Construction of an Effective Delivery System for DNA Vaccines Using Biodegradable Polylactic Acid Based Microspheres

Background: Nanotechnology represents a new impetus for biomedical research applications, especially using nanotechnology to formulate microspheres or nanospheres based delivery system for treatment of infectious diseases in animals. Results: : Polylactic acid (PLA) microspheres with an average size of 156nm were prepared by combining emulsion polymerization coupled with emulsion−solvent evaporation. Coating with three different molecular weights of polyethylenimine (PEI) polymers increased the surface charges of the resulting PLA/PEI microspheres. Electrostatic interactions enabled plasmid DNA to adsorb tightly to the microspheres. After pig kidney-15 cells were cultured with the PLA/PEI/DNA complexes for 48 h, all three PLA/PEI microspheres successfully transferred plasmid DNA into the cells with high transfection efficiency. The protection rate of PLA/PEI microspheres loaded with DNA vaccine against foot-and-mouth disease in guinea pigs reached 87.5%, which was significantly higher than that of the control group injected with only DNA vaccine. Conclusions: : In this work, PLA/PEI microspheres were constructed by preparing PLA microspheres and modifying with PEI polymers, and were shown a great potential in improve the efficacy, biosafety and economic effects of DNA vaccines. The results indicated PLA/PEI microspheres were expected to be an effective delivery system for DNA vaccines.