Ciprofloxacin intercalated in fluorohectorite clay: identical pure drug activity and toxicity with higher adsorption and controlled release rate

Different natural clay minerals, including halloysite, montmorillonite and kaolinite, have been proven to be efficient drug carriers providing for high and long lasting drug concentrations owing to their adsorption capacity and ion exchange property. Synthetic clays, however, are advantageous over the natural clay minerals in terms of purity of composition and controllable cation exchange capacity, factors that contribute to improve reproducibility of the host system. Here we studied a synthetic smectite clay as a candidate for high adsorption and controlled release rate. Via X-ray powder diffraction we verified that, under acidic conditions, the antibiotic ciprofloxacin was successfully incorporated in the synthetic clay fluorohectorite, while via UV-VIS spectroscopy we showed that the degree of the drug incorporation is at least 25% higher than for other systems reported in the literature. Furthermore, temperature dependent release studies allowed us to show that the release process is thermally activated and diffusion-controlled. Finally, via bacterial and toxicological tests, we demonstrated that the effectiveness and toxicity of pure ciprofloxacin is unaffected in the clay–drug complex.