A multi-in-one strategy with glucose-triggered long-term antithrombogenicity and sequentially enhanced endothelialization for biological valve leaflets

Tailored extracellular matrix-mimetic coating facilitates reendothelialization and tissue healing of cardiac occluders

Minimally invasive transcatheter interventional therapy utilizing cardiac occluders represents the primary approach for addressing congenital heart defects and left atrial appendage (LAA) thrombosis. However, incomplete endothelialization and delayed tissue healing after occluder implantation collectively compromise clinical efficacy. In this study, we have customized a recombinant humanized collagen type I (rhCol I) and developed an rhCol I-based extracellular matrix (ECM)-mimetic coating. The innovative coating integrates metal-phenolic networks with anticoagulation and anti-inflammatory functions as a weak cross-linker, combining them with specifically engineered rhCol I that exhibits high cell adhesion activity and elicits a low inflammatory response. The amalgamation, driven by multiple forces, effectively serves to functionalize implantable materials, thereby responding positively to the microenvironment following occluder implantation. Experimental findings substantiate the coating's ability to sustain a prolonged anticoagulant effect, enhance the functionality of endothelial cells and cardiomyocyte, and modulate inflammatory responses by polarizing inflammatory cells into an anti-inflammatory phenotype. Notably, occluder implantation in a canine model confirms that the coating expedites reendothelialization process and promotes tissue healing. Collectively, this tailored ECM-mimetic coating presents a promising surface modification strategy for improving the clinical efficacy of cardiac occluders.

Folic acid modified silver nanoparticles promote endothelialization and inhibit calcification of decellularized heart valves by immunomodulation with anti-bacteria property

Xenogeneic decellularized heart valves (DHVs) have become one of the most commonly used scaffolds for tissue engineered heart valves (TEHVs) due to extensive resources and possessing the distinct three-layer structure similar to native heart valves. However, DHVs as scaffolds face the shortages such as poor mechanical properties, proneness to thrombosis and calcification, difficulty in endothelialization and chronic inflammatory responses etc., which limit their applications in clinic. In this work, we constructed a novel TEHV with immunomodulatory functions by loading folic acid modified silver nanoparticles (FS NPs) on DHVs to overcome these issues. The FS NPs preferentially targeted M1 macrophages and reduced their intracellular H2O2 level, resulting in polarizing them into M2 phenotype. The increased M2 macrophages facilitated to eliminate inflammation, recruit endothelial cells, and promote their proliferation and endothelialization by secreting relative factors. We founded that FS NPs with the size of 80 nm modified DHVs (FSD-80) performed optimally on cytocompatibility and regulating macrophage phenotype ability in vitro. In addition, the FSD-80 had excellent mechanical properties, hemocompatibility and anti-bacteria property. The results of the subcutaneous implantation in rats revealed that the FSD-80 also had good performance in regulating macrophage phenotype, promoting endothelialization, remolding the extracellular matrix and anti-calcification in vivo. Therefore, FS NPs-loaded DHVs possess immunomodulatory functions, which is a feasible and promising strategy for constructing TEHVs with excellent comprehensive performance.

Preparation of Time-Sequential Functionalized ZnS-ZnO Film for Modulation of Interfacial Behavior of Metals in Biological Service Environments

Blood-contact devices are prone to inflammation, endothelial dysfunction, coagulation, and the uncontrolled release of metal ions during implantation and service. Therefore, it is essential to make these multifunctional. Herein, a superhydrophobic DE@ZnS-ZnO@SA film (composed of dabigatran ester, zinc sulfite, zinc oxide, and stearic acid, respectively) is produced. The prepared film has non-adhesion and antibacterial properties, superior mechanical stability, durability, corrosion resistance, and is self-cleaning and blood-repellent. The results of the hemolysis, cytotoxicity, and other anticoagulant experiments revealed that the film had good blood compatibility, no cytotoxicity, and excellent anticoagulant properties. The film displays anticoagulant properties even after being immersed in Phosphate-Buffered Saline (PBS) for 7 days. Furthermore, the film can spontaneously release H2S gas for 90 h after soaking in an acidic environment (pH = 6) for 90 h. This property improves the acidic microenvironment of the lesion and promotes the proliferation of endothelial cells by using H2S gas. In addition, the film can inhibit the uncontrollable release of Zn2+ ions, avoiding its toxicity even when immersed in an acid environment for 35 days. This time-sequential functionalized surface has the potential to typify the future of blood-contacting scaffolds for long-lasting use.

