Fabrication of CS/SA Double-Network Hydrogel and Application in pH-Controllable Drug Release

In order to promote the application range, double-network hydrogels are usually fabricated to improve the mechanical properties. In this work, chitosan (CS) single-network hydrogels were prepared firstly and sodium alginate (SA) was introduced as the second network. According to scanning electron microscopy (SEM), the microstructures of the CS and SA single-network were identified as three-dimensional network of pore and fiber structure, respectively. The microstructure maintained the pore structure after the formation of CS/SA double-network due to the small amount of SA. The size of the pores was reduced, indicating the cross-linking of the double-network. The rheological results indicated that CS/SA double-network with small amount of SA could enhance the mechanical strength of the hydrogel effectively. Finally, the in vitro release was operated, verifying the sustained release ability of the double-network hydrogel. In addition, only small amount of the drug could be release in physiological environment (pH 7.4), while a quickly release was obtained in pathological tissue (pH 5.5), decreasing the side effect of the drug.