| Layered double hydroxides(layered double hydroxides)is a kind of inorganic layered materials.The layered double hydroxides have positive charge and good interlayer anion exchange performance.The structure diversity of LDHs enables them to be prepared by various methods,and the drug LDHs drug loading system can be constructed by ion exchange method due to its good interlayer anion exchangeability.Captopril is a kind of antihypertensive drug.Its thermal stability is poor,and it will be oxidized and decomposed at low temperature.Moreover,its release rate in vivo is fast and the duration of its efficacy is not long.Therefore,it is necessary to use appropriate drug carrier to improve its drug characteristics to enhance the thermal stability of captopril and control its release rate.As a new drug carrier,LDHs has unique advantages such as good biocompatibility and biodegradability.According to the unique structure and properties of LDHs,captopril was loaded into the interlayer of LDHs,and the sustained-release effect of captopril was achieved through the abundant hydroxyl active sites and steric hindrance of LDHs.In this paper,Zn-Ti-LDHs were prepared by coprecipitation method and hydrothermal method(Cop-Zn-Ti-LDHs was prepared by coprecipitation method and hyd Zn-Ti-LDHs by hydrothermal method).Captopril was loaded between the two LDHs by ion exchange method(Cap/Cop-Zn-Ti-LDHs for coprecipitation method and Cap/Hyd-Zn-Ti-LDHs for hydrothermal samples).The samples were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),thermogravimetry(TG-DTG)and Fourier transform infrared spectroscopy(FT-IR).The physical and chemical properties of Zn-Ti-LDHs prepared by different methods were obtained,and the host guest interaction between LDHs laminates and guest drug molecules was explored.The release experiments of captopril were carried out in phosphoric acid buffer solution with different p H to simulate the internal environment of human intestinal tract(p H=6.8)and human body fluid(p H=7.4).The concentration of captopril in the solution at different times was determined by UV Vis,and the drug release curve was drawn.The release mechanism of LDHs complex was obtained by kinetic analysis of drug release curve.The results are as follows:XRD showed that Zn-Ti-LDHs were successfully prepared by coprecipitation method and hydrothermal method.Compared with Cop-Zn-Ti-LDHs,Hyd-Zn-TiLDHs has smaller interlayer distance and better crystallinity,and it can be calculated from the change of(003)crystal face peak position that the interlayer distance of the two compounds has increased significantly.TG-DTG results show that the amount of crystal water in Hyd-Zn-Ti-LDHs is less and has better thermal stability.The difference of crystal form and stability between Hyd-Zn-Ti-LDHs and Cop-Zn-Ti-LDHs is mainly due to the higher reaction time and temperature of hydrothermal method compared with coprecipitation method,which leads to the better growth of Zn-Ti-LDHs laminates prepared by hydrothermal method.The FT-IR results showed that captopril was successfully intercalated into the two LDHs layers,and the acidic-COOH and S-H groups of captopril interacted with the metal base hydroxyl groups exposed between Zn-Ti-LDHs layers through dehydration or dehydrogenation condensation.The recombination of guest captopril molecules after intercalation into the host laminate mainly depends on the acid-base interaction between host and guest.The standard curve of captopril was drawn by UV-vis.The drug loading of LDHs complex was calculated by the standard curve of captopril,and the release curve was determined in phosphoric acid buffer solution with different p H.The results showed that Cap/Cop-Zn-Ti-LDHs had a high release rate,but its release amount had a great change with the change of release environment;Although the release amount of Cap/Hyd-Zn-Ti-LDHs is low,the stability of the release under different p H conditions is better,and the release performance of Cap/Hyd-Zn-Ti-LDHs is more excellent.The results showed that the drug release process of Cap/Cop-Zn-Ti-LDHs and Cap/HydZn-Ti-LDHs complexes could be described by quasi second order kinetic equation;the release mechanism was that the whole release rate was mainly dominated by the internal diffusion of the particles,and the diffusion process between the Zn-Ti-LDHs layers into the solution determined the drug release behavior.Figure 23 table 7 reference 20... |
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