Calcium Phosphate Mineralization of Bulk Alginate Hydrogels Composites With Metal and Metal Oxide Nanoparticles

Alginate hydrogels are promising materials for biomedical applications due to their biocompatibility and ability to mimic the extracellular matrix. However, poor mechanical stability and limited bioactivity hinder their wider clinical application. This problem can be overcome by incorporating nanoparticles (NPs) and calcium phosphates (CaPs). In this study, the simultaneous gelation and CaP mineralization of bulk alginate hydrogels in the presence of antimicrobial silver (AgNP), copper oxide (CuONP), and zinc oxide (ZnONP) was investigated. Calcium-deficient hydroxyapatite forms at pH 7.4, and stable amorphous calcium phosphate at pH 9.0. The incorporation of NPs influences the morphology of mineral phases but not composition. Rheological testing revealed that mineralized hydrogels exhibit earlier network breakdown compared to the non-mineralized ones, with critical strain values dependent on both pH and NP type. Ion release is pH-dependent, with generally higher metal ion release from non-mineralized hydrogels. Antibacterial assays demonstrate significant inhibition of S. aureus by hydrogels prepared at pH 9.0, except for hydrogels containing CuONPs. For P. aeruginosa, the differences in inhibition rates between different hydrogels were less pronounced. The obtained results indicate that CaP-mineralized alginate hydrogels incorporating metal and metal oxide NPs exhibit tunable properties, confirming their potential for bone tissue engineering applications and infection prevention.