Study On Drug Delivery System Based On Er³⁺-doped ZnAl-LDH

In the field of medicine,the efficacy and side effects of drugs are two issues that must be concerned when they enter clinical use.However,the efficacy and side effects of a drug are not only related to the nature of the drug,but also to the mode of administration.Therefore,the mode of administration of drug delivery system has attracted attention.As a drug delivery system,it should have the advantages of non-toxicity,low cost,good biocompatibility,and little damage to biological tissues.Therefore,the present work is to study the erbium-doped zinc-aluminum layered double metal hydroxide(Er³⁺-doped ZnAl-LDH)with near-infrared fluorescence as the drug delivery system for the anti-inflammatory drug ibuprofen（IBU）and the anticancer drug 5-fluorouracil（5-Fu）.The specific contents are followed as:1.Using Zn（NO₃）₂·6H₂O、Al（NO₃）₃·9H₂O and Er₂O₃ as raw materials,a series of Er³⁺-doped ZnAl-LDH with Zn²⁺/(Al³⁺+Er³⁺)molar ratio of 2.0 and Er³⁺/(Al³⁺+Er³⁺)molar ratios of 0.01,0.05,0.1,0.2 and 0.3,respectively,were synthesized by the co-precipitation method.The structural analysis showed that the crystallinity of the samples gradually decreased as the molar ratio of Er³⁺/(Al³⁺+Er³⁺)increased from 0.01to 0.3.The fluorescent spectra of the samples showed that all samples exhibited fluorescent peaks at 780,820,and 850nm,and the fluorescent intensity reached the maximum while the molar ratio of Er³⁺/(Al³⁺+Er³⁺)is 0.1.In view of its crystallinity,fluorescent intensity,and preparing cost,the Er³⁺-doped ZnAl-LDH with Zn²⁺/(Al³⁺+Er³⁺)molar ratio of 2.0 and Er³⁺/(Al³⁺+Er³⁺)molar ratio of 0.05 was considered as the optimal drug delivery system for IBU and 5-Fu in this master thesis.2.The Er³⁺-doped ZnAl-LDH/IBU drug delivery system was obtained by the intercalation of the Er³⁺-doped ZnAl-LDH with IBU using the co-precipitation method.XRD results indicated that the IBU should be inserted into the interlayer of the Er³⁺-doped ZnAl-LDH with its ring plane in the direction either parallel to or slightly inclined to the laminate.Then,the release of IBU from the Er³⁺-doped ZnAl-LDH/IBU in a system simulating the human intestinal environment（namely phosphate buffer solution with p H 7.4 and 37℃）was investigated.It was found that the cumulative concentration of IBU released from the drug delivery system was exponentially related to the releasing time,and fitted with the exponential equation C=a（1-b^t）.The release behaviors of IBU exhibited firstly rapid,then slow,and finally steady.What is more,the near-infrared fluorescence intensity of of Er³⁺-doped ZnAl-LDH showed an obvious difference before drug loading,during drug delivery,and after the release of the drug.Based on this fluorescent change,it may be used to"identify"whether the drug is in a delivery or release state.3.The Er³⁺-doped ZnAl-LDH/5-Fu drug delivery system was obtained by the intercalation of the Er³⁺-doped ZnAl-LDH with 5-Fu using the co-precipitation method.Structural analysis showed that 5-Fu molecules were inserted into the interlayer of the Er³⁺-doped ZnAl-LDH in a single layer plane perpendicular to the laminate or multilayer plane parallel to the laminate.Similarly,the kinetic behavior of 5-Fu released from the Er³⁺-doped ZnAl-LDH/5-Fu drug delivery system has been studied in the simulated intestinal medium（namely phosphate buffer system with p H 7.4 and37℃）.Results indicated that the cumulative concentration of 5-Fu is exponential with releasing time and well conformed to the exponential equation C=a（1-b^t）.Fluorescent analysis showed that the fluorescent intensity of the Er³⁺-doped ZnAl-LDH changed significantly during drug delivery and release,which may be used to identify whether5-Fu is in the state of storage,and delivery,or release.