SMCr. VIII Congreso Nacional de Cristalografía. II Reunión Latinoamericana de Cristalogfrafía

VI Reunión de Usuarios de Luz Sincrotrón Mérida, Yucatán, México 23-27 de octubre del 2016.

Mesoporous Silica as a Vehicle for Oral Vaccines Márcia C. A. Fantini1,*, Francisco Mariano Neto1, Paulo R. A. F. Garcia1, Cristiano L. P. Oliveira1, Karina Scaramuzzi2, Osvaldo A. Sant´Anna2

1Laboratório de Cristalografia, Instituto de Física, Universidade de São Paulo, São Paulo - SP, Brazil 2 Laboratório de Imunoquímica, Instituto Butantan, São Paulo - SP, Brazil *e-mail: mfantini@if.usp.br Abstract. The ordered mesoporous SBA-15 silica was proved to be an effective adjuvant vector for oral vaccination. Different antigens were encapsulated into the SBA-15 matrix and the antibody production was monitored for recombinant protein Int1β (16.5 kDa), ~20 venom proteins and peptides of the snake Micrurus ibiboboca (84 to 7 kDa), Bovine Serum Albumin (66 kDa) and HBsAg protein (> 3000 kDa). The encapsulation yield of the antigens was determined by nitrogen adsorption isotherm (NAI) and small angle X-ray scattering (SAXS). Simulation of the in-situ SAXS scattered intensity of the Bovine Serum Albumin (BSA) release in PBS, gastrointestinal fluids revealed a slow evolution of BSA content, independent on the media. The studies included experiments regarding the coating of the SBA-15 silica with the Eudragit® polymer and the stability of SBA-15 in experimental media (water and PBS solution) and in simulated body fluids. The experiments showed the silica’s capacity of incorporating various molecules in its structure, as well as the influence of Eudragit® on the release dynamics. Biological studies showed that SBA-15 is a valuable adjuvant when compared to the traditional Al(OH)3 vehicle, and it is non-toxic to mice, rats, dogs and even cells, such as macrophages and dendritic cells. The silicon from the amorphous SiO2 walls of SBA-15 is released from mice organs and faeces. Recent studies showed that the immunological response is improved by enhancing the inflammatory response and the recruitment of immune competent cells to the site of injection as by the oral route and, most importantly, by increasing the phagocyte of a particulate antigen by antigen presenting cells. Key words: SBA-15, antigen, vaccine Ordered mesoporous silicas (OMS) have applications in several areas such as petroleum refining industry, catalysis and microelectronics [1-3]. The capacity of these materials to release and adsorb molecules inside their pores has been extensively studied also for medical applications, such as the encapsulation of drugs like anti-inflammatory ibuprofen [4], camptothecin and immobilization of globular enzymes [5]. In the field of immunology, the pioneer studies of Mercuri et al. [6] and Carvalho et al. [7] demonstrated that the SBA-15 acts as an efficient adjuvant. These studies showed unusual antibody production when the isogenic BALB/c line and the genetically selected High or Low outbred antibody responders mice were immunized with the SBA-15 as a vehicle to transport antigens. The objective of this work was to evaluate the ability of SBA-15 to protect and deliver antigens, producing high title of antibodies, as well as to determine the presence of silicon in mice organs and faeces. The analyis of antigen loading in SBA-15 was carried out by Nitrogen Adsorption Isotherm (NAI) and Small Angle X-ray Scattering (SAXS). The studies included experiments regarding the coating of the SBA-15 silica with the Eudragit® polymer and the stability of SBA-15 in experimental media (water and PBS solution) and in simulated body fluids. The experiments were performed mainly with bovine serum albumin (BSA), and showed the silica’s capacity of incorporating, in its structure, the various molecules, as well as the influence of Eudragit® on the release dynamics. The analysis of SAXS data included a theoretical model [8], whose results allowed determining the optimal antigen loading and releasing dynamics. Proton Induced X-ray Emission (PIXE) results obtained in calcined mouse organs showed that silica was present only in spleen after 35 days and it was completely eliminated after 10 weeks from all mouse organs. The PIXE experiments also showed the silicon release in mice faeces after second dose immunization. The Int1β protein is one of the subtypes of proteins found in Escherichia coli that is responsible for the infectivity of this pathogen and is a potential candidate for a vaccine based on its ability to induce immunity in infected humans (Figure 1). Also, the SBA-15 potentially acts in the enhancement of phagocytosis, the recruitment of inflammatory

SMCr. VIII Congreso Nacional de Cristalografía II Reunión Latinoamericana de Cristalogfrafía

VI Reunión de Usuarios de Luz Sincrotrón Mérida, Yucatán, México 23-27 de octubre del 2016