Stealthy nanodevices have been developed that may in future conduct "secret army" missions in the body to monitor or treat disease.
The large molecules, described as "bar-coded materials", only reveal their true identity and become active when they reach an intended target, for instance a tumour cell.
Each spherical chemical complex wears a plastic-like "invisibility cloak" that shields its biologically active components from the external environment.
DNA-based "zips" hold the cloak in place until they come into contact with a specific trigger. Only then does the device spring into action.
Because any DNA sequence can be chosen for the "zip", the release mechanism can be designed like a bar code that is selectively triggered by a cancer protein or other disease biomarker.
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The nanodevices could be made to deliver medicines, plant molecular "tags" to identify and track diseased tissue, or provide a "beacon" signal for other therapeutic agents to home in on.
Project leader Professor Cameron Alexander, from the University of Nottingham, said: "These types of switchable nanoparticles could be extremely versatile. As well as initial detection of a medical condition, they could be used to monitor the progress of diseases and courses of treatment, or adapted to deliver potent drugs at particular locations in a patient's body.
"It might even become possible to use mobile phones rather than medical scanners to detect programmed responses from later generations of the devices."
The scientists have so far conducted proof-of-concept tests in the laboratory which show that the nanoparticles respond as expected when presented with the right molecular signals.
Their findings are published in the journal Nanoscale.
Funding for the work has come from the Engineering and Physical Sciences Research Council (EPSRC).
While an early application of the technology might be testing for specific infections in blood or saliva samples, the team has much more ambitious aims.
In the long term the researchers hope to see "self-authenticating medicines" developed using the nanodevices that can seek out diseased tissue and report on their success.