Like "cellular foreign ministers", membrane-bound proteins govern the interactions of the cell with its environment. They thus hold important key positions and are accordingly very popular among research scientists – at least in theory, because in practice these active membrane proteins are difficult to control. Ultimately, they often have complex structures and exert their biological activity only in certain spatial conformations and arrangements.

At the Fraunhofer IGB, therefore, hybrid biological and synthetic particles have been developed which simulate the properties at the cell surfaces. On the surface of these cell-mimetic, i.e. cell-imitating, nanoparticles, membrane proteins are bound in such a way that their biological properties are fully maintained.

Fig.: Silica nanoparticles, scanning electron microscopic image.

The basis of these so-called Nanocytes^® is constituted by chemically customized nanoparticles which are created either from silicon oxide and other inorganic materials or from different organic polymers. The surface of the tiny particles can be modified according to their use so that different biomolecules can be bound to them.

With the hybrid particles, research scientists at the Fraunhofer IGB have created a variable building block system which can be used as a qualitatively new tool in cell biological or immunological research and in diagnostic systems. Nanocytes^® can also be used in medical technology as a component of composite membranes.

Fig.: Active principle of Nanocytes®. Silica nanoparticles are functionalized with a cytokine (TNF) and induce the specific cell response by binding to the target cell receptor.

Anyone with cancer not only has to suffer from the disease, but also from surgery, chemotherapy and radiation with their sometimes severe side-effects. No wonder that intensive work is being undertaken on gentler treatment alternatives. One source of hope is to be found in the cytokines of tumour necrosis factors (TNF). These membrane-bound signal proteins induce programmed cell death (apoptosis) in tumor cells. In co-operation with the Institute for Cell Biology and Immunology of the University of Stuttgart (Prof. Klaus Pfizenmaier), bio-active cytokine (TNF) has been coupled to silica particles. The resultant Nanocytes^® cause suicidal reactions in cultured human cells, which otherwise are known only with membrane-bound cytokines.

Cytokine-functionalized Nanocytes^® thus open the way to entirely new experimental approaches in immunological and cell biological research, as well as in the development of diagnostic procedures. For therapeutic use, Nanocytes^® would also have to be provided with a biological target function in addition to the cytokine. As a result of this detection function, cytokine Nanocytes^® could then one day journey through the human body, identify cancer cells among thousands upon thousands of body cells, bind to them and trigger targeted self-destruction.

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Fig.: Nanocytes® (marked in red) link up with a target cell (with proteins marked in green inside the cell) and trigger programmed cell death.
Top: after 20 minutes.
Bottom: after 40 minutes.