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Stable aqueous suspensions of colloidal C60 fullerenes free of toxic organic solvents were prepared by two methods: ethanol to water solvent exchange (EthOH/nC60 suspensions) and extended mixing in water (aqu/nC60 suspensions). The extended mixing method resulted in the formation of larger (dp approximately 178 nm) and less negatively charged (zeta approximately -13.5 mV) nC60 colloids than nC60 prepared by ethanol to water solvent exchange (dp approximately 122 nm, zeta approximately -31.6 mV). Genotoxicity of these suspensions was evaluated with respect to human lymphocytes using single-cell gel electrophoresis assay (Comet assay). The assay demonstrated genotoxicity for both types of suspensions with a strong correlation between the genotoxic response and nC60 concentration, and with genotoxicity observed at concentrations as low as 2.2 microg/L for aqu/nC60 and 4.2 microg/L for EtOH/nC60. The Olive tail moments (OTM) for these two concentrations were 1.54 +/- 0.24 and 1.34 +/- 0.07, respectively, which in comparison to the negative control OTM of 0.98 +/- 0.17 is statistically different with a p value of at least 0.05. Aqu/nC60 suspensions elicited higher genotoxic response than EthOH/nC60 for the same nC60 concentration. The results represent the first genotoxicity data for colloidal fullerenes produced by simple mixing in water.

Erythrocyte invasion by Plasmodium falciparum merozoites is a highly intricate process in which Plasmodium falciparum reticulocyte binding-like homologous protein 5 (PfRH5) is an indispensable parasite ligand that binds with its erythrocyte receptor, Basigin. PfRH5 is a leading blood-stage vaccine candidate because it exhibits limited polymorphisms and elicits potent strain-transcending parasite neutralizing antibodies. However, the mechanism by which it is anchored to the merozoite surface remains unknown because both PfRH5 and the PfRH5-interacting protein (PfRipr) lack transmembrane domains and GPI anchors. Here we have identified a conserved GPI-linked parasite protein, Cysteine-rich protective antigen (CyRPA) as an interacting partner of PfRH5-PfRipr that tethers the PfRH5/ PfRipr/CyRPA multiprotein complex on the merozoite surface. CyRPA was demonstrated to be GPI-linked, localized in the micronemes, and essential for erythrocyte invasion. Specific antibodies against the three proteins successfully detected the intact complex in the parasite and coimmunoprecipitated the three interacting partners. Importantly, full-length CyRPA antibodies displayed potent straintranscending invasion inhibition, as observed for PfRH5. CyRPA does not bind with erythrocytes, suggesting that its parasite neutralizing antibodies likely block its critical interaction with PfRH5-PfRipr, leading to a blockade of erythrocyte invasion. Further, CyRPA and PfRH5 antibody combinations produced synergistic invasion inhibition, suggesting that simultaneous blockade of the PfRH5-Basigin and PfRH5/PfRipr/CyRPA interactions produced an enhanced inhibitory effect. Our discovery of the critical interactions between PfRH5, PfRipr, and the GPI-anchored CyRPA clearly defines the components of the essential PfRH5 adhesion complex for P. falciparum erythrocyte invasion and offers it as a previously unidentified potent target for antimalarial strategies that could abrogate formation of the crucial multiprotein complex. malaria | erythrocyte invasion | protein-protein interactions | blood-stage vaccines | PfRH5

Titanium dioxide nanoparticles (TiO(2) NPs), widely used in consumer products, paints, pharmaceutical preparations and so on, have been shown to induce cytotoxicity, genotoxicity and carcinogenic responses in vitro and in vivo. The present study revealed that TiO(2) NPs induce significant (p < 0.05) oxidative DNA damage by the Fpg-Comet assay even at 1 µg/ml concentration. A corresponding increase in the micronucleus frequency was also observed. This could be attributed to the reduced glutathione levels with concomitant increase in lipid peroxidation and reactive oxygen species generation. Furthermore, immunoblot analysis revealed an increased expression of p53, BAX, Cyto-c, Apaf-1, caspase-9 and caspase-3 and decreased the level of Bcl-2 thereby indicating that apoptosis induced by TiO(2) NPs occurs via the caspase-dependent pathway. This study systematically shows that TiO(2) NPs induce DNA damage and cause apoptosis in HepG2 cells even at very low concentrations. Hence the use of such nanoparticles should be carefully monitored.

Cerium oxide nanoparticles (CeO2 NPs) have promising industrial and biomedical applications. In spite of their applications, the toxicity of these NPs in biological/physiological environment is a major concern. Present study aimed to understand the molecular mechanism underlying the toxicity of CeO2 NPs on lung adenocarcinoma (A549) cells. After internalization, CeO2 NPs caused significant cytotoxicity and morphological changes in A549 cells. Further, the cell death was found to be apoptotic as shown by loss in mitochondrial membrane potential and increase in annexin-V positive cells and confirmed by immunoblot analysis of BAX, BCl-2, Cyt C, AIF, caspase-3, and caspase-9. A significant increase in oxidative DNA damage was found which was confirmed by phosphorylation of p53 gene and presence of cleaved poly ADP ribose polymerase (PARP). This damage could be attributed to increased production of reactive oxygen species (ROS) with concomitant decrease in antioxidant “glutathione (GSH)” level. DNA damage and cell death were attenuated by the application of ROS and apoptosis inhibitors N-acetyl-L- cysteine (NAC) and Z-DEVD-fmk, respectively. Our study concludes that ROS mediated DNA damage and cell cycle arrest play a major role in CeO2 NPs induced apoptotic cell death in A549 cells. Apart from beneficial applications, these NPs also impart potential harmful effects which should be properly evaluated prior to their use.

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