Researchers have created a microneedle platform using fluorescent quantum dots that can deliver vaccines and invisibly encode vaccination history in the skin.
The team synthesised, encapsulated, and delivered cadmium-free and lead-free photostable biocompatible quantum dots into the dermis using a custom array of microneedles. The dots were applied in various patterns, which remain invisible to the naked eye but can be detected in infrared light.
The dots resisted photobleaching (simulating five years of sunlight) after delivery in isolated pigmented human skin.
Longitudinal in vivo imaging using a smartphone adapted to detect near-infrared light demonstrated that the microneedle-delivered quantum dot patterns remained bright and could be accurately identified using a machine learning algorithm nine months after application in rats.
In addition, inactivated poliovirus vaccine could also be delivered alongside the quantum dots in the rats, which produced neutralising antibody titers above the threshold considered protective.
This technology could be highly valuable in the developing world where poor vaccination record keeping is a challenge, by enabling decentralised data storage and biosensing, the study authors say.
They add that future safety studies and improvements to manufacturing will help take their idea beyond the proof-of-concept stage and towards real-world implementation.
The study appears in Science Translational Medicine.