Study on montmorillonite–chlorhexidine acetate–terbinafine hydrochloride intercalation composites as drug release systems

This paper focuses on the intercalation of chlorhexidine acetate (CA) and terbinafine hydrochloride (TBH) into montmorillonite as sustained release drug carriers. The intercalation compounds were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA). The basal spacing of montmorillonite increased from 1.23 to 2.97 nm. It was confirmed that CA and TBH molecules were well-stabilized in the interlayer space of clay via mono-, double or triplicate layer stacking. The adsorption amounts and molecular structures of CA and TBH appeared to depend on the cation exchange capacity of MMT, which in turn, tailored the drug release patterns. In vitro release tests of MMT–CA–TBH in 0.9 wt% NaCl solution at 37 °C show a biphasic and sustained profile of CA and TBH ion release. After release, dissolution–diffusion kinetic models were fitted. The mechanism of MMT–CA–TBH release is probably due to surface diffusion and bulk diffusion via ionic exchange of MMT ions on or in the MMT with ions in the NaCl solution. The in vitro release experiments revealed that CA and TBH were released from MMT steadily, depending on the cooperation between the drugs themselves and the electrostatic interactions between the drugs and MMT. It was found that the cross-linking ratio increased due to a decrease in the free volume available for diffusion.