Tiny silica 'cages' to keep vaccines safe at high temperatures

Vaccines and antibodies could be transported and stored without refrigeration by capturing them in tiny silica 'cages', scientists have found.

The discovery by researchers at University of Bath in the UK could make transporting vital medicines to remote or dangerous places much easier, cheaper and safer.

Vaccines and many other medicines contain proteins which break down and become unusable at room temperatures, meaning they must be kept refrigerated for storage and transportation in a so-called "cold chain".

Loss of vaccines through breaks in the cold chain are a serious global public health issue, in particular for mass childhood vaccination programmes in the developing world.

Breaks in cold chain storage result in the loss of millions of doses of vaccines each year, researchers said.
The team, working with colleagues at the University of Newcastle in the UK, created a technique which can keep proteins intact at high temperatures up to 100 degrees Celsius, by encasing them in silica cages.

Silica, which sand is made from, is non-toxic and inert. Once the protein has been encased in silica it can be stored or transported without refrigeration before the silica coat can be removed chemically, leaving the proteins unaffected.

The method called ensilication will solve the costly and often impractical need for a cold chain to protect protein- based products including vaccines, antibodies and enzymes, researchers said.

"Once the proteins in a vaccine break down and tangle up, it is useless. You can think of it like an egg that has been boiled - it can not be unboiled," said Asel Sartbaeva from Bath's Department of Chemistry.

"The ability to store and transport proteins at room temperatures or even hotter would remove a major logistical problem for safely delivering vaccines and other medicines to patients around the world," said Sartbaeva, who led the project.

"We have demonstrated with ensilication that we can simply and reliably keep proteins from breaking down even at up to 100 degrees Celsius, or store them as a powder for up to three years at room temperature without loss of function.

When a protein in solution is mixed with silica, silicon dioxide binds closely around protein to match its shape and quickly builds up many layers, encasing the protein.

A major advantage of this method is that unlike similar techniques it does not require freeze-drying, something that around half of all vaccines would not survive intact. The finding was published in the journal Scientific Reports.