Influenza viruses can cause global pandemics with severe socioeconomic and lethal consequences. Today, whole inactivated influenza vaccines represent the most common strategy against pandemic influenza, although they are still poorly efficient in adults and elderlies. The combination of immunostimulants adjuvants with particulate carriers has led to the development of adjuvant systems capable of improving the efficacy and safety profiles of vaccines. This report investigates the co-encapsulation of two different immunostimulants, I.e. a saponin and a NOD2 agonist, in polymeric or lipid-based nanoparticles. Poly(D,L)-lactic-co-glycolic acid (PLGA) nanoparticles co-encapsulating α-tomatine, a saponin, and SG101, a NOD2-agonist synthesized by the University of Ljubljana, were prepared using a O/W emulsification and solvent evaporation technique. Dynamic light scattering and scanning electron microscopy are performed to measure particle size, polydispersity, and morphology of three selected polymeric nanoformulations, previously optimized, while their toxicity is assessed through in vitro studies on RAW 264.7 murine macrophages and sheep red blood cells. PLGA formulations 1 and 3 possess small and monodispersed particles that do not exhibit toxic activities on these two cell types, whereas the second one displays polydispersed and cytotoxic nanoparticles. Based on these results, only formulations 1 and 3 are chosen for further in vitro studies. In addition, two distinct conventional techniques, i.e. nanoprecipitation and thin-film rehydration, are applied to assemble liposomes co-entrapping SG101 with α-solanine, another saponin. Again, particle size, polydispersity, and surface charge of liposomes are studied. Results of dynamic light scattering highlight the presence of unstable lipid particles in the suspension fabricated via the nanoprecipitation technique, in contrast to small unilamellar liposomes obtained through the second method.