Study On Synthesis And Properties Of β- Cyclodextrin -g- Alginate

Sodium alginate is a linear anion natural polysaccharide, with the property of gel-forming, film-forming ability, biocompatibility and biodegradability, etc. Sodium alginate only has strong hydrophilicity, so it has some defects in its application. We could obtain a new kind of amphiphilic biomacromolecular by grafting different compounds on sodium alginate. Cyclodextrin is a cyclic oligosaccharide, P-CD has a moderate size cavity, so that it has strong inclusion ability. Cyclodextrin can be absorbed in body and is non-toxic to human, and can be largely produced, so it has been widely researched in recent years.β-CD was grafted onto the macromolecular chain of sodium alginate by esterification reaction. Modified sodium alginate as a new type of amphiphilic material keeps the advantages like biocompatibility and gel-forming ability, further more, it has introduced the inclusion ability of organic molecules by hydrophobic cavity. It shows the slow-release effect to certain molecules, and is expected to be used in pharmaceutical, daily chemical and other industries.P-CD-g-NaAlg of different grafting degree were synthesized by the reaction of sodium alginate with P-CD, using p-TSA acidifying agent, EDC-HCl as a couping agent and DMF as solvent. The products were characterized by fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, differential scanning calorimetry and thermogravimetry. The appearance of ester bond peaks in FTIR spectrum, the peaks of the methylene proton in NMR spectrum and the ester-bond rupture exothermic peak in DSC spectrum, suggust that β-CD successfully grafted onto sodium alginate.The grafting degree of P-CD-g-NaAlg was analysised by ultrabiolet-visible spectroscopy. The influence of molar ratio of alginate unit to β-CD, reaction time, reaction temperature, the mass of EDC-HCl and p-TSA on grafting degree were investigated systematacially. The result showed that, the grafting rate of P-CD-g-NaAlg could reach20.4%in the reaction conditions as followed:the molar ratio of NaAlg/β-CD/EDC-HCl was1:5:1.2:1.5, reaction time was24h and reaction temperature was50℃.We found that β-CD-g-NaAlg presents spherical morphology by transmission electron microscope. The viscosity and paticle size of P-CD-g-NaAlg in aqueous solution were studied. As the grafting degree increased, the viscosity and paticle size go up; at the same grafting degree, as the concentration of β-CD-g-NaAlg increased, the paticle size of the aggregation increased. The solution of P-CD-g-NaAlg crosslinking with Ca2+to form hydrogel, results show that the modified alginate remain good gelation properties, as the grafting degree goes up, the water content of hydrogel decreased but the thermal stability of the gel increased.The probe molecule methylene blue was absorbed through gelation-adsorption process, results showed that the hydrogel grafted cyclodextrin presents higher adsorption effect of methylene blue than that of sodium alginate hydrogel. Then we used the method of mixed-gelation-disintergraion to closure and removal of methylene blue in the solution, results show that almost all methylene blue molecules could be removed. The methylene blue in hydrogel could be eluted by pure ethanol. As Ca2+and Na2CO3could form precipitation, the hydrogel disintergrated, after centrifugation to remove precipitate, the solution of β-CD-g-NaAlg could be reused. Repeat the process above four times, the removel rate of methylene blue still reached89.0%. These all showed that β-CD-g-NaAlg kept the gel-forming properties and had well inclusion ability of small organic molecules.Ag+was included by modified hydrogel, the inclusion ability was proved by TEM and TG The inhibitory effect of the hydrogel to e.coli and staphylococcus were studied. Results show that after Ag+included, the product has the inhibition of bacteria, as the forming of outer gel, the bacteriostatic effect is not as good as the original sample, but is more durable as the extension of time. Thus, we know that Ag+included by modified hydrogel shows the slow-release and sustained bacteriostatic effect.