Biomembrane interactions in the toxicology of nanoparticles to microorganisms

Nanoparticles and nanomaterials are having in increasing application in modern life. There are concerns however about their effect on the ecosystem and associated organisms and possible harmful effects directly and indirectly on human health. This is very important because the physics and chemistry of nanoparticles is rather anomalous. The size of nanoparticles means that their behaviour in aqueous systems lies somewhere in between dissolved and particulate species. This will also apply to their interaction with and possible accumulation by biological organisms. This proposal is a pilot study which attempts to address these issues. We propose to use two simple but well established, fundamental models to obtain a deeper understanding of the biological activity and bioaccumulation of nanoparticles and nanomaterials which are generally considered as safe. The objective of the study is to evaluate the mechanism of the biological response to the nanoparticles, the involvement of the cell membrane in the process and the relationship of the mechanism to the physical chemical characteristics of the nanoparticles in the culture meda. The classical membrane electrochemical model consisting of a phopholipid monolayer on a mercury electrode will be employed to evaluate the putative biomembrane activity of the nanoparticles. A bacterial bioassay method will be used with cultures of cyanobacteria to assess the biological activity and the bioaccumulation of the nanoparticles. Both series of experiments on the two models will be closely coordinated. The bulk of the study will be spent:(i) Characterising the nanoparticles with respect to their particle size, shape, surface charge, crystal structure and composition both initially and when added to culture medium with particular attention to their properties in dispersion, (ii)Studying the effects of the nanoparticles on a model biological membrane system, (iii) Studying the effects of the nanoparticles on the viability of cyanobacterial cultures. In these initial experiments both the electrochemical and bioassay experiments will be carried out in a buffered culture medium. The aim is to test the hypothesis that the biological membrane is critical in the mechanisms of toxicity of the nanoparticles At the end of the study we shall have developed a protocol based on this hypothesis for relating the biological activity of nanoparticles towards cyanobacteria to their physical and chemical functionality.