Biomaterials as a new option for treating sensorineural hearing loss

Sensorineural hearing loss (SNHL) usually involves damage to complex auditory pathways such as inner ear cells and auditory nerves. The highly intricate and nuanced characteristics of these cells render their repair and regeneration extremely challenging, making it difficult to restore hearing to normal levels once it has been compromised. The effectiveness of traditional drugs is so minimal that they provide little help with the treatment. Fortunately, extensive experiments have demonstrated that combining biomaterials with conventional techniques significantly enhances drug effectiveness. This article reviews the research progress of biomaterials in protecting hair cells and the auditory nerve, repairing genes related to hearing, and developing artificial cochlear materials. By organizing the knowledge presented in this article, perhaps new insights can be provided for the clinical management of SNHL.

Nanogels: Recent Advances in Synthesis and Biomedical Applications

In the context of advanced nanomaterials research, nanogels (NGs) have recently gained broad attention for their versatility and promising biomedical applications. To date, a significant number of NGs have been developed to meet the growing demands in various fields of biomedical research. Summarizing preparation methods, physicochemical and biological properties, and recent applications of NGs may be useful to help explore new directions for their development. This article presents a comprehensive overview of the latest NG synthesis methodologies, highlighting advances in formulation with different types of hydrophilic or amphiphilic polymers. It also underlines recent biomedical applications of NGs in drug delivery and imaging, with a short section dedicated to biosafety considerations of these innovative nanomaterials. In conclusion, this article summarizes recent innovations in NG synthesis and their numerous applications, highlighting their considerable potential in the biomedical field.

Design and performance of double-layered artificial chordae

Surgical repair with artificial chordae replacement has emerged as a standard treatment for mitral regurgitation. Expanded polytetrafluoroethylene (ePTFE) sutures are commonly employed as artificial chordae; however, they have certain limitations, such as potential long-term rupture and undesired material/tissue response. This study introduces a novel approach to artificial chordae design, termed the New Artificial Chordae (NAC), which incorporates a double-layered structure. The NAC comprises a multi-strand braided core composed of ultra-high molecular weight polyethylene (UHMWPE) fibers as the inner core, and an outer tube made of hydrophobic porous ePTFE. Compared to traditional ePTFE sutures, NAC exhibits increased flexibility, enhanced tensile strength, longer elongation and improved fatigue resistance. Moreover, NAC exhibits a more hydrophobic surface, which contributes to enhanced hemocompatibility. The study also includes in vivo investigations conducted on animal models to evaluate the biocompatibility and functional efficacy of the artificial chordae. These experiments demonstrate the enhanced durability and biocompatibility of the NAC, characterized by improved mechanical strength, minimal tissue response and reduced thrombus formation. These findings suggest the potential application of NAC as a prosthetic chordae replacement, offering promising prospects to address the limitations associated with current artificial chordae materials and providing novel ideas and approaches for the development of sustainable and biocompatible regenerative biomaterials.

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 strategy for mechanically integrating robust hydrogel-tissue hybrid to promote the anti-calcification and endothelialization of bioprosthetic heart valve

Bioprosthetic heart valve (BHV) replacement has been the predominant treatment for severe heart valve diseases over decades. Most clinically available BHVs are crosslinked by glutaraldehyde (GLUT), while the high toxicity of residual GLUT could initiate calcification, severe thrombosis, and delayed endothelialization. Here, we construed a mechanically integrating robust hydrogel-tissue hybrid to improve the performance of BHVs. In particular, recombinant humanized collagen type III (rhCOLIII), which was precisely customized with anti-coagulant and pro-endothelialization bioactivity, was first incorporated into the polyvinyl alcohol (PVA)-based hydrogel via hydrogen bond interactions. Then, tannic acid was introduced to enhance the mechanical performance of PVA-based hydrogel and interfacial bonding between the hydrogel layer and bio-derived tissue due to the strong affinity for a wide range of substrates. In vitro and in vivo experimental results confirmed that the GLUT-crosslinked BHVs modified by the robust PVA-based hydrogel embedded rhCOLIII and TA possessed long-term anti-coagulant, accelerated endothelialization, mild inflammatory response and anti-calcification properties. Therefore, our mechanically integrating robust hydrogel-tissue hybrid strategy showed the potential to enhance the service function and prolong the service life of the BHVs after implantation.

