3D‐printed magnesium/nanodiamond dual‐doped hydroxyapatite composite hydrogels with antibacterial and in vitro bioactive properties for bone tissue engineering

Bone regeneration remains a critical challenge in personalized healthcare, particularly when combating bacterial infections that impede healing. While various scaffold systems have been developed, the combination of magnesium and nanodiamond dual‐doped hydroxyapatite (MgND‐HAp) with natural polymers in a 3D‐printable format, offering both antimicrobial protection and enhanced cellular response, has not been previously explored. In this study, we developed 3D‐printable hydrogel scaffolds combining carboxymethyl chitosan, gelatin, and MgND‐HAp for bone tissue engineering applications. The carboxymethyl chitosan–gelatin (CMG) hydrogel scaffolds were comprehensively evaluated for structural, physicochemical, and biological characteristics. x‐Ray diffraction confirmed successful MgND‐HAp incorporation, while rheological studies showed improved printability with increasing MgND‐HAp concentration. The CMG 4% formulation exhibited optimal viscoelastic behavior (elastic modulus ∼12.5 kPa) and toughness (2.1 MJ/m 3 ) with increasing concentration of MgND‐HAp. Biocompatibility studies revealed enhanced cell viability and migration of human mesenchymal stem cells compared to control scaffolds. The increasing concentration of MgND‐HAp demonstrated remarkable antibacterial efficacy against Escherichia coli (90%) and methicillin‐resistant Staphylococcus aureus (95%) bacteria. Crystal violet staining assays confirmed significant biofilm inhibition across all MgND‐HAp‐containing formulations. These findings suggest that the developed CMG hydrogel scaffolds, particularly the CMG 2% and CMG 4% formulations, offer a promising platform combining excellent printability, mechanical stability, biocompatibility, and antimicrobial properties for bone tissue engineering applications.