Hybrid thiolated polyacrylic acid and Schizochytrium sp-based particles: Synthesis, characterization, and initial evaluation as antigen delivery vehicles

Abstract

The development of safe and effective vaccines is key to public health. However, emerging diseases such as Ebola, COVID-19, Malaria, and Zika require innovative approaches. Vaccines activate the adaptive immune system through the innate response, enabling antigen presentation to lymphocytes and a long-lasting immune reaction.

Conventional vaccines (attenuated or inactivated) generate strong immune responses but may pose risks for pregnant and immunocompromised individuals. While subunit vaccines are safer, they require adjuvants to enhance their immunogenicity. Adjuvants can be immunostimulants or delivery systems, such as polymeric nanoparticles, which optimize antigen presentation and vaccine stability.

Natural and synthetic polymers, such as PLGA and PAA, are used in delivery systems due to their biocompatibility. Functionalization with thiol groups has improved immune cell uptake and mucosal adhesion. This study developed thiolated PAA/Schizo hybrid particles by combining PAA with the cell wall fraction of the microalga Schizochytrium sp., evaluating them as carriers for the SARS-CoV-2 RBD antigen.

The COVID-19 pandemic highlighted the urgency of developing fast and safe vaccines. Although platforms such as DNA, RNA, and viral vectors were approved in record time, the emergence of new variants justifies continued research. Nanotechnology has driven the design of nanoparticles with enhanced properties. Combining synthetic polymers with Schizochytrium sp. cell walls offers an innovative approach to creating biocompatible materials that function as both adjuvants and antigen delivery systems.