Chemists in France have trapped live bacteria inside an aluminium-based ceramic, paving the way for new biomedical materials such as artificial bone.

Thibaud Coradin and colleagues at the Pierre and Marie Curie University, Paris, successfully encapsulated the live cells within an aluminium oxide gel. Many of the cells remained alive a month after being confined.

While it is relatively straightforward to encapsulate robust biomolecules such as enzymes and nucleic acids, live cells need careful handling, said Coradin. Metal oxide gels are typically made from the corresponding metal alkoxide, a strongly basic starting material that is toxic to cells. Coradin therefore developed an alternative route to the gel, using a pre-formed aluminium oxide colloid.

Bacteria can survive for a month trapped in an alumina matrix

On adding the bacterial culture to the colloid mixture, the gel formed within seconds. 'We think our colloidal approach could be extended to many other metal oxide materials,' said Coradin. 'It should then be possible to design living materials that combine the properties of an inorganic phase, such as conductivity and magnetism, with the biological activity of living cells.'

Jeffrey Brinker from the University of New Mexico, in Albuquerque, US, who studies encapsulated cells, said the material could lead to new ways to repair bone. 'This is the first demonstration of cell encapsulation in a nanocrystalline 3D matrix. It suggests that cells could be easily confined in nanocrystalline hydroxyapatite gels - the basic component of bone - perhaps providing a 3D matrix to assist new bone growth.'

James Mitchell Crow