Every year, a lack of vaccination leads to about 1.5 million preventable deaths, primarily in developing nations. One factor that makes vaccination difficult is the lack of infrastructure for storing medical records, so there’s often no easy way to determine who needs a particular vaccine.
Researchers have developed a way to record a patient’s vaccination history by storing the data in a pattern of dye, invisible to the naked eye, that is delivered under the skin at the same time as the vaccine. The new dye, which consists of nano-crystals called quantum dots, can remain for at least five years under the skin, where it emits near-infrared light that can be detected by a specially equipped smartphone.
To create an “on-patient,” decentralized medical record, the researchers developed a new type of copper-based quantum dots that emit light in the near-infrared spectrum. The dots are only about 4 nanometers in diameter but they are encapsulated in biocompatible micro-particles that form spheres about 20 microns in diameter. This encapsulation allows the dye to remain in place under the skin after being injected. The dye is delivered by a microneedle patch rather than a traditional syringe and needle. Such patches are now being developed to deliver vaccines for measles, rubella, and other diseases and the dye could be easily incorporated into these patches.
The microneedles are made from a mixture of dissolvable sugar and a polymer called PVA as well as the quantum-dot dye and the vaccine. When the patch is applied to the skin, the microneedles — which are 1.5 millimeters long — partially dissolve, releasing their payload within about two minutes. By selectively loading microparticles into microneedles, the patches deliver a pattern in the skin that is invisible to the naked eye but can be scanned with a smartphone that has the infrared filter removed. The patch can be customized to imprint different patterns that correspond to the type of vaccine delivered. Incorporating the vaccine with the dye in the microneedle patches does not affect the efficacy of the vaccine or the ability to detect the dye.
The researchers are working on expanding the amount of data that can be encoded in a single pattern, allowing them to include information such as the date of vaccine administration and the lot number of the vaccine batch.