Preparation And Modification Of Chitosan Microflower And Its Loading On Procyanidins And Curcumin

Chitosan（CS）is widely used in various fields because of its wide range of sources,abundant reserves and excellent properties.However,among the many studies,there are few reports on the construction of special morphology of CS-based materials.Therefore,in this study,CS was used as the basic raw material,pretreated by ultrasound and hydrogen peroxide,and a kind of CS-based material with special morphology was constructed by ion cross-linking method.It was used as the carrier,and some drugs were loaded.The specific research contents are as follows:First of all,we use CS as raw material and dissolve it by ultrasound and hydrogen peroxide during its dissolution process.After that,sodium tripolyphosphate（TPP）was implanted into CS solution by ion cross-linking method,and chitosan microflower（CSMF）was obtained by freeze-drying.A series of characterizations were carried out and the factors affecting its flower formation were studied.The results show that the size of CSMF is 1-2μm;the Fourier transform infrared spectrum（FTIR）of CSMF shows the vibration peak of phosphate group in532cm-1;the crystal form of CSMF changes from semi-crystalline structure of CS to hydrated polycrystalline structure;the X-ray photoelectron spectroscopy（XPS）of CSMF shows that it produces C-N⁺bond,while the thermogravimetric analysis（TGA）results show that the thermal stability of CSMF is slightly lower than that of CS.Through the single factor experiment,it is found that the pretreatment method,ultrasonic time,CS solution temperature and the ratio of CS to TPP will affect the flower structure of CSMF,while ultrasonic power and hydrogen peroxide addition will not affect the flower structure.Furthermore,it is inferred that the flower formation mechanism is that the original CS is degraded into short and long chain CS within a certain molecular weight range,and then TPP is cross-linked with the relatively long CS chain after degradation to form the pedestal of micro-flower structure,and cross-linked with the relatively short CS chain after degradation to form nanosheets.Finally,through the interaction between the-NH₃⁺on the CS structure and phosphate ions,the nanosheets were self-assembled on the substrate,and then the micro-flower structure was formed.It provides a reference value for the construction of special morphology of CS-based materials.Secondly,the microflower structure of CSMF has a larger specific surface area of 48.9m²/g.Therefore,in the application,we consider it as the drug carrier,using the water-soluble drug Procyanidins（PC）as the model drug,and adsorbing it with CSMF.The results show that the adsorption load does not change the morphology,crystallinity and thermal stability of CSMF.On the other hand,the FTIR of PC-CSMF has a vibration peak of benzene ring at 1456 cm^-1,and XPS showed that the ratio of carbon to oxygen on the surface of PC-CSMF increased,which proved that PC was successfully loaded.The single factor experimental results show that when the room temperature is27℃and the mass concentration of PC is 10g/L,the maximum load of CSMF to PC is 352.88mg/g.The adsorption kinetics shows that the adsorption of PC by CSMF accords with the quasi-second-order kinetic model,and the adsorption rate is affected by the interaction between particle diffusion and boundary layer diffusion.The adsorption isotherm shows that the Freundlich adsorption isotherm model can more accurately reflect the whole adsorption process,indicating that the adsorption process of CSMF to PC is a kind of surface energy inhomogeneous multilayer adsorption.Adsorption thermodynamics shows that the adsorption of PC by CSMF is a spontaneous physical adsorption process with entropy reduction.Finally,in vitro sustained-release and antioxidant experiments proved that PC-CSMF had sustained-release effect and the biological activity of PC after loading was improved.It has been proved that CSMF can be the carrier of some water-soluble drugs.Finally,because CSMF has a large number of amino groups and hydroxyl groups,it is hydrophilic.In order to make CSMF loaded with fat-soluble drugs,we hydrophobically modified CSMF with citral and n-octadecylthiol mercaptan.Curcumin（Cur）was used as a fat-soluble model drug and adsorbed on hydrophobic chitosan microflowers（HPCSMF）.The samples were characterized by contact angle measurement,SEM,FTIR,XPS and so on.The experimental results show that the contact angle of the modified HPCSMF is75.4°,which is 127.8%higher than that of CSMF,and the characteristic peak of-CH₃ in the FTIR of HPCSMF is also enhanced,and the surface elements C:O ratio of XPS is also changed from 56.7:43.3 to 64:36.,which proves that the hydrophobic modification is successful,and the modification will not affect the morphology,crystallinity and thermal stability of CSMF.When the Cur was adsorbed by HPCSMF,the drug-carr ying par ticles were obtained.The FTIR of drug-loaded particles showed the characteristic peak of the benzene ring at 1456cm^-1,and the C:O ratio of surface elements changed from 64:36 to 68.4:31.6,which proved that Cur was successfully loaded.The adsorption did not change the morphology,crystallinity and thermal stability of HPCSMF Through the experiments of sustained release and antioxidation in vitro,it was proved that the drug loaded particles have sustained release function.It provided a feasible way for chitosan-based materials to load lipid-soluble drugs.In this study,a special morphology CS-based material was prepared,which provided a new method and idea for the preparation of CS-based material with special morphology.The application of CSMF in the field of drug loading found that it has a good loading effect on water-soluble drug PC.After modifying CSMF hydrophobic,it also has a good loading effect on Cur.These have been proved that CSMF is an excellent drug carrier.