Hydrogel hybrid porcine pericardium for the fabrication of a pre-mounted TAVI valve with improved biocompatibility

Degeneration mechanisms and advancements in optimization for preparation and crosslinking strategy of pericardium-based bioprosthetic heart valves

Valvular heart disease (VHD), clinically manifested as the malfunction of heart valves, greatly threatens public health worldwide. The morbidity and mortality of VHD increase significantly with age, and the high prevalence of VHD in aging society has prompted the urgency for effective treatment. Prosthetic heart valve replacement is currently recognized as the gold standard for VHD treatment. Bioprosthetic heart valves (BHVs), generally manufactured from glutaraldehyde crosslinked xenogeneic tissue, exhibited better hemodynamics and lower thrombogenicity than mechanical heart valves (MHVs) and could be implanted by transcatheter valve replacement systems, which markedly improved the efficiency of VHD therapy, especially for the elderly patients. However, BHVs degenerate within 10-15 years after implantation, which is greatly associated with their defects including cytotoxicity, calcification, immune response, matrix degradation, mechanical damage, and thrombosis. To prolong the service life of BHVs, recent studies have developed a series of innovative modification strategies to improve the biocompatibility, mechanical performance, matrix components stability, anticalcification, and antithrombotic properties of conventional glutaraldehyde crosslinked BHVs. Moreover, a series of new crosslinking and modification strategies have been proposed and developed to fabricate non-glutaraldehyde crosslinked BHVs with good stability, biocompatibility, hemocompatibility, anticalcification property, durability, and hydrodynamics. In this review, we first summarized the defects of BHVs and the related reasons from the perspective of biomaterials, and then comprehensively detailed the functional modification strategies for BHVs based on glutaraldehyde crosslinking. We provided detailed insights into novel non-glutaraldehyde crosslinking and modification strategies for BHVs. Finally, the current challenges and prospects of BHVs were also discussed. STATEMENT OF SIGNIFICANCE: Bioprosthetic heart valves (BHVs) currently face challenges such as cytotoxicity, thrombosis, calcification, and immunoinflammatory responses, which contribute to structural valve degeneration and reduce the longevity of BHVs. This review provides a comprehensive introduction to the detailed defects associated with glutaraldehyde crosslinked BHVs from the perspective of biomaterials. It then thoroughly elaborates on the modification strategies based on glutaraldehyde crosslinking, as well as detailed insights into novel non-glutaraldehyde crosslinking strategies for BHVs. Finally, the challenges and prospects facing BHVs are discussed.

Catechol crosslinked bioprosthetic valves derived from caffeic acid and dopamine-conjugated porcine pericardia exhibit enhanced antithrombotic, immunomodulatory and anticalcification performance

The global aging population has led to an increasing prevalence of valvular heart disease (VHD), and the clinical application of bioprosthetic heart valves (BHVs) are growing with the advancement of transcatheter heart valve replacement surgery. However, BHVs, as xenogeneic pericardial tissue crosslinked with glutaraldehyde, have been affected by suboptimal cytocompatibility, thrombosis, immune response, and calcification, leading to premature degeneration and failure. Herein, a catechol-crosslinking strategy for BHVs was developed by conjugating porcine pericardia (PP) with catechols and subsequently coupling the grafted catechols to achieve the crosslinking and stabilization of BHVs. Caffeic acid and dopamine were exploited to conjugate the bioactive catechols on PP through amide condensation, and the catechols were further coupled under oxidation to impart the PP with enhanced stability and cytocompatibility as well as comparable mechanical properties to those of glutaraldehyde crosslinked PP (GLUT-PP). With the enrichment of catechols, the crosslinked PP not only demonstrated improved hydrophilicity to resist the blood components adhesion and thrombosis, but also enhanced the performance of endothelialization and antioxidation. Furthermore, the introduced catechols exhibits favorable anti-inflammatory properties, which significantly ameliorated the foreign body response and regulated the local immune responses of crosslinked PP. In conclusion, the catechol crosslinked PP is expected to be explored as a potential substitute for GLUT-PP to extend the lifespan of BHVs. STATEMENT OF SIGNIFICANCE: Bioprosthetic heart valves (BHVs) are mainly prepared from glutaraldehyde crosslinked porcine or bovine pericardia (GLUT-PP). Currently, BHVs are affected by cytotoxicity, thrombosis, calcification, and immunoinflammatory responses, which would accelerate degeneration and failure of BHVs. In this study, we developed a catechol crosslinking strategy for BHVs and engineered caffeic acid and dopamine-conjugated porcine pericardia (PP). In summary, catechol crosslinked porcine pericardia demonstrated enhanced collagen stability, antithrombosis, endothelialization, anticalcification and immunomodulation which reduced the risk of structural degeneration, suggesting that the catechol crosslinked porcine pericardia could serve as a potential alternative to GLUT-PP.

