Preparation And Properties Of Functional Materials Based On Pectin Derivatives

Pectin,an acidic heteropolysaccharides,which is widely existed in the cell wall of plant cells,is composed of D-1,4 Galacturonic acid connected by?-1,4-configurations.Pectin has characteristics of natural,green,nutrition and health,which is widely used in food,health products,cosmetics and pharmaceutical industry.In pharmaceutical industry,pectin has many excellent properties,such as antibacterial,hemostatic,detoxification,hypolipidemic and anti-radiation effect.The development of a variety of functional materials and biological material based on pectin is the inevitable trend of future research and application.Because of its high molecular weight and different source of the structure,its application in food and pharmacy-eutical industry is limited.In this work,the research and application of the modification of pectin,including chemical modification,graft and irradiation,was introduced.Firstly,pectin sulfates and quaternized pectin have been synthesized through the esterification and etherification,and the properties of the derivatives,such as anticoagulant property,moisture absorption and moisture retention and antibacterial property,have been studied.Secondly,two kinds of pectin-based hydrogels were prepared by irradiation and chemical crosslinking.Besides,the properties and applications of the hydrogels were also studied.Finally,the properties of the water soluble medical dressings,which were prepared by the combination of polysaccharide and protein,have been studied.The main research contents and conclusions were as follows:?1?Pectin sulfates?PS?were prepared from pectin through reacting with an uncommon sulfating agent?N?SO₃Na?₃?in aqueous solution.The main factors affecting the degree of substitution?DS?of the products were studied.The optimum reaction conditions are as following:The pH value of the reaction medium is 6,the reaction temperature is 60?,the reaction time is 12 h,the ratio of sulfating agent to pectin is 2.5/190?mol/g?.The structure and properties of PS were investigated.The results indicated that PS is relatively stable to the temperature,unstable to acid,alkali,oxidation conditions.In vitro cytotoxicity test showed that PS is not cytotoxicity.In addition,the influence of molecular weight,concentration and degree on the the anticoagulation property were studied,which indicated that the anticoagulation property of PS increased with an increase of DS,and the best anticoagulation of molecular weight and concentration of PS was 2×10⁴ Da and 50?g/mL,respectively.Blood coagulation tests showed that PS could prolong APTT and TT by inhibiting the activity of thrombin,which showed that the introduction of the sulfate group could improve its anticoagulation.?2?Quaternized pectin?QP?was prepared from pectin by reacting with3-chloro-2-hydroxypropyl trimethyl ammonium chloride?CHPTAC?in the presence of NaOH.The structure and properties of QP were investigated.The DS of QP could be controlled by adjusting the molar ratio of CHPTAC/pectin,the ratio of NaOH/CHPTAC,and the reaction temperature.The optimal conditions are as following:The molar ratio of CHPTAC and QP is 7,the molar ratio of NaOH/CHPTAC is 1.2,and the reaction temperature is 70?.The moisture absorption property of QP is closely related to its DS value.With the increase of DS,the moisture absorption and moisture retention property of QP was gradually enhanced.The forced degradation study showed that the QP is relatively stable to the temperature,unstable to acid,alkali,oxidation conditions.In vitro cytotoxicity test showed that QP is not cytotoxicity.In vitro antibacterial test showed that QP displayed significantly inhibitory effect on staphylococcus aureus,staphylococcus epidermidis,bacillaceae,candida albicans,candida tropicalis and pityrosporum.?3?QP/PVA blend hydrogels were prepared from QP and PVA by irradiation,and the structure and properties of the hydrogels were studied.The results showed that gel fraction of the hydrogel reached the maximum 90%when the mass ratio of QP/PVA was 1:2 and radiation intensity was 60 KGy;swelling properties of the hydrogel reached the maximum 40g/g when the mass ratio of QP/PVA was 1:1 and radiation intensity was 20 KGy;tensile strength of the hydrogel reached the maximum 2.50MPa when the mass ratio of QP/PVA was 1:2 and irradiation intensity was 40 KGy.Moreover,the hydrogels displayed significantly antibacterial activities on staphylococcus aureus and escherichia coli.?4?Through the single factor experiment,pectin-collagen peptides derivatives were prepared in aqueous solution by using 1-?3-dimethylaminopropyl?-3-ethyl carbodiimide?EDC?and N-hydroxysuccinimide?NHS?as crosslinking agents.The optimum reaction conditions are as following:The reaction time is 20 h,the reaction temperature is 35?,the mass ratio of collagen protein and pectin is 1.2/0.6.The moisture absorption and moisture retention of the pectin-collagen peptides with different DS and concentration were investigated.With the increase of DS,the moisture absorption and moisture retention rate of the pectin-collagen peptides significantly increased.With the increase of DS and the concentration of pectin-collagen peptides,the scavenging rate of hydrogen peroxide and DPPH radicals increased.Fibroblast cells proliferation experiment results showed that cell viability first increased and then decreased with increasing DS and concentration of pectin-collagen peptides.?5?Oxidized pectin?OP?containing double aldehyde were prepared by oxidation,and water-soluble amine-ethyl-chitosan?AECS?were synthesized from chitosan and2-chloro ethylamine hydrochloride.The hydrogels were prepared through the Schiff base reaction of the aldehyde group of OP and the amino group of the AECS.The structure and properties of the hydrogels were studied.The results indicated that the swelling equilibrium of liquid content of the hydrogels were in the range of 87-95%.Hydrogels prepared with high oxidation degree of OP and high amino content of AECS displayed a high degree of crosslinking and the best water absorption.OP1-AECS1 hydrogel has the maximum water vapor transmission rate?500±10g/m²/h?.Under the same degree of oxidation,and the higher content of amino group in AECS,the degree of crosslinking is higher,and the moisture content of hydrogel is smaller.OP1-AECS1 displayed larger water loss rate,while OP2-AECS2 displayed smaller water loss rate.Moreover,the degree of hemolysis of the OP-AECS hydrogels was smaller than 5%,which meets the standard.