Formulation and antibacterial profiles of clay–ciprofloxacin composites

• Ciprofloxacin was adsorbed onto montmorillonite K-10, kaolin, and Laponite® RD.
• Dispersion pH of 7.4 favoured ciprofloxacin adsorption.
• Positively charged amino group responsible for ciprofloxacin adsorption.
• Ciprofloxacin adsorption was shown to follow pseudo-second order kinetics.
• Clay-ciprofloxacin composites were effective against P. acnes and S. epidermidis

The ability of clay minerals to adsorb and desorb drugs, including antibacterial molecules, is an attractive and exciting prospect for healthcare applications. The antibacterial ciprofloxacin was adsorbed onto kaolin, montmorillonite K-10, and Laponite® RD then the subsequent antibacterial activity of the composites formed was confirmed. The effects of time, pH, and CIP concentration were investigated. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to confirm the mechanism of ciprofloxacin adsorption onto the clay minerals. Dispersion pH was the most important variable influencing the adsorption of ciprofloxacin onto the clay minerals and the mechanism of adsorption was confirmed as cation exchange. Adsorption isotherms and application of Langmuir and Freundlich models showed that a ciprofloxacin monolayer was formed at different concentrations on each of the clay minerals tested. Kinetic studies showed that maximal CIP adsorption was achieved within the first hour of adsorption. Antibacterial activity of clay–ciprofloxacin composites against the common skin bacteria Staphylococcus epidermidis and Propionibacterium acnes was demonstrated. This work showed that clay–ciprofloxacin composites are potential delivery systems for ciprofloxacin molecules. As a result, this could make them ideal candidates to take forward for healthcare applications, including the development of novel wound dressings.

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