Silk stabilizers could eliminate need for ‘cold chain’

Researchers have developed a new silk-based stabilizer that kept some vaccines and antibiotics stable up to temperatures of 140 degrees Fahrenheit.

The team said this result is a step toward eliminating the need to keep some vaccines and antibiotics refrigerated from manufacture until use with a “cold chain.” This could save billions of dollars every year and increase the accessibility of such drugs.

The investigators used silk protein matrices to immobilize the bioactive molecules in vaccines and antibiotics. These silk stabilizers protected the drugs when they were stored at higher-than-recommended temperatures and for periods far longer than recommended.

David Kaplan, PhD, of Tufts University School of Engineering in Massachusetts, and his colleagues described these results in PNAS.

Keeping medications cold from production until use is a costly process, accounting for as much as 80% of the price of vaccinations. And failures in the cold chain result in the loss of nearly half of all global vaccines, according to researchers.

In an attempt to solve these problems, Dr Kaplan and his colleagues have been working with silk films that essentially wrap up the live bioactive molecules present in antibiotics and vaccines. This protects these bioactive elements and can greatly extend the shelf-life of the medication.

“Silk protein has a unique structure and chemistry that makes it strong, resistant to moisture, stable at extreme temperatures, and biocompatible, all of which make it very useful for stabilizing antibiotics, vaccines, and other drugs,” Dr Kaplan said.

To test their silk stabilizers, the researchers stored measles, mumps, and rubella vaccines for 6 months at the recommended 39.2 degrees Fahrenheit, as well as at 77, 98.6, and 113 degrees Fahrenheit.

The results showed that encapsulation in the silk films maintained the potency with minimal loss over time and enhanced stability, even at very high storage temperatures.

Similarly, antibiotics entrapped in silk films maintained near optimal activity, even at temperatures as high as 140 degrees. In addition, the silk films protected one antibiotic against the detrimental effects of light exposure.

Dr Kaplan said the silk stabilizers are likely to combine well with a silk microneedle system he developed. The tiny needles can deliver medication directly to skin cells that contain a specified antigen.

This targeted approach permits the administration of lower doses of medication or vaccine and generates longer-lasting immune responses. The combination could prove to be a simple way to stabilize, distribute, and deliver the medication in one system.

Of course, more research is needed to determine if this approach will be effective and to ascertain the full potential of the silk stabilizers. 

“New studies are already under way,” Dr Kaplan said. “We have already begun trying to broaden the impact of what we’re doing to apply to all vaccines. Based on what we’ve seen with other proteins, peptides, and enzymes, there’s no reason to believe that this wouldn’t be universal. This could potentially eliminate the need for a cold-chain system, greatly decreasing costs and enabling more widespread availability of these life-saving drugs.”

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