A new type of implantable, diagnostic ‘invisible tattoo’ has been developed, which could realize the reality of a long-lasting, medical sensor.
The new sensor was developed by researchers at Johannes Gutenberg University Mainz (JGU; Germany), and comprises gold nanoparticles (aka, ‘nanogold’) embedded into an artificial polymeric tissue that can be implanted under the skin, and reports on drug concentrations through changing its color.
Previously, the idea of implantable diagnostic sensors has been thwarted by the need for regular replacement owing to the body’s rejection of the implant, or the sensor’s color changing abilities fading over time.
The team, led by Carsten Soennichsen (JGU), solved these issues with the new sensor. The body’s cells populate the tissue-like, porous hydrogel, protecting the nanoparticles from rejection and degradation. The gold nanoparticles also do not suffer from bleaching and are adept as sensors, being easily coated with receptors. The team has been using their ability to change color depending on their surroundings to detect tiny amounts of protein in microscopic flow cells for a number of years.
The gold nanoparticles are infrared, resulting in an invisible ‘tattoo’ sensor of less than 1-mm thick, capable of detecting changes of drug concentration in the blood stream through their aptamer receptors.
In their latest study, the team implanted their gold nanoparticle sensors under the skin of hairless rats, using them to monitor the administration of various doses of an antibiotic. The sensor was mechanically and optically stable for several months.
The team hopes the sensor will make waves in a variety of fields, noting: “Because of the easy adaptability of gold nanoparticles toward different analytes, our concept will find versatile applications in personalized medicine or pharmaceutical development.” Theoretically, the concentrations of multiple drugs or biomarkers could be monitored simultaneously.
Soennichsen noted the new sensor is the result of a lot of teamwork, with his initial idea to use gold nanoparticles as implanted sensors arising in 2004. “Such a project requires many people with different scientific backgrounds. Step by step we were able to convince more and more people of our idea,” he mused.
While the results are the result of an already long period of work and are promising, human trials could still be far off – back in 2018 we reported on another implantable diagnostic sensor, this time to give an early warning for melanoma, where the team noted that the time period from animal trials to the market was expected to be at least 10 years owing to labor requirements and expenses associated with implant development that were beyond the reach of their lab.
