Synthesis of water-dispersible zinc oxide quantum dots with antibacterial activity and low cytotoxicity for cell labeling.

Typical photoluminescent semiconductor nanoparticles, called quantum dots (QDs), have potential applications in biological labeling. When used to label stem cells, QDs may impair the differentiation capacity of the stem cells. In this study, we synthesized zinc oxide (ZnO) QDs in methanol with an average size of ∼2 nm. We then employed two different types of polyethylene glycol (PEG) molecules (SH-PEG-NH2 and NH2-PEG-NH2) to conjugate ZnO QDs and made them water-dispersible. Fourier transform infrared spectroscopy spectra indicated the attachment of PEG molecules on ZnO QDs. No obvious size alteration was observed for ZnO QDs after PEG conjugation. The water-dispersible ZnO QDs still retained the antibacterial activity and fluorescence intensity. The cytotoxicity evaluation revealed that ZnO QDs at higher concentrations decreased cell viability but were generally safe at 30 ppm or below. Cell lines of hepatocytes (HepG2), osteoblasts (MC3T3-E1) and mesenchymal stem cells (MSCs) were successfully labeled by the water-dispersible ZnO QDs at 30 ppm. The ZnO QD-labeled MSCs maintained their stemness and differentiation capacity. Therefore, we conclude that the water-dispersible ZnO QDs developed in this study have antibacterial activity, low cytotoxicity, and proper labeling efficiency, and can be used to label a variety of cells including stem cells.

Transparent nanocomposites of high refractive index based on epoxy resin and TiO2 nanoparticle.

A stepwise sol-gel method for the synthesis of stable colloidal TiO2 using hydrolysis and condensation reactions of titanium tetraisopropoxide (TTP) was investigated. The surface modification was carried out using 3-glycidoxypropyltrimethoxysilane (GPTMS). The particle size range of the modified TiO2 observed by TEM was 3-8 nm. The nanocomposites based on an epoxy resin and the modified TiO2 showed strong UV absorption, but maintained high transmittance within the visible region. TEM images of the nanocomposites confirmed the homogenous and fine dispersion of the TiO2 nanoparticles in the epoxy resin. The refractive index of the nanocomposites increased linearly with increasing TiO2 content. With 60% TiO2 by weight, the transmittance and refractive index of the nanocomposite were 98.4% and 1.657, respectively.

Preparation and characterization of the transparent hybrids of silicone epoxy resin and titanium dioxide nanoparticles via sol-gel reactions.

In order to prepare transparent hybrid films of high refractive index, nanoparticles of TiO2 were prepared and dispersed in a silicone epoxy (SE) resin synthesized from diphenyl silane diol and [2-(3,4-epoxycyclohexyl)ethyl] trimethoxysilane by sol-gel reactions. It was found that amorphous TiO2 nanoparticles of about 5 nm modified with hexahydro-4-methyl phthalic anhydride [HMPA] were dispersed in the SE resin without agglomerations. The refractive index of the hybrids increased linearly with increasing the TiO2 contents. The hybrid containing 30 wt% of the TiO2 particles showed light transmittance of 94% at 450 nm and refractive index of 1.63. The fine dispersion of the TiO2 nanoparticles was attributable to the sol-gel reactions between the SE resin and TiO2 nanoparticles and the modification of the TiO2 particles with HMPA.

Effects of colloidal nanosilica on the rheological properties of epoxy resins filled with organoclay.

The rheological properties of epoxy resins filled with organoclay and colloidal nanosilica were investigated by employing a parallel plate rheometer in flow mode at 25 degrees C. Shear thickening and shear thinning behaviors were observed in the epoxy resins filled with a mixture of organoclay and colloidal nanosilica. Minima were observed in the relaxation time of the systems consisting of epoxy resins filled with organoclay and colloidal silica as the content of colloidal nanosilica was increased. It seems that the colloidal nanosilica increased the mobility of the filled epoxy resins and reduced the interactions between the silicate layers in the systems.

A household survey on morbidity and treatment of acute respiratory infections in communities in Vietnam

<p><b>OBJECTIVE</b>To ascertain the extent of under-utilization and insufficiency or inappropriateness in provision of health services as one of the possible causes of high mortality from pediatric pneumonia in pilot areas in Vietnam.</p><p><b>METHOD</b>The household survey on morbidity and treatment of acute respiratory infections, simple cough, and cold and pneumonia, was conducted in two communities with 10% sampling of the child population.</p><p><b>RESULTS</b>Both under-treatment of "fast breathing", a proxy for pneumonia, and over-treatment of simple cough and cold with antimicrobials by health workers, mothers, and private practitioners were common.</p><p><b>CONCLUSIONS</b>A household survey on morbidity and treatment was found to be useful to clarify actual practices in the treatment of acute respiratory infections in the community, which cannot be obtained by mere interview with health workers or mothers. Since a change of knowledge did not automatically lead to change of practice, the training of health workers, health education of mothers and provision of antimicrobials at village health stations would not guarantee improved practice of health workers and mothers. Therefore, constant supervision for health workers, continued health education of mothers and involvement of private practitioners are needed to improve the situation.</p>

A Household Survey on Morbidity and Treatment of Acute Respiratory Infections in Communities in Vietnam

Objective: To ascertain the extent of under-utilization and insufficiency or inappropriateness in provision of health services as one of the possible causes of high mortality from pediatric pneumonia in pilot areas in Vietnam. Method: The household survey on morbidity and treatment of acute respiratory infections, simple cough, and cold and pneumonia, was conducted in two communities with 10% sampling of the child population. Results: Both under-treatment of “fast breathing”, a proxy for pneumonia, and over-treatment of simple cough and cold with antimicrobials by health workers, mothers, and private practitioners were common. Conclusions: A household survey on morbidity and treatment was found to be useful to clarify actual practices in the treatment of acute respiratory infections in the community, which cannot be obtained by mere interview with health workers or mothers. Since a change of knowledge did not automatically lead to change of practice, the training of health workers, health education of mothers and provision of antimicrobials at village health stations would not guarantee improved practice of health workers and mothers. Therefore, constant supervision for health workers, continued health education of mothers and involvement of private practitioners are needed to improve the situation.