Fibrin-Based Nanoparticles as a Novel Sealant for Vascular Anastomosis

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PROJECT SUMMARY Vascular anastomosis is an important surgical technique whereby closely spaced stitches are used to connect blood vessels. This process is used frequently in organ transplantation, trauma repairs, and cardiovascular surgery. However, vascular anastomosis is time consuming and associated with serious complications and long recovery times. Use of fibrin glue in anastomosis has led to improved surgical outcomes and shorter operating times, but these glues are frequently impractical as their concentrated formulations create high-density gels with short working times, low cellular infiltration, and cold storage limitations. We have developed fibrin-based nanoparticles (FBNs) which we have used to deliver growth factors and promote healing in vivo. Unlike traditional fibrin glues, FBNs are pre-polymerized and use physiologically relevant fibrin/thrombin concentrations. Owing to their colloidal structure and the aforementioned properties, FBNs exhibit tunable gelation, increased cellular infiltration, room temperature storage, and enhanced drug delivery capabilities – including of fibroblast growth factor 2 (FGF2), a known stimulant of vascular repair. The objective of this proposal is the optimization, characterization and in vivo analysis of paintable and patch formulations of an FBN surgical sealant with tunable growth factor release. It is expected that these FBN sealants will demonstrate better functionality than current fibrin glues, with the benefit of longer work time, extended stability at room temperature, targeted growth factor delivery, and improved healing outcomes. Aim 1 will optimize the formulation of patch and flowable FBN glues. This will occur through characterization of the effects of changes in FBN concentration, thrombin concentration, and cofactor used, on the mechanics and functionality of the glues. Testing will probe polymerization and degradation dynamics, structure, mechanical properties, sealant ability, and safety profile. Modalities used will include rheometry, microscopy, mechanical testing, and novel ex vivo and microfluidic assays. Aim 2 will optimize the loading/release of FGF2 by FBNs and characterize the effects of FGF2-FBN sealants on vascular wound healing in vitro. FGF2 loading efficiency and release characteristics of FBN sealants will be determined and compared to high-density bulk fibrin glues. Endothelial and fibroblast scratch tests and wound closure assays will be used to assess healing outcomes in vitro. Aim 3 will compare FBN formulations (gel and patch; unloaded and loaded with FGF2) to current fibrin glues using an in vivo leporine model of carotid artery anastomosis. Angiography will be use to characterize vascular morphology and histology of sampled tissues will be used to evaluate signs of healing, restenosis, and hyperplasia. This proposal’s use of FBNs will lead to a novel surgical sealant with improved work time and tunable drug delivery profiles that boasts superior wound healing – allowing for faster operating times, fewer complications, and improved recovery. This technology will also increase the accessibility of surgical glues by removing cold-chain requirements, opening up their use in varied global health applications. Training in the associated research techniques and clinical skills required for this project will contribute to the success of the applicant during the next phases of her career on the path to becoming an independent physician scientist.