Functionalization And Application Of The Polysaccharide Of Carboxymethylated Curdlan

Polysaccharides are a group of biopolymers that widely distributed in animal, plant andmicroorganism, and play essential roles in living organisms. Glucan is one of the mostimportant polysaccharides, wherein, β-1,3-glucan has been widely recognized to havebiological activity. Curdlan is a linear β-1,3-glucan formed by bacterial fermentation. Dueto the unique gelling properties, curdlan is widely used in the food industry, medicine andhealthcare field. However, curdlan is insoluble in water, which limits its widerapplications. After introducing the carboxymethyl groups, carboxymethyl curdlan(CMc)has good water solubility as well as better bioactivities, such as the antitumor activitiesand immunological enhancement. In this paper, based on the good biological activities ofCMc, the futher functionalization and application of CMc are carried out.Due to the three-dimensional network and good swelling properties, hydrogel has beenwidely used as drug delivery system and obtained more and more attention. Hydrogel canbe divided into physical and chemical hydrogel. For chemical hydrogel, due to the use oftoxic crosslinking agent and organic solvent, it has potentially cytotoxic. In this paper,aimed at the functionalizing study of CMc and the design of biocompatible drug carrier,the physical hydrogels of CMc are prepared by different ways and are applied in the drugdelivery. CMc physical hydrogel is prepared by freeze-thaw technique. The pH value of CMcsolution is essential for the formation of CMc gel. If the pH value is larger than2.4, it cannot be formed by freeze-thaw gel. The influences of CMc concentration, freeze-thaw cycle,freezing time on the gel strength are studied by rheological measurements. The resultsshow that the gel strength increases with the increase of freeze-thaw cycle. Combined withthe studies on PVA freeze-thaw gel, the gelation mechanaim of CMc freeze-thaw gel wasmainly due to hydrogen bond among CMc chains. The freezing process is facilitated theaggregation among CMc chains, benefit for the formation of hydrogen bonds. Using5-fluorouracil as a model drug, the release condition of CMc gel in simulatedgastrointestinal pH buffer is studied. The results show that the gel in pH=1.2buffer haslower release rate than that in pH=7.2PBS buffer, which indicated that the CMcfreeze-thaw gel is suitable for colonic drug delivery system.Based on the host-guest inclusion between β-cyclodextrin (β-CD) and adamantane (AD),the β-CD and AD was firstly grafted onto the CMc chains, and a temperature-sensitiveCMc host-guest gel is successfully obtained. The gel strength depends on the molar ratioof β-CD with AD in the mixed solution. When the ratio is1, the gel strength is maximum.2D-NOESY results indicate that the system has the host-guest interaction. Using bovineserum albumin (BSA) as model drug to study the release content, the results show that therelease rate decreases with increasing the molar ratio of β-CD and AD.Based on the sol-gel technique, the hybrid gel of Tetrakis(2-hydroxyethyl) orthosilicate(THEOS)/CMc is prepared, and this gel is biocompatible. Through dynamic time sweep,the influence of CMc, THEOS concentration and temperature on gelation time is studied.The results show that with the increase of CMc concentration, gelation time is firstlyshorten and then increases again. This is because at low CMc concentration, CMc roles asa template through hydrogen bonding with sol particle, to guide sol particle aggregation;when CMc increases further, electrostatic repulsion between CMc with negatively charged sol particles is high enough to weaken the hydrogen bonding and the catalysis of CMc.The gel strength increases with increasing THEOS concentration, and decreases withincreasing CMc concentration.Carboxymethylcellulose (CMC) is widely used as the stabilizer of casein micelle andacidified milk drinks. CMc and CMC are both water soluble polyanionic glucan, and theirmolecular structure is similar, only has the different linkage. The interactions betweenCMc, CMC and casein micelles during acidification are studied, in order to elucidate therelation of conformation and adsorption performance. The results show that the CMcadsorbs onto casein micelles earlier than that of CMC; particle size in the systemstabilized by CMc is smaller than that of CMC; to keep the system stable, the requiredCMc concentration is greater than that of CMC, and the stabilizing effect of CMc is lessthan that of CMC. From the view of molecular flexibility, the persistence length iscalculated by using the wormlike chain model. The results show that the persistence lengthof CMc is smaller, suggesting that CMc molecular chain is more flexible and it can adsorbmore closely, to provide lower steric repustion than CMC. CMc is also used to stabilizethe acidified whole milk drinks. The results show that CMc can prevent proteinaggregation and creaming, and the stability of milk drinks increases with increasing theCMc concentration.Due to the unique optical, magnetic and chemical properties, silver nanoparticle hasbeen widely applied in catalysis, optoelectronic devices, surface enhanced Ramanscattering (SERS) and biosensor. In this paper, using CMc as the stabilizer and reducingagent, silver nanoparticles is prepared under UV irradiation. The size and morphology ofthe as-prepared silver nanoparticle can be changed by adjusting CMc concentration.Through the measurements of zeta potential, UV-vis and FTIR, the role of CMc in thesysthesis of silver nanoparticle is discussed. The results show that CMc can catalyze theformation of silver nanoparticles. This is because CMc can complex with silver ion or silver particles to facilitate the charge transfer, which is in favor of the formation of silvernanoparticle. The as-prepared silver nanoparticles is applied in SERS. The results showthat CMc-stabilized silver nanoparticle can result in more obvious SERS.