This illustration depicts a proteoliposome — a spherical bilayer of fat molecules (white and blue) — stabilized in a structure called a zeolitic-imidazole framework composed of zinc and methylimidazole. Inserted into the lipid bilayer — which mimics a cell membrane — are modeled structures of CopA proteins, with a section (in pink) that resides inside the lipid and sections above the lipid surface (brown) and slightly inside the liposome (also brown, but inside). UT Dallas scientists developed a method to stabilize liposomes in a crystalline exoskeleton, which allows the biomolecules to remain stable at room temperature. (Credit: UT Dallas)

New research could help solve a major challenge in the deployment of certain COVID-19 vaccines worldwide — the need for the vaccines to be kept at below-freezing temperatures during transport and storage.

The new, inexpensive technique generates crystalline exoskeletons around delicate liposomes and other lipid nanoparticles and stabilizes them at room temperature for an extended period — up to two months — in their proof-of-concept experiments.

The researchers mixed liposomes — some with embedded proteins, some without — with a combination of two inexpensive chemicals, zinc acetate and methylimidazole, in a buffer solution. In about a minute, a crystal matrix began to form around individual liposomes. Once the biomolecules have grown a shell, they are locked in, and the lipids remain stable. While the exoskeleton is very stable. To release and reconstitute the liposomes, they used a zinc chelating factor called EDTA (ethylenediaminetetraacetic acid), which is a common, inexpensive food additive and medicine used to treat lead poisoning.