Preparation And Properties Of Hemicellulose-based Hydrogels From Enteromorpha Prolifera

As a kind of widely distributed temperate type large green algae, Enteromorpha prolifera has a strong ability of growth and reproduction. Enteromorpha prolifera is a kind of high sugar, high fiber, high fatty acid, low fat algae. There are 18 kinds of amino acids in the protein, containing 6 kinds of essential amino acid for the human body(EAA) and some flavor amino acid(DAA). It also contains vitamins and minerals. The Enteromorpha prolifera green tide hazards frequently occurred in the Yellow Sea, Bohai Sea and Southeast coast of China. However, the treatment of Enteromorpha prolifera mostly were burying or rough machining as feed.Taking Enteromorpha prolifera as experiment materials, optimization of alkaline hydrogen peroxide extraction conditions of hemicellulose by response surface method(RSM), so as to improve the extraction efficiency. Base on the single factor experiment, using Box-Benhnken central composite experimental design principle of RSM, design four factor three level experiment, to explore the effect of sodium hydroxide concentration, extraction temperature, extraction time, ratio of Enteromorpha prolifera and extraction solvent on the extraction efficacy of hemicellulose. The regression equation was obtained by the experiment, and the fitting model was established to determine the optimum conditions for the extraction of hemicellulose. The component of hemicellulose extracted from Enteromorpha prolifera was analyzed by using infrared spectroscopy(FT-IR) and ion chromatography(IC). The results showed that the regression equation had a high degree of significance, could be used to analyze and forecast the extraction amount of hemicellulose in Enteromorpha prolifera. The factors influencing the extraction amount of hemicellulose were in the order as follows: extraction time > extraction temperature > ratio of Enteromorpha and extraction solvent > concentration of sodium hydroxide. Ultimately the optimal extraction conditions were: the concentration of sodium hydroxide were 4.8g/L, temperature were 92℃, time were 5h, the ratio of solid to liquid were 1:70, the extraction rate were 56.75%, consisting with the predicated value 57.30% in the range of allowable error.FT-IR results showed that it contains obvious xylose and arabinose characteristic absorption peak, and the pyran ring structure was connected by beta glycosidic bond. IC analysis showed that hemicellulose of Enteromorpha prolifera mainly composed of xylose and arabinose, contain little amounts of glucose and galactose. Among them, xylose content up to 54.4%. Secondly, the arabinose was 15.3%, the content of glucose and galactose were 5.6% and 2.7%.Hydrogel is a kind of polymer with three-dimensional network structure which has good water holding capacity and biocompatibility. Due to its excellent physicochemical properties and biological properties, it was more and more popular. It was widely used in agricultural water retaining materials, fruits and vegetables fresh-keeping agents, antibacterial agent of fruit and melon, heavy metal ion adsorbent in industrial wastewater, biological medicine, tissue engineering, contact lenses, et al. Chitosan is the only one cationic polyelectrolyte of the natural high molecular polysaccharide, which was rich in active hydroxyl groups(-OH) and amino groups(-NH2). As a natural polymer biomaterial, the application in biological engineering and tissue materials has received great attention. Hemicellulose is a mixture composed of xylose, arabinose, galactose, glucose and other monosaccharide in a certain proportion, which was rich in active hydroxyl groups(-OH) and some functional groups of carbohydrates, such as uronic acid groups. Therefore, the hemicellulose has various biological functions.The hydrogel was prepared with the natural polymer as monomers by methods of physical crosslinking, which has good biocompatibility and biodegradability, without toxicity of crosslinking agentand initiator agent. It has better application prospect in biomedicine and functioning of the tissue.Preparation of hydrogels with chitosan and hemicellulose from Enteromorpha prolifera by self-assembling method. Effect of preparation conditions on hydrogels was analysed, such as the ratio of hemicellulose and chitosan, reaction temperature, reaction