MIT engineers design a safer, more efficient vaccination system for farmed fish.
Researchers at MIT and the U.S. Department of Agriculture developed water-resistant, food-grade silk microneedles that can deliver vaccines through fish skin, and tested them in rainbow trout as small as 1 to 2 grams.
A team at MIT and the U.S. Department of Agriculture (USDA) has developed a possible alternative to injecting farmed fish by hand. The system uses water-resistant, food-grade microneedles that lightly penetrate fish skin, stay attached, and then decompose. In a paper in ACS Nano, the researchers showed the needles could carry a range of cargos, including bacterial vaccines.
The most effective vaccination method today relies on metal needles. Farmers sedate the fish, lift them out of the water, and place them on a conveyor belt, where workers inject them one by one. First author Meng Li, an MIT postdoc, said the work is labor intensive, costly, stressful for fish, and risky for workers, with a chance of cross contamination and accidental needle sticks. Other options, such as medicated feed or immersion in treated water, may not reach every fish, and immersion requires far larger quantities of treatment.
The microneedles are made of silk, a material Benedetto Marelli's MIT lab has used for years to deliver nutrients to plants. Early silk designs dissolved too quickly in water and failed to pierce fish skin. Li solved this by adding a thin shellac layer, a resin used in food coatings and pills, which acts as a moisture barrier. "Our criteria were safety for fish and humans alike," Li said.
The team made versions that lasted longer in water or released vaccine faster, with release times ranging from 15 minutes to 10 or 24 hours. The needles also preserved half of the structure of DNA plasmids after four weeks of dry storage. Marelli said this could help farms in rural areas that lack cold-chain infrastructure.
Gregory Wiens, a USDA researcher, said needle vaccination does not work well in trout until they reach about 30 grams, leaving small juveniles unprotected. He reported that the silk microneedles delivered bacterin or DNA vaccines underwater to fish as small as 1 to 2 grams. The researchers tested the approach in rainbow trout.
The authors said more work is needed before the device can be used at scale on fish farms. "We have all the components to believe this technology could be developed further," Marelli said. MIT's Abdul Latif Jameel Water and Food Systems Lab and the USDA supported the work.
Note: The headline describes the system as safer and more efficient, but the page calls it a potentially better approach, tested in rainbow trout, with more work needed before use at scale.
At a Glance
- The study was published in ACS Nano by researchers at MIT and the U.S. Department of Agriculture.
- Silk microneedles are coated with a thin shellac layer to keep them water-resistant until injection.
- The microneedles delivered vaccines to rainbow trout as small as 1 to 2 grams, per USDA researcher Gregory Wiens.
- Release times ranged from 15 minutes to 10 or 24 hours depending on the needle design.
- Microneedles preserved half of the DNA plasmids' structure after four weeks of dry storage.
Sources
This brief was written by Brightside Report from the reporting linked above. Spot an error? Request a correction.