Materials scientist Molly Stevens believes that when it comes to sensing changes in the environment, nothing beats biological systems. Thats why shes turning to biological molecules to create "smart" nanomaterials that could lead to new, implantable sensing and drug delivery devices. Such devices would quickly detect physiological changes in the body, such as a rise in cholesterol, and respond by releasing the appropriate dose of a stored drug. Thats the vision, at least. But realizing it will require new kinds of materials that behave differently under different chemical conditions. Stevens has recently shown that she can control the behavior of gold nanoparticles by changing the pH of the solution in which they are suspended. She attached the particles to specially designed peptide molecules that, under the right pH conditions, interact with each other to pull the particles together into an organized structure. A change in pH alters the shape of the peptides so that they repel each other, and the particles disperse. "Were taking the best of natures creativity and using it for ourselves," says Stevens. The experiment shows that its possible to create materials that automatically reshape themselves in response to chemical changes in the body. Such a material could yield implantable drug delivery devices that act as their own biological sensors. Stevens is tapping into the versatility of peptides for the next stage of her work. Shes now engineering the peptides so that they change shape in subtler and more varied ways. A drug delivery device made using such peptides would be more sensitive to physiological changes and could offer more control over a multitude of different drug dosages. If her new project succeeds, Stevens will have played an instrumental role in making not only nanomaterials but drug delivery far smarter.