Once the probe is inside a cell, laser light shone on to it is absorbed then re-emitted, causing nearby proteins in the cell to vibrate according to their shape. As molecules change shape with disease progression, they give rise to different vibrational frequencies. Scientists can measure and interpret these vibrations, to understand how the cell is responding to disease.

Gold is used to coat the sensor because it is an un-reactive metal, preventing the body from rejecting the implant. The laser technique is highly sensitive, fast and uses a low-power laser. By observing how molecules interact, the probes could be a useful tool to learn more about diseases at a very small scale, say researchers.

Further studies will look at diseases linked to the immune system in the first instance, but researchers say the technique has potential to help doctors diagnose and monitor a range of conditions.

"By creating a sensor that can safely be implanted into tissue and combining this with a sensitive light-measurement technique, we have developed a useful device that will help diagnose and track disease in patients," said Dr Colin Campbell, who led the research.