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Tailored silver nanoparticles (NPs) in biological environments: Interactions with phase boundaries, biomolecules and cells

Mechanisms, rates and effects of the interactions between nanoparticles (NPs) and biological systems are expected to depend on a number of NP properties including size, shape, morphology, charge, and surface functionalities. Since silver has a well known bactericidal effect, tailored silver NPs have been selected for study in this work. However, despite their suspected biological activity very little is known about the detailed biological properties of silver NPs on a fundamental scientific level. This applies to all aspects of the "bio-nano response" including their ability to interact with biomolecules, to transfer across phase boundaries and membranes, to penetrate into cells and nuclei as well as to impact on important biological functions. Moreover, whilst it is frequently suggested that the biologically active agent of silver is the Ag-Ion itself, this suggestion has never been tested for silver in nanoparticulate form. In this project, therefore, silver NPs will be investigated with respect to the following aspects:

• The liquid-phase synthesis and characterization of silver NPs with variable but well defined size, shape, charge and surface functionalities.
• The kinetics and mechanisms of the transfer of silver NPs across surfactant layers and membranes as well as their interactions with proteins using state-of-the-art spectroscopic and optical tweezing techniques.
• The transport of silver NPs across carefully engineered artificial and bio-mimetic model membranes as well as the size selectivity of these membranes.
• The kinetics and mechanisms of the uptake of silver NPs into cells (leucocytes and mesenchymal stem cells) and cell nuclei and their impact on the selected cell-biological functions (cytokine release, proliferation, apoptosis, phagocytosis, chemotaxis and differentiation).
• The separation of the biological influences of silver NPs compared to that of silver ions.

It is expected that such investigations will help to identify and quantify the influence of selected physical-chemical properties of tailored silver NPs on their fate in complex biological environments. The collaborations between the partners will permit to link physical-chemical aspects of the interaction directly to the chemical and morphological characteristics as well as the biological response of human cells. This generates a new interdisciplinary level of comprehension of the processes involved.