Effects of Process Variables on Properties of CoFe2O4 Nanoparticles Prepared by Solvothermal Process.

Controlling the morphology and magnetic properties of CoFe2O4 nanoparticles is crucial for the synthesis of compatible materials for different applications. CoFe2O4 nanoparticles were synthesized by a solvothermal method using cobalt nitrate, iron nitrate as precursors, and oleic acid as a surfactant. The formation of CoFe2O4 nanoparticles was systematically observed by adjusting synthesis process conditions including reaction temperature, reaction time, and oleic acid concentration. Nearly spherical, monodispersed CoFe2O4 nanoparticles were formed by changing the reaction time and reaction temperature. The oleic acid-coated CoFe2O4 nanoparticles inhibited the growth of particle size after 1 h and, therefore, the particle size of CoFe2O4 nanoparticles did not change significantly as the reaction time increased. Both without and with low oleic acid concentration, the large-sized cubic CoFe2O4 nanoparticles showing ferromagnetic behavior were synthesized, while the small-sized CoFe2O4 nanoparticles with superparamagnetic properties were obtained for the oleic acid concentration higher than 0.1 M. This study will become a basis for further research in the future to prepare the high-functional CoFe2O4 magnetic nanoparticles by a solvothermal process, which can be applied to bio-separation, biosensors, drug delivery, magnetic hyperthermia, etc.

On-Demand Release of Drug from Magnetic Nanoparticle-Loaded Alginate Beads.

Targeted delivery and controlled release of drugs has been considered to be an important therapeutic approach since it could allow a better treatment efficiency and less side effects. In this research, magnetite Fe3O4 nanoparticles were successfully synthesized via the coprecipitation method and then loaded in alginate beads with berberine as a drug model for drug release application. Various factors such as pH values of the suspended environment and surface modifications of the drug carrier could be exploited to adjust the amount of drug release. More importantly, the amount of drug release could be effectively controlled by an on-off switching operation of a static magnetic field.

Controlled Deposition of Gold Nanoparticles on Titania Support.

In our research, the commercial TiO2 (Degussa P25) was modified with gold nanoparticles (Au NPs) by reduction reaction with trisodium citrate. A remarkable influence of pH on particle size, size distribution and dispersion of Au on TiO2 support was observed. The size of Au NPs on TiO2 surface decreased with increase in the pH of the precursor solution. The increase of pH involved a transformation of [AuCl4]- complexes to [Au(OH)xCl(4-x)]- complexes which could induce strong Au-TiO2 interactions, resulted in uniform dispersion of Au NPs. Complete citrate reduction of Au precursor facilitated the deposition of stable Au NPs with small particle size and narrow size distribution.

Excessive screen viewing time by adolescents and body fatness in a developing country: Vietnam.

BACKGROUND AND OBJECTIVES: Screen time among youth has been increasingly recognized as a public health problem because of its link with obesity. This has been demonstrated in many studies conducted in developed countries but few studies have addressed the problem in developing countries, despite an increase literature about the emergence of obesity and a greater access to screen devices in a country like Vietnam. Our study aimed at assessing screen time and its relationship with BMI in adolescents of Ho Chi Minh City (HCMC), Vietnam. METHODS AND STUDY DESIGN: In a cross-sectional study of 2024 junior high school students aged 11-14 of HCMC, students were measured for BMI and questioned on time spent watching television/Video/DVD or using computer for fun. High users were defined as time >=2 h/d. International Obesity Task Force BMI cutoffs were used to define overweight and obesity. RESULTS: Adolescents spent 2.2 h/d in screen time, with higher values for boys than girls (p<0.001). 53.8% of the respondents were high users. Time spent using computers for fun increased with age, and with the household wealthy index. The overall prevalence of overweight and obesity was 21.1%. Using multiple logistic regression, overweight and obesity was higher in boys (adjusted OR=2.66, 95% CI: [2.06; 3.44], p<0.001) and in children aged 11-12 who had a screen time >=2 h/d (adjusted OR=1.48, 95% CI: [1.09; 1.99], p<0.02). CONCLUSIONS: In HCMC, a majority of adolescents spent >=2 h/d on screen time. High screen time is associated with an increased prevalence of overweight and obesity in young adolescents. Public health intervention programs are needed to reduce screen time among youth.

Controlled Synthesis of Magnetite Porous/Hollow Nanoparticles Through a Template-Free Solvothermal Process.

Magnetite Fe3O4 porous/hollow nanospheres were synthesized controllably through a one-pot template-free solvothermal process, requiring only FeCl3 x 6H2O as iron precursor and addition of ammonium acetate in an ethylene glycol solution. SEM observations indicated that the porous/hollow nanospheres were composed of numerous small grains. The initial concentrations of Fe precursor and ammonium acetate as well as the molar ratio of Fe precursor to ammonium acetate played crucial roles to control particle diameter and porosity of the Fe3O4 porous/hollow nanospheres. The Fe3O4 porous/hollow nanospheres exhibited a ferromagnetic behavior with high magnetization saturation.

Preparation of magnetite hollow structure for drug delivery application.

Monodispersed Fe3O4 nanospheres with hollow interior and porous shell structures were synthesized without any template by refluxing iron precursor solution in a Teflon-line autoclave at 200 degrees C. Those nanoparticles exhibited a ferromagnetic behavior with a high saturation magnetization of 76 emu/g. The hollow structure was formed based on the assembly of many small particles to form large-sized spheres, followed by chemical conversion coupled with Oswald ripening process. Due to the differences in size, density and/or crystallinity between the outer and interior particles in the spheres, the inner particles migrated to the outer shell, resulting in the formation of the empty space inside nanostructures. The potential application of Fe3O4 hollow nanoparticles as a drug carrier was evaluated with Rhodamine6G as a model drug, showing a pH-dependent release profile due to the difference of proton concentration.

Template-free synthesis and characterization of monodisperse magnetite hollow nanoparticles through solvothermal process.

Monodispersed Fe3O4 nanospheres with hollow interior structures were synthesized without any template. Those nanoparticles exhibited a ferromagnetic behavior with a high saturation magnetization of 81.0 emu g(-1). The hollow structure was formed based on the aggregation of many primary particles, followed by Oswald ripening process. Due to the energy difference between the outer and interior particles in the aggregates, the inner particles migrated to the outer shell. This resulted in the formation of the empty space inside nanostructures.

External birth defects in Southern Vietnam: a population-based study at the grassroots level of health care in Binh Thuan Province.

BACKGROUND: There currently exists no data on birth defects from population-based studies in Vietnam. Our study's aim was to assess external birth defect (EBD) prevalence among live newborns in Binh Thuan Province in Vietnam with the help of health workers at all levels of the health system. METHODS: A 2-month training session for 452 health professionals (HP) practicing delivery care in 127 Commune Health Stations (CHS) and in 12 provincial or district hospitals (DH) was setup in 2006. After a successful 6-month pilot study, a one-year registry of EBDs was established in 2008. All live newborns were screened for EBDs within 24 hours after birth in all DH obstetric departments and in all CHSs. Trained local HPs collected information by filling out a predesigned form and by photographing the affected newborn. EBDs were coded using the International Classification of Diseases system-10, Clinical Modification. The study was repeated in 2010. RESULTS: Throughout 2010, out of a total of 13,954 newborns, 84 cases with one or more EBDs were reported, representing an overall prevalence rate of 60.2 per 10,000 live births. The most common groups of EBDs were limbs (27.2/10,000), orofacial clefts (20.1/10,000) and the central nervous system (7.9/10,000). CONCLUSIONS: This first population-based study in Vietnam, which required coordination efforts at the local level, provides baseline prevalences of external birth defects. Data on EBDs from this study in southern Vietnam may be useful for setting up a regional population-based registry of birth defects in Vietnam.

High prevalence of overweight among adolescents in Ho Chi Minh City, Vietnam.

BACKGROUND: Two previous surveys conducted in Ho Chi Minh City revealed an increasing prevalence of overweight and obese adolescents, from 5.9% in 2002 to 11.7% in 2004. From 2004 to 2010, the government set up and implemented health promotion programs to promote physical activity and good nutritional habits in order to prevent overweight and obesity in children and adolescents. Our study aimed to estimate the prevalence of overweight and obesity among adolescents in urban areas of Ho Chi Minh City in 2010. METHODS: A representative sample of 1,989 students aged 11-14 years was selected using a multistage cluster sampling method. 23 schools were randomly selected from the full list of all public junior high schools. In each selected school, 2 classes were chosen at random and all students from the class were examined. Age- and sex-adjusted overweight and obesity were defined using International Obesity Taskforce cut-offs. RESULTS: The prevalences of overweight and obesity were 17.8% and 3.2%, respectively. Prevalences of overweight and obesity were significantly higher in boys (22%, 5.4% ) than in girls (13.3%, 1.3%, p<0.001) and higher in children from districts with a high economic level (20.5% , 3.8% ) than in those from districts with a low economic level (12.1%, 3.8%, p<0.001). Additionally, children living in wealthier families were more overweight and obese than those living in less wealthy families. When using WHO cutoffs, the overall prevalences of overweight and obesity reached 19.6% and 7.9%, respectively. CONCLUSION: Our study's findings suggest that the prevalence of overweight and obesity among secondary school students remains high, especially among boys living in wealthier families. Public health programs should therefore be developed or improved in order to promote good eating habits and physical activity among youth in HCMC.

Seed-mediated synthesis of iron oxide and gold/iron oxide nanoparticles.

In this study, we prepared magnetic iron oxide and gold/iron oxide nanoparticles (NPs) and characterized their morphologies and properties by XRD, TEM, EDX, VSM and UV-vis measurements. The magnetite iron oxide NPs of 10 nm were synthesized by coprecipitation of Fe2+ and Fe+3 in the solution of NH4OH and then they were used as seed particles for the subsequent growth to prepare the magnetite NPs of different particle sizes and also to prepare gold/iron oxide composite NPs. All those magnetite NPs are superparamagnetic and the gold/iron oxide composite NPs combine the optical and magnetic properties, which are contributed by gold and iron oxide components, respectively.

Controlled synthesis and biomolecular probe application of gold nanoparticles.

In addition to their optical properties, the ability of gold nanoparticles (Au NPs) to generate table immobilization of biomolecules, whilst retaining their bioactivities is a major advantage to apply them as biosensors. Optical biosensors using Au NPs are simple, fast and reliable and, recently, they have been moving from laboratory study to the point of practical use. The optical properties of Au NPs strongly depend on their size, shape, degree of aggregation and the functional groups on their surface. Rapid advances in the field of nanotechnology offer us a great opportunity to develop the controllable synthesis and modification of Au NPs as well as to study on their properties and applications. The size-controlled growth of Au NPs requires the isotropic growth on the surface of Au nuclei whereas anisotropic growth will induce the formation of Au NPs of varying shape. Functionalized Au NPs provide sensitive and selective biosensors for the detection of many targets, including metal ions, small organic compounds, protein, DNA, RNA and cell based on their optical, electrical or electrochemical signals. In this review, we will discuss the size- and shape-controlled growth and functionalization of Au NPs to obtain Au nanoprobes. The basis of the optical detection of Au nanoprobes and their applications in nucleic acid, protein detection and cell imaging are also introduced.