Adriano de Sousa

Immune response by nasal delivery of hepatitis B surface antigen and codelivery of a CpG ODN in alginate coated chitosan nanoparticles

Alginate coated chitosan nanoparticles were previously developed with the aim of protecting the antigen, adsorbed on the surface of those chitosan nanoparticles, from enzymatic degradation at mucosal surfaces. In this work, this new delivery system was loaded with the recombinant hepatitis B surface antigen (HBsAg) and applied to mice by the intranasal route. Adjuvant effect of the delivery system was studied by measuring anti-HBsAg IgG in serum, anti-HBsAg sIgA in faeces extracts or nasal and vaginal secretions and interferon-gamma production in supernatants of the spleen cells. The mice were primed with 10 microg of the vaccine associated or not with nanoparticles and associated or not with 10 microg CpG oligodeoxynucleotide (ODN) followed by two sequential boosts at three week intervals. The association of HBsAg with the alginate coated chitosan nanoparticles, administered intranasally to the mice, gave rise to the humoral mucosal immune response. Humoral systemic immune response was not induced by the HBsAg loaded nanoparticles alone. The generation of Th1-biased antigen-specific systemic antibodies, however, was observed when HBsAg loaded nanoparticles were applied together with a second adjuvant, the immunopotentiator, CpG ODN. Moreover, all intranasally vaccinated groups showed higher interferon-gamma production when compared to naïve mice.

Inclusion complexation of tolbutamide with β-cyclodextrin and hydroxypropyl-β-cyclodextrin

Inclusion complexes of tolbutamide with β-cyclodextrin and hydroxypropyl-β-cyclodextrin were prepared using different methods: kneading, coprecipitation and freeze-drying. Inclusion complexation in aqueous solution and in solid phase state was studied by the solubility method, X-ray diffractometry, thermal analysis and Raman spectroscopy. The solubility of tolbutamide increased as a function of cyclodextrin concentration, showing Bs and AL type diagrams for β-cyclodextrin and hydroxypropyl-β-cyclodextrin, respectively. The dissolution rate of tolbutamide/cyclodextrin complexes were investigated and compared with those of the physical mixtures and pure drug. The dissolution rate of tolbutamide from the inclusion complexes was much more rapid than tolbutamide alone.

Alginate coated chitosan nanoparticles are an effective subcutaneous adjuvant for hepatitis B surface antigen

We recently described a delivery system that is composed of a chitosan core to which the hepatitis B surface antigen (HBsAg) was adsorbed and subsequently coated with sodium alginate. In this present work, alginate coated chitosan nanoparticles were evaluated as a subcutaneous adjuvant for HBsAg. HBsAg loaded, alginate coated or uncoated chitosan nanoparticles, associated or not with CpGODN were subcutaneously administered to mice and several immunological parameters were evaluated. A high anti-HBsAg IgG titer (2271+/-120 mIU/ml), with the majority of antibodies being of Th2 type, was observed within group I, vaccinated with HBsAg loaded onto coated nanoparticles. However, regarding cellular immune response, no significant differences were observed for antigen-specific splenocyte proliferation or for the secretion of IFN-gamma and IL-4, when compared to the control group. The co-delivery of antigen-loaded nanoparticles in the presence of the immunopotentiator, CpG ODN 1826, resulted in an increase of anti-HBsAg IgG titers that was not statistically different from the first group; however, an increase of the IgG2a/IgG1 ratio from 0.1 to 1.0 and an increase (p<0.01) of the IFN-gamma production by the splenocytes stimulated with the HBV antigen was observed. The enhancement of the immune response observed with the antigen-loaded nanoparticles demonstrated that chitosan is a promising platform for parenteral HBsAg delivery and, when co-administered with the CpG ODN, resulted in a mixed Th1/Th2 type immune response.

Dissolution rate studies of pharmaceutical multisized powders : a practical approach using the Coulter method

Abstract The aim of this work is the study of the influence of particle size and related properties on the dissolution rate of a sparingly soluble drug indomethacin. Different size fractions were fully characterized concerning particle size distribution, specific surface area, density, degree of crystallinity and solubility. A particle size counter the Coulter Multisizer II — was used, not only to characterize the primary particle size distribution of the different fractions, but also to monitor the size and number of the suspended particles during the dissolution process. Although this information was applied to evaluate dissolution profiles (dissolution drug concentration vs. time) it can be further used to thoroughly study the dissolution phenomenon. The accuracy of this instrument to assess dissolution profiles was confirmed by comparing its results with those obtained by HPLC. As expected a strong influence of the fraction size on the dissolution rate was found. A correlation was established between the mean dissolution time (MDT) and the mean particle size of the various indomethacin fractions.

Complexos de inclusão de indometacina com hidroxipropil-beta-ciclodextrina: estudos de dissolução e coeficiente de partição

Indomethacin, a non steroidal anti-inflamatory, is practically water insoluble. Hydroxypropyl-b-cyclodextrin grants better solubility characteristics to included drugs. Indomethacins complexation protects from hydrolysis, enhancing solubility and dissolution. The aim is to study the influence of complexation methods, freeze and spray-dryer, on indomethacin dissolution and partition coefficient. Dissolution results show that freeze-dried inclusion complex has a better time needed to dissolve 50% and 90% - 1 and 1.8 minutes then other products. The same happens with percentage of indomethacin dissolved at 5, 30 and 60 minutes - 92.6±1.8%; 98.9±1.2% e 100.01±0.1% and also with dissolution efficiency and dissolution profile. Partition coefficient results with the complexes obtained by both methods corroborate the theory that there are several intervenient strengths on this process and not only drugs free fraction that regulates transport to organic phase, reinforcing the environmental pH significance. With phosphate buffer pH 7.0, variations on transport grade by cyclodextrin addition are very small, showing no significant changes on log P*. With phosphate buffer pH 5.5, although not significant, variations are slightly higher. We can conclude that complexation enhances dissolution capacities of lipophylic drugs without changing the characteristics that give them a good ability for membrane diffusion.

Characterization of the In Vitro Dissolution of Some Commercial Sustained Release Theophylline Dosage Forms

AbstractA dissolution study of five commercial sustained release theophylline dosage forms, concerning their pH dependency, is described. The experiment was carried out in a flow through dissolution apparatus, at constant pH and at pH gradient, being the pH values of 1, 2, 6, 5 and 7, 5. In both cases, they were treated in terms of the dissolution profile and the dissolution rate, complemented with the dissolution efficiency at pH gradient in order to make a correlation with the in vivo experiments that will be done in the future. The absorbance was measured at a wavelength of 264 nm. According to the results obtained, was selected the best pharmaceutical form, concerning the pH dependency and taking as a basis, just, the in vitro experiments.

Using a particle counter to assess in vitro dissolution studies

Abstract The purpose of this work was to establish a comparison between the dissolution profiles obtained with the Coulter technique and the Paddle method, for a sparingly soluble drug. Four fractions of indomethacin were tested and the corresponding mean dissolution times were calculated and plotted against the fraction mean diameter ( d sv ). A unique correlation was found for both methods. The importance of this correlation is also discussed.