Nano-encapsulation of modified protective antigen in PLA-PEG nanoparticles

Background: The Bacillus anthracis causes anthrax lethal disease. Traditional Anthrax vaccines require multiple injection doses due to their low stability to be fully effective. Polylactic acid (PLA) has been approved as a biodegradable and biocompatible polymer for drugs and vaccines delivery applications. The aim of this study is to encapsulate modified Bacillus anthracis protective antigen (mPA63) by PEG-PLA copolymers and characterizing the synthesized nanoparticles. Methods: After expression of the PA63 in E. coli, the produced antigen was purified by affinity chromatography and the encapsulation in PLA-PEG copolymer was done using double emulsion solvent evaporation method. The morphological characteristics of produced nanoparticles were evaluated by scanning electron microscopy and particle size, polydispersity index and Zeta potential were measured using dynamic light scattering. Results: The results of this study showed that the size of free protein-PLA-PEG nanoparticles and the protein-loaded nanoparticles were 162 nm and 233 nm, respectively and the polydispersity index for abovmentationed particles were 0.034 and 0.340, respectively. Also, electron microscopic images showed spherical shape of nanoparticles. The Zeta potential of PLA-PEG nanoparticles was -32.2 and PLA-PEG-PA63 nanoparticles have an average peak at -10.8mV. The encapsulation efficiency of the PA63 recombinant antigen in nanoparticles was 34%. Conclusion: From the result of this study it was showed that PLA-PEG copolymer has an appropriate ability to encapsulate the mPA63 and this system can be recommended as a candidate for an effective vaccine carrier in future investigation.

Anthrax vaccine, Recombinant antigen, Nano-carrier, PEG-PLA copolymer.