Coating polymeric nanoparticles with extracellular vesicles as hybrid biomimetic nucleic acid vaccines

In recent years, traditional cancer therapies such as chemotherapy and radiotherapy have reached a plateau in terms of effectiveness, underscoring the need for innovative and targeted therapeutic approaches. Immunotherapy, specifically therapeutic cancer vaccines, have emerged as promising alternatives, boosting the immune system to combat cancer more safely, effectively, and specifically. In the present study, we addressed one of the main challenges associated with using mRNA as a therapeutic agent: its instability and susceptibility to degradation. The mRNA used encodes Ovalbumin, a specific antigen presented to monocytes differentiated into antigen-presenting cells (APCs), triggering a targeted and enhanced immune response against cancer cells. To overcome the limitations associated with mRNA instability, we employed poly(β-amino ester) (PBAE) polymeric nanoparticles to encapsulate mRNA. However, using polymeric nanoparticles alone poses challenges such as targeting specific cell types and potential immunogenicity. To further enhance mRNA stability and optimize its targeted delivery, we encapsulated these nanoparticles in extracellular vesicles derived from monocytes, the THP1 cell line. These vesicles leverage their inherent advantages, such as natural tropism for specific cell types, lower immunogenicity and greater biological compatibility, ensuring more efficient and targeted delivery of mRNA. The hybrid complexes were first characterized, and the encapsulation efficiency was assessed both qualitatively and quantitatively to determine the ability of the complexes to retain and deliver the drug to target cells. In vitro studies proved the efficacy of these hybrids, initially using permissive cell lines to compare transfection efficiency against nanoparticles alone. Subsequent studies on THP-1 cells, employing mRNA-GFP complexes, investigated the inherent tropism and targeting efficacy of extracellular vesicles. Once the targeting potential was confirmed, the immunological response of monocytes transfected with complexes containing the ovalbumin antigen was analyzed. Parallel experiments were conducted on monocytes and cytokine-induced monocytes differentiated into immature dendritic cells (APCs). The cellular response to antigen presentation was assessed by examining changes in cellular phenotypes, i.e. measuring the variations in marker expression and comparing them to the effects of nanoparticles containing the same antigen. This comparison aimed to confirm the enhanced targeting efficacy of the complexes due to encapsulation in extracellular vesicles. The results suggest that these hybrid complexes offer a promising approach for targeted drug delivery and effective antigen presentation, potentially improving the efficiency of immunotherapy strategies.