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.

Functionalization of in vivo tissue-engineered living biotubes enhance patency and endothelization without the requirement of systemic anticoagulant administration

Vascular regeneration and patency maintenance, without anticoagulant administration, represent key developmental trends to enhance small-diameter vascular grafts (SDVG) performance. In vivo engineered autologous biotubes have emerged as SDVG candidates with pro-regenerative properties. However, mechanical failure coupled with thrombus formation hinder translational prospects of biotubes as SDVGs. Previously fabricated poly(ε-caprolactone) skeleton-reinforced biotubes (PBs) circumvented mechanical issues and achieved vascular regeneration, but orally administered anticoagulants were required. Here, highly efficient and biocompatible functional modifications were introduced to living cells on PB lumens. The 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine-N-methoxy (DMPE)-PEG-conjugated anti-coagulant bivalirudin (DPB) and DMPE-PEG-conjugated endothelial progenitor cell (EPC)-binding TPS-peptide (DPT) modifications possessed functionality conducive to promoting vascular graft patency. Co-modification of DPB and DPT swiftly attained luminal saturation without influencing cell viability. DPB repellent of non-specific proteins, DPB inhibition of thrombus formation, and DPB protection against functional masking of DPT's EPC-capture by blood components, which promoted patency and rapid endothelialization in rat and canine artery implantation models without anticoagulant administration. This strategy offers a safe, facile, and fast technical approach to convey additional functionalization to living cells within tissue-engineered constructs.

A chlorogenic acid functional strategy of anti-inflammation, anti-coagulation and promoted endothelial proliferation for bioprosthetic artificial heart valves

Heart valve replacement has become an optimal choice for the treatment of severe heart valve disease. At present, most commercial bioprosthetic heart valves (BHVs) are made from porcine pericardium or bovine pericardium treated with glutaraldehyde. Nevertheless, due to the toxicity of residual aldehyde groups left after glutaraldehyde cross-linking, these commercial BHVs exhibit poor biocompatibility, calcification, risk of coagulation and endothelialization difficulty, which greatly affects the durability of the BHVs and shortens their service life. In this work, based on a chlorogenic acid functional anti-inflammation, anti-coagulation and endothelialization strategy and dual-functional non-glutaraldehyde cross-linking reagent OX-CO, a kind of functional BHV material OX-CA-PP has been developed from OX-CO cross-linked porcine pericardium (OX-CO-PP) followed by the convenient modification of chlorogenic acid through a reactive oxygen species (ROS) sensitive borate ester bond. The functionalization of chlorogenic acid can reduce the risk of valve leaf thrombosis and promote endothelial cell proliferation, which is beneficial to the formation of a long-term interface with good blood compatibility. Meanwhile, such a ROS responsive behavior can trigger intelligent release of chlorogenic acid on-demand to achieve the inhibition of acute inflammation at the early stage of implantation. The in vivo and in vitro experimental results show that the functional BHV material OX-CA-PP exhibits superior anti-inflammation, improved anti-coagulation, minimal calcification and promoted proliferation of endothelial cells, showing that this non-glutaraldehyde functional strategy has great potential for the application of BHVs and providing a promising reference for other implanted biomaterials.

