| Montmorillonite(MMT), a layered silicate, has character of suitablecapability of cation exchange, selected absorption and nontoxic. Studies based onthese properties to investigate MMT as a novel sustained-release drug carrier areimportant both on theoretical and practical. In this study, three drugs with different type of amino group (acyclovir,tegafur, propantheline bromide) and one drug with carboxy group were employedto prepare drug/MMT sustained-release systems by solution intercalation method.The effect of reaction temperature, reaction time, the pH value and initialconcentration of drug on drug-loaded amount of MMT was investigated. Thesamples were characterized by UV spectrophotometer, XRD, FT-IR, and TGA. Thein vitro release experiment was employed to investigate the release behavior ofthem. The effect of initial concentration of drug on drug-loaded amount (DLA) ofMMT was significant in the intercalation process. At the initial stage, DLAincreased with increasing the initial concentration. But the degree of this trendbecame slow when it arrived certain amount. It indicated that DLA was determinedby the reacting sites of MMT. However, reaction temperature and reaction time hadlittle effect on DLA. XRD, FT-IR, TGA proved that all drugs had successfullyintercalated into the interlayers of MMT, formed intercalation structure betweenthem. The in vitro release behavior of these systems was determined by two factors:diffusion and ion exchange. The drug/MMT sustained-release systems with amidodepended on diffusion and cation exchange. However, drug/MMTsustained-release systems with carbxy group depended on diffusion and anionexchange. The in vitro release experiments showed that acyclovir/MMT andibuprofen/MMT sustained-release system had larger release percentage in thephosphate buffer (pH 7.4). It suggested that these systems were pH-sensitive andcould be prepared as sustained-release oral administrations in the future. |
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