Comparison of mechanical compressive properties of commercial and autologous fibrin glues for tissue engineering applications

High-Performance Dopamine-Based Supramolecular Bio-Adhesives

The need for wound closure or surgical procedures has been commonly met by the application of sutures. Unfortunately, these are often invasive or subject to contamination. Alternative solutions are offered by surgical adhesives that can be applied and set without major disruption; a new class of supramolecular-based adhesives provides potential solutions to some of these challenges. In this study, a series of polymers utilizing dopamine as a self-assembling unit are synthesized. It is found that these motifs act as extremely effective adhesives, with control over the mechanical strength of the adhesion and materials' tensile properties enabled by changing monomer feed ratios and levels of cross-linking. These materials significantly outperform commercially available bio-adhesives, showing yield strengths after adhesion at least two times higher than that of BioGlue and Tisseel, as well as the ability to re-adhere with significant recovery of adhesion strength. Promisingly, the materials are shown to be non-cytotoxic, with cell viability > 90%, and able to perform in aqueous environments without significant loss in strength. Finally, the removal of the materials, is possible using benign organic solvents such as ethanol. These properties all demonstrate the effectiveness of the materials as potential bio-adhesives, with potential advantages for use in surgery.

Lung-Mimetic Hydrofoam Sealant to Treat Pulmonary Air Leak

Pulmonary air leak is the most common complication of lung surgery, contributing to post-operative morbidity in up to 60% of patients; yet, there is no reliable treatment. Available surgical sealants do not match the demanding deformation mechanics of lung tissue; and therefore, fail to seal air leak. To address this therapeutic gap, a sealant with structural and mechanical similarity to subpleural lung is designed, developed, and systematically evaluated. This "lung-mimetic" sealant is a hydrofoam material that has alveolar-like porous ultrastructure, lung-like viscoelastic properties (adhesive, compressive, tensile), and lung extracellular matrix-derived signals (matrikines) to support tissue repair. In biocompatibility testing, the lung-mimetic sealant shows minimal cytotoxicity and immunogenicity in vitro. Human primary monocytes exposed to sealant matrikines in vitro upregulate key genes (MARCO, PDGFB, VEGF) known to correlate with pleural wound healing and tissue repair in vivo. In rat and swine models of pulmonary air leak, this lung-mimetic sealant rapidly seals air leak and restores baseline lung mechanics. Altogether, these data indicate that the lung-mimetic sealant can effectively seal pulmonary air leak and promote a favorable cellular response in vitro.

Biochemical and biomechanical characterization of an autologous protein-based fibrin sealant for regenerative medicine

Accidental events or surgical procedures usually lead to tissue injury. Fibrin sealants have proven to optimize the healing process but have some drawbacks due to their allogeneic nature. Autologous fibrin sealants present several advantages. The aim of this study is to evaluate the performance of a new autologous fibrin sealant based on Endoret®PRGF® technology (E-sealant). One of the most widely used commercial fibrin sealants (Tisseel®) was included as comparative Control. E-sealant´s hematological and biological properties were characterized. The coagulation kinetics and the microstructure were compared. Their rheological profile and biomechanical behavior were also recorded. Finally, the swelling/shrinkage capacity and the enzymatic degradation of adhesives were determined. E-sealant presented a moderate platelet concentration and physiological levels of fibrinogen and thrombin. It clotted 30 s after activation. The microstructure of E-sealant showed a homogeneous fibrillar scaffold with numerous and scattered platelet aggregates. In contrast, Control presented absence of blood cells and amorphous protein deposits. Although in different order of magnitude, both adhesives had similar rheological profiles and viscoelasticity. Control showed a higher hardness but both adhesives presented a pseudoplastic hydrogel nature with a shear thinning behavior. Regarding their adhesiveness, E-sealant presented a higher tensile strength before cohesive failure but their elastic stretching capacity and maximum elongation was similar. While E-sealant presented a significant shrinkage process, Control showed a slight swelling over time. In addition, E-sealant presented a high enzymatic resorption rate, while Control showed to withstand the biodegradation process in a significant way. E-sealant presents optimal biochemical and biomechanical properties suitable for its use as a fibrin sealant with regenerative purposes.

