Digestive enzymes as door opener –
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:
„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)
Professor Thomas Bein
Department for Chemistry and Biochemistry LMU Munich
Phone: ++49 (0) 89 / 2180 - 77621
Dr. Peter Sonntag
Nanosystems Inivitative Munich (NIM)
Phone: ++49 (0) 89 / 2180 - 5091