SARS-CoV‑2 Nanovaccine Composed of Microfluidic-Produced Gold Nanoparticles Induces Neutralizing Immune Responses

The pursuit of effective and safe vaccines against severe acute respiratory syndrome caused by SARS-CoV-2 has posed a significant challenge for science in recent years, allowing the emergence of new vaccine strategies and platforms. Here, we present a coronavirus disease candidate vaccine based on gold nanoparticles (AuNPs), synthesized using a microfluidic process and conjugated to a SARS-CoV-2 Spike protein receptor binding domain (RBD). AuNPs of different sizes and morphologies were able to bind the RBD protein. Immunization of C57BL/6 mice demonstrated that conjugated AuNPs have consistently improved antigen-specific antibody responses in comparison with RBD alone, not only inducing higher IgG titers but also boosting the neutralizing capacity of antibodies. In addition, immunization with AuNPs of different sizes and morphologies led to significant differences in serum-virus-neutralizing antibody titers, suggesting that these factors play an essential role in the interaction of AuNPs and the immune system. In conclusion, our study highlights the use of conjugated AuNPs as an antigen-delivery system for protein-based vaccines against SARS-CoV-2 and opens perspectives for the application of this technological platform for the future development of nanoparticle-based vaccines against other infectious diseases.