Angewandte Chemie International Edition

Cover image for Vol. 56 Issue 23

Editor: Peter Gölitz, Deputy Editors: Neville Compton, Haymo Ross

Online ISSN: 1521-3773

Associated Title(s): Angewandte Chemie, Chemistry - A European Journal, Chemistry – An Asian Journal, ChemistryOpen, ChemPhotoChem, ChemPlusChem, Zeitschrift für Chemie

For full article and contact information, see Angew. Chem. Int. Ed. 2002, 41 (20), 3878 - 3881

No. 20/2002

Communication through Cellular Walls

Synthetic receptor system mimics
transmission of biological signals

Living organisms are made of individual cells that are separated from their environment by a lipid membrane. In order to have a meaningful coexistence, these cells must communicate with each other. For example, hormones are messenger compounds that carry information throughout the body. It is not necessary for these messenger molecules to gain entrance into the interior of the cell in order to "deliver" their message; communication can also occur through the cell wall - like a knock.

A British research team led by Christopher A. Hunter and Nicholas H. Williams of the University of Sheffield has been able to recreate such a signal transmission system using relatively simple chemical compounds. The artificial transmitter works according to the following principle: Synthetic receptors are embedded in a membrane made of artificial vesicles. A vesicle is a bubble of liquid surrounded by a membrane. The receptors consist of rod-shaped molecules with reactive groups at both ends, which protrude from the membrane. Half of the receptors have a small dye molecule coupled to the end that is inside the vesicle. Next, the messenger molecules are introduced. These cause the endgroups on the exterior surface to react with each other, coupling the receptors together, pair by pair, into dimers. This causes the coupled receptors’ endgroups on the interior of the vesicle to come very near each other - near enough that they too can now react. Under the conditions inside the vesicle a reaction can only occur between one endgroup with and one endgroup without a dye molecule. This causes the dye to be split off and released into the vesicle - as the receptor system’s reply to the exterior messenger. In principle, this could now trigger further steps in a signal cascade.

The concept of a vesicle that reacts to its environment could be used for the development of "intelligent" transport systems for pharmaceutical agents. An inactive drug precursor could thus be injected while enclosed in vesicles. A messenger molecule that occurs only in the target organ or in diseased tissue could then start off a catalytic reaction within the vesicle, converting the precursor to the active drug right on the spot. When the contents of the vesicles are released, healthy cells are only exposed to the inactive precursor substance, while the diseased cells get the effective medicine.