Osteoporosis leads to bone fractures and irregular bone defects. Current treatments, such as bone grafts and implants, have limitations like availability issues, disease transmission, infection, and brittleness. We need innovative, injectable, antibacterial biomaterials to address osteoporotic bone defects. The aim of this study was to synthesize and characterize composite hydrogels based ɛ-polylysine (ɛ-PL), hyaluronic acid (HA), and strontium substituted hydroxyapatite nanoparticles (Sr-nHAp), and to evaluate, which of the 8 proposed compositions are most suitable for filling osteoporotic bone defects.