A nanoscopic capsule might be used to deliver pharmaceuticals at a specific disease site in the body. The self-powered capsule would wend its way to the site and on entering a cell exploit the specific redox chemistry it encounters in a diseased cell self-destruct releasing its payload. The research undertaken by a team at the Institute for Molecules and Materials at Radboud University in Nijmegen, The Netherlands, uses hydrogen peroxide as fuel to propel the capsule through a concentration gradient. It is held together by disulfide bridges which are broken in the presence of raised levels of the redox molecule glutathione found in a tumor cell.