Preparation And Properties Of Isolated Soy Protein Based Hydrogel Material

Soy protein isolate（SPI） is a kind of soluble and inexpensive plant protein, whose surface contains many active groups. The protein has some advantages, such as biocompatible, biodegradable, non-toxic and High amino acid content. Based on the above advantages, SPI has been widely used in drug delivery, water treatment, plastics, cosmetics and other fields.This paper mainly uses SPI as a raw material, which was composited with chitosan（CS） and polyvinyl alcohol（PVA）. Three kinds of hydrogels were prepared, respectively, namely SPI/CS-SHMP-HB spherical hydrogel, SPI/CS-mG microgel and SPI PVA hydrogel. The best preparation conditions were examined.The structure, thermal stability and hydrogel surface morphology of hydrogels have been characterized by using flourier-infrared spectrometry（FT-IR）, thermogravimetric analysis（TG） and scanning electron microscope（SEM）, respectively. The swelling rate, drug release and superoxide anion(O₂^·-) performance of the hydrogels were studied.Firstly, it was introduced that the main extraction methods and applications of plant proteins. On this basis, the source, structure, extraction methods and applications of the common plant proteins were described. These proteins include Zein, Rice protein and soy protein isolates. At last, classifications, preparations and applications of hydrogel were stated.Secondly, SPI acted as polyanions, CS acted as polycationic, and SHMP acted as ionic crosslinking agents, the SPI/CS-SHMP-HB spherical hydrogel were prepared. The structure and morphology of the hydrogel were characterized by FT-IR, SEM and TG. The results showed that hydrogel has a multi-layered network structure. The swelling behaviors of the SPI/CS-SHMP-HB spherical hydrogel were tested in different media. The results indicated the hydrogel possess a significant response of pH and ionic strength. Besides, the drug loading and drug release behavior of the SPI/CS-SHMP-HB spherical hydrogel were investigated by using BSA and 5-FU. It was found the hydrogel owns a good sustained release properties and high cumulative release rate for small molecule drugs. Especially, the cumulative release rate achieved 63.66% in pH=7.4 buffer solution. Therefore, SPI/CS-SHMP-HB spherical hydrogel has great prospects in oral enteric small molecule drug carrier field.Thirdly, cysteine（Cys） and 2,4-dihydroxybenzaldehyde（HOSal） acted as raw materials, hydroxyl salicylaldehyde-cysteine Schiff base ligand（HOSalCys） were synthesized. Then, amino acid Schiff base metal complexes HOSalCysM were prepared by complexing Schiff base ligand（HOSalCys） and metal ions（M=Cu^Ⅱ,Zn^Ⅱ）.The structure of ligand and complexes was characterized by FT-IR, UV-vis. Next, SPI and CS as raw materials, SPI compositing CS microgel（SPI/CS-mG） was prepared by urea dispersion solution purification-compounding method. The structure and morphology of the hydrogel were characterized by FT-IR, SEM and TG. The results showed that microgel is spherical, and the diameter about 200nm-300nm.TheZeta potential and particle size of microgel is smallest using this way. At last, HOSCM@SPI/CS-mG were prepared by combining metal complexes（HOSalCysM） with microgel（SPI/CS-mG）. The structure of HOSCM@SPI/CS-mG was characterized by FT-IR, UV-vis and SEM. The O₂^·- scavenging activities were determined via nitrobule tetrazolium assay method. After combining HOSalCysM into SPI/CS-mG, the poor water-solubility of HOSalCysM was improved, and the O₂^·- scavenging activity of SPI/CS-mG increased dramatically.The analog quantity HOSalCysCu reached 41% of natural SOD, and that of HOSalCys Zn reached 62.12%. Therefore, HOSCCu@SPI/CS-mG is a kind of excellent mimic of SOD enzyme.Finally, SPI and CS acted as the raw materials, the SPI/PVA hydrogel was prepared by freeze-thaw method.The structure and morphology of the hydrogel were characterized by FT-IR, SEM and TG. The results showed that hydrogel has a desired porous structure. The swelling behaviors of SPI/PVA hydrogel were tested in different media. The results indicated the hydrogel possess a significant response of pH and ionic strength. Besides, the drug loading and drug release behavior of the SPI/PVA hydrogel were investigated by using BSA and 5-FU. It was found the hydrogel owns a good sustained release properties and high cumulative release rate for small molecule drugs. Especially, the cumulative release rate achieved 64.04% in pH=7.4 buffer solution. Therefore, SPI/PVA hydrogel an ideal enteric pharmaceutical carrier material.To be concluded,the paper prepared hydrogels can be applied not only to the field of pharmaceutical carrier, may also be used in anti-oxidation, protein for further research to develop a new natural polymer directions in the biomedical field has broad application prospects.