Hydrogel could ease need for vaccine ‘cold chain’

An employee unseals a shipment of Sinopharm COVID-19 vaccine at the Harare International Airport on February 15, 2021 in Harare, Zimbabwe. The shipment comprised 200,000 doses of the Sinopharm vaccine donated by China. (Credit: Tafadzwa Ufumeli/Getty Images)

Even without refrigeration, a new hydrogel vastly improves the shelf life of vaccines, say researchers.

Nearly half of all vaccines go to waste due to the logistical obstacles involved in transporting them around the world. Most vaccines require strict temperature regulation from the manufacturing line to injection into a patient’s arm.

“Most vaccines are sensitive to hot and cold. This creates a large barrier for global immunization campaigns…”

Maintaining a constant temperature along the cold (supply) chain is a challenging feat in the best of circumstances. In Sub-Saharan Africa and other developing regions, for example, limited transport infrastructure and unreliable electricity compounds the already immense challenges of delivering viable vaccines.

A team from ETH Zurich’s Macromolecular Engineering and Organic Chemistry Labs and Colorado-based start-up Nanoly Bioscience worked together to develop a safe, versatile platform to increase the thermal stability of vaccines.

“Think of it like an egg,” explains Bruno Marco-Dufort, a doctoral researcher in professor Mark Tibbitt’s macromolecular engineering lab. “At room temperature or in the refrigerator the egg maintains its viscous-like protein structure, but once it hits boiling water or the frying pan its structure changes permanently.” It is similar for the proteins in a vaccine—once exposed to certain temperatures they clump together. Cooling them down again will not reverse their denaturation—you can’t ‘un-cook” the egg.

Hydrogel protection

So rather than altering mother nature, Marco-Dufort and the research team developed a new type of hydrogel, the details of which appear in the journal Science Advances. The gel is based on a biocompatible, synthetic polymer known as “PEG” that serves as a protective, “cloaking device” for very large—yet invisible to the naked eye—complex molecules such as the proteins found in vaccines, antibodies, or gene therapies.

The packaging works kind of like a molecular Tupperware, encapsulating the proteins and keeping them separate. It lets the proteins withstand a higher range of temperature fluctuations. Instead of the traditional +2 to +8 °C (35 to 45 °F) range for the cold chain, encapsulation allows for a range of 25 to 65 °C (75 to 150 °F). Most importantly, the encapsulated cargo is simply released by adding a sugar solution, enabling easy on-demand recovery of the vaccines at the place where they’ll be used.

The ‘cold chain’ is costly

In addition to a higher rate of vaccine viability, the real game changer of this new biomedical hydrogel technology is the potential economic effect it could have on reducing costs and health risks associated with the cold chain.

“In 2020, the overall market for cold chain services (from manufacturing to distribution) was $17.2 billion and forecasted to rise,” the researchers report. Rising costs pose potentially dire consequences for public health and public trust if vaccines arrive via a compromised cold chain.

“Most vaccines are sensitive to hot and cold. This creates a large barrier for global immunization campaigns, because vaccine distribution and administrative costs often exceed the costs of production,” explains Marco-Dufort. While more investments will be needed to shore up the cold chain, encapsulation offers a cost saving solution that could be put towards production of more vaccines and thus, save more lives.

Vaccines aren’t the only use

Yet, there is still a long way to go in terms of further research, safety studies, and clinical trials before the hydrogels can be implemented for vaccine distribution. Their more immediate use is for transporting heat sensitive enzymes used in cancer research, for example, or protein molecules for research in lab settings.

While new biotechnologies and cost savings are a step in the right direction, there are still tremendous logistical, political, and socio-economic challenges in resolving the global issues surrounding equitable vaccine distribution and vaccine hesitancy.

Marco-Dufort’s childhood experience living in the Democratic Republic of the Congo instilled a deep appreciation for the need for vaccines against infectious diseases, not just for COVID-19, but also for polio, meningitis, and Ebola. He’s particularly aware of the tremendous challenges people living in Sub-Saharan Africa face in terms of access to vaccines where infectious diseases are still prevalent.

Source: ETH Zurich