A versatile drug-controlled release polymer brush hybrid non-glutaraldehyde bioprosthetic heart valves with enhanced anti-inflammatory, anticoagulant and anti-calcification properties, and superior mechanical performance

Transcatheter heart valve replacement (THVR) is a novel treatment modality for severe heart valves diseases and has become the main method for the treatment of heart valve diseases in recent years. However, the lifespan of the commercial glutaraldehyde cross-linked bioprosthetic heart valves (BHVs) used in THVR can only serve for 10-15 years, and the essential reason for the failure of the valve leaflet material is due to these problems such as calcification, coagulation, and inflammation caused by glutaraldehyde cross-linking. Herein, a kind of novel non-glutaraldehyde cross-linking agent bromo-bicyclic-oxazolidine (OX-Br) has been designed and synthesized with both crosslinking ability and in-situ atom transfer radical polymerization (ATRP) function. Then OX-Br treated porcine pericardium (OX-Br-PP) are stepwise modified with co-polymer brushes of reactive oxygen species (ROS) response anti-inflammatory drug conjugated block and anti-adhesion polyzwitterion polymer block through the in-situ ATRP reaction to obtain the functional BHV material MPQ@OX-PP. Along with the great mechanical properties and anti-enzymatic degradation ability similar to glutaraldehyde-crosslinked porcine pericardium (Glut-PP), good biocompatibility, improved anti-inflammatory effect, robust anti-coagulant ability and superior anti-calcification property have been verified for MPQ@OX-PP by a series of in vitro and in vivo investigations, indicating the excellent application potential as a multifunctional heart valve cross-linking agent for OX-Br. Meanwhile, the strategy of synergistic effect with in situ generations of reactive oxygen species-responsive anti-inflammatory drug blocks and anti-adhesion polymer brushes can effectively meet the requirement of multifaceted performance of bioprosthetic heart valves and provide a valuable reference for other blood contacting materials and functional implantable materials with great comprehensive performance.

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.

Polyphenol based hybrid nano-aggregates modified collagen fibers of biological valve leaflets to achieve enhanced mechanical, anticoagulation and anti-calcification properties

Glutaraldehyde (Glut)-crosslinked porcine pericardium and bovine pericardium are mainly consisted of collagen and widely used for the preparation of heterogenous bioprosthetic heart valves (BHV), which play an important role in the replacement therapy of severe valvular heart disease, while their durability is limited by degeneration due to calcification, thrombus, endothelialization difficulty and prosthetic valve endocarditis. Herein, we develop a novel BHV, namely, TPly-BP, based on natural tannic acid and polylysine to improve the durability of Glut crosslinked bovine pericardium (Glut-BP). Impressively, tannic acid and polylysine could form nanoaggregates via multiple hydrogen bonds and covalent bonds, and the introduction of nanoaggregates not only improved the mechanical properties and collagen stability but also endowed TPly-BP with good biocompatibility and hemocompatibility. Compared to Glut-BP, TPly-BP showed significantly reduced cytotoxicity, improved endothelial cell adhesion, a low hemolysis ratio and obviously reduced platelet adhesion. Importantly, TPly-BP exhibited great antibacterial and in vivo anti-calcification ability, which was expected to improve the in vivo durability of BHVs. These results suggested that TPly-BP would be a potential candidate for BHV.

Graphical abstract

Assessment of the Anti-Thrombogenic Activity of Polyurethane Starch Composites

The increasing morbidity and mortality of patients due to post-surgery complications of coronary artery bypass grafts (CABPG) are related to blood–material interactions. Thus, the characterization of the thrombogenicity of the biomaterial for cardiovascular devices is of particular interest. This research evaluated the anti-thrombogenic activity of polyurethanes–starch composites. We previously synthesized polyurethane matrices that were obtained from polycaprolactone diol (PCL), polyethylene glycol (PEG), pentaerythritol (PE), and isophorone diisocyanate (IPDI). In addition, potato starch (AL-N) and zwitterionic starch (AL-Z) were added as fillers. The anti-thrombogenic property was characterized by the clot formation time, platelet adhesion, protein absorption, TAT complex levels, and hemolysis. Additionally, we evaluated the cell viability of the endothelial and smooth muscle cells. Statically significant differences among the polyurethane matrices (P1, P2, and P3) were found for protein absorption and the blood clotting time without fillers. The polyurethanes composites with AL-Z presented an improvement in the anti-thrombogenic property. On the other hand, the composites with AL-Z reduced the viability of the endothelial cells and did not significantly affect the AoSCM (except for P1, which increased). These results classify these biomaterials as inert; therefore, they can be used for cardiovascular applications.

