Microsomal glutathione transferase 1 (MGST1) is an antioxidant enzyme located predominantly in the mitochondrial outer membrane and endoplasmic reticulum and has been shown to protect cells from lipid peroxidation induced by a variety of cytostatic drugs and pro-oxidant stimuli. We hypothesized that MGST1 may also protect against nanomaterial-induced cytotoxicity through a specific effect on lipid peroxidation. We evaluated the induction of cytotoxicity and oxidative stress by TiO(2), CeO(2), SiO(2), and ZnO in the human MCF-7 cell line with or without overexpression of MGST1. SiO(2) and ZnO nanoparticles caused dose- and time-dependent toxicity, whereas no obvious cytotoxic effects were induced by nanoparticles of TiO(2) and CeO(2). We also noted pronounced cytotoxicity for three out of four additional SiO(2) nanoparticles tested. Overexpression of MGST1 reversed the cytotoxicity of the main SiO(2) nanoparticles tested and for one of the supplementary SiO(2) nanoparticles but did not protect cells against ZnO-induced cytotoxic effects. The data point toward a role of lipid peroxidation in SiO(2) nanoparticle-induced cell death. For ZnO nanoparticles, rapid dissolution was observed, and the subsequent interaction of Zn(2+) with cellular targets is likely to contribute to the cytotoxic effects. A direct inhibition of MGST1 by Zn(2+) could provide a possible explanation for the lack of protection against ZnO nanoparticles in this model. Our data also showed that SiO(2) nanoparticle-induced cytotoxicity is mitigated in the presence of serum, potentially through masking of reactive surface groups by serum proteins, whereas ZnO nanoparticles were cytotoxic both in the presence and in the absence of serum.

The adsorption of palladium(II), rhodium(III), and platinum(IV) from diluted hydrochloric acid solutions onto Fe(3)O(4) nanoparticles has been investigated. The parameters studied include the contact time and the concentrations of metals and other solutes such as H(+) and chloride. The equilibrium time was reached in less than 20 min for all metals. The maximum loading capacity of Fe(3)O(4) nanoparticles for Pd(II), Rh(III), and Pt(IV) was determined to be 0.103, 0.149, and 0.068 mmol g(-1), respectively. A sorption mechanism for Pd(II), Rh(III), and Pt(IV) has been proposed and their conditional adsorption equilibrium constants have been determined to be logK=1.72, 1.69, and 1.84, respectively. Different compositions of eluting solution were tested for the recovery of Pt(IV), Pd(II), and Rh(III) from Fe(3)O(4) nanoparticles. It was found that 0.5 mol L(-1) HNO(3) can elute all of the metal ions simultaneously, while 1 mol L(-1) NaHSO(3) was an effective eluting solution for Rh(III), and 0.5 mol L(-1) NaClO(4) for Pt(IV). In competitive adsorption, the nanoparticles showed stronger affinity for Rh(III) than for Pd(II) and Pt(IV).

The adsorption of Co(2+) ions from nitrate solutions using iron oxide nanoparticles of magnetite (Fe(3)O(4)) and maghemite (gamma-Fe(2)O(3)) has been studied. The adsorption of Co(2+) ions on the surface of the particles was investigated under different conditions of oxide content, contact time, solution pH, and initial Co(2+) ion concentration. It has been found that the equilibrium can be attained in less than 5 min. The maximum loading capacity of Fe(3)O(4) and gamma-Fe(2)O(3) nanoparticles is 5.8x10(-5) and 3.7x10(-5) molm(-2), respectively, which are much higher than the previously studied, iron oxides and conventional ion exchange resins. Co(2+) ions were also recovered by dilute nitric acid from the loaded gamma-Fe(2)O(3) and Fe(3)O(4) with an efficiency of 86 and 30%, respectively. That has been explained by the different mechanisms by including both the surface and structural loadings of Co(2+) ions. The surface adsorption of Co(2+) on Fe(3)O(4) and gamma-Fe(2)O(3) nanoparticles has been found to have the same mechanism of ion exchange reaction between Co(2+) in the solution and proton bonded on the particle surface. The conditional equilibrium constants of surface adsorption of Co(2+) on Fe(3)O(4) and gamma-Fe(2)O(3) nanoparticles have been determined to be logK=-3.3+/-0.3 and -3.1+/-0.2, respectively. The structural loading of Co(2+) ions into Fe(3)O(4) lattice has been found to be the ion exchange reaction between Co(2+) and Fe(2+) while that into gamma-Fe(2)O(3) lattice to fill its vacancy. The effect of temperature on the adsorption of Co(2+) was also investigated, and the value of enthalpy change was determined to be 19 kJ mol(-1).