vander Straeten, AurélienDupont-Gillain, Christine C.Laurent, EulalieEulalieLaurent2025-05-142025-05-142025-05-142023https://hdl.handle.net/2078.2/33355The Covid 19 pandemic has contributed to highlight the worldwide inequalities to access vaccination, from which African developing countries suffered the most. If those countries are to be truly resilient in the event of any new pandemic, they have to increase their local vaccine production capacity. “Africa vaccinating Africa” can be achieved through the development of low-cost vaccines, simple and inexpensive local manufacturing processes and easy storage conditions, while maintaining adequate immune performance. In this context, Quantoom Biosciences is developing a new technology for producing mRNA vaccines to ensure vaccination is accessible to all. The aim of present study, performed in collaboration with Quantoom Biosciences, was to develop formulation strategy for mRNA encapsulation and delivery based on novel lipid-polymer hybrid nanoparticles that are free of intellectual property, cheap, easily processable and effective. Polymers and lipids were selected on the basis of literature review and criteria such as their availability, cost and freedom to operate. Several experimental designs were then implemented to model the effect of various parameters on physico-chemical properties of nanoparticles such as their size, size dispersion (PDI) and charge. Particles must be monodispersed (PDI<0.3), small (size<200 nm) and have a low absolute charge. By selecting promising systems step by step, nanoparticles meeting these criteria are obtained. To have monodispersed particles, the quantities of polymer and lipid must be adjusted and the higher they are, the lower the PDI. To have small particles, high ionic strength is recommended and particles of charge of low absolute value can be obtained by adding more or less polymer and lipid. The next step was to test the ability of most promising systems to efficiently encapsulate mRNA and to deliver mRNA in the cell cytosol with in-vitro and in-vivo assays. The ability of systems to encapsulate mRNA is mainly governed by the molar ratio of polymer to mRNA and by the pKa of polymer. The most crucial parameter to efficiently deliver mRNA in cell cytosol is the pKa of the polymer. To disrupt the membrane of the endosome, the polymer must have a pKa ranging from 6 to 7.4 and to release mRNA in the cytosol the polymer must have a pKa below 7. This work showed that the most promising systems are made up of polyplex core composed of two polymers (poly-histidine and poly-arginine) and a lipid shell composed of three lipids (DOPS, CHEMS and DMG-PEG). This work is a first contribution towards the development of simple technology for mass-producing vaccines that are cheap, effective, stable and accessible to all. It leads the way to further research on hybrid formulation optimization.Lipid-polymer hybridVaccineDelivery vehiclemRNA encapsulationNanoparticlesPolydispersity indextext::thesis::master thesisthesis:41007