Catalase-templated nanozyme-loaded microneedles integrated with polymyxin B for immunoregulation and antibacterial activity in diabetic wounds

Diabetic wounds are characterized by chronic trauma , with long-term non-healing attributed to persistent inflammation and recurrent bacterial infections. Exacerbation of the inflammatory response is largely due to increased levels of reactive oxygen species (ROS). In this study, catalase (CAT) was used as a biological template to synthesize nanozyme-supported natural enzymes (CAT-Mn(SH) x ) using a biomimetic mineralization method. Subsequently, polymyxin B (CAT-Mn(SH) x @PMB) was immobilized on its surface through electrostatic assembly. CAT-Mn(SH) x @PMB demonstrates the ability for slow and sustained release of hydrogen sulfide (H 2 S). Finally, CAT-Mn(SH) x @PMB loaded microneedles (MNs) substrate were synthesized using polyvinyl alcohol (PVA) and hydroxyethyl methacrylate (HEMA), and named CAT-(MnSH) x @PMB-MNs. It exhibited enhanced enzyme and antioxidant activities , along with effective antibacterial properties. Validation findings indicate that it can up-regulate the level of M2 macrophages and reduce the level of pro-inflammatory cytokine tumor necrosis factor-α (TNF-α). Additionally, it promotes angiogenesis and rapid nerve regeneration, thereby facilitating wound healing through its dual anti-inflammatory and antibacterial effects . Hence,   this study introduces a time–space tissue-penetrating and soluble microneedle patch with dual anti-inflammatory and antibacterial effects for the treatment of diabetic wounds.