Biological and Adhesive Properties of an Autologous Protein-Based Fibrin Sealant for Ophthalmological Applications

Purpose

The aim of this study was to evaluate the biological and adhesive properties of a new autologous sealant based on plasma rich in growth factors (PRGF), named E-Sealant.

Methods

Conventional PRGF and a commercial fibrin sealant (Tisseel) were included as controls. The hematological and protein content of E-Sealant was determined. Its bioactivity and biocompatibility were tested for human keratocytes (HKs). To evaluate its adhesion and regenerative capacity, E-Sealant was used on an animal model of conjunctival autograft surgery and compared to Tisseel.

Results

E-Sealant presented a high growth factor content with levels similar to those of conventional PRGF. E-Sealant induced proliferative and migratory activity on HK cells equivalent to PRGF. Although autologous membranes induced the proliferation of HKs, cells cultured over Tisseel did not adhere nor proliferate. HK cells showed increased number and flattened morphology over PRGF and E-Sealant compared to scarce and round-shape cells detected in Tisseel. Conjunctival autograft glued with E-Sealant adhered successfully, whereas Tisseel application formed irregular clots. During follow-up, both adhesives showed good integration and no dehiscence. However, Tisseel-treated samples presented slightly increased hemorrhage and inflammation. In contrast to Tisseel, E-Sealant-treated autografts presented a continuous layer of non-keratinized stratified squamous epithelium. Inflammatory infiltrates were minimal in E-Sealant-treated conjunctiva, whereas the Tisseel group showed noticeable immune reactions. Unlike Tisseel-treated grafts, E-Sealant presented low immunoreactivity for smooth muscle actin (SMA), suggesting decreased fibrotic tissue formation.

Conclusions

E-Sealant presents optimal biological and adhesive properties suitable for use as an ophthalmic glue, with regenerative purposes superior to commercial fibrin sealants.

Translational Relevance

Our study analyzed the characterization and biological activity of a new autologous fibrin sealant in ocular surface cells and in an animal model in which the adhesive and regenerative properties of the fibrin sealant were evaluated.

Prevention of postoperative anemia in hip hemiarthroplasty for femoral neck fractures: comparison between local haemostatic agents

Background

Tranexamic acid and fibrin sealant have been shown to be effective in reducing the need for transfusion after hip fracture surgery.

Objective

The aim of this study was to evaluate the efficacy of local haemostatic agents to reduce the need of postoperative transfusion in elederly patients after hip hemiarthroplasty.

Methods

All patients admitted to our institution with a diagnosis of proximal femur fracture from September 2018 to March 2021 were involved. Inclusion criteria were: diagnosis of femoral neck fracture, classified as AO 31B2-3, surgical treatment with hip hemiarthroplasty, hemoglobinemia on admission > 8 gr/dL. Patients were divided in four groups.

Results

EVICEL was used on 25 patients, TRANEX was used on 52 patients, standard hemostatic care was used on 73 patients, while post-surgical drain was used on 21 patients. 3 patients were transfused in the EVICEL group while 26 patients were transfused in the control group (p 0,0404), there was also statistical significant difference in the need of perioperative transfusion between EVICEL group and drain group with 10 patients transfused (p 0,0102). Statistical significant differences was found about haemoglobin variation in the first post-operative day between TRANEX group and control group (p 0,000155) and between TRANEX group and drain group (p 0,013) and also between TRANEX group and control group in the third post-operative day (p 0,0004).

Conclusion

This study demonstrates that the use of both fibrin sealant or TXA can reduce total blood loss and the need of transfusions in geriatric population with intracapsular femur fracture.

