Electronic vascular conduit for in situ identification of hemadostenosis and thrombosis in small animals and nonhuman primates

Patients suffering from coronary artery disease (CAD) or peripheral arterial disease (PAD) can benefit from bypass graft surgery. For this surgery, arterial vascular grafts have become promising alternatives when autologous grafts are inaccessible but suffer from numerous postimplantation challenges, particularly delayed endothelialization, intimal hyperplasia, high risk of thrombogenicity and restenosis, and difficulty in timely detection of these subtle pathological changes. We present an electronic vascular conduit that integrates flexible electronics into bionic vascular grafts for in situ, real-time and long-term monitoring for hemadostenosis and thrombosis concurrent with postoperative vascular repair. Following bypass surgery, the integrated bioelectronic sensor based on the triboelectric effect enables monitoring of the blood flow in the vascular graft and identification of lesions in real time for up to three months. In male nonhuman primate cynomolgus monkeys, the electronic vascular conduit, with an integrated wireless signal transmission module, enables wireless and real-time hemodynamic monitoring and timely identification of thrombi. This electronic vascular conduit demonstrates potential as a treatment-monitoring platform, providing a sensitive and intuitive monitoring technique during the critical period after bypass surgery in patients with CAD and PAD.

Functional Efficacy of Tissue-Engineered Small-Diameter Nanofibrous Polyurethane Vascular Grafts Surface-Modified by Methacrylated Sulfated Alginate in the Rat Abdominal Aorta

Improved design to imitate natural vascular scaffolds is critical in vascular tissue engineering (VTE). Smooth muscle cells originating from surrounding tissues require larger pore sizes relative to those of endothelial progenitor cells found in the bloodstream. Furthermore, biofunctionalized scaffolds mimic the microenvironment, cellular function, and tissue morphogenesis. Here, we fabricated macroporous and nanofibrous polyurethane (PU) bilayer tissue-engineered vascular grafts (TEVGs) by a salt-leaching method to achieve high porosities up to 30 μm. These grafts have a low porosity on the luminal side and a high porosity on the abluminal side. To enhance their properties, we surface-modified the PU scaffolds using heparin-mimicking methacrylated sulfated alginate (PU-MSA). We then evaluated these tubular scaffolds for their anticoagulation effect, protein adsorption, and cell attachment in vitro. The results revealed that TEVGs modified with sulfated alginate (PU-MSA) exhibited better anticoagulation (25 ± 1 min) and higher VEGF protein adsorption (75 ± 5 ng/mL) compared to other scaffolds. Moving to in vivo testing, we examined the TEVGs in a rat model for either 1 or 5 months. Through ultrasonication and various histological analyses, we assessed the functionality and biocompatibility of the TEVGs. Notably, the PU-MSA scaffold created a microenvironment conducive to cell homing and regeneration in the field of VTE.

Platelet Membrane-Encapsulated Poly(lactic-co-glycolic acid) Nanoparticles Loaded with Sildenafil for Targeted Therapy of Vein Graft Intimal Hyperplasia

Autologous vein grafts have attracted widespread attention for their high transplantation success rate and low risk of immune rejection. However, this technique is limited by the postoperative neointimal hyperplasia, recurrent stenosis and vein graft occlusion. Hence, we propose the platelet membrane-coated Poly(lactic-co-glycolic acid) (PLGA) containing sildenafil (PPS). Platelet membrane (PM) is characterised by actively targeting damaged blood vessels. The PPS can effectively target the vein grafts and then slowly release sildenafil to treat intimal hyperplasia in the vein grafts, thereby preventing the progression of vein graft restenosis. PPS effectively inhibits the proliferation and migration of vascular smooth muscle cell (VSMCs) and promotes the migration and vascularisation of human umbilical vein endothelial cells (HUVECs). In a New Zealand rabbit model of intimal hyperplasia in vein grafts, the PPS significantly suppressed vascular stenosis and intimal hyperplasia at 14 and 28 days after surgery. Thus, PPS represents a nanomedicine with therapeutic potential for treating intimal hyperplasia of vein grafts.

Tetramethylpyrazine-derived polyurethane for improved hemocompatibility and rapid endothelialization

Thrombosis and intimal hyperplasia (IH) are the main factors affecting the long-term patency of small-diameter vascular grafts (SDVGs). Fabricating a confluent endothelial cell (EC) layer on surfaces with physiological elasticity to mimic vascular endothelium should be an effective strategy to prevent restenosis that is caused by thrombosis and IH. However, the vascular endothelialization process is time-consuming and always constrained by hemocompatibility of the vascular grafts, since excellent hemocompatibility could guarantee a sufficient time window for the endothelialization process. Tetramethylpyrazine (TMP)-derived polyurethane (PU) with improved hemocompatibility and accelerated endothelialization ability is synthesized by incorporating TMP moieties into PU backbones. Results show that TMP-contained PU films possess improved hemocompatibility by down-regulating platelet adhesion/activation and increasing the clotting time. Furthermore, the in vitro human umbilical vein endothelial cell (HUVEC) test demonstrates that the introduction of TMP can significantly promote HUVEC adhesion and proliferation, and thus accelerate luminal endothelialization of vascular grafts. Moreover, the TMP-containing PU films exhibit excellent biocompatibility especially for HUVECs, and their excellent, adjustable elasticity (1123%) guarantees compliance accommodation of vascular grafts. This newly synthesized TMP-containing material with multiple biological functions is expected to make up for the shortcomings of available SDVGs in clinical practice, and has significant potential in improving the long-term patency of SDVGs.

3D-Printed Stents Loaded with Panax notoginseng Saponin for Promoting Re-endothelialization and Reducing Local Inflammation in the Carotid Artery of Rabbits

Endovascular treatment (EVT) using stents has become the primary option for severe cerebrovascular stenosis. However, considerable challenges remain to be addressed, such as in-stent restenosