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Objectives and questions: Bone infections, including osteomyelitis and post-surgical infections, remain a major challenge in orthopedic and trauma surgery, often leading to implant failure, chronic inflammation, and compromised bone healing. Conventional treatment strategies, including systemic antibiotics and surgical debridement, are often ineffective due to high recurrence rates and rising antibiotic resistance. Therefore, localized, sustained-release alternatives are necessary to enhance treatment outcomes.

This study aims to evaluate the antimicrobial efficacy, biocompatibility, osteogenic potential, and injectability of a newly formulated bone paste designed to prevent bacterial colonization, eliminate infections, and support bone regeneration in infected bone defects.

Materials and Methods: The past containing Calcium Hydroxide (Ca(OH)₂), Polyvinylpyrrolidone (PVP), and Collagen, underwent a comprehensive in vitro study was conducted to assess the biological, antimicrobial, and rheological properties of the bone paste. Cell viability, proliferation, and osteogenic differentiation were analyzed using MSC cultures, while flowability and injectability tests were performed under various storage conditions to ensure handling feasibility. Furthermore, Agar diffusion assays evaluated antibacterial activity against Escherichia coli and Staphylococcus aureus, among others, while co-culture models of bacteria and mesenchymal stem cells (MSCs) assessed the paste’s ability to simultaneously suppress bacterial growth while supporting MSC proliferation.

Results: The antimicrobial bone paste demonstrated potent antibacterial effects, with inhibition zones of 1.32 ± 0.15 cm for E. coli and 1.41 ± 0.19 cm for S. aureus, indicating broad-spectrum efficacy. Co-culture experiments confirmed that the paste significantly reduced bacterial growth (>80%) while improving MSC proliferation by 27% compared to controls. Cell viability assays showed 92.5% ± 3.1% survival, corresponding to 1.3 million viable MSCs/mL, with osteogenic markers (Runx2, ALP) up-regulated by 1.5–2.2 fold, suggesting a pro-osteogenic microenvironment. Flowability and injectability tests confirmed that the paste retained its homogeneous consistency and optimal viscosity, maintaining stable injectability (1.8 ± 0.2 N) for at least 21 days, ensuring ease of clinical application. The paste also showed a controlled degradation rate, maintaining structural integrity for up to four weeks in simulated physiological conditions.

Discussion and conclusion: The injectable antimicrobial bone paste demonstrated strong antibacterial activity, excellent biocompatibility, and sustained injectability in vitro. Its ability to suppress bacterial growth while promoting osteogenesis underscores its potential as a next-generation treatment for bone infections. Ongoing pilot in vivo studies will further assess its efficacy in infection clearance and bone regeneration, paving the way for future clinical translation possibilities.