Hydrogel "smart tattoo": a "barometer" for future health testing
During the microneedle patch test, the microneedle only penetrates less than 1 mm under the skin, and will not touch the nerves and blood vessels, so it will not bleed and the patient will feel no pain.
The four detection agents used as "ink" after the microneedle is pierced under the skin will detect human glucose, pH, uric acid and temperature, and show different colors on the tested part.
Recently, researchers from the Institute of Biomimetic Engineering and Biomechanics, School of Life Sciences, Xi'an Jiaotong University, have developed a "smart tattoo" made from a hydrogel microneedle patch, which may become a "barometer" for future health testing.
The research results were published in the international high-impact journal Advanced Science under the title "Multi-physiological index monitoring tattoos based on microneedle patches".
For many years, blood testing has been the gold standard of clinical biochemical analysis and has the advantages of high accuracy. However, blood testing is an invasive test, which greatly reduces user compliance and affects the feasibility of long-term monitoring.
For this reason, the development of a new minimally invasive sensing platform that can directly detect relevant biomarkers in body fluids has become an urgent need.
Hydrogel is a kind of extremely hydrophilic three-dimensional network structure gel, which can quickly absorb water and swell in water. Common hydrogels in life include jelly and aloe gel.
The "smart tattoo" developed by researchers at Xi'an Jiaotong University is actually a hydrogel microneedle patch.
On a 1.5 cm square microneedle patch, 100 microneedles made of hyaluronic acid are distributed. These microneedles are divided into 4 areas, and the microneedles in each area are loaded with different detection reagents.
Different detection reagents are equivalent to different colors of "ink" used in "tattoo".
When performing microneedle patch testing, you can choose to stick the patch on the flat skin. The microneedle only penetrates less than 1 mm under the skin and will not touch the nerves and blood vessels. Therefore, the microneedle test will not bleed and painless.
After the microneedle is pierced into the skin, hyaluronic acid will dissolve in the interstitial fluid under the skin. At this time, the four detection agents used as "inks" are like "hunters", which will quickly penetrate the epidermis and reach the dermis within a few minutes. The "prey" they look for are human glucose, pH, uric acid and temperature.
Many chronic diseases need to use these 4 indicators as auxiliary diagnostic methods.
When different detection reagents meet their own "preys", they start their respective "performances"-reagents for detecting pH will undergo acid-base reactions, and reagents for detecting glucose and uric acid will undergo redox reactions. The new substance produced will show a certain color on the surface of the skin, resulting in a "tattoo" effect on the epidermis.
The detection agent used to detect temperature is mainly temperature-sensitive powder. The temperature-sensitive powder will change the particle aggregation degree when encountering different temperatures, that is to say, different temperatures will also be displayed in different colors.
The test is usually completed within two or three minutes, and the tested part will show 4 different colors, as if it was a "tattoo" with different "inks".
At this point, the doctor can compare the color displayed by the "tattoo" with the standard chart to determine the human body's glucose, pH, uric acid, and temperature values.
At present, the research team has performed pH, glucose, uric acid and body temperature tests on live rabbits. Experimental results show that this "smart tattoo" can monitor pH and temperature changes for at least 4 days.
According to animal experiments, the use of the "smart tattoo" did not produce obvious skin toxicity, such as rash, redness, blisters or papules, cracking and thickening of the skin, etc., proving that it has good biocompatibility.
"Smart tattoo" can realize in-situ monitoring of a variety of targets, proving the feasibility of its application in health management.