Alginate Microsphere as a Delivery System and Adjuvant for Autoclaved Leishmania major and Quillaja Saponin: Preparation and Characterization

The goal of this study was to prepare and characterize alginate microspheres as an antigen delivery system and adjuvant for immunization against leishmaniasis. Microspheres encapsulated with autoclaved Leishmania major (ALM) and Quillaja saponin (QS) were prepared by an emulsification technique and characterized for size, encapsulation efficiency and release profile of encapsulates. Selection of appropriate parameters (viscosity of alginate, emulsifier and sonication times) enabled the preparation of alginate microspheres with a mean diameter of 1.92±1.0 μm, as determined by scanning electron microscopy and particle size analyzer. The encapsulation efficiency was about 34.2±6.7% for ALM and 31.0±4.4% for QS, as determined by spectrophotometric assays. In vitro release profile showed a slow release rate for encapsulated ALM and QS, 35.7±8.7% of ALM and 36.9±4.7% of QS were released during 1 week. The molecular weight was evaluated by SDS-PAGE and showed that the process of encapsulation did not affect the molecular weight of the entrapped antigen. With regard to the optimum diameter (less than 5 m), slow release rate and preservation of antigen molecules, formulated alginate microspheres could be considered as a promising antigen delivery system and adjuvant for ALM and QS.