Preparation And Performance Research Of Microcapsule Wall Material Based On Resistant Starch

The object of this paper is to improve the medical efficiency for colon targeted delivery system,and prepare the colon targeted microcapsules with excellent targeted release properties in colon through adding the Resistant Starch(Type4)to the microcapsule wall material—RS4 is a kind of starch which cannot be digested in stomach and small intestine,while can be fermented in colon.This project involves two main parts,part one is the preparation of RS4-Citrate Waxy Corn Starch(WCS)through the dry heat treatment method to cross link the citric acid and waxy corn starch.By testing the Degree of Substitution(DS)of ester group,optimize the ratio of Citric Acid/WCS to get the RS4-Citrate WCS with strong resistant properties,and detecting the impact of cross-linking on the granular morphology,functional group,pasting properties and crystal structure of starch.Part two is the preparation of Chitosan-Alginate-RS4(EGCG)microcapsules to encapsulate the EGCG model drug through the emulsion cross-linking technology by forming W/O emulsion,adding RS4-Citrate WCS to the Chitosan-Alginate complex proportionally.Determine the best preparation technology by comparing the properties of Chitosan-Alginate-RS4(EGCG)microcapsules using three different preparation technologies,involving the microcapsules’appearance,drug release properties,the combination between RS4 and Chitosan-Alginate complex and the biocompatibility between EGCG and the microcapsule wall material.Through the preparation in five different Citric acid/WCS reaction ratio(0.2、0.25、0.35、0.55、0.85),testing DS value and the Resistant Starch content,get the conclusion that both DS of Resistant Starch increase to a peak and decrease later as the increase of Citric Acid/WCS(CA/WCS)reaction ratio(w/w),and has the maximum value of 0.124 and 98.99%respectively when the CA/WCS reaction ratio is 0.35.Through the detection of Scanning Electron Microscope(SEM),Fourier Transform Infrared Spectroscopy(FTIR),Stirring in the boiling water,X-ray Diffractometer(XRD),find that the appearance of starch becomes more rough,the granular morphology is more irregularly due to the cross-linking,meanwhile,a new functional group C=O can be observed,gelatinization becomes much harder in water and the crystalline structure changes to B+Vtype from the A-type with the decrease ratio of crystalline region/amorphous region.As for the second part of this project,by contrast the CS-Alginate-RS4(EGCG)microcapsules’ properties produced through three different preparation technology gets the conclusion that CS-Alginate-RS4(EGCG)microcapsules show the most smooth surface,most regular granular morphology and particle size concentrates on 100um when the Alginate/CS is 4:1(w/w),Alginate/CaCl2 is 5.56:1(w/w)(The concentration of Alginate aqueous solution,Chitosan acetic acid solution and CaCl2 is 1%,1%,1.5%respectively),aqueous phase/oil phase is 1:6(v/v),surfactant/oil phase is 20:80(v/v),Span80/Tween80 is 75:25(v/v),the stirring speed is 10000rpm.However,the dispersibility of CS-Alginate-RS4(EGCG)microcapsules is terrible.Meanwhile,the RS4 Citrate WCS combines to the CS-Alginate complex at a low degree and the compatibility between EGCG and microcapsule wall material can be proved.Therefore,this project provides a theoretical basis for the application of RS4-Citrate WCS to the colon targeted drug release.