In situ-formed micro silk fibroin composite sutures for pain management and anti-infection

Surgical sutures close wounds and promote healing. Sutures need to meet appropriate mechanical properties and biocompatibility, so complex and high-cost braiding processes have been developed for better mechanical properties. However, they still cannot work ideally in some scenarios, such as pain and infection. Pain is the most common symptom in almost all injuries, infections, and diseases. Inadequate management of pain leads to untoward physical and psychological outcomes in patients. For these purposes, we designed a multifunctional composite suture of micro silk fibroin fiber (SF). It was extracted in situ ultra-long and ultra-fine SFs where a single thread can reach hundreds of meters from a cocoon. The suture can adsorb anti-infection vancomycin by turning pH and then coated with methacrylated gelatin as a sheath to load a pain-killer ibuprofen (SMG-VC-IB). SMG-VC-IB can withstand a tension force of nearly 18 N, two times the Mersilk® suture. SMG-VC-IB can maintain prolonged release for efficient pain management and anti-infection. We applied PET/CT to investigate objective metabolic data in brain regions and found that the pain-killer reached efficacy in our built pain model of quadriceps femoris incision in rats. We found SMG-VC-IB reduced metabolic levels in pain-related brain regions, including the classical pain matrix. It was also verified that the pain-killer ibuprofen from sutures helps to pass through the postoperative inflammatory period to a comfortable recovery period. Our research presented an eco-friendly manufacturing solution for designing multifunctional composite sutures for pain management and infection control.