Characterization of supramolecular gels based on β-cyclodextrin and polyethyleneglycol and their potential use for topical drug delivery.

Novel gels were prepared by blending β-cyclodextrin and polyethyleneglycol (PEG) in the presence of K2CO3. The objective of this study was thus to characterize the gels using rheology, modulated temperature differential scanning calorimetry (MTDSC), turbidity measurements, and hot stage microscopy, and then investigate the potential use of the gel for topical drug delivery. Two types of supramolecular gels, GelL and GelH were prepared at a low temperature (below 50 °C) and at a high temperature (above 70 °C), respectively. Both gels were thermo-reversible. Upon heating, GelL could turn to GelH. Nevertheless, upon cooling, GelH that was more stable than GelL precipitated and GelL could not be reformed. GelL may form through simple complexation of polyethyleneglycol (PEG) with β-cyclodextrin in the presence of K2CO3. However, GelH may form a specific complex or a pseudopolyrotaxane gel. For pharmaceutical application, GelL was investigated instead of GelH because the forming temperature of this gel was close to the human body temperature. The interactions among diclofenac sodium (DS), a model drug, and the components of the gel were examined using FTIR. These interactions may include ionic attraction and hydrogen bonds between the carboxylate groups of DS and the hydroxyl groups of PEG or β-cyclodextrin and probably also the inclusion of the aromatic ring of DS into the cavity of β-cyclodextrin. Furthermore, the release and permeation of diclofenac from GelL were significantly greater than those from a commercial gel. Therefore, GelL may be useful for the topical delivery of drugs.