Preparation and properties of reversible thermoresponsive hydrogels based on chitosan and silver ion
A series reversible thermoresponsive chitosan(CS)-Ag hydrogels were prepared from supermolecule complexation of CS with Ag+of AgNO3,and characterized by FTIR,XRD,XPS,SEM and EDS for structure and chemical state analyses.The results showed that the CS-Ag hydrogels with the same gelation temperature could be obtained by adjusting the AgNO3 amount and pH simultaneously.CS-Ag-19 hydrogel,prepared under conditions of CS amount 0.60 g,AgNO3 amount 0.19 g,total volume 21 mL,and hydrogel pH 4.24,exhibited the best thermoreversible property,with cycle phase transformation for at least 5 times and stability for 5 months when stored at room temperature away from light.Moreover,the hydrogel displayed good antibacterial performance against Escherichia coli.The reversible thermoresponsiveness of CS-Ag hydrogel was controlled by supramolecular interactions among amino group at different temperatures.The equilibrium relationship between H+and Ag+,driven by changes in temperature and concentration,and competitive reactions(protonation and complexation)against free amino groups made the hydrogel temperature sensitive and reversible.The injectability and thermo sensitivity of CS-Ag-19 made it promising as antibacterial dressing.
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