Thermally stable vaccines
The encasing of proteins in silica to improve their thermal stability
Scientists have unveiled a novel technique, ensilication, for improving the storage of proteins, such as vaccines and antibodies. The study, detailed in Scientific Reports, showed that by trapping proteins in a silica cage, they could be protected from denaturation at room temperature, while retaining their structure and function.
The transportation of biopharmaceuticals can be a logistical headache. A ‘cold chain’ is needed, constant refrigeration throughout the transit, and breaks in this chain are a particular threat to vaccination programmes in developing countries. New strategies are urgently needed to facilitate the distribution of temperature-sensitive medicines, which will help us to get rid of continuous refrigeration.
A team of scientists took inspiration from marine diatoms - organisms, which secrete an enzyme building silica shell to sound their bodies for protection from the environment. In the same fashion, scientists apply silica coating on a variety of proteins and this coating prevents the protein from unfolding. The proteins are encased in ‘silica cages’ and subjected to high temperatures and prolonged storage times to test the limits of stabilisation and protection acquired by the silica application. Circular Dichroism (CD) at the dedicated B23 beamline at Diamond Light Source and an array of other techniques were used to assess the structure and function of the stored proteins.
Amazingly, ensilication shielded the proteins from the harmful effects of heat treatment and long-term storage at room temperature. The proteins did not need to be refrigerated to prevent degradation, as the silica preserved their structure and function. This new storage method could revolutionise the transportation and storage of medicine worldwide, making them more accessible to developing countries.
Figure 1: Dr Asel Sartbaeva observing the silcia encased vaccines. (Photo courtesy of University of Bath).
Biopharmaceuticals, such as antibodies and vaccines, must be transported and stored in cold conditions (2–8°C) in order to maintain their function. At room temperature, these proteins unfold and undergo denaturation, rendering them inactive. Although methods such as freeze-drying, biomineralisation and pegylation have been employed to preserve function, many vaccines cannot withstand such processes.
Scientists from the University of Bath and the University of Newcastle set out to improve the outlook for vaccine transportation with the application of silica. Silica has been used to improve the stability of enzymes during catalysis and there have been many other previous studies looking at adding silica to proteins for various applications. Specifically, to improve thermal stability
Chen YC et al. Thermal stability, storage and release of proteins with tailored fit in silica Scientific Reports 7, 46568 (2017). DOI: 10.1038/srep46568.
(Thumbnail photo courtesy of University of Bath).