This work aimed at characterizing Arrabidaea chica dry extracts obtained by spray dryer, after blending with gum arabic and/or maltodextrin in different proportions. Thermogravimetry, derivative thermogravimetry and differential thermal analysis were used to determine their thermal profile. Thermal analysis demonstrated that the blend containing 25% A. chica extract, 25% gum arabic and 50% maltodextrin had the strongest interaction between adjuvants and hydroalcoholic extracts, thus proving the best blending proportion. Infrared spectroscopy profile, which was used to infer the chemical composition of both the plant material and such a blend, showed typical absorption bands deriving from links of functional groups remained over the plant material. Scanning electron microscopy revealed a heterogeneous morphology of both dry extract and formulations with smooth surface and rough surface. Thermoanalytical techniques and spectrophotometry proved valuable tools to investigate physicochemical characteristics of formulations

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The development of a nanoparticulate system for the carrier antigen is now an important tool in the vaccination process, since a smaller number of doses is necessary for effective immunization. Thus, in this work a nanoparticulate system using polymers of chitosan and poly (methacrylic acid) (CS–PMAA) to adsorb the Vi antigen of Salmonella Typhi was developed. CS–PMAA nanoparticles with different proportions of chitosan and poly (methacrylic acid) were obtained and reached sizes from 123.9 ± 2.48 to 234.9 ± 2.66 nm, and spherical shapes were seen in transmission microscopy. At pH 7.2, the nanoparticles had a cationic surface charge that contributed to the adsorption of the Vi antigen. Qualitative analyses of the isolated Vi antigen were performed using Fourier-transform infrared spectroscopy, which indicated the presence of all the characteristic bands of the capsular polysaccharide, and nuclear magnetic resonance, which showed signals for the five hydrogens and the N-acetyl and O-acetyl groups which are characteristic of the Vi antigen structure. In the adsorption kinetics study, the Vi capsular antigen, contained in a phosphate buffer solution of pH 7.2, experienced 55% adsorption on the 1–1% (CS–PMAA) nanoparticles. The adsorption kinetics results showed the ability of the nanoparticulate system to adsorb the Vi antigen.