Near-Infrared Responsive Property and Nanozyme Effect-Mediated 3D-Printed Gradient Bioactive Scaffold for Intelligent...

Restoring large segmental bone defects remains a significant clinical challenge. Current approaches often fail to create a supportive environment for intrinsic tissue repair. While calcium phosphate scaffolds offer osteoconductive properties, they lack the ability to actively regulate immune responses. This limitation, combined with reduced mechanical strength due to porosity, hampers their effectiveness. Prior research has shown that immune modulation is crucial for successful bone regeneration. However, no prior work had resolved how to integrate immune regulation with mechanical stability in a single scaffold. That uncertainty drove the need for a new approach that could modulate macrophage activity while maintaining mechanical integrity. Existing studies have explored immunomodulatory biomaterials, but none have combined them with 3D-printed gradient structures. This gap motivated the development of a new scaffold design that could address both mechanical and biological challenges in bone regeneration.

This study aimed to develop a novel 3D-printed scaffold that could actively regulate immune responses during bone regeneration. The specific problem addressed was the lack of a supportive microenvironment for intrinsic repair processes in large bone defects. The motivation stemmed from the need to enhance both mechanical strength and bioactivity in a single scaffold. The researchers proposed integrating a gradient structure with immunomodulatory properties to overcome current limitations. The goal was to create a scaffold that could modulate macrophage polarization through controlled release of bioactive ions. The design aimed to combine mechanical robustness with the ability to respond to external stimuli. The study sought to establish a new paradigm for smart bone grafts by integrating immunomodulation with 3D-printing technology. This approach could potentially improve the success rate of bone regeneration therapies.

The scaffold was fabricated using digital light processing (DLP) printing combined with secondary sintering. This method allowed for the creation of a core-shell-like gradient structure with a dense interior and porous exterior. The gradient design was intended to balance mechanical strength and bioactivity. Manganese iron Prussian blue analogue (MnFePBA) nanozymes were incorporated onto the scaffold surface. These nanozymes were selected for their ability to scavenge reactive oxygen species (ROS) and release Mn²⁺ ions. The scaffold was tested under near-infrared (NIR) irradiation to assess its responsiveness. In vitro experiments evaluated macrophage polarization and ROS scavenging. In vivo studies were conducted to observe bone regeneration and immune modulation. The combination of 3D printing and nanozyme integration enabled the scaffold to respond to external stimuli while maintaining structural integrity.

The scaffold demonstrated a core-shell-like gradient structure with a dense interior and porous exterior. This design provided mechanical robustness while maintaining bioactivity. Under NIR irradiation, MnFePBA nanozymes effectively scavenged ROS and released Mn²⁺ ions. These actions synergistically drove macrophage polarization from M1 to M2 phenotypes. In vitro studies confirmed that the scaffold reduced oxidative stress and promoted proregenerative immune responses. In vivo experiments showed significant enhancement in bone regeneration. The scaffold fostered a favorable immune microenvironment post-implantation. The combination of NIR responsiveness and nanozyme activity enabled intelligent immunomodulation. These findings suggest that the scaffold could serve as a next-generation smart bone graft. The results highlight the potential of integrating immunomodulation with 3D-printed scaffolds for bone repair.

The authors concluded that the gradient scaffold design effectively combined mechanical strength with immunomodulatory properties. The integration of MnFePBA nanozymes allowed for controlled ROS scavenging and ion release under NIR irradiation. This dual functionality enabled macrophage polarization from M1 to M2 phenotypes. The scaffold's ability to modulate immune responses was confirmed in both in vitro and in vivo studies. The results suggest that the scaffold creates a favorable microenvironment for bone regeneration. The combination of 3D printing and nanozyme integration offers a new approach to smart bone grafts. The study supports the potential of using NIR-responsive scaffolds for intelligent immunomodulation. These findings may guide future developments in osteoimmunological therapies for bone repair.