Development and Evaluation of Thrombin-Loaded Gelatin Hemostatic Sheets for Spinal Surgery Applications

During spinal surgery, management of intraoperative bleeding and effective hemostasis are required to clearly visualize the surgical field and to safely perform procedures and positive postoperative outcomes. However, it is challenging to stop bleeding from the venous plexus around the dural sac due to the potential risk of neural tissue damage. We aimed to develop hemostatic sheets with appropriate characteristics for spinal surgery, such as softness, appropriate thickness, biodegradability, thrombin bioactivity, and minimal water-induced expansion.

Hemostatic sheets were made by dissolving bovine bone-derived gelatin in water and aerating it to form foam, followed by freeze-drying, crosslinking, and thrombin-soaking. Sheets A to H were produced with different gelatin concentrations, foam densities, and crosslinking times by additional heat treatment. The sheets were then soaked in thrombin solution for enhanced hemostasis. Material properties, such as density, tensile strength, biodegradability, and hemostatic capacity, were evaluated. Sheet efficacy was further assessed with liver bleeding and spinal venous plexus bleeding models in a miniature pig.

High-density gelatin sheets showed stable shape retention in wet conditions and robust tensile strength. Sheets with higher density and more crosslinking had prolonged persistence in the pepsin test and lower biodegradability in vivo. Sheet B, produced from a 4% gelatin solution with heating at 155°C for 4 h, showed the best balance of properties, such as no deformation cracks, rapid water absorption, minimal expansion, and faster degradation within 10 weeks, compared with TachoSil and other sheets. In hemostasis models, Sheet B outperformed Avitene and TachoSil, achieving higher success rates in spinal (four out of six sites) and liver bleeding (five out of five sites) models.

A thrombin-loaded hemostatic sheet produced from 4% gelatin solution with a short heating time for crosslinking demonstrated well-balanced material properties, such as shape retention, biodegradability, and wet expansion rate, which resulted in effective hemostasis in in vivo models. These advances may contribute to surgical hemostatic applications.