MMT-supported Ag nanoparticles for chitosan nanocomposites: structural properties and antibacterial activity.

Multifunctional bionanocomposites have been prepared by loading chitosan matrix with silver-montmorillonite antimicrobial nanoparticles obtained by replacing Na(+) ions of natural montmorillonite with silver ions. This filler has been chosen for its twofold advantage to serve as silver supporting material and to confer new and better performance to the obtained material. It has been proved that the achievement of the intercalation of chitosan into the silicate galleries of montomorillonite as well as the interaction between chitosan and Ag ions and silver particles lead to an enhancement of the thermal stability, to an improvement of mechanical strengths and to a reduction of the liquid water uptake of the obtained bionanocomposites. Results also show that silver ions are released in a steady and prolonged manner providing, after 24 h, a significant reduction in the microbial growth of Pseudomonas spp.

In-situ sol-gel synthesis and characterization of bioactive pHEMA/SiO2 blend hybrids.

A novel procedure to synthesize poly(2-hydroxyethylmethacrylate)-silica blend hybrids is presented. Methacrylate monomers bearing an alkoxysilyl unit, prepared by Michael addition of 2-hydroxyethylmethacrylate (HEMA) to 3-Aminopropyltriethoxysilane (APTS) were employed. By (13)C NMR and mass analysis it was possible to establish the formation of coupling hybrid species. Hybrid materials, with final concentration ranging from 10% to 30% w/w of silica gel to the mass of polymer, were obtained through basic catalyzed sol-gel process of tetraethoxysilane (TEOS) and the alkoxysilyl unit of the hybrid monomer, followed by in-situ free-radical polymerization. The hybrids were characterized as far as concerns their thermal properties (glass transition temperature, decomposition temperature), their sorption behavior in water, and in-vitro bioactivity. Optical transparency, higher glass transition temperature, and higher decomposition temperature than pHEMA suggest an increase in either density or intensity of cross-links between the organic and the inorganic phases. The swelling ratio of the 30% hybrids is comparable to pHEMA, whereas it is lower for the other compositions. In-vitro bioactivity of the hybrids, due to the inorganic phase, was ascertained. Soaking time required for apatite deposition on the samples surface decreases as the content of silica gel increases. Therefore, the obtained bioactive hybrids can be used to make bioactive scaffolds for bone engineering.

Bioactive poly(2-hydroxyethylmethacrylate)/silica gel hybrid nanocomposites prepared by sol-gel process.

A hybrid of poly(2-hydroxyethylmethacrylate) (pHEMA), a polymer widely employed for biomedical applications, and silica gel, exhibiting a well-known bioactivity, was produced by sol-gel. The amount of the inorganic precursor, tetraethoxysilane (TEOS), was mixed to the organic monomer, so as to have a final concentration of 30% (w/w) of silica gel to the mass of polymer. The nanocomposite was characterized for its composition by thermogravimetric (TG) analysis, swelling behavior, glass transition temperature using differential thermal analysis (DTA), morphology through scanning electron microscopy (SEM), and bioactivity using FT-IR spectroscopy, SEM, and energy dispersive system (EDS). The nanocomposite showed phase separation between the polymer and the silica gel, improved thermal stability and swelling properties and higher glass transition temperature than pHEMA. Moreover, bioactive SiO(2) gel nanoparticles promoted apatite formation on the surface of the modified hydrogel, when it was soaked in SBF. Therefore, the obtained bioactive nanocomposite can be used to make bioactive scaffold for bone engineering.