Preparation and formation mechanism of Ag/Ni(OH)2 composites with enhanced catalytic activity for reduction of 4-nitrophenol were systematically studied.

This paper reviewed our research progress in respects of th intercalation law of acetylsalicylic acid (ASP) with magnesium aluminate layered double hydroxide (LDH), the drug release mechanism and the tablet preparation effect of LDH-ASP system. We also discussed the propositions about the composite assembly rules, slow-release mechanism, and dosage form processing of the layered double hydroxide drug delivery system. Intercalation way and drug structure should be taken into consideration in assembly LDH-drugs system. The characteristic parameter of the composite LDH-drug reflected finely their loading efficiency and correlated definitely with drug release property. It had been found that the release rate and extent of intercalated drug was closely linked to the retarding status of LDH interlayer, which was dependent on the exchange mole ratio of n(drug) with n[HnPO4(3-n)-]. In addition, the grafting reaction and phase transformation degree of LDH layer was hinged on the acidity of solution. The slow-release function of the LDH-drug system could be improved significantly by compositing with dextran (DET). A sustained-release skeleton tablet was producted with DET-LDH-ASP drug delivery system and hydrophilic gel material HPMC, which could effectively overcome the "first pass effect" and " burst release problem" of LDH-drug oral agents. The slow-release effect of LDH drug delivery system could be ulteriorly improved in systemic circulation environments, attributed to the triple control of HPMC-DET-LDH, DET-LDH-drugs three-level supramolecular assembly and the special circulation in vivo. Key words: Layered double hydroxide, Supramolecular assembly, Release control, Slow controlled release drug delivery system