Study On The Diffusion Behavior Of Drug Molecules In Supramolecular Gel

In recent years there has been immense interest in studying gels derived from low molecular mass gelators (supramolecular or simply molecular gels). The motivation is not only to understand the fundamental aggregate structures in the gels at different length scales, but also to explore their potential for futuristic technological applications. Supramolecular is a kind of solid-like gel which has 3D matrix formed by self-assembled of gelator in solvent, It is a promising media for applications involving controlled release of drug molecules because of its good biocompatibility and simply preparing process.In this paper, the diffusion behaviors of drug molecules (salicylic acid(SA), methimazole(TAP), ciprofloxacin(CPFX), and 5-fluorouracil(5-Fu) )) and the interaction between drug molecules and supramolecular gel were studied in the suprmolecular gels formed by benzylidene-D-sorbitol derivatives in 1,2-propylene and PEG400. The results are as follows:1.The morphology of supramolecular gels was observed by FE-SEM . The FE-SEM images showed that gelator creates entangled three–dimensional networks consisting of the bundles of fibrous aggregates. This three-dimensional network is the base for drug molecules delivery. The fall-ball experiment indicated that the phase transition temperature (TGS) increases with the increase of the concentration of gelator .2.The diffusion behaviors of drug molecules were affected by temperature, polarity of media, concentration of gelator and the solvent property significantly. It revealed that the diffusion rate and the accumulated release ratio increased with temperature and the polarity of media.On the other hand, the enhancement of concentration of gelator and the viscosity of solvent which formed suprmolecular gel resulted in low diffusion rate and low accumulated release ratio of drug molecules. The results also suggested the structure of drug molecules and gelator influenced the diffusion behavior of drug molecules.3.The interaction between drug molecules(guest) (SA, CPFX, 5-Fu) and supramolecular gel(host) was investigated by differential UV spectra. The red shift of UV absorption band of CPFX and 5–Fu revealed that the interactions between these two drug molecules and supramolecular gel were stronger than SA because fluorin in CPFX and 5-Fu is more electronegative than oxygen in SA. It was also found that when the guest and host ratio was above 1:1, the absorbtive band splitted to two peaks, one is at low wavelength ,which is not changed with the ratio of guest/host, but the absorbance andλmax of another peak changed with the ratio of guest/host, indicated that 5-Fu distributed in different environment: Part of guest molecules were in solvent which were trapped in supramolecular gel, another part of guest molecules was incorporated in the gel fibers. The DSC results showed that the decrease of phase transition temperature of guest molecules trapped supramolecular gel, because guest molecules affected the self-assembled of gelator, which clarified that the guest molecules incorporated in gel fibers. The results match that of differential spectra.