Autologous Fibrin Sealants Have Comparable Graft Fixation to an Allogeneic Sealant in a Biomechanical Cadaveric Model of Chondral Defect Repair

Purpose

The purpose of this study is to assess the integrity of chondral defect repairs filled with a cartilage allograft and sealed with either allogeneic fibrin sealant or autologous fibrin sealants created with platelet-rich plasma (PRP) or platelet-poor plasma (PPP) in a cadaver model.

Methods

Twenty-millimeter medial femoral condyle (MFC) chondral defects were created in five human cadaveric knees. The defects were filled with particulated cartilage allograft hydrated with PRP from human donors until slightly recessed. Sealants were applied until flush with the articular surface using PRP and autologous thrombin serum, PPP and autologous thrombin serum, or commercial allogeneic sealant. The MFC defects were cycled using a multiaxial testing system to simulate continuous passive motion undergone during rehabilitation. After testing, the repairs were assessed for integrity by quantitatively comparing defect exposure and qualitatively assessing sealant delamination.

Results

The mean defect exposures were 4.20% ± 5.02% for the PRP group, 4.60% ± 5.18% for the PPP group, and 1.80% ± 2.95% for the allogeneic sealant group. No significant differences were observed between groups (P = .227), and each group had significantly less defect exposure when compared to the critical clinically relevant value assigned to be 30% (P = <.001 for all). No complete sealant delamination was observed, although the allogeneic sealant delaminated with a higher magnitude than did the autologous sealants.

Conclusions

The PRP and PPP sealants were comparable to the allogeneic sealant for graft fixation when used in conjunction with an underlying PRP-hydrated particulated cartilage allograft. The autologous sealants had better delamination resistance than the allogeneic sealant.

Clinical Relevance

The time-zero model is critical in elucidating the retention properties of fibrin and allogenic sealants after cartilage repair and before healing processes help stabilize the repair.

Effects of beta-tricalcium phosphate nanoparticles on the properties of a thermosensitive chitosan/collagen hydrogel and controlled release of quercetin

In the present study, an inorganic matrix of beta-tricalcium phosphate (bTCP) nanoparticles and quercetin was incorporated into an organic matrix of 2:1 (w/w) chitosan/collagen composite to fabricate thermosensitive bTCP-chitosan/collagen-quercetin hydrogels. A sol-gel transition of the hydrogels was stimulated by beta-glycerophosphate (bGP) and temperature changes at physiological temperature and pH levels. Thereafter, the effects of 1%-3% (w/v) bTCP on properties of the bTCP-bGP-2:1 (w/w) chitosan/collagen hydrogels were investigated. Notably, the incorporation of 1%-3% (w/v) bTCP in the hydrogels did not interfere with the gelation process and time of the hydrogels at physiological temperature and pH levels. The bTCP-hydrogels exhibited a porous structure, interconnecting pore architecture, and median pore size of 100-200 μm. The incorporation of 3% bTCP increased the mechanical strength but decreased the swelling and degradation rates, pore size, permeability, and quercetin release rate of the hydrogels. The hydrogels were noncytotoxic and able to support cell encapsulation. A sustained quercetin release profile of the 3% bTCP-hydrogel further suggested the applicability of the hydrogel as a delivery vehicle of natural flavonoids for bone regeneration.

The development of a novel autologous blood glue aiming to improve osseointegration in the bone-implant interface

Aims

For cementless implants, stability is initially attained by an interference fit into the bone and osteo-integration may be encouraged by coating the implant with bioactive substances. Blood based autologous glue provides an easy, cost-effective way of obtaining high concentrations of growth factors for tissue healing and regeneration with the intention of spraying it onto the implant surface during surgery. The aim of this study was to incorporate nucleated cells from autologous bone marrow (BM) aspirate into gels made from the patient’s own blood, and to investigate the effects of incorporating three different concentrations of platelet rich plasma (PRP) on the proliferation and viability of the cells in the gel.

