Silk Film Acts As Vaccine Preservative

Researchers at Tufts University report that silk can keep vaccines from degrading without refrigeration (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.1206210109). The finding could help vaccine treatments reach more people in the developing world, where refrigeration is scarce and vaccines often heat up and lose potency before they can be administered. David L. Kaplan and colleagues dissolved silk protein in a salt solution, mixed it with measles, mumps, and rubella vaccine, and then dried the mixture into films. In the silk film, the vaccine was effective for more than six months at temperatures up to 45 ºC, whereas the dried vaccine alone lost nearly all potency. The researchers propose that silk protein traps the vaccine’s viral particles in spaces between its β-sheets, holding the particles in their native, folded state and preventing denaturation. Silk’s structure also excludes some water, enhancing its preservative qualities. The low toxicity and price of silk make it a good candidate for application, says Randolph V. Lewis, a silk protein expert at Utah State University. “It has huge potential in the human health area,” he says.