Formation of intraneuronal iron deposits following local release from nanostructured silica injected into rat brain parenchyma.

Nanostructured materials with controllable properties have been used to cage and release various types of compounds. In the present study, iron-loaded nanostructured sol-gel SiO2-Fe materials were prepared and injected into the rat brain to develop a method for gradual iron delivery into the neurons with the aims to avoid acute iron toxicity and develop an animal model of gradual, metal-induced neurodegeneration. Nanoparticles were prepared by the traditional method of hydrolysis and condensation reactions of tetraethyl orthosilicate at room temperature and subsequent heat treatment at 200 °C. FeSO4 was added in situ during the silica preparation. The resulting materials were characterized by UV-VIS and infrared spectroscopies, X-ray diffraction, and N2 adsorption-desorption. An in vitro ferrous sulfate release test was carried out in artificial cerebrospinal fluid as the release medium showing successful ferrous sulfate loading on nanostructured silica and sustained iron release during the test time of 10 h. Male Wistar rats administered with SiO2-Fe nanoparticles in the substantia nigra pars compacta (SNpc) showed significant intraneuronal increase of iron, in contrast to the animals administered with FeSO4 that showed severe neuronal loss, 72 h post-treatment. Both treatments induced lipid fluorescent product formation in the ventral midbrain, in contrast to iron-free SiO2 and PBS-only injection controls. Circling behavior was evaluated six days after the intranigral microinjection, considered as a behavioral end-point of brain damage. The apomorphine-induced ipsilateral turns in the treated animals presented significant differences in relation to the control groups, with FeSO4 administration leading to a dramatic phenotype, compared to a milder impact in SiO2-Fe administrated animals. Thus, the use of SiO2-Fe nanoparticles represents a slow iron release system useful to model the gradual iron-accumulation process observed in the SNpc of patients with idiopathic Parkinson's disease.

Removal of aqueous chromium and environmental CO2 by using photocatalytic TiO2 doped with tungsten.

Removal of hexavalent chromium was accomplished by using photocatalyst materials of TiO2 doped with tungsten oxide, environmental air as oxygen supply and white light as irradiation source. Dichromate anions in concentration ranges of 50 to 1000 µg/L were removed by means of aqueous dispersions of TiO2 doped with tungsten. The aqueous chromium analyses were performed by Differential Pulse Voltammetry technique. Additionally, mineralization of CO2 gas was promoted by the photocatalysis process, as was clearly shown by Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS) analyses obtained from the TiO2 samples recovered after photocatalytic experiments. Results of sample analyses by Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM) are presented and discussed.