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Structure And Properties Of Collagen-based Materials Modified By Dialdehyde Pullulan

Posted on:2020-03-03Degree:MasterType:Thesis
Country:ChinaCandidate:L R ZhangFull Text:PDF
GTID:2381330575459811Subject:Leather Chemistry and Engineering
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Pullulan is a non-ionic,non-reducing microbial extracellular polysaccharide,which has the characteristics of non-mutagenic,non-immunogenic,non-toxic,edible,degradable and so on.It is widely used in food,textile,cosmetics,medicine and other industrial fields.For now,the aldehyde polysaccharides,a class of derivatives of polysaccharides,have attracted a wide spread attention of researchers.Aldehyde-based polysaccharides can be used as green and safe crosslinking agents instead of traditional small-molecule aldehydes crosslinkers.At the same time,the potential application value of polysaccharides in food,biomedical,chemical and other fields can be further developed.However,studies on the use of dialdehyde pullulan as a crosslinking agent have rarely been reported in the literature.The aim of this paper is to obtain dialdehyde pullulan by selective oxidation of pullulan with sodium periodate,and to further study its effect on crosslinking modification of collagen-based materials.To investigate the effect ofdialdehyde pullulan on the structure and properties of collagen-based materials,and to preliminarily study its application in tissue engineering,green packaging and leather industry.In this paper,firstly,dialdehyde pullulan was prepared by oxidative modification of sodium periodate with pullulan as raw material.The effects of reaction temperature,reaction time,pH and sodium periodate dosage on the content of aldehyde groups in dialdehyde pullulan were studied.The results showed that the dosage of sodium periodate had the most significant effect on the oxidation degree of pullulan.The formation of aldehyde groups and the change of aldehyde groups content were confirmed by FTIR and hydroxylamine hydrochloride titration.The aldehyde groups on the oxidized pullulan have high reactivity,which lays a foundation for the preparation of modified collagen-based materials.High strength gelatin hydrogels were successfully synthesized by chemical and physical crosslinking using the prepared dialdehyde pullulan modified gelatin.The effect of the dosage of dialdehyde pullulan on the structure and properties of gelatin hydrogel was studied.Studies have shown that dialdehyde pullulan as a macromolecular crosslinker can form short-range and long-range crosslinks between gelatin molecular chains,combined with physical crosslinking formed by physical entanglement points,and can form a single network structure with double crosslinks(physical and covalent crosslinking).The pore structure and size of gelatin hydrogel can be controlled by adjusting the amount of dialdehyde pullulan.The results showed that the dialdehyde pullulan crosslinked gelatin hydrogel had homogeneous porous structure.Compared with pure gelatin hydrogel,its mechanical strength increased significantly.Under the condition of 80%strain,the compressive stress of dialdehyde pullan crosslinked gelatin hydrogel can reach 5.80 MPa,which is 152 times of the compressive stress of pure gelatin hydrogel.The results also showed that changing the amount of dialdehyde pullulan could regulate the swelling behavior,crosslinking index and enzymatic degradation properties of gelatin hydrogels.The cytotoxicity of hydrogel on MC3T3 cells was determined by MTT.The results showed that the RGR values of all tested samples were high,indicating that the dialdehyde pullulan crosslinked gelatin hydrogels had good biocompatibility and could well support cells proliferation and growth.Gelatin film was modified by dialdehyde pullulan with different aldehyde content as crosslinking agent.The effect of dialdehyde pullulan on the structure and properties of gelatin-based films was discussed in detail.With the increase of the content of aldehyde groups in the dialdehyde pullulan,the properties of light barrier,crosslinking degree,tensile strength and thermal stability of the crosslinked gelatin-based film were significantly enhanced.The highest tensile strength of gelatin-based films was about 15.68 MPa,which is 2.7 times higher than that of pure gelatin film..The highest glass transition temperature of gelatin-based films was 86.5 ?,which is 17 ? higher than that of pure gelatin film.At the same time,the moisture permeability,water solubility and thermal decomposition temperature of gelatin-based films were reduced,which made the comprehensive properties of gelatin-based films more excellent.Meanwhile,the application scope of gelatin film in packaging field is broadened.Dialdehyde pullulan with different aldehyde groups content was used as a tanning agent to crosslink(tanning)the leather collagen fibers.The effect of the change of aldehyde groups in the dialdehyde pullulan on the tanning properties was investigated.The differences in tanning properties of dialdehyde pullulan with different oxidation degrees were investigated.DSC results showed that the tanning effect of dialdehyde pullulan on collagen fibers was remarkable.Compared with pure collagen fibers,the thermal denaturation temperature of modified collagen fibers was increased by 19.43 ?,which greatly improved the thermal stability of collagen fibers.FESEM analysis showed that the dispersion of collagen fiber modified by dialdehyde pullulan was better.These studies lay the foundation for the application of dialdehyde pullulan in leather field.
Keywords/Search Tags:Pullulan, dialdehyde pullulan, crosslinking agent, gelatin, collagen fiber
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