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Digestive enzymes as door opener –

Store active ingredients in nanocapsules and release them selectively

Munich, 04/16/2009

Packed in capsules, active pharmaceutical substances are to be released only at the place of destination in the body, and detergents are to be dissolved only in the correct washing cycle: LMU scientists have now come a major step closer to achieving these ambitious goals. Thomas Bein, Professor of Chemistry, and his co-workers have developed a system, consisting completely of biological materials, for closing nanocapsules. These components are safe from a health point of view and, at the same time, ensure that the encapsulation is secure. The active ingredients stored can then be released selectively, for instance, by the addition of human digestive enzymes, which decompose a building block of the capsule. The work originated within the "Nanosystems Initiative Munich (NIM)" cluster of excellence.

Nanoporous capsules of silica are exceptionally suitable for encapsulating medicinal drugs, additives in detergents or other active ingredients. These substances can be stored very stably in tiny channels of a few nanometers (that is, 10-6 millimeters) in diameter. The objective is to release them at the desired place of destination or under certain conditions, for instance, by the addition of chemical substances or by a change in temperature. For this purpose, the capsules must first be closed off tightly. However, the materials primarily used previously for this purpose, such as cadmium sulfide, are either unstable or poisonous in a biological environment. They are therefore not suitable for storing active medicinal ingredients or detergent additives.

Professor Thomas Bein and his coworkers at the chair of Physical Chemistry II of the Ludwig-Maximilians-Universität (LMU) München have now found a very promising solution for this problem. For closing the capsules, they use a combination of biotin, that is vitamin B7, and avidin, a natural "adhesive" for biotin molecules. Both materials are safe from a health point of view and, at the same time, make it possible to close off the nanocapsules securely. The active ingredients stored may be released, for example, by the addition of trypsin, which is a mixture of human digestive enzymes. The trypsin decomposes the avidin and, in doing so, opens the capsule, so that the encapsulated active ingredient is released. "In principle, the trypsin functions as a door opener for the active ingredient", stated Bein. "This mechanism could be used, for example, for releasing detergent additives. However, applications in nanomedicine are also conceivable." (NIM/suwe)

The work, introduced in the current issue of "Angewandte Chemie", came about within the "Nanosystems Initiative Munich" (NIM) cluster of excellence, the objective of which is to develop, investigate and bring to fruition functional nanostructures for applications in information processing and the life sciences.

Printable pictorial material under:
www.nano-initiative-munich.de/press/press-material

Publication:
„Biotin-Avidin as Protease-Responsive Cap-System for Controlled Guest Release from Colloidal Mesoporous Silica“,
Axel Schlossbauer, Johann Kecht, and Thomas Bein
Angewandte Chemie, 2009, 48,3092 (April 14 2009)

Contact:

Professor Thomas Bein
Department for Chemistry and Biochemistry LMU Munich
Phone: ++49 (0) 89 / 2180 - 77621
E-mail: bein@cup.uni-muenchen.de

Dr. Peter Sonntag
Nanosystems Inivitative Munich (NIM)
Phone: ++49 (0) 89 / 2180 - 5091
E-mail: peter.sonntag@lmu.de

Responsible for content: Communications & Press Relations