Microcontainers made from amino acids and polymers have potential uses in the controlled release of drugs, say German scientists.

Markus Antonietti and colleagues from the Max Planck Institute of Colloids and Interfaces, Potsdam-Golm, have made microcontainers with hollow centres from alternating layers of a positively charged amino acid-based compound and a negatively charged polymer. Attractions between the opposite charges hold the layers together.

Increasing the amount of carbon dioxide in the environment around the microcontainer, causes the positively charged amino groups to reversibly switch to negatively charged carbamates.  The carbamates and negatively charged polymer then repel each other causing the structure to open up.

The mild conditions needed for the switching means the microcontainers could be used to deliver medical drugs to specific locations in the body, said Antonietti. He hopes that when a microcontainer carrying a drug is administrated to oxygen starved tissues - with raised levels of carbon dioxide - the container will open releasing the drug it is carrying.

These microcontainers are made by layering a compound with 11 positively charged amino groups - based on the natural amino acid lysine - and a water-soluble polymer on to a silicon dioxide template. Removal of the template leaves a hollow container. Antonietti describes this as like casting a chocolate figure. 

Nicola Tirelli, Chair in Polymers & Biomaterials at the University of Manchester, UK, said that 'there is little doubt that this method can be utilised in a vast range of biomedical applications, and possibly also in bioreactor technology'.

Nicola Burton