A comparative study of non-covalent encapsulation methods for organic dyes into silica nanoparticles

Numerous luminophores may be encapsulated into silica nanoparticles (< 100 nm) using the reverse microemulsion process. Nevertheless, the behaviour and effect of such luminescent molecules appear to have been much less studied and may possibly prevent the encapsulation process from occurring. Such nanospheres represent attractive nanoplatforms for the development of biotargeted biocompatible luminescent tracers. Physical and chemical properties of the encapsulated molecules may be affected by the nanomatrix. This study examines the synthesis of different types of dispersed silica nanoparticles, the ability of the selected luminophores towards incorporation into the silica matrix of those nanoobjects as well as the photophysical properties of the produced dye-doped silica nanoparticles. The nanoparticles present mean diameters between 40 and 60 nm as shown by TEM analysis. Mainly, the photophysical characteristics of the dyes are retained upon their encapsulation into the silica matrix, leading to fluorescent silica nanoparticles. This feature article surveys recent research progress on the fabrication strategies of these dye-doped silica nanoparticles

In Situ Loading of Basic Fibroblast Growth Factor Within Porous Silica Nanoparticles for a Prolonged Release

Basic fibroblast growth factor (bFGF), a protein, plays a key role in wound healing and blood vessel regeneration. However, bFGF is easily degraded in biologic systems. Mesoporous silica nanoparticles (MSNs) with well-tailored porous structure have been used for hosting guest molecules for drug delivery. Here, we report an in situ route to load bFGF in MSNs for a prolonged release. The average diameter (d) of bFGF-loaded MSNs is 57 ± 8 nm produced by a water-in-oil microemulsion method. The in vitro releasing profile of bFGF from MSNs in phosphate buffer saline has been monitored for 20 days through a colorimetric enzyme linked immunosorbent assay. The loading efficiency of bFGF in MSNs is estimated at 72.5 ± 3%. In addition, the cytotoxicity test indicates that the MSNs are not toxic, even at a concentration of 50 μg/mL. It is expected that the in situ loading method makes the MSNs a new delivery system to deliver protein drugs, e.g. growth factors, to help blood vessel regeneration and potentiate greater angiogenesis

Effects of intermicellar exchange rate on the formation of silver nanoparticles in reverse microemulsions of AOT

We report the effects of intermicellar exchange rate on absorption spectra and particle size of silver nanoparticles synthesized in reverse micelles of AOT. The silver nanoparticles are prepared by the method of mixing of two microemulsions, one containing the silver nitrate and the other containing sodium borohydride. The intermicellar exchange rate is varied by changing the organic solvent, surfactant (SDS, NP-5, and DTAB), and organic (benzyl alcohol and toluene) additives. The higher intermicellar exchange rate is found to give smaller particle size and blue shift in the absorption spectra. An interesting and potentially useful effect has been observed in that addition of a small amount of a nonionic surfactant significantly reduces the particle size

Effects of the intermicellar exchange rate and cations on the size of silver chloride nanoparticles formed in reverse micelles of AOT

Nanoparticles of silver chloride have been synthesized by the method of mixing of two microemulsions, one containing silver ions and other containing chloride ions. The effects of changing the intermicellar exchange rate by varying the continuous phase, by adding benzyl alcohol, and by varying the water to surfactant molar ratio as well as the effect of cations (metal chlorides from the first and second group of the periodic table) on the particle size and the size distribution and the number density have been studied. The particle diameters are measured from the photomicrographs obtained by transmission electron microscopy. The average particle size, the polydispersity, and the number of particles formed are shown to be dependent on the intermicellar exchange rate and/or the rigidity of the surfactant shell. This dependency can be qualitatively explained by means of nucleation and growth phenomena, as mediated by the intermicellar exchange of contents

Effect of chain length of oxyethylene group on particle size and absorption spectra of silver nanoparticles prepared in non-ionic water-in-oil microemulsions

The formation of silver nanoparticles by the method of reduction of silver ions by sodium borohydride in non-ionic water-in-oil microemulsion was investigated as a function of structure of the surfactant. Three types of non-ionic surfactants were selected differing in the chain length of the oxyethylene groups for example: NP-5. NP-9 and NP-II. The silver nanoparticles were characterized by UV-Visible Absorption Spectroscopy and Transmission Electron Microscopy, TEM. The results of this study showed that the particle size is relatively smaller incase of NP-9 while for NP-5 and NP-II the sizes are comparable. This observation is explained on the basis of structure of the droplets and the influence of intermicellar exchange on nucleation and growth of particles

Silicoaluminophosphate molecular sieves SAPO-11, SAPO-31 and SAPO-41: Synthesis, characterization and alkylation of toluene with methanol

Medium pore molecular sieves SAPO-11, SAPO-31 and SAPO-41 have been synthesized using di-n-propylamine as the organic template. They have been characterized by various methods such as X-ray powder diffraction, solid state MAS NMR spectroscopy, thermal analysis, chemical analysis and temperature programmed desorption (TPD) of ammonia. Catalytic activities of these materials in the alkylation of toluene with methanol have been studied. While SAPO-11 and SAPO-31 showed moderate activity, very high catalytic activity was shown by SAPO-41. All the catalysts showed varying degrees of shape selectivity towards p-xylene. SAPO-41 gave a large amount of 1,2,4-trimethylbenzene in addition to the xylenes