Infectious diseases caused by mucosal pathogens remain a major global health threat, with lower respiratory infections ranking among the leading causes of death worldwide. The COVID-19 pandemic highlighted the need for efficient immunization campaigns with vaccine platforms capable of targeting pathogens at the site of infection and effective widespread distribution. The shortfall of vaccine distribution infrastructure and global immunization effort comes mainly from the form of the vaccines themselves. Vaccines, primarily injectable vaccines, have high sensitivities to degradation and spoil, often needing to be kept thermally stable, requiring strict cold-chain storage. Orally administered, film-based mucosal vaccines have been proposed to be a viable alternative to current liquid-based injectable vaccinations. Thin films represent a versatile and promising mucosal delivery platform with improved thermostability and reduced reliance on cold-chain infrastructure. Films can be engineered to incorporate a wide range of antigens, including proteins, microparticles, and nanoparticles, and can be modified with organic adjuvants such as the polysaccharides chitin and chitosan to enhance antigen efficacy. Outer membrane vesicles (OMVs), naturally shed from gram-negative bacteria, retain outmembrane components that mimic pathogenic bacteria and elicit immune responses, yet are incapable of causing infection. Genetic engineering can be used to enable bacteria to present protein antigens on their outer membrane, which are subsequently incorporated into OMVs during shedding. Ultracentrifugation can then be used to isolate outer membrane vesicles at high concentrations from genetically engineered bacteria, enabling these vesicles to be viable antigen-presenting particles. Like liquid vaccines, OMVs do not possess long term stability at room temperature, needing to be kept thermally stable at -20°C. Thin films may provide a shelf stable platform for OMVs at room temperature.
This study evaluates the feasibility of thin film formulations as a platform for OMV-based mucosal vaccines by evaluating long-term nanoparticle recovery, film dissolution, and mechanical stability. Additionally, we explore the incorporation of organic polymers, including chitin and chitosan, as alternatives to synthetic polymers in OMV-loaded thin films. This work aims to investigate if OMVs can be structurally stable for up to 8 weeks depending on film components.
Acknowledgements: This work was partially funded by NSF-ERI: "Evaluation of the Immune Response to Lyme Disease Antigens Using Bacterially-Derived Outer Membrane Vesicles" (CBET 2347479).