Structural blueprint for dry mRNA vaccine patches eliminates need for cold-chain storage

An international research team has mapped the structural changes that occur when fragile genetic vaccines are dehydrated, establishing a clear blueprint for room-temperature mRNA microneedle patches

By removing the need for ultra-cold refrigeration, this technology addresses a massive logistical barrier to global immunisation efforts.

The study, published in the journal Advanced Functional Materials, is a collaboration between RMIT University, the Massachusetts Institute of Technology (MIT), and Harvard Medical School.

Overcoming the cold-chain barrier

Standard mRNA vaccines must be kept at sub-zero temperatures (ranging from -90° to -15°) to prevent their delicate components from breaking down. This strict “cold chain” adds steep costs and specialised infrastructure requirements to transport networks, often excluding low-resource regions.

According to data from the World Health Organisation and UNICEF, complex logistics contributed to 14.3 million children worldwide receiving no vaccines in 2024.

Dissolvable microneedle patches offer a solution. These patches feature hundreds of microscopic tips that painlessly deliver a vaccine directly into the skin, dissolving upon contact. While prior MIT research demonstrated that these patches could technically be printed and stored at room temperature using a model system, the exact physics governing how the payload survives drying remained unknown.

The microscopic impact of drying and rehydration

The new study fills this knowledge gap by explaining why certain dry formulations successfully safeguard the vaccine while others fail.

mRNA cannot travel into the body alone; it is encapsulated inside lipid nanoparticles (LNPs)—tiny, engineered fat bubbles that protect the genetic material and assist its entry into human cells. When these LNPs are blended into a wet polymer matrix and dried into a solid patch, they undergo intense structural stress.

To track this transformation, the research team used advanced imaging and in situ small-angle X-ray scattering (SAXS) to analyse the LNPs before drying, during dehydration, and after rehydration. They made several key structural discoveries:

• The inverse hexagonal phase:

  • Healthy LNPs display a specific internal arrangement known as an inverse hexagonal phase. The team discovered that if the nanoparticle is properly supported, it can completely recover this vital structure upon rehydration.

• The polymer-to-mRNA ratio:

  • The volume of polymer used in the patch matrix directly dictates LNP survival. If the polymer loading is too low, the LNPs become unstable, separate, and form destructive cholesterol crystals. The researchers found that a high polymer-to-mRNA ratio prevents this degradation.

• The molecular charge (N/P Ratio):

  • Adjusting the ratio of positively charged amines in the lipids to the negatively charged phosphates in the mRNA makes the particles physically tougher. Optimising this charge balance led to a 100-fold increase in transfection (the efficiency with which cells successfully absorb the mRNA and generate an immune response) upon rehydration.

Next steps toward global equity

By establishing the optimal balance between polymer thickness and nanoparticle architecture, the researchers have provided practical engineering rules for manufacturing shelf-stable, dry mRNA therapies.

Moving forward, the collaborative team from RMIT, MIT, and Harvard will continue optimising these patch formulas, transitioning to live trials to measure the precise immune responses they generate, and exploring whether this dry-stabilisation method can be applied to other advanced mRNA therapeutics.