Ordered mesoporous silicas for potential applications in solid vaccine formulations.

In an effort to develop efficient vaccine formulations, the use of ordered mesoporous silica (SBA-15) as an antigen carrier has been investigated. SBA-15 has required properties such as high surface area and pore volume, including narrow pore size distribution to protect antigens inside its matrix. This study aimed to examine the impact of solvent removal methods, specifically freeze-drying and evaporation on the intrinsic properties of an immunogenic complex. The immunogenic complexes, synthesized and incorporated with BSA, were characterized by various physicochemical techniques. Small Angle X-ray Scattering measurements revealed the characteristic reflections associated to pure SBA-15, indicating the preservation of the silica mesostructured following BSA incorporation and the formation of BSA aggregates within the macropore region. Nitrogen Adsorption Isotherm measurements demonstrated a decrease in surface area and pore volume for all samples, indicating that the BSA was incorporated into the SBA-15 matrix. Fluorescence spectroscopy evidenced that the tryptophan residues in BSA inside SBA-15 or in solution displayed similar spectra, showing the preservation of the aromatic residues' environment. The Circular Dichroism spectra of BSA in both conditions suggest the preservation of its native secondary structure after the encapsulation process. The immunogenic analysis with the detection of anti-BSA IgG did not give any significant difference between the non-dried, freeze-dried or evaporated groups. However, all groups containing BSA and SBA-15 showed results almost three times higher than the groups with pure BSA (control group). These facts indicate that none of the BSA incorporation methods interfered with the immunogenicity of the complex. In particular, the freeze-dried process is regularly used in the pharmaceutical industry, therefore its adequacy to produce immunogenic complexes was proved Furthermore, the results showed that SBA-15 increased the immunogenic activity of BSA.
Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Tereza S. Martins reports financial support and equipment, drugs, or supplies were provided by State of Sao Paulo Research Foundation. Tereza S. Martins reports financial support and equipment, drugs, or supplies were provided by Coordination of Higher Education Personnel Improvement. Osvaldo A. Sant Anna reports financial support and equipment, drugs, or supplies were provided by State of Sao Paulo Research Foundation. Marcia C.A. Fantini reports financial support and equipment, drugs, or supplies were provided by State of Sao Paulo Research Foundation. Marcia C.A. Fantini reports financial support and equipment, drugs, or supplies were provided by National Council for Scientific and Technological Development. Cristiano L.P. Oliveira reports financial support and equipment, drugs, or supplies were provided by State of Sao Paulo Research Foundation. Cristiano L. P. Oliveira reports financial support and equipment, drugs, or supplies were provided by National Council for Scientific and Technological Development. Jose L.S. Lopes reports financial support and equipment, drugs, or supplies were provided by State of Sao Paulo Research Foundation. Matheus C. R. Miranda reports financial support was provided by State of Sao Paulo Research Foundation. Jessica A. F. Pedro reports financial support was provided by State of Sao Paulo Research Foundation. Leonardo B. da Silva reports financial support was provided by Coordination of Higher Education Personnel Improvement. Carmen M. Nunes reports financial support was provided by National Council for Scientific and Technological Development. Luana F. Santos reports financial support was provided by National Council for Scientific and Technological Development.
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