Recent Advances in the Modification and Improvement of Bioprosthetic Heart Valves

Valvular heart disease (VHD) has become a burden and a growing public health problem in humans, causing significant morbidity and mortality worldwide. An increasing number of patients with severe VHD need to undergo heart valve replacement surgery, and artificial heart valves are in high demand. However, allogeneic valves from donors are lacking and cannot meet clinical practice needs. A mechanical heart valve can activate the coagulation pathway after contact with blood after implantation in the cardiovascular system, leading to thrombosis. Therefore, bioprosthetic heart valves (BHVs) are still a promising way to solve this problem. However, there are still challenges in the use of BHVs. For example, their longevity is still unsatisfactory due to the defects, such as thrombosis, structural valve degeneration, calcification, insufficient re-endothelialization, and the inflammatory response. Therefore, strategies and methods are needed to effectively improve the biocompatibility and longevity of BHVs. This review describes the recent research advances in BHVs and strategies to improve their biocompatibility and longevity.

A multifunctional bio-patch crosslinked with glutaraldehyde for enhanced mechanical performance, anti-coagulation properties, and anti-calcification properties

Bio-patches for the treatment of valvular disease have been evaluated in clinical trials. It has been shown that failure of these devices, occurring within a few years of implantation, may be due to cytotoxicity, immune response, calcification and thrombosis. Some of these effects may be due to the glutaraldehyde crosslinking process used in the preparation of the materials. A number of studies have focused on strategies to control calcification, while others have concentrated on the prevention of micro-thrombus formation. In the present work, we have introduced amino-terminated poly(ethylene glycol) (NH2-PEG-NH2) as an intermolecular bridge, which not only eliminates free aldehyde groups to prevent calcification, but also introduces sites for the attachment of anticoagulant molecules. Furthermore, PEG, itself a hydrophilic polymer with good biocompatibility, may effectively prevent protein adsorption in the early stages of blood contact leading to thrombus formation. After further covalent attachment of heparin, modified bovine pericardium (BP) showed strong anti-calcification (calcium content: 39.3 ± 3.1 μg mg-1) and anti-coagulation properties (partial thromboplastin time: >300 s). The biocompatibility and mechanical properties, important for clinical use, were also improved by modification. The strategy used in this work includes new ideas and technologies for the improvement of valve products used in the clinic.

Recent progress in functional modification and crosslinking of bioprosthetic heart valves

Valvular heart disease (VHD), clinically manifested as stenosis and regurgitation of native heart valve, is one of the most prevalent cardiovascular diseases with high mortality. Heart valve replacement surgery has been recognized as golden standard for the treatment of VHD. Owing to the clinical application of transcatheter heart valve replacement technic and the excellent hemodynamic performance of bioprosthetic heart valves (BHVs), implantation of BHVs has been increasing over recent years and gradually became the preferred choice for the treatment of VHD. However, BHVs might fail within 10-15 years due to structural valvular degeneration (SVD), which was greatly associated with drawbacks of glutaraldehyde crosslinked BHVs, including cytotoxicity, calcification, component degradation, mechanical failure, thrombosis and immune response. To prolong the service life of BHVs, much effort has been devoted to overcoming the drawbacks of BHVs and reducing the risk of SVD. In this review, we summarized and analyzed the research and progress on: (i) modification strategies based on glutaraldehyde crosslinked BHVs and (ii) nonglutaraldehyde crosslinking strategies for BHVs.

Development of Innovative Biomaterials and Devices for the Treatment of Cardiovascular Diseases

Cardiovascular diseases have become the leading cause of death worldwide. The increasing burden of cardiovascular diseases has become a major public health problem and how to carry out efficient and reliable treatment of cardiovascular diseases has become an urgent global problem to be solved. Recently, implantable biomaterials and devices, especially minimally invasive interventional ones, such as vascular stents, artificial heart valves, bioprosthetic cardiac occluders, artificial graft cardiac patches, atrial shunts, and injectable hydrogels against heart failure, have become the most effective means in the treatment of cardiovascular diseases. Herein, an overview of the challenges and research frontier of innovative biomaterials and devices for the treatment of cardiovascular diseases is provided, and their future development directions are discussed.

Hybrid heart valves with VEGF-loaded zwitterionic hydrogel coating for improved anti-calcification and re-endothelialization

With the aging of the population in worldwide, valvular heart disease has become one of the most prominent life-threatening diseases in human health, and heart valve replacement surgery is one of the therapeutic methods for valvular heart disease. Currently, commercial bioprosthetic heart valves (BHVs) for clinical application are prepared with xenograft heart valves or pericardium crosslinked by glutaraldehyde. Due to the residual cell toxicity from glutaraldehyde, heterologous antigens, and immune response, there are still some drawbacks related to the limited lifespan of bioprosthetic heart valves, such as thrombosis, calcification, degeneration, and defectiveness of re-endothelialization. Therefore, the problems of calcification, defectiveness of re-endothelialization, and poor biocompatibility from the use of bioprosthetic heart valve need to be solved. In this study, hydrogel hybrid heart valves with improved anti-calcification and re-endothelialization were prepared by taking decellularized porcine heart valves as scaffolds following grafting with double bonds. Then, the anti-biofouling zwitterionic monomers 2-methacryloyloxyethyl phosphorylcholine (MPC) and vascular endothelial growth factor (VEGF) were utilized to obtain a hydrogel-coated hybrid heart valve (PEGDA-MPC-DHVs@VEGF). The results showed that fewer platelets and thrombi were observed on the surface of the PEGDA-MPC-DHVs@VEGF. Additionally, the PEGDA-MPC-DHVs@VEGF exhibited excellent collagen stability, biocompatibility and re-endothelialization potential. Moreover, less calcification deposition and a lower immune response were observed in the PEGDA-MPC-DHVs@VEGF compared to the glutaraldehyde-crosslinked DHVs (Glu-DHVs) after subcutaneous implantation in rats for 30 days. These studies demonstrated that the strategy of zwitterionic hydrogels loaded with VEGF may be an effective approach to improving the biocompatibility, anti-calcification and re-endothelialization of bioprosthetic heart valves.

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A new and promising strategy of overcoming defects of bioprosthetic heart valves.

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The zwitterionic hydrogel with VEGF is utilized to improve anti-calcification and re-endothelialization properties of heart valves.

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The hybrid heart valves with a VEGF-loaded zwitterionic hydrogel coating exhibits excellent biocompatibility.

Double-Network Hydrogel Armored Decellularized Porcine Pericardium as Durable Bioprosthetic Heart Valves

Heart valves have extraordinary fatigue resistance which beat ≈3 billion times in a lifetime. Bioprosthetic heart valves (BHVs) made from fixed heteroplasm that are incrementally used in heart valve replacement fail to sustain the expected durability due to thrombosis, poor endothelialization, inflammation, calcification, and especially mechanical damage induced biocompatibility change. No effective strategy has been reported to conserve the biological properties of BHV after long-term fatigue test. Here, a double-network tough hydrogel is introduced, which interpenetrate and anchor into the matrix of decellularized porcine pericardium (dCell-PP) to form robust and stable conformal coatings and reduce immunogenicity. The ionic crosslinked hyaluronic acid (HA) network mimics the glycocalyx on endothelium which improves antithrombosis and accelerates endothelialization; the chemical crosslinked hydrophilic polyacrylamide (PAAm) network further enhances antifouling properties and strengthens the shielding hydrogels and their interaction with dCell-PP. In vitro and rabbit ex vivo shunt assay demonstrate great hemocompatibility of polyacrylamide/HA hydrogel hybrid PP (P/H-PP). Cell experiments and rat subcutaneous implantation confirm satisfactory endothelialization, biocompatibility, and anticalcification properties. For hydrodynamic experiment, P/H-PP gains full mark at different flow conditions and sustains excellent biomechanical and biological properties after 200 000 000 cycles. P/H double-network hydrogel armoring dCell-PP is a promising progress to extend BHV durability for clinical implantation therapy.

Recent progress and perspectives in applications of 2-methacryloyloxyethyl phosphorylcholine polymers in biodevices at small scales

Bioinspired materials have attracted attention in a wide range of fields. Among these materials, a polymer family containing 2-methacryloyloxyethyl phosphorylcholine (MPC), which has a zwitterionic phosphorylcholine headgroup inspired by the...

Glycidyl methacrylate-crosslinked fish swim bladder as a novel cardiovascular biomaterial with improved antithrombotic and anticalcification properties

At present, commercial artificial biological valves are mostly prepared by crosslinking bovine or porcine pericardia with glutaraldehyde. Swim bladder has similar components and lower immunogenicity compared to bovine or porcine pericardium. In this study, we used a glycidyl methacrylate (GMA)-based radical polymerization method to crosslink decellularized swim bladders. Amino and carboxyl groups in the swim bladder were reacted with epoxy groups on GMA to introduce carbon-carbon double bonds to the swim bladder. The results showed that the platelet adhesion of GMA-crosslinked swim bladders (GMA-SBs) decreased by 35%, as compared to that of glutaraldehyde-crosslinked swim bladders (GLUT-SBs). Moreover, the superior anticoagulant property was further verified by the ex vivo arteriovenous shunt assay. Meanwhile, the subcutaneous implantation in rats showed that GMA-SBs were able to effectively inhibit the calcification compared with GLUT-SBs. In conclusion, GMA-SBs showed improved antithrombotic and anticalcification properties compared to GLUT-SBs.

Zwitterionic hydrogel-coated heart valves with improved endothelialization and anti-calcification properties

Valve replacement surgery is the golden standard for end-stage valvular disease due to the lack of self-repair ability. Currently, bioprosthetic heart valves (BHVs) crosslinked by glutaraldehyde (GA) have been the most popular choice in clinic, especially after the emerge of transcatheter aortic valve replacement (TAVR). Nevertheless, the lifespan of BHVs is limited due to severe calcification and deterioration. In this study, to improve the anti-calcification property of BHVs, decellularized heart valves were modified by methacrylic anhydride to introduce double bonds (MADHVs), and a hybrid hydrogel made of sulfobetaine methacrylate (SBMA) and methacrylated hyaluronic acid (MAHA) was then coated onto the surface of MADHVs. Followed by grafting of Arg-Glu-Asp-Val (REDV), an endothelial cell-affinity peptide, the BHVs with improved affinity to endothelial cell (SMHVs-REDV) was obtained. SMHVs-REDV exhibited excellent collagen stability, reliable mechanical property and superior hemocompatibility. Moreover, enhanced biocompatibility and endothelialization potential compared with GA-crosslinked BHVs were achieved. After subcutaneous implantation for 30 days, SMHVs-REDV showed significantly reduced immune response and calcification compared with GA-crosslinked BHVs. Overall, simultaneous endothelialization and anti-calcification can be realized by this strategy, which was supposed to be benefit for improving the main drawbacks for available commercial BHVs products.

A conformally adapted all-in-one hydrogel coating: towards robust hemocompatibility and bactericidal activity

A conformally adapted all-in-one hydrogel coatings that exhibit both hemocompatibility and bactericidal activity possess the potential for applications in blood-contacting devices.

Heart Valves Cross-Linked with Erythrocyte Membrane Drug-Loaded Nanoparticles as a Biomimetic Strategy for Anti-coagulation, Anti-inflammation, Anti-calcification, and Endothelialization

In recent years, valvular heart disease has become a serious disease threatening human life and is a major cause of death worldwide. However, the glutaraldehyde (GLU)-treated biological heart valves (BHVs) fail to meet all requirements of clinical application due to disadvantages such as valve thrombus, cytotoxicity, endothelialization difficulty, immune response, and calcification. Encouragingly, there are a large number of carboxyls as well as a few amino groups on the surface of GLU-treated BHVs that can be modified to enhance biocompatibility. Inspired by natural biological systems, we report a novel approach in which the heart valve was cross-linked with erythrocyte membrane biomimetic drug-loaded nanoparticles. Such modified heart valves not only preserved the structural integrity, stability, and mechanical properties of the GLU-treated BHVs but also greatly improved anti-coagulation, anti-inflammation, anti-calcification, and endothelialization. The in vitro results demonstrated that the modified heart valves had long-term anti-coagulation properties and enhanced endothelialization processes. The modified heart valves also showed good biocompatibility, including blood and cell biocompatibility. Most importantly, the modified heart valves reduced the TNF-α levels and increased IL-10 compared to GLU-treated BHVs. In vivo animal experiments also confirmed that the modified heart valves had an ultrastrong resistance to calcification after implantation in rats for 120 days. The mechanism of anti-calcification in vivo was mainly due to the controlled release of anti-inflammatory drugs that reduced the inflammatory response after valve implantation. In summary, this therapeutic approach based on BHVs cross-linking with erythrocyte membrane biomimetic nanoparticles sparks a novel design for valvular heart disease therapy.