonmal of Colloid and Interface Science, 288, 149-154, (2005). 

Modification of mesoporous silica nanoparticles using the bifunctional strategy, post-synthesis grafting, and backfilling strategy in order to make them suitable for drug delivery applications was reported (Lu et al. 2007). The modified nanoparticles were able to deliver the water insoluble drug camptothecin into different types of human cancer cells (Johansson et al. 2008). 

Hirai et al [365] reported fabrication of silica-CdS composites by first adding 3-mercaptopropyltrimethoxysilane into freshly prepared CdS nanoparticles in a two -microemulsion system (AOT/isooctane/aqueous solution of cadmium nitrate and sodium sulfide). The surface modified nanoparticles were collected, washed in hexane, and dispersed in tetramethyl orthosilicate, dimethyl formamide, dichloromethane, chloroform etc. When selected dispersions were added to silica sols and properly processed, 100 nm silica particles with CdS core could be prepared. In an earlier work [366], silica particles were first obtained by precipitation in a microemulsion containing Igepal CO-520 i.e. poly(oxyethylene)nonylphenyl ether or Triton N-101 with a similar chemical structure, cyclohexane, hexanol (for the Triton surfactant) and ammonium hydroxide solution. The source of silica was TEOS which was injected into the reverse microemulsion. After this injection, two microemulsions of similar compositions but containing Cd(N03)2 or (NH4)2S in the aqueous phase were simultaneously injected into the microemulsion prepared for silica synthesis. After several hours, the hydrolysis-condensation product of TEOS grew into particles of size 35-50 nm depending on experimental conditions, with uniformly dispersed, 10 mol % CdS nanoparticles (size about 2.5 nm) incorporated in them. Zinc-doped, alkanedithiol-modified silica particles obtained by hydrolysis of TEOS were also used for immobilization of CdS from a reverse micelle system. The general motivation was the development of photocatalysts [367]. 

In the work of Rong et al. [108], various polymers were grafted on the surface of nanoscale silica filler particles through the simultaneous irradiation polymerization technique. In this way, the modified nanoparticles can be more effectively utilized in thermoplastics (such as PP) than conventional particulate fillers, when using the same direct compounding technology. 

Figure 5.9 Synthesis of gold nanoparticles within Zr02. A gold colloid is first prepared then coated with silica using a modified Stober process [75]. The silica is removed using NaOH. Reproduced with permission from [74],...

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],... 

The alcohol evaporation under vacuum, the treatment of cells and microcapsules by silica precursor supplied by gas carrier and infiltration of silica nanoparticles, whose are discussed above, are the examples of such modified approaches. There are two original methods whose would be well to consider. 

Kneur, C., Sameti, M., Haltner, E.G., Schiestel, T., Schirra, H. and Schmidt, H.K. (2000) Silica nanoparticles modified with aminosilanes as carriers... 

Roy, I., Ohulchanskyy, T.Y., Bharali, D.J., Pudavar, H.E., Mistretta, R.A., Kaur, N. and Prasad, P.N. (2005) Organically modified silica nanoparticles A non-viral vector for in-vivo gene delivery and expression. Proceedings of the National Academy of Sciences of the United States of America, 102, 11539-11544. 

These Ru(H)bpy32+ fluorescent silica nanoparticles were used to detect single bacterial cells using antibodies conjugated to the surface after functionalization with trimethoxysilyl-propyldiethylenetriamine followed by succinylation to create carboxylates. Specific antibody molecules against E. coli 0157 then were coupled to this modified fluorescent particle using the carbodiimide method with EDC and NHS (Zhao et al., 2004). 

Fluorescent silica nanoparticles, called FloDots, were created by Yao et al. (2006) by two synthetic routes. Hydrophilic particles were produced using a reverse micro-emulsion process, wherein detergent micelles formed in a water-in-oil system form discrete nanodroplets in which the silica particles are formed. The addition of water-soluble fluorescent dyes resulted in the entrapment of dye molecules in the silica nanoparticle. In an alternative method, dye molecules were entrapped in silica using the Stober process, which typically results in hydrophobic particles. Either process resulted in luminescent particles that then can be surface modified with... 

Figure 14.25 The preparation of highly controlled fluorescent silica nanoparticles can be done by first polymerizing APTS that has been covalently modified with an amine-reactive dye to form fluorescent core particles. The core then is capped by a shell of silica by polymerization of TEOS. The shell layer can be further derivatized with silane coupling agents to provide functional groups for conjugation.

Organically modified silica nanoparticles a nonviral vector for in vivo gene delivery and expression in the brain, Proc. Natl. Acad. Sci. USA, 2005, 102, 11539. 

I. Roy, T. Y. Ohulchanskyy, D. J. Bharali, H. E. Pudavar, R. A. Mistretta, N. Kaur and P. N. Prasad, Optical tracking of organically modified silica nanoparticles as DNA carriers a nonviral, nanomedicine approach for gene delivery, Proc. Natl. Acad. Sci. USA, 2005, 102, 279. 

---