Rapidly photocurable silk fibroin sealant for clinical applications

The demand for effective medical glues, encompassing hemostatic agents, sealants, and adhesives, has risen significantly with the increased prevalence of minimally invasive surgery. The ideal medical glue must be safe, user-friendly, cost-effective, and compliant with regulatory requirements. While various glues exist, each faces limitations. For instance, many hemostatic agents are suitable for surface wounds or large areas but are less adaptable to irregularly shaped wounds. Fibrin sealant, while versatile, poses risks of virus transmission and poor wet adhesion. Silk fibroin (SF), known for its biocompatibility, has been explored in various biomedical applications, including wound dressings, enzyme immobilization, and tissue engineering. Previous attempts to utilize SF as a medical glue often involved blending it with other materials or employing lengthy gelation methods. This study aims to address these shortcomings by developing a rapidly crosslinkable, colloidal medical glue based solely on SF methacryloyl, leveraging its fast crosslinking, ease of use, and biocompatibility to create a versatile hemostatic agent, sealant, and adhesive.

Existing literature extensively documents the biocompatibility of silk fibroin (SF) and its applications in diverse biomedical fields. Studies have explored SF's use in wound dressings, enzyme immobilization, tympanic membranes, ridge preservation grafts, and vascular prostheses, highlighting its suitability for biological applications. Several studies have also investigated SF-based medical glues, often incorporating SF with other polymers like polyvinyl alcohol or hyaluronic acid to enhance properties. However, these approaches often involve complex fabrication processes, long crosslinking times, or reliance on additional components. The use of SF methacryloyl to achieve rapid photocuring represents a significant advance in this field, allowing for better spatial and temporal control over material properties.

The study involved synthesizing methacrylated silk fibroin (Sil-MAS) using a previously established protocol. *Bombyx mori* cocoons were degummed, dissolved in lithium bromide, and methacrylated using glycidyl methacrylate. The resulting methacrylated SF solution was purified, freeze-dried, and then dissolved in water with a photoinitiator (LAP) to create liquid Sil-MAS (l-Sil-MAS). Crosslinking was achieved via UV irradiation (365 nm), yielding crosslinked Sil-MAS (c-Sil-MAS). Characterizations encompassed 1H NMR spectroscopy to confirm methacrylation, rheological analysis to assess viscoelastic properties, and mechanical testing (compression, tensile, and swelling) to evaluate the hydrogel's strength and stability. In vitro adhesion tests (lap shear, pull-off adhesion strength, and wound closure strength) used rat skin as a substrate. Ex vivo porcine aorta burst pressure tests evaluated the sealant's effectiveness in vascular applications. In vivo studies in rats assessed wound healing, hemostasis in skin, femoral artery, and liver models and biocompatibility through subcutaneous implantation. Finally, laparoscopic surgery on a rabbit liver/stomach laceration model demonstrated Sil-MAS's suitability for minimally invasive procedures. Western blotting and histology analyses were employed to examine protein expression and tissue responses.

In vitro mechanical tests showed that Sil-MAS possessed desirable rheological and mechanical properties. The lap shear, pull-off adhesion, and wound closure strength tests demonstrated significantly superior adhesive properties compared to a polyurethane control (MLB). Ex vivo porcine aorta burst pressure tests revealed Sil-MAS effectively sealed incisions and enhanced the burst pressure of sutured aortas. In vivo studies in rats revealed that Sil-MAS displayed remarkable hemostatic capabilities in skin, femoral artery, and liver injury models, significantly reducing bleeding time and promoting faster wound healing than Avitene or gauze. Subcutaneous implantation studies indicated good biocompatibility and slow in vivo degradation. The successful application of Sil-MAS in a rabbit laparoscopic model further validated its utility as a versatile surgical glue.

The results demonstrate that Sil-MAS offers a significant improvement over existing medical sealants and adhesives. Its rapid photocuring capability, high adhesion, and biocompatibility address key limitations of current technologies. The superior performance in both in vitro and in vivo models, coupled with successful laparoscopic application, highlights Sil-MAS's potential for diverse clinical uses, from wound closure to minimally invasive surgeries. The ease of application and rapid crosslinking make it a practical and effective alternative to traditional methods. The study's comprehensive evaluation, including both in vitro and in vivo studies, provides strong evidence supporting the clinical translation of Sil-MAS.

This study successfully developed and characterized a novel rapidly photocurable silk fibroin sealant (Sil-MAS) exhibiting excellent biocompatibility, high adhesion, and rapid crosslinking. Preclinical studies confirmed its effectiveness as a hemostatic agent, sealant, and adhesive in various tissues and its suitability for minimally invasive surgical procedures. Future research should focus on further optimizing Sil-MAS for specific clinical applications, conducting larger-scale preclinical studies, and initiating clinical trials to evaluate its safety and efficacy in humans.

The study primarily focused on rat and rabbit models. Further research is necessary to confirm the findings in larger animal models and ultimately in human clinical trials. While the biocompatibility was demonstrated, long-term effects of Sil-MAS implantation remain to be fully assessed. The laparoscopic application was performed with a homemade device, and the scalability and manufacturing of a clinical-grade device need to be considered.