Development, Characterization, and In Vitro Evaluation of Chitosan and Alginate Microspheres Loaded Tetanus Toxoid Vaccine: A Comparative Study

ABSTRACT

The feasibility and utility of in vitro methods to assess the release pattern of chitosan and alginate microspheres containing experimental tetanus toxoid (TT) vaccines were evaluated. Herein, TT was stabilized and encapsulated in chitosan (TTCH) and alginate (TTAL) microspheres by a W/O/W multiple emulsion method using sucrose as a protein stabilizer. Optimization of processing parameters was studied with regard to polymer concentration, cross-linker concentration, and stirrer speed. The morphology of TTCH and TTAL microspheres prepared was smooth and spherical in shape with a diameter of around 10 μm. The vaccine entrapment and the in vitro release efficiency of both TTCH and TTAL were evaluated by differing stabilizer (sucrose) concentrations (5, 7, 10, and 12% w/v) for a period of 70 days. Antigen releases from microspheres were determined by enzyme-linked immunosorbent assay (ELISA). From the results it was concluded that 1 and 4% (polymers), 1700 and 8000 rpm (stirrer speed), and 5 and 8% (cross-linking agent) were suitable for the preparation of TTCH and TTAL microspheres, respectively. In both TTCH and TTAL microspheres, sucrose with 10% w/v concentration gave good sustained antigen delivery for a period of 70 days. Both TTCH and TTAL vaccine formulations produced more or less equal release characteristics. Between the two polymers screened, both TTCH and TTAL were found to be good adjuvants, because the initial release characteristics were observed after 4 days, followed by constant release and almost 100% complete release after 70 days. This novel approach in TTCH and TTAL microspheres may have potential advantages for single-step immunization of vaccines.

KEYWORDS:

• tetanus toxoid
• chitosan microspheres
• adjuvant
• vaccine delivery systems
• alginate microspheres
• biodegradable polymers

Acknowledgments

We thank Sourabh Sharma and Tejpal Kashyap in the DTP section, Central Research Institute, Kasauli, for offering the gift sample of plain tetanus toxoid.