Fabrication Of Polyethylene Glycol/Cyclodextrin Self-assembled Hydrogel Carrier And Its Application In Enzyme Loading

The polyethylene glycol?PEG?/?-cyclodextrin??-CD?self-assembled hydrogel was a promising immobilized carrier for biomacromolecules due to its good hydrophilicity,permeability,biocompatibility and mechanical strength.In this work,4-arm PEG derivatives were used to self-assemble with ?-CD and further crosslinked to fabricate polyrotaxane?PRX?hydrogels.Certain enzymes were selected to be loaded in the PRX hydrogels,and the structures,properties,and application of them were investigated.Firstly,the PRX hydrogel was fabricated by oxidizing the end-sulphydryl group of ?-CD threaded 4-arm polyethylene glycol thiol?4arm-PEG-SH?with hydrogen peroxide,and urease and glucose oxidase?GOD?were loaded in the PRX hydrogels.Infrared spectra,X-ray powder diffraction?XRD?and scanning electron microscopy?SEM?analysis were used to characterize the structure of the PRX hydrogels.It indicated that the fabricated hydrogels showed pseudopolyrotaxane?PPRX?channel pattern and porous network structure.When the mass ratio of 4arm-PEG-SH to ?-CD was 1:2,the PRX hydrogel obtained with compact structure and good mechanical strength.Next,the enzymatic activity and stability of the urease-loaded and GOD-loaded PRX hydrogel was investigated,and the enzymatic property difference between the two immobilized enzymes on molecular structure was compared as well.It was found that urease-loaded PRX hydrogel showed not obvious activity,which might be attributed to the oxidation of the free sulphydryl group close to the catalytic center of urease.Whereas the GOD-loaded PRX hydrogel showed relative stable activity,and has good resistance to pH,which could exhibit its enzymatic activity under acidic and neutral conditions.As PRX gel prepared by oxidation method is sensitive to reducing agent and has poor stability,PRX gel prepared by click chemical method is used instead.The thiol-ene click chemical reaction was initiated by the free radical cations ABTS^?+generated from laccase catalyzing the oxidation of 2,2'-diazide-bis?3-ethylbenzothiazole-6-sulfonic acid?salt?ABTS?.It caused crosslinking between the 4-arm polyethylene glycol acrylate?4arm-PEG-AA?and 4arm-PEG-SH which were threaded with ?-CD,and further fabricated laccase-loaded PRX hydrogel.Infrared spectra,XRD and SEM were used to characterize the structure of the PRX hydrogel,and the PPRX channel pattern and porous network structure were confirmed.At last,the laccase-loaded PRX hydrogel was applied to the decolorization of several triphenylmethane and azo dyes and dyes,and the decolorization effect of them was investigated.It was found that the laccase-loaded PRX hydrogel had bad decolorization effect on the azo dye methyl orange,while,it performed preferable decolorization effect on the triphenylmethane dyes such as malachite green,crystal violet,methyl blue and bromothymol blue,with the decolorization rate reaching about 60% within 12 h.Especially,the decolorization rate of malachite green could reach about 90% within 12 h.Compared with the free laccase,the loaded laccase showed better tolerance to the dye inhibition,but the inhibition effect of dyes could not be totally removed.As a result,when the laccase-loaded PRX hydrogel was reused,the decolorization rate would decrease to some extent.