A team of German scientists develop a new implantable sensor with promising results, according to a study published in Nano Letters (1). When implanted in rats, the new gold nanoparticle sensors not only measured the levels of antibiotic kanamycin accurately but also stayed in place for several months.
The idea of implantable sensors that can transmit information about the patient’s health has been on many researcher’s wish list for a very long time. These sensors would enable doctors to constantly monitor disease progression or the concentrations of drugs in the body to achieve higher rates of therapeutic success.
There are some prototypes being developed at the moment, but they’re not suitable to stay in the body for long periods of time and have to be replaced every couple of days. They also often trigger rejection by the body or become unstable and unreliable over time.
Now, a team of researchers from Johannes Gutenberg University Mainz (JGU) in Germany has created a new type of implantable sensors that can safely stay in the body for several months.
These tiny sensors are built with gold nanoparticles. The team opted to use this type of nanoparticles because gold can absorb and emit light and, as a consequence, the sensors look colourful. However, as gold particles only emit in the infrared, colour changes are invisible to the eye, and researchers need to use a special device to measure their colour through the skin. “Our sensor is like an invisible tattoo, not much bigger than a penny and thinner than one millimetre,” said Professor Carsten Soennichsen, head of the Nanobiotechnology Group at JGU.
To stop these sensors from being targeted by immune cells and rejected by the body, they’re embedded in a porous hydrogel with a soft tissue-like consistency. Once implanted under the skin, small blood vessels and cells can grow into the pores to connect the sensor to the body. Form this secure position, it can then report changes in the patient by altering its colour.
To test these new sensors, the team implanted them under the skin in hairless rats and monitored colour changes after administering various doses of the antibiotic kanamycin. Thanks to specific receptors located on the surface of the gold nanoparticles, the sensor was able to detect varying doses of kanamycin and changed colour according to the concentration. What’s more, the tissue-integrating hydrogel worked perfectly, and the sensor remained in place and stable for several months.
The team believe this is only the beginning, and there is a huge potential for gold particle sensors as long-lasting medical sensors. “We are used to coloured objects bleaching over time. Gold nanoparticles, however, do not bleach but keep their colour permanently. As they can be easily coated with various different receptors, they are an ideal platform for implantable sensors,” explained Dr Katharina Kaefer, first author of the study.
In addition, this new gold nanoparticle implantable sensor can be used in a wide range of conditions, including monitor concentrations of different biomarkers and drugs in the body. It’s not unreasonable to think these sensors could have applications in drug development, medical research or even personalised medicine, such as the management of chronic conditions.
(1) Kaefer K, Krüger K, Schlapp F, Uzun H, Celiksoy S, Flietel B, Heimann A, Schroeder T, Kempski O, and Sönnichsen C (2021) Implantable Sensors Based on Gold Nanoparticles for Continuous Long-Term Concentration Monitoring in the Body. Nano Lett. 2021 https://doi.org/10.1021/acs.nanolett.1c00887