Effects of Guar Gum and Sodium Benzoate on the Properties and Hydrophilicity of Silk Fibroin Hydrogels

Silk fibroin (SF)-based hydrogels were prepared by the simple evaporation method. The outcomes of SF-based hydrogels were assessed for consideration in terms of practical and convenient use. Guar gum (GG) and sodium benzoate (SB) are blending reagents to the SF solution and are poured into the petri dish to make the hydrogels. After leaving the mixture solution for three days to solidify, all SF-based hydrogels were peeled off and characterized. The SF-blend guar gum (SF-GG) and SF-GG-blend sodium benzoate (SF-GG-SB) could be constructed, but in different textures and levels of transparency. The SB affected the solid texture and resulted in a higher water contact angle (WCA) value of the prepared SF hydrogel than of the SF-GG. The results from Fourier transform infrared spectroscopy (FTIR) indicated all the main functional groups of substances that were contained in the blending hydrogels. Moreover, some interactions between the functional groups were also detected. A thermogravimetric analyzer (TGA) was used to determine the hydrogel decomposition as a function of temperature. The DTG thermograms, which exhibit the maximum decomposition temperature, revealed that the interaction forces between blending substances and SF, as well as their structure, are the reason for the thermal stability of the SF-based hydrogels. SF-GG-SB hydrogels have higher tensile strength than the SF-GG hydrogels. In conclusion, the appearance, texture, hydrophilicity, thermal stability, and tensile strength of the SF-based hydrogels were affected by the types and concentrations of the blending substances. This suggests that the SF-based hydrogel properties could be designed and adjusted to attain desirable textures for fitting target applications.