A Polyphenol-Network-Mediated Coating Modulates Inflammation and Vascular Healing on Vascular Stents

Localized drug delivery from drug-eluting stents (DESs) to target sites provides therapeutic efficacy with minimal systemic toxicity. However, DESs failure may cause thrombosis, delay arterial healing, and impede re-endothelialization. Bivalirudin (BVLD) and nitric oxide (NO) promote arterial healing. Nevertheless, it is difficult to combine hydrophilic signal molecules with hydrophobic antiproliferative drugs while maintaining their bioactivity. Here, we fabricated a micro- to nanoscale network assembly consisting of copper ion and epigallocatechin gallate (EGCG) via π-π interactions, metal coordination, and oxidative polymerization. The network incorporated rapamycin and immobilized BVLD by the thiol-ene "click" reaction and provided sustained rapamycin and NO release. Unlike rapamycin-eluting stents, those coated with the EGCG-Cu-rapamycin-BVLD complex favored competitive endothelial cell (EC) growth over that of smooth muscle cells, exhibited long-term antithrombotic efficacy, and attenuated the negative impact of rapamycin on the EC. In vivo stent implantation demonstrated that the coating promoted endothelial regeneration and hindered restenosis. Therefore, the polyphenol-network-mediated surface chemistry can be an effective strategy for the engineering of multifunctional surfaces.

A nitric oxide-eluting and REDV peptide-conjugated coating promotes vascular healing

Drug-eluting stents (DESs) placement remarkably reduces the over-proliferation of smooth muscle cells (SMCs) and thus neointimal hyperplasia. However, the pharmacological agent also slows down the re-endothelization, delays injury vascular healing and increases the risk of in-stent restenosis (ISR). Here, inspired by mussel foot proteins (Mfps), a mimicking endothelium functional stent coating was efficiently fabricated by thiol-ene "click" reaction, consisting of catechol grafted chitosan (CS-C), zinc sulfate, and Arg-Glu-Asp-Val (REDV) peptide. The mimicking endothelium coating could continuously catalyze endogenous nitric oxide (NO) gas and maintain the bioactivity of REDV peptide. Compared with bare stents, the mimicking coatings significantly inhibited the acute thrombosis for the first 1-week, accelerated re-endothelization and decreased in-stent restenosis for 1- and 3-month after implantation. In addition, the synergistic effect of NO and REDV peptide also regulated inflammation response and promoted the expression of muscle fiber.

A Well-Designed Two-Fold Crosslinked Biological Valve Leaflets with Heparin-Loaded Hydrogel Coating for Enhancing Anticoagulation, Endothelialization, and Anticalcification

Commercial biological valve leaflets (BVLs) crosslinked with Glutaraldehyde (GA) are at risk of accelerating damage and even failure, owing to high cell toxicity of GA, acute thrombosis, and calcification in...

A tailored extracellular matrix (ECM) - Mimetic coating for cardiovascular stents by stepwise assembly of hyaluronic acid and recombinant human type III collagen

Collagen, a central component of the extracellular matrix (ECM), has been widely applied in tissue engineering, among others, for wound healing or bone and nerve regeneration. However, the inherent thrombogenic properties of collagen hinder the application in blood-contacting devices. Herein, a brand-new recombinant human type III collagen (hCOLIII) was explored that does not present binding sites for platelets while retaining the affinity for endothelial cells. The hCOLIII together with hyaluronic acid (HA) were deposited on the substrates via layer-by-layer assembly to form an ECM-mimetic multilayer coating. In vitro platelet adhesion and ex vivo blood circulation tests demonstrated prominent thromboprotective properties for the hCOLIII-based ECM-mimetic coating. In addition, the coating effectively guided the vascular cell fate by supporting the proliferation of endothelial cells and inhibiting the proliferation of smooth muscle cells by differentiating them to a more contractile phenotype. A polylactic acid (PLA) stent coated with hCOLIII-based ECM-mimetic coating was implanted in the abdominal aorta of rabbits to investigate the healing of the neointima. The enhanced endothelialization, suppressed inflammatory response, inhibition of excessive neointimal hyperplasia, and the superior thromboprotection strongly indicated the prospect of the hCOLIII-based ECM-mimetic coating as a tailored blood-contacting material for cardiovascular stents.