The delivery of antigens as DNA vaccines is an efficient alternative to induce immune responses against antigens, which are difficult to produce in recombinant form. However, the delivery of naked DNA is ineffective or relies on sophisticated ballistic devices. Here, we show a combination of liposome application and naked DNA vaccine that successfully overcomes these problems. Upon entrapment of plasmids encoding different antigens in cationic particles, transfection efficiencies similar to commercial kits were achieved in in vitro cell cultures. The liposome-based approach provided strong humoral responses against three malarial antigens, namely the Circumsporozoite protein and the C terminus of merozoite surface protein 1 from Plasmodium vivax (titers 104 or 103–104, respectively) and P. falciparum Rhoptry antigen 5 from Plasmodium falciparum (titers 103–104). When employed in P. falciparum growth-inhibition assays, antibodies demonstrated consistent reinvasion-blocking activities that were dose dependent. Liposome-formulated DNA vaccines may prove useful when targets cannot be produced as recombinant proteins and when conformation-dependent and highly specific antibodies are mandatory.

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Poly(ε-caprolactone)-block-poly(ethylene glycol)-poly(ε-caprolactone) (PCL-PEG-PCL, triblock) and Poly(ε-caprolactone)block-(poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide)-poly (ε-caprolactone) (PCL-PEO-PPO-PEO-PCL, pentablock) copolymers were synthesized by transesterification with reduction of PCL molecular mass, enabling fewer reactions, lower temperatures, and eliminating extensive purification steps. Free hydrophilic groups were removed from the samples by selective precipitation, and 1 H-NMR, FTIR, GPC and DSC analyses characterized the structure and properties of the resulting copolymers. The detection of remaining hydrophilic groups indicates the formation of the amphiphilic block copolymers (BCPs). Further, we obtained polymeric nanoparticles with monodisperse size distribution profiles by nano-precipitation from both the triblock and the pentablock copolymers using a microfluidic device, resulting 144.6 and 188.9 nm size and 0.093 and 0.102 nm polydispersity index, respectively. The nanoparticle assembly depends on the copolymer composition, and the possibility of nanoparticle assembly corroborates to the block structure of the copolymers, and the success of this synthesis route to obtain BCPs.