Injectable and Self-healing microgels repairing infected irregular tubular fistula in anal and muscle

Abstract

An anal fistula caused by a perianal abscess is a hollow tubular structure connecting anal canal with skin and often in irregular shapes. The surgical treatment causes damage to the surrounding tissues and results in complications. Current filling plugs in the clinic, derived from the porcine small intestinal submucosa, only seal the opening and cannot fill into the irregular fistula passage due to the poor liquidity, and fails to control the high-frequent infections around fistulas. Injecting gel-like material is a direct and effective way. To this end, we reported injectable microgels from elastic cryogels of biodegradable disulfide-based crosslinking. Microgels with shear-thinning and self-healing remain solid under low strain and fluid under high strain to ensure successful filling and repair the multiple-branched irregular canals. Nano-silver dopped microgels presented antibacterial efficacy. In rabbit models of anal and muscle fistula, the inflammatory cells significantly decreased. CD31 and α-smooth muscle actin (α-SMA) showed the fistula healing was improved considerably. These findings demonstrated that self-healable microgels have enormous potential to repair the abnormal and complicated tubular passages caused by ulcers and fistulas.