Si‐Modified Biogenic Hydroxyapatite/Alginate Hydrogel Composites for Injectable Application: Preparation, Structure, and Properties

Alginate‐based injectable hydrogels have held the attention of researchers due to their significant biomedical potential and unique properties. In this study, Si‐modified biogenic hydroxyapatite/alginate hydrogel composites (AlgNa/Si‐BHA) were prepared by ionic crosslinking with different amounts of the inorganic component (1%, 2% and 3%), which contain 2 and 5 wt.% silicon. The composites were characterized using X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), differential thermogravimetric analysis (DTGA), scanning electron microscopy (SEM), helium pycnometry, and swelling behavior analysis. XRD and FTIR analyses confirmed the presence of AlgNa hydrogel and hydroxyapatite phases as well as silica bands. The DTGA results demonstrated that the presence of silicon in composites increases thermal stability at high temperatures. SEM imaging showed the formation of specific porous relief structures for all types of composites. SEM/EDS analysis confirms the presence of all main elements of the composite, such as calcium, phosphorus, oxygen, silicon, sodium, and carbon. For AlgNa/2Si‐BHA and AlgNa/5Si‐BHA composites with different ratios of components, the skeleton density was in the range of 1.14–1.66 g/cm 3 . Swelling studies demonstrated a significant effect of silicon on equilibrium swelling degree; namely, it is increasing for AlgNa/Si‐BHA compared to AlgNa/BHA and allows obtaining composites with swelling higher by 30% in contrast to a pure hydrogel, which confirms the feasibility of creating this type of hydrogels.