Methods

The autologous blood glue (ABG) that constituted 1.25, 2.5, and 5 times concentration PRP were made with and without equal volumes of BM nucleated cells. Proliferation, morphology, and viability of the cells in the glue was measured at days 7 and 14 and compared to cells seeded in fibrin glue.

Results

Overall, 2.5 times concentration of PRP in ABG was capable of supporting the maximum growth of cells isolated from the BM aspirate and maintain their characteristics. Irrespective of PRP concentration, cells in ABG had statistically significantly higher viability compared to cells in fibrin glue.

Conclusion

In vitro this novel autologous gel is more capable of supporting the growth of cells in its structure for up to 14 days, compared to commercially available fibrin-based sealants, and this difference was statistically significant.

Cite this article: Bone Joint Res 2020;9(7):402–411.

Fibrin sealant reduces need for transfusions after hip hemiarthroplasty for femoral neck fractures

INTRODUCTION

Every year more than 300,000 proximal femur fractures are diagnosed. Their number will double within 30 years. In femoral neck fractures treated with hip hemiarthroplasty 90-days mortality is 29.5-51.6%. Haemorrhage is one amongst other complications that is associated with increasing postoperative mortality. Transfusion rate in these patients ranges from 25.7% to 39%. Blood transfusions expose to complications. Fibrin sealants are useful in reducing perioperative need for transfusions, total blood loss, blood loss from drainage. The aim of this study is to assess whether the use of a fibrin sealant during hip hemiarthroplasty implant reduces the need for transfusion.

PATIENT AND METHODS

All patients admitted with a proximal femur fracture from September 2018 to May 2019 were reviewed. Inclusion criteria were: femoral neck fracture AO 31B2-3, hip hemiarthroplasty. Exclusion criteria were: previous surgery on the affected hip, coagulation disorders, hematopoietic disorders. Patients were divided in fibrin sealant group and control group. All patients underwent partial hip replacement through a posterolateral approach. 4 ml of fibrin sealant (EVICEL, Omrix Biopharmaceuticals, Diegem, Belgium) were sprayed on the soft tissues of patients included in the fibrin sealant group. Primary outcome of our study was need for perioperative transfusion. Secondary outcomes were: mean red blood cell transfused volume, variations in haematocrit and haemoglobin and total blood volume loss.

RESULTS

Eighty-one consecutive patients were enrolled. EVICEL was used on 19 patients, standard haemostatic care on 62 patients. Two patients were transfused in the fibrin sealant group, 22 in the control group (p 0,0371). Mean transfused volume was 21,05 ml in the fibrin sealant group and 116,16 ml in the control group (p 0,0017). No significant difference could be found in haematocrit and haemoglobin variation and total blood loss.

DISCUSSION

A reduction in transfusional need with the use of fibrin sealants was reported in studies on total hip arthroplasty and was confirmed by our study.

CONCLUSION

EVICEL reduces need for transfusion in patients undergoing hip hemiarthroplasty for a femoral neck fracture. It must be held among the options when a stricter control on transfusional requirement is needed.

Surgical applications of intracorporal tissue adhesive agents: current evidence and future development

Introduction: Traditional mechanical closure techniques pose many challenges including the risk of infection, tissue reaction, and injury to both patients and clinicians. There is an urgent need to develop tissue adhesive agents to reform closure technique. This review examined a variety of tissue adhesive agents available in the market in an attempt to gain a better understanding of intracorporal tissue adhesive agents as medical devices.Areas covered: Fundamental principles and clinical determinants of the tissue adhesives were summarized. The available tissue adhesives for intracorporal use and their relevant clinical evidence were then presented. Lastly, the perspective of future development for intracorporal tissue adhesive were discussed. Clinical evidence shows current agents are efficacious as adjunctive measures to mechanical closure and these agents have been trialed outside of clinical indications with varied results.Expert opinion: Despite some advancements in the development of tissue adhesives, there is still a demand to develop novel technologies in order to address unmet clinical needs, including low tensile strength in wet conditions, non-controllable polimerization and sub-optimal biocompatibility. Research trends focus on producing novel adhesive agents to remit these challenges. Examples include the development of biomimetic adhesives, externally activated adhesives, and multiple crosslinking strategies. Economic feasibility and biosafety are limiting factors for clinical implementation.

