Synthesis Of Novel Multiple Active Ester And Its Cross-linking Modification Research Of Gelatin

In this paper,three materials were applied to functionalize the primary alcohol at C6 of microcrystalline cellulose(MCC).Then the functionalized MCC was reacted with N-Hydroxy succinimide(NHS)in the preaence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride(EDC)to obtain three different cross-linkers: functionalized MCC by EDTA dianhydride-NHS active ester(MEN),functionalized MCC by citric acid anhydride-NHS active ester(MCN)and oxidated MCC by TEMPO-NHS active ester(TMN).The properties and applications of modified gelatin by the three cross-linkers were investigated.The structure of MEN and its reaction with gelatin were confirmed by FT-IR,elemental analysis,TGA-DSC,Van Slyke method,XRD and SEM.The in vitro degradation results showed the relationship of MEN concentration and degradation ratio was dose-dependent.TGA-DTG curves suggested the cross-linking improved the thermal stability of films and the Gel/MCC blending films,as comparison,presented severe phase separation.This fact further declared the modification of gelatin by MEN was through amidation.Mechanical properties,especially elasticity and flexibility were incressed to some degree and the surface hydrophobicity,swelling ability and light barrier property were also enhanced.The preparation of macromolecule cross-linker MEN enriched the existing EDC/NHS cross-linking system.The unique gelatin film material with advanced properties broke up the limitation of blending modification method for gelatin with macromolecule and broadened its application as novel sustained-release material in food,medicine and agriculture etc.The gelatin composites modified by MCN could be used as controlled drug delivery system to load and release the model drug omeprazole.The drug was loaded in gelatin complex by electrostatic interaction and hydrogen bonds.Thermal stability,anti-biodegradability,mechanical property and surface hydrophobicity of the composites with different cross-linking extents and drug loading were systematically investigated.SEM images demonstrated the honeycomb structural cells of cross-linked gelatin networks and this ensured drug entrapment.The drug release mechanism was dominated by a combined effect of diffusion and degradation,and the release rate decreased with cross-linking degree increased.In addition,the in vitro degradation experiment in lysozyme of modified gelatin with/without drug loading showed the degradation rate was closely related to the cross-linker concentration.The developed drug delivery system had profound significance in improving pesticide effect and bioavailability of drugs.TEMPO-oxidized cellulose ester(TMN)with MCC and NHS as raw materials was synthesized to modify gelatin films by amidation.The film material(Gel-TMN)properties,such as thermal property,surface hydrophobicity,biodegradation behavior in PBS and lysozyme,light barrier performance,mechanical property and swelling ability were measured for the application of food packaging.Additionally,the biodegradation behavior in PBS and lysozyme were compared and analysed by degradation test and SEM,and a hypothesis was proposed to simply explain the mechanism of PBS and lysozyme degradation.The unique gelatin film material Gel-TMN with advanced properties obtained in this work was safe,stable eco-friendly and biorefractory,and also could be decomposed completely by the environment after disposal because of the nature properties ofgelatin and MCC.So the film material was an ideal choice to form a packaging in food industry.