Preparation, Characterization, and In Vitro Osteogenic Properties of a Novel Glucose-Sensitive 3D-Printed Scaffold Containing Metformin Based on Enzymatic Cascade Reaction

Restoring alveolar bone defects in patients with diabetes poses a significant challenge in the treatment of oral disease. This study involved the fabrication of porous composite hydrogel scaffolds composed of photo-crosslinked chitosan/nanohydroxyapatite via extruded 3D printing. Additionally, glucose oxidase (GOx) and catalase (CAT) were immobilized onto the composite scaffold through EDC/NHS covalent cross-linking to develop a novel 3D-printed glucose-sensitive scaffold utilizing an enzyme cascade reaction. The 3D-printed porous composite scaffolds had high drug encapsulation efficiency (91.94% ± 1.69%). After co-immobilization of GOx and CAT on the scaffolds, the activity of GOx was increased due to the ability of CAT to scavenge H₂O₂, which is a by-product of the glucose-catalyzed reaction. The results showed that dual enzyme scaffolds with co-immobilized GOx/CAT produced better swelling behavior than the single immobilized GOx enzyme scaffolds. Meanwhile, with the increase of glucose concentration, the release of Met also increased, indicating that the dual enzyme scaffolds possess favorable glucose sensitivity. Additionally, the dual enzyme-immobilized 3D-printed scaffolds facilitated cell adhesion and proliferation and exhibited good biocompatibility. Finally, in vitro cellular experiments revealed that the scaffolds effectively promoted MC3T3-E1 osteogenic differentiation in a high-glucose environment. This study demonstrates that novel glucose-sensitive 3D-printed composite hydrogel scaffolds based on enzymatic cascade reaction may provide a feasible new strategy to enhance diabetic alveolar bone repair.