Probing the Nano-Bio Interface Using Surface Based Analytical Techniques

Doctoral thesis, 2012

In recent years, the use of manufactured nanomaterials has been rapidly increasing in a wide range of application areas. Among others, these areas of application include cosmetics, medicine, clothing, and sporting goods. The small size of nanomaterials offers unique properties that are not possible to obtain by the same material in bulk. Although the use of nanomaterials holds great promises for society, the increased use and production also increases the concern that engineered nanomaterials may have adverse effects on human health or the environment. Unlike chemical substances, which have a defined structure and mass, nanomaterials need to be described by a large number of descriptors, e.g., size distribution, shape, and composition. In addition, to address possible effects on humans or the environment, it is of great importance to determine how nanomaterials interact with biological matter. Interactions with proteins, cell membranes, and cells may cause protein coronas, cellular uptake, or biocatalytic processes. To fully characterize such interactions there is a strong need for novel analytical techniques or methodologies. In this thesis, I have investigated how the lipid membrane, one of the most vital structures of a cell, interacts with various types of nanomaterials (e.g. polyelectrolyte complexes, graphene oxide, and TiO2 nanoparticles). The interactions between the model membranes and the nanomaterials have been studied using several complementary surface sensitive techniques. The results have showed conformational changes of polyelectrolyte complexes upon adsorption to the membranes and triggered disintegration of such complexes upon exposure to an acidic or a reducing environment. Furthermore, TiO2 nanoparticles have been shown to be able to disrupt lipid membranes in a Ca2+-mediated mechanism and a novel nanocomposite material, composed of alternating layers of graphene oxide and lipid membranes, has been prepared. In addition, the quartz-crystal microbalance with dissipation monitoring technique (QCM-D) has been explored in studies of intracellular transport processes using living cells. Specifically, pigment translocation in Xenopus laevis melanophores, has been shown to generate significant QCM-D responses. By using the described methodology, it is possible to evaluate the nanoparticle design and study how nanomaterials behave at a biological interface or effect specific cellular functions.