Washington (AFP)
MIT engineers have invented injectable nanoparticles under the skin that emit fluorescent light invisible to the naked eye but visible by a smartphone, and which could one day be used to confirm that the person has been vaccinated.
The idea is to write proof of the vaccine on the body itself, in developing countries where paper vaccination cards are often wrong or incomplete, and where electronic medical records do not exist.
The system, described Wednesday in the journal Science Translational Medicine, has so far only been tested on rats but the researchers, funded by the Bill and Melinda Gates Foundation, hope to test them on humans in Africa in the next two years, says co-author Ana Jaklenec, biomedical engineer at MIT.
Engineers have spent a great deal of time finding components that are safe for the body, stable and capable of lasting for several years.
The final recipe is composed of copper-based nanocrystals, called quantum dots, 3.7 nanometers in diameter, and encapsulated in microparticles of 16 micrometers (1 micrometer equals one millionth of a meter, and 1 nanometer equals one billionth). The whole is injected by a patch of micro-needles 1.5 millimeters in length.
After being applied to the skin for two minutes, the micro-needles dissolve and leave small dots under the skin, distributed for example in the form of a circle or a cross. These small dots are excited by a part of the light spectrum invisible to us, close to infrared.
A modified smartphone, pointed at the skin, makes the circle or the cross appear fluorescent on the screen. Researchers would like to see the measles vaccine injected with these little dots. A doctor could years later point to a smartphone to check if the person has been vaccinated.
The technique is said to be more durable than indelible marking - the researchers simulated five years of exposure to the Sun. And it requires less technology than an iris scan or the maintenance of medical databases.
The limit of the concept is that the technique will only be useful for identifying unvaccinated children if it becomes the exclusive tool. Also, will people accept multiple markings under the skin for each vaccine? And what will happen to the points when the children's bodies grow?
The Gates Foundation is continuing the project and funding opinion polls in Kenya, Malawi and Bangladesh to determine whether people will be ready to adopt these microscopic quantum dots, or prefer to stick to old vaccination cards.
© 2019 AFP