Cytotoxicity of ZnO Nanoparticles Can Be Tailored by Modifying Their Surface Structure: A Green Chemistry Approach for Safer Nanomaterials

ZnO nanoparticles (NP) are extensively used in numerous nanotechnology applications; however, they also happen to be one of the most toxic nanomaterials. This raises significant environmental and health concerns and calls for the need to develop new synthetic approaches to produce safer ZnO NP, while preserving their attractive optical, electronic, and structural properties. In this work, we demonstrate that the cytotoxicity of ZnO NP can be tailored by modifying their surface-bound chemical groups, while maintaining the core ZnO structure and related properties. Two equally sized (9.26 ± 0.11 nm) ZnO NP samples were synthesized from the same zinc acetate precursor using a forced hydrolysis process, and their surface chemical structures were modified by using different reaction solvents. X-ray diffraction and optical studies showed that the lattice parameters, optical properties, and band gap (3.44 eV) of the two ZnO NP samples were similar. However, FTIR spectroscopy showed significant differences in the surface structures and surface-bound chemical groups. This led to major differences in the zeta potential, hydrodynamic size, photocatalytic rate constant, and more importantly, their cytotoxic effects on Hut-78 cancer cells. The ZnO NP sample with the higher zeta potential and catalytic activity displayed a 1.5-fold stronger cytotoxic effect on cancer cells. These results suggest that by modifying the synthesis parameters/conditions and the surface chemical structures of the nanocrystals, their surface charge density, catalytic activity, and cytotoxicity can be tailored. This provides a green chemistry approach to produce safer ZnO NP

Estudios sobre la valoración del principio ocitócico del lóbulo posterior de hipófisis. Análisis matemático de los resultados y determinación del error del método

Fil: Torino, A. Ministerio del Interior; Instituto Bacteriológico "Dr. Carlos G. Malbrán"; Argentin

Estudios sobre la valoración del principio ocitócico del lóbulo posterior de hipófisis. Análisis matemático de los resultados y determinación del error del método

Fil: Torino, A. Ministerio del Interior; Instituto Bacteriológico "Dr. Carlos G. Malbrán"; Argentin

Estudios de farmacología cuantitativa : 1. Curvas de la toxicidad de la dolantina

Fil: Litter, M. Ministerio del Interior; Instituto Bacteriológico "Dr. Carlos G. Malbrán"; Argentinal° — Se ha estudiado la toxicidad de la dolantina para el ratón blanco y por vía intravenosa, empleando én total 805 animales. 2° — Se ha construido la curva característica de toxicidad y la línea de regresión; esta última también se ha obtenido por cálculo. 3° — La dosis mortal 50 % (DL 50) oscila entre 42,5 y 50,0 mg/kg (método de Trevan, 1929), éntre 44,2 y 55,3 mg/kg (método gráfico de Gaddum, 1933) y entré 44,3 y 55,1 mg/kg (cálculo por el método de Gaddum, 1933). 4° — Nuestros resultados están de acuerdo con lo establecido por Gaddum (1933), a saber, qué los logaritmos de las dosis mortales individuales están distribuidos en forma aproximadamente normal. 5° — La dosis mortal 50 % (DL 50), no representa una constante biológica, sino que varía aún empleando en las experiencias un gran numéro de animales

Estudios de farmacología cuantitativa : 1. Curvas de la toxicidad de la dolantina

Fil: Litter, M. Ministerio del Interior; Instituto Bacteriológico "Dr. Carlos G. Malbrán"; Argentinal° — Se ha estudiado la toxicidad de la dolantina para el ratón blanco y por vía intravenosa, empleando én total 805 animales. 2° — Se ha construido la curva característica de toxicidad y la línea de regresión; esta última también se ha obtenido por cálculo. 3° — La dosis mortal 50 % (DL 50) oscila entre 42,5 y 50,0 mg/kg (método de Trevan, 1929), éntre 44,2 y 55,3 mg/kg (método gráfico de Gaddum, 1933) y entré 44,3 y 55,1 mg/kg (cálculo por el método de Gaddum, 1933). 4° — Nuestros resultados están de acuerdo con lo establecido por Gaddum (1933), a saber, qué los logaritmos de las dosis mortales individuales están distribuidos en forma aproximadamente normal. 5° — La dosis mortal 50 % (DL 50), no representa una constante biológica, sino que varía aún empleando en las experiencias un gran numéro de animales

Phenol photodegradation on platinized TiO2 photocatalysts related to charge carrier dynamics

Three commercial TiO2 compounds Degussa P25, Sachtleben UV100, and Millenium PC50 and their platinized forms have been studied by the time resolved microwave conductivity TRMC method to follow their charge carrier dynamics and to relate it to the photocatalytic activity for phenol degradation in TiO2 aqueous suspensions. The degradation reaction has been studied in detail, following the time evolution of the concentration of phenol and its intermediates by liquid chromatography. The results show that platinization has a distinct influence on the commercial compounds, decreasing globally the activity of P25 and increasing the activity of PC50 and UV100. An influence of charge carrier lifetimes on the photoactivity of pure and platinized TiO2 samples has been evidence

Identifying occurrences of groundwater arsenic in Latin America: a continent-wide problem and challenge

The first reports of arsenic(As)-rich ground­water in Latin America are those of Argentina (Goyenechea, 1917; Ayerza, 1917a,b, 1918). The discoveries of As-contaminated water resources in Chile and Mexico fall about together with the first important discovery made in Asia (Taiwan) at the beginning of the 1960s. Until today, remediation of the problem was performed only in some big­ger cities. The population of rural areas and those from isolated urban areas without centralized water supply systems still suffer from ingesting As-contaminated water. In Latin America, at least conditions (e.g., Chaco-Pampean Plain of Argentina and Uruguay). Geothermal water mixing with freshwater resources is important in many regions of the Andes as well as the active volcanic areas of Central America and Mexico. Detailed infor­mation about As occurrence in water resources of Latin America, the related health effects and experiences on remediation are described in Bundschuh et al.(2008 2009). In this paper, we will only give a short summary of the principal regions of Latin America where the water resources are contaminated by As

Sonochemical reduction of Cr(VI) in air in the presence of organic additives: What are the involved mechanistic pathways?

The sonochemical (850 kHz) reduction of Cr(VI) (0.3 mM, pH 2, reactor open to air) was analyzed in the presence of different additives. The effects on Cr(VI) reduction efficiency of added formic acid (FA, 10 mM), citric acid (Cit, 2 mM), ethylenediaminetetraacetic acid (EDTA, 1 mM), methanol (MeOH, 0.1 M), ethanol (EtOH, 0.1 M), 2-propanol (2-PrOH, 0.1 M), tert-butanol (t-BuOH, 0.1 M), phenol (PhOH, 2 mM) and sodium lauryl sulfate (SLS, 1 mM) have been evaluated in comparison with the system in the absence of additives. Complete Cr(VI) reduction was obtained only when using EDTA (at 120 min) and Cit (at 180 min). Cr(III) complexes with these compounds or with their degradation products were detected as final products. For EDTA, Cit, t-BuOH, FA and SLS, the Cr(VI) decay could be adjusted to a zero-order kinetics; in the cases of MeOH, EtOH and 2-PrOH, there was a deviation from the zero-order kinetics. The Cr(VI) conversion increased in the order SLS (very low) < no additive ≅ MeOH ≅ EtOH ≅ 2-PrOH < FA < t-BuOH < PhOH < Cit < EDTA. The role of EDTA and Cit in stabilizing intermediate Cr(V) peroxo compounds and enhancing their direct transformation into different Cr(III) species is considered a major factor in the acceleration of Cr(VI) reduction processes. Mechanistic pathways are proposed

Low-cost technologies for arsenic removal in the Chaco-Pampean Plain, Argentina

Groundwater of the Chaco-Pampean plain of Argentina contains levels of arsenic (As) exceeding drinking water standards. The situation is more serious in rural areas, causing a high incidence of CERHA (Chronic Endemic Regional Hydroarsenicism). Results of treatment experiments involving either heterogeneous photocatalysis (HP) or zerovalent iron (ZVI) in plastic bottles to remove As from groundwater are presented as low-cost technologies to remove As. For HP tests, synthetic or natural samples containing As placed in bottles impregnated with a TiO2 layer and exposed to solar or artificial UV light followed by an addition of iron resulted in As concentration well below drinking water standards. For ZVI tests, iron wool was shown to be a better iron source than packing wire for As removal. Solar irradiation, in synthetic as well as in natural samples, improves As removal, avoiding the use of high amounts of iron