In Vitro Evaluation of Optimized Diphtheria and Tetanus Toxoids Loaded Alginate Nanoparticles

Diphtheria and tetanus vaccine contains a high quantity of aluminum as an adjuvant potential to affect the nervous system, particularly in infants with kidney disease. Thus, the focus of this study was on in vitro preparation and evaluation to co-deliver DT toxoids by loading on alginate nanoparticles (NPs) as a non-toxic substance without antigenicity.

Using the gel-ionization method, alginate NPs samples were prepared and characterized in respect of size, zeta potential, and polydispersity index (PDI). The effects of alginate concentrations, calcium chloride, and Poly Lysine and the stirring time and speed in addition to the loading efficiency, loading capacity, and in vitro release profile were assessed.

The optimized NPs were prepared at a concentration of 0.02 %w/v sodium alginate, 0.1 %w/v calcium chloride, and 0.04% w/v Poly L-Lysine during 45 minutes of stirring at 1300 rpm. They also had a mean particle size <150 nm with a mean PDI of around 0.5. The appropriate  loading efficiency was obtained at a concentration of loaded toxoids similar to a conventional DT vaccine, which resulted in the prolonged release of about 85% of loaded toxoids over 120 hours. The SDS-PAGE and dot-blot confirmed the stability and antigenic activity of the released toxoids.

These results can significantly contribute to further developing alginate NPs containing DT toxoids in optimized in vitro conditions as a platform for in vivo evaluation to achieve a promising vehicle for immunization of infants and children against diphtheria and   tetanus.