The clot thickens: Autologous and allogeneic fibrin sealants are mechanically equivalent in an ex vivo model of cartilage repair

Fibrin sealants are commonly used in cartilage repair surgeries to adhere cells or grafts into a cartilage defect. Both autologous and commercial allogeneic fibrin sealants are used in cartilage repair surgeries, yet there are no studies characterizing and comparing the mechanical properties of fibrin sealants from all-autologous sources. The objectives of this study were to investigate (i) the effect of fibrinogen and thrombin sources on failure mechanics of sealants, and (ii) how sealants affect the adhesion of particulated cartilage graft material (BioCartilage) to surrounding cartilage under physiological loading. Allogeneic thrombin and fibrinogen were purchased (Tisseel), and autologous sources were prepared from platelet-rich plasma (PRP) and platelet-poor plasma (PPP) generated from human blood. To compare failure characteristics, sealants were sandwiched between cartilage explants and pulled to failure. The effect of sealant on the adhesion of BioCartilage graft to cartilage was determined by quantifying microscale strains at the graft-cartilage interface using an in vitro cartilage defect model subjected to shear loading at physiological strains well below failure thresholds. Fibrinogen sources were not equivalent; PRP fibrinogen created sealants that were more brittle, failed at lower strains, and resulted in sustained higher strains through the graft-cartilage interface depth compared to PPP and allogeneic sources. PPP clotted slower compared to PRP, suggesting PPP may percolate deeper into the repair to provide more stability through the tissue depth. There was no difference in bulk failure properties or microscale strains at the graft-cartilage interface between the purely autologous sealant (autologous thrombin + PPP fibrinogen) and the commercial allogeneic sealant. Clinical Significance: All-autologous fibrin sealants fabricated with PPP have comparable adhesion strength as commercial allogeneic sealants in vitro, whereas PRP creates an inferior all-autologous sealant that sustains higher strains through the graft-cartilage interface depth.

Visualisation of the insertion of a membrane for the treatment of preterm rupture of fetal membranes using a synthetic model of a pregnant uterus

Preterm premature rupture of fetal membranes is a leading cause of preterm delivery. Preterm labour can compromise fetal survival, and even if a pregnancy affected by preterm premature rupture of fetal membrane continues, major complications associated with leakage of amniotic fluid and risk of infection can affect the normal development and survival of the baby. There are limited management options for preterm premature rupture of fetal membrane other than delivery of the baby if ascending infection (chorioamnionitis) is suspected. We have previously reported the development and characterisation of an implantable membrane with the aim of using it to occlude the internal os of the cervix, in order to prevent amniotic fluid loss, allow fluid reaccumulation and reduce the risk of chorioamnionitis. For this, an electrospun biocompatible and distensible bilayer membrane was designed with mechanical properties similar to the human amniotic membrane. In this study, we consider the effects of sterilization on the membrane, how to insert the membrane and visualise it using routine clinical methods. To do this, we used e-beam sterilisation and examined the ability of the membrane to adhere to ex vivo human cervical tissues. We also studied its insertion into a custom-synthesised model of a 20-week pregnant uterus and imaged the membrane using ultrasound. Sterilisation produced minor effects on physical and mechanical properties, but these did not affect the capacity of the membrane to be sutured or to provide a fluid barrier. We demonstrated that fibrin glue can successfully adhere the bilayer membrane to cervical tissues. Finally, we demonstrated that the membrane can be inserted through the cervix as well as visualized in place using ultrasound imaging and an endoscope. In summary, we suggest this membrane is a candidate for further development in an appropriate animal model, supported by appropriate imaging, to precede possible future human studies if judged to demonstrate satisfactory safety and efficacy profiles.