Bio-Based Silica-Reinforced Chitosan/Collagen Thermogels: Synthesis, Structure, and Rheological Behavior

Silica-reinforced chitosan/collagen hydrogels are useful for biomedical applications. In this study, thermosensitive chitosan/collagen hydrogels were made with different amounts of rice husk ash-derived silica (RHA-Si). FTIR was used to study the chemical structure. The results showed that adding silica did not change the main chemical groups but caused some small shifts, meaning there were physical interactions. Micro-CT showed that silica changed the shape and size of the pores in the hydrogel. The pore structure became more spherical at some silica levels but not in a straight pattern. Rheological tests showed that more silica made the hydrogel stiffer and shortened the gelation time. However, at high strain, the hydrogel became weaker because of broken physical bonds. Compression tests showed that low silica (1% w/v) made the hydrogel stronger at small deformation. But at higher silica levels (2–3% w/v), the hydrogel was weaker when pressed hard. In summary, adding RHA-Si can improve the structure and strength of chitosan/collagen hydrogels, but too much silica can make the hydrogel less flexible. The amount of silica must be adjusted to fit the use of the hydrogel.