Macrophage metabolic reprogramming-based diabetic infected bone defect/bone reconstruction though multi-function silk hydrogel with exosome release

Diabetic infected bone defects (DIBD) with abnormal immune metabolism are prone to the hard-to-treat bacterial infections and delayed bone regeneration, which present significant challenges in clinic. Control of immune metabolism is believed to be important in regulating fundamental immunological processes. Here, we developed a macrophage metabolic reprogramming hydrogel composed of modified silk fibroin (Silk-6) and poly-L-lysine (epsilon-PL) and further integrated with M2 Macrophage-derived Exo (M2-Exo), named Silk-6/epsilon-PL@Exo. This degradable hydrogel showed a broad-spectrum antibacterial performance against both Gram-positive and -negative bacteria. More importantly, the release of M2-Exo from Silk-6/epsilon-PL@Exo could target M1 macrophages, modulating the activity of the key enzyme hexokinase II (HK2) to control the inflammation-related NF kappa B pathway, alleviate lactate accumulation, and inhibit glycolysis to normalize the cycle, thereby promoting M1to-M2 balance. Using a rat model of DIBD, Silk-6/epsilon-PL@Exo hydrogel promoted infection control, balanced immune responses and accelerated the bone defect healing. Overall, this study demonstrates that this Silk-6/epsilon-PL @Exo is a promising filler biomaterial with multi-function to treat DIBD and emphasizes the importance of metabolic reprogramming in bone regeneration.