Invisible tattoo<\/strong><\/h3>\nProfessor Carsten S\u00f6nnichsen\u2019s research group at JGU has been using gold nanoparticles as sensors to detect tiny amounts of proteins in microscopic flow cells for many years. Gold nanoparticles act as small antennas for light: They strongly absorb and scatter it and, therefore, appear colourful. They react to alterations in their surrounding by changing colour. Prof. S\u00f6nnichsen\u2019s team has exploited this concept for implanted medical sensing.<\/p>\n
To prevent the tiny particles from swimming away or being degraded by immune cells, they are embedded in a porous hydrogel with a tissue-like consistency. Once implanted under the skin, small blood vessels and cells grow into the pores. The sensor is integrated in the tissue and is not rejected as a foreign body.<\/p>\n
\u201cOur sensor is like an invisible tattoo, not much bigger than a penny and thinner than one millimetre,\u201d said Prof S\u00f6nnichsen, head of the Nanobiotechnology Group at JGU. Since the gold nanoparticles are infrared, they are not visible to the eye. However, a special measurement device can detect their colour noninvasively through the skin.<\/p>\n
In their study published in Nano Letters<\/em>, the JGU researchers implanted their gold nanoparticle sensors under the skin of hairless rats. Colour changes in these sensors were monitored following the administration of various doses of an antibiotic. The drug molecules are transported to the sensor via the bloodstream. By binding to specific receptors on the surface of the gold nanoparticles, they induce colour change that is dependent on drug concentration. Thanks to the colour-stable gold nanoparticles and the tissue-integrating hydrogel, the sensor was found to remain mechanically and optically stable over several months.<\/p>\n