Tailoring osteoimmunity and hemostasis using 3D-Printed nano-photocatalytic bactericidal scaffold for augmented bone regeneration

Bone hemorrhage, infection, and large bone defects following surgical treatment of traumatic bone injury have raised potential concerns, underscoring the urgent need to develop multifunctional therapeutic platforms that can effectively address traumatic bone regeneration. Advancements in three-dimensional (3D) printing technology have propelled the development of several engineering disciplines, such as tissue engineering. Nevertheless, 3D-printed frameworks with conventional materials often lack multifunctional capabilities to promote specific activities for diverse regeneration purposes. In this study, we developed a highly oxidized two-dimensional (2D) graphitic carbon nitride (Ox-gCN) as a nano-photocatalyst to reinforce alginate/gelatin (ALG)-based hydrogel scaffolds (ALG/CN) to achieve an anti-inflammatory and osteo-immunomodulatory niche with superior hemostatic ability for traumatic bone injury repair. Sulfuric acid oxidation enhances the oxygen-containing functional groups of the g-CN surface and promotes cell adhesion and differentiation of human bone marrow-derived mesenchymal stem cells (hBMSCs) in vitro. Moreover, the excellent visible light-activated photocatalytic characteristics of the ALG/CN scaffold were used in antibacterial studies. In addition, the ALG/CN bio/nanocomposite scaffold facilitates M2 polarization of macrophages than did pristine ALG scaffolds. Furthermore, ALG/CN scaffold induced hBMSCs differentiation by upregulating ERK and MAPKs phosphorylation during osteo-immunomodulation. In a rat calvaria defect model, the fabricated ALG/CN scaffolds induced new bone formation through collagen deposition and activation of osteocalcin proteins without inflammation in vivo. These results highlight the potential of 3D-printed functionalized 2D carbon nitrides in regulating the bone immune microenvironment, which may be beneficial for developing advanced tissue constructs, especially for traumatic bone regeneration in clinical settings.