DNA 'cages' to deliver drugs

By combining DNA macromolecules with polymers containing iron, molecular 'cages' can be made: porous structures capable of carrying and delivering drugs or DNA-fragments.

By using small molecules as keys, the cage can be opened or part of the DNA can be freed. Scientists of the MESA+ Institute for Nanotechnology of the University of Twente in The Netherlands report about this in Angewandte Chemie International Edition, in their cover article on February 26, 2007.

DNA, being the carrier of genetic information in living creatures, can also be used in man-made technology, for instance in bioinformatics and DNA-computing. Scientists Yujie Ma and Mark Hempenius of the University of Twente managed to combine DNA macromolecules with synthetic polymers containing iron. The result is a novel way of creating porous structures, spherical 'cages' for example.

The walls of these cages are built step by step. The scientist therefore ingeniously use the different properties the two types of molecules have. DNA has a negative electrical charge while the polymer containing iron is positively charged. Another essential features of DNA is that the molecule is much more rigid than the polymer. The polymer wraps around the DNA and forms a very stable couple with it. What binds them together are electrostatic forces.

The spherical cage can transport medicine and deliver it locally. The cage can be opened by letting small molecules function as 'keys': they oxidize the iron and break the bond between the DNA and the polymer locally. In the same way, it is possible to free DNA-fragments from the cage, and apply them in gen therapy. Genes are then inserted into cells and tissue to treat inherited disease.

Macroporous materials like the new cages, with pore sizes larger than 50 nanometers, have a wide range of possible applications, but they are not easily fabricated until now. The DNA-polymer combination is an example of 'self-assembly' in which molecules organize themselves. It is a powerful new method to create the materials and an important step towards innovative applications.

The research, led by prof. Julius Vancso of the MESA+ Institute for Nanotechnology of the University of Twente and prof. Helmuth Möhwald of the Max-Planck-Institut für Kolloid- und Grenzflächenforschung in Golm, Germany, is published in the February 26 issue of Angewandte Chemie International.

http://www.utwente.nl

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