Propriétés de surface des argiles camerounaises et leur application en ph armacologie

Abstract

The aim of this thesis was to explore a pharmacological application of clays by setting up a ciprofloxacin (CFX) delivery system using smectite from Bana (West Cameroon) as a carrier-releaser from the clay fraction (≤ 2 µm) and the less clayey, silty-clay fraction (≤ 40 µm). Raw clay materials were (BN: fraction ≤ 40 µm; BNNa: fraction ≤ 40 µm saturated with NaCl; BNNa-F: clay fraction ≤ 2 µm). The results show that ciprofloxacin (CFX) is perfectly intercalated in the interfoliar space of clay minerals with equilibrium intercalated quantities, in mg per g of clay, are 146 mg/g, 153.4 mg/g and 156.9 mg/g for BN-CFX, BNNa-CFX and BNNa-F-CFX respectively. SEM images don’t show any influence of CFX on the material morphology. X-ray diffractograms of the composites show an increase in the basal distance d001 around 1.61 and 4.11 Å, attributed to the intercalation of CFX in the interfoliar space of the clay minerals. On the infrared spectra, the appearance of the characteristic CFX bands and the displacement of some of these bands confirm the intercalation of the CFX. The thermograms (TG/dTG) of the composites show a first decomposition stage between 200 °C and 500 °C attributed to the decomposition of the intercalated CFX, and a second stage that follows and goes up to 700 °C, due to the complete disintegration (560 °C) of the composite structure. The CFX released in the experimental media increase rapidly in the first hours, become constant from 24 h, after which time the release remains constant and lasts up to 96 h. CFX release is prolonged, continuous and controlled, with ~29%, ~41% and ~51% of CFX released after 96h in gastric juice, intestinal juice and NaCl-modified intestinal juice respectively. The inhibition diameters (1.8-3.1 cm) obtained following the microbiological tests show that the intercalated CFX has an antibacterial effect on the strains of E. coli and S. aureus. The silty-clay fractions (40 ≤ µm) gave results as interesting as those of the clay fraction, ≤ 2 µm. These results thus open the way to possibility of using Bana smectite both in its clay fraction and in its silty-clay fraction (especially saturated with NaCl), as a carrier-releaser of ciprofloxacin in the ciprofloxacin delivery system.