- The cold chain is used to transport most vaccines at stable temperatures, usually between 2 and 8 degrees Celsius.
- It’s an expensive process, unavailable in many developing countries, and doesn’t always work in extreme climates such as the desert.
- NYUAD is working on ways to stabilize vaccines not thermally but chemically, eliminating the need for a cold chain.
- The research could improve access to critical vaccines for remote populations and reduce the cost of shipment.
A majority of conventional vaccines and therapeutic proteins require storage within a narrow temperature range to maintain efficacy, which poses severe limitations on the delivery of vaccines to remote locations with extreme climates or with underdeveloped infrastructure.
A process known as the cold chain was designed to provide a continuous chain of movement under optimal transport and storage conditions for vaccines and other medicines that are not stable at room temperature or when heated, from the point of manufacturing until the administration of vaccines in immunization programs.
Human lives depend on this cold chain. But in many developing countries, employing cold chain infrastructure proves challenging due to the high cost. And if you want to deliver vaccines to a remote village in a hot desert climate, like the UAE for example, those that cannot stabilize at 7-10 degrees Celsius will degrade. So, by the time they’re delivered they will be useless.
According to the World Health Organization
Absence of cold chain storage for antivenoms in rural health facilities is a contributing factor in delayed treatment for life-threatening snake bites.
Stabilizing vaccines chemically, not thermally
Since calcite, a common constituent of rocks and limestone, is cheap to produce, storing vaccines and other heat liable medications into calcite could circumvent this problem. By doing so, we can overcome the need to utilize other, more expensive vaccine delivery services such as the cold chain.
Different concentrations of the viral solution were added to a known concentration of calcite (calcium carbonate) solution prepared by mixing calcium chloride with ammonium carbonate). Next, the solution that was mixed with suspension of plant virus, used to model some of the vaccines, was left out to evaporate for several days. This causes the calcite to slowly crystallize and form small crystals that has the viral particles encapsulated within the crystals.
Calcite is a form of calcium carbonate that is abundant in nature. It is the main constituent of certain geological rocks and shells of various sea creatures. Calcite is safe, cheap, easy to synthesis and is known to be good host in encapsulating foreign substances making it a good candidate for this research project.
Although other compounds have been incorporated in the past, the results of this work have shown the ability of calcite to incorporate very large macromolecules, the size of viral particles, into its matrix. The embedded viral particles are thermally more stable than when they are free. The ability of calcite to encapsulate viruses can provide a simple and scalable method to incorporate viral particles into inorganic matrix and could prove useful in thermal stabilization of sensitive viral biological agents such as vaccines in the future.
Previous studies have shown calcite to be a good inorganic host in encapsulating small active biomolecules such as proteins inside its crystals. In this study, we took this concept a step further by successfully incorporating even larger biomolecules (viruses) into the crystals of calcite. The incorporation of thermally unstable molecules such as viral particles into these inorganic crystals can enhance their thermal stability allowing vaccines to be delivered under the harshest conditions (desert) without the use of expensive services that deals with vaccine transportation.
About the Author
Marieh Bassam Al Handawi is a Global PhD student in chemistry at NYU and NYU Abu Dhabi who earned her undergraduate degree in pharmacy at the University of Sharjah. Her research was recently highlighted on the cover of the journal Advanced Biosystems and won the UAE Undergraduate Research Competition.