BackgroundRecent advances in development and industrial production of nanomaterials require assessment of their effects on human and animal health. Toxicity of nanomaterials has therefore become an issue regarding the question which methods are the most appropriate for determining health risk [1,2]. Nanomaterial introduces also effects that cannot be explained by composition of the material and chemical reactions, but require consideration of non-specific properties, such as size and shape of particles, their electromagnetic properties and interactions with biological material [3]. Since the underlying mechanisms are largely unknown, standard methods for research, testing and safety are not necessarily relevant for these materials. Standard methods for research and testing of various compounds include experiments on experimental animals. These methods were found to have poor predictability regarding other species, in particular human, as shown by carcinogeneity studies [4][5][6]. It was suggested that in vitro research may provide essential information pertaining to the human health risks posed by nanoparticle exposure [7]. With fast and extensive development of new nanomaterials and their use in medicine and industry there is urgent need to develop effective and low cost methods that will enable understanding basic processes in living organisms. The role of nonspecific biophysical mechanisms has hitherto been underestimated as potentially essential in revealing biological processes but should be considered in future paradigms of research and testing of nanomaterials.Exogenously added substances first come in contact with cells by interacting with the membrane, so it is of great interest to study the interaction of these substances with biological membranes. Convenient systems for such studies are mammalian erythrocytes and giant unilamelar phospholipid vesicles (GUVs) composed of a closed bilayer membrane. These entities do not have internal structure (other than cortical membrane skeleton in case of erythrocytes) so their equilibrium shape is determined by the minimum of the membrane free energy [8]. Interaction of the added substance with the membrane causes changes in the membrane properties and in the constraints imposed upon the cell/vesicle (fixed area of the membrane, fixed difference between the areas of the two membrane layers, fixed cell/vesicle volume) which is reflected in the shape change [9]. Since mammalian erythrocytes and phospholipid vesicles (sized up to 100 micrometers) can be observed under the optical microscope, the effect of the exogenously added substances can be directly followed in real time.Further, of special interest are processes caused by exogenously added substances that increase the risk for thromboembolic events [ 10]. Some parameters of these processes, e.g. activation of platelets and coalescence of membranous structures due to the presence of nanomaterial have previously been studied [11].Membrane -nanomaterial interactions could be considered as one of the basic elements i...