p H. The hydrogels were characterized by Fourier transform infrared spectroscopy(FT-IR) and scanning electron microscopy(SEM). The gel strength were analyzed by Texture Analyzer,and the swelling kinetics of hydrogels were analyzed in phosphate buffer solution(PBS) which ionic strength is 0.015 M, p H is 7.4 and concentration is 0.02 M. The experimental results show that the complexation between the negative charged glucuronic acid groups of hemicellulose and the positive charged amino of chitosan were formed by electrostatic interaction under acidic conditions. The unreacted active hydroxyl groups(-OH) of hemicellulose, active hydroxyl groups(-OH) and amino groups(-NH2) of chitosan can form hydrogen bonds, which makes the gel network more compacter and stable. The hemicellulose-based hydrogels have honeycomb-like three-dimensional structure from the electron microscope(SEM) images. The gel strength, water holding capacity, equilibrium swelling ratio were affected by the ratio of hemicellulose and chitosan,p H and temperature. When the ratio of chitosan and hemicellulose was 3:7, the temperature was 95℃, the p H was 4.0,the gel strength and water holding capacity were the largest, the equilibrium swelling ratio was minimal on the contrary. As the gel strength increasing, the internal threedimensional honeycomb network of prepared gel is more compacter, pore size is smaller, then, the absorption of water is less when the gel reaching equilibrium swelling state. On the other hand, the more compacter network will generate more powerful restrictive force, which will prevent the loss of water, keeping the moisture in the gel network better, leading to the water holding capacity better.Fast absorbing water(0~1h), relatively slow absorbing water(1~10h), dynamic equilibrium(10~24h) were three stages of the gel swelling in PBS buffer. In 0~1 hours, the hydrogel rapidly absorbing solution due to the presence of honeycomb-like threedimensional structure when placed in PBS buffer solution. In 1~10 hours, the polymer network of hydrogel swelling after water absorption, which was profitable to the absorption of water, however the process was relatively slow. In 10~24 hours, the gel is reaching to the dynamic balance and no longer swelling.Tea polyphenols is an antioxidant with a strong ability to remove free radicals, which has reduce blood sugar, antimicrobial effects and so on, but it is easy to oxidize and lose its biological activity. Therefore, to improve the stability and realized slow releasing of polyphenols, it had been encapsulated in hemicellulose-based hydrogel.With the increasing of tea polyphenols input, the encapsulation efficiency decreased gradually and the loading capacity increased step by step. When the tea polyphenols investment amount was 200 mg, the two curves were intersect. The encapsulation efficiency was 85.04% and the loading capacity was 86.20%, reaching a relatively ideal equilibrium state at this point. The dried hydrogel contained tea polyphenol was placed in the PBS buffer solution, then the effect of hemicellulose-based hydrogel on controlling release of tea polyphenols was investigated. The release process is also divided into three stages, corresponding to the swelling ratio of the hydrogel. In 0~1h, the gel in the tea polyphenol is released rapidly. In 1~10h, tea polyphenol was slowly released by the hydrogel when the polymer network slow swelling and the tea polyphenols concentration difference inside and outside of gel. After 10 h, the release of tea polyphenols was relatively slow and gradually reached to balance. The hemicellulose-based hydrogel can effectively control the sustained release of tea polyphenols, as an ideal carrier of the active substance, which providing the technical support for the application of the hydrogel in the field of biomedical field.Using L929 cells as target cells to research the biocompatibility of hemicellulose, chitosan and hydrogels. The results shows that the 1.00 μg/m L chitosan and 1.00 μg/m L hemicellulose have a significant promotion effect on the cell growth, which belong to the 0~1 level of RGR cytotoxicity grade and almost non-toxic. Gel-1,Gel-1(tp),Gel-3 and Gel-3(tp) belong to the 0~1 level of RGR cytotoxicity grade and almost non-toxic. Therefore, the prepared hemicellulose based hydrogels have better safety and can be used for medical materials.