Synthesis And Characereization Of Tegafur-ldhs And Pyridaben-ldhs Nanohybrids

Layered double hydroxides (LDHs) are consisting of divalent and trivalent metal ions and with the same layered crystal structure as Hydrotalcite, they are a family of layered solids with structurally positively charged layers and interlayer balancing anions which can be replaced by the desired anions. Some drug molecules can be intercalated into the gallery of LDHs to form drug-LDHs nanohybrids because of their special structure. The drugs can be evidently stabilized in the interlayer of such nanohybrids because of the electrostatic, hydrogen bond, and steric hindrance in the gallery, and thus they have controlled-release characters under certain condition. Therefore, drug-LDHs nanohybrid material was considered as a potential drug carrier for controlled release.In this paper, Tegafur and Pyridaben were selected as the guest molecules and their drug-LDHs nanohybrids were synthesized via coprecipitation or reconstruction. Powder X-ray diffraction (PXRD) and FT-IR spectroscopy were used to characterize the achieved products, and the drug releases and kinetics from nanohybrids were investigated as well.1. Synthesis and characterisation of LDHsThe pristine MgAl-Cl LDHs and ZnAl-NO3 LDHs were prepared by coprecipitation method. The effects of the molar ratio of M3+/ [M2+ + M3+] molar ratio show that M3+/ M2+ molar ratio of the syntheized product was lower than that of the raw mixed salt solution. The interlayer space is about 0.78 nm for MgAl-Cl LDHs, 0.86 nm for ZnAl-NO3 LDHs. Moreover, a simple environmentally friendly method was used to prepare the ZnAl-NO3 LDHs, in which ammonia was not needed in the coprecipitation, as well as the washing or purification of the final product.2. Tegafur-LDHs nanohybridsTegafur-ZnAl-LDHs were prepared by coprecipitation method, while Tegafur-MgAl-LDHs were syntesized by reconstruction. The loading amount of Tegafur on LDHs was dependent on the Tegafur initial concentration, i.e. the loading amount increased with the initial concentration. The release results of Tegafur from the nanohybrid at pH 7.2 and pH 4.8 in buffer solution at 37℃suggest that the Tegafur-LDHs have a good controlled-release character. The drug release kinetics from the nanohybrids showed the pseudo-second order kinetic model. The release rate at pH 7.2 is remarkably lower than that at pH 4.8, and that in pure water is lower than that in the buffer solution, which can be ascribed to a possible difference in the release mechanism. 3. Pyridaben-LDHs nanohybridsPyridaben-MgAl-LDHs were prepared by coprecipitation method. The loading amount of Pyridaben on LDHs was dependent on the Tegafur initial concentration, similar to that of Tegafur-ZnAl-LDHs. The releases of Pyridaben from the Pyridaben-MgAl-LDHs nanohybrids in ethanol-water solution at 15℃indicate that the Pyridaben-LDHs nanohybrids have potential for development of new controlled-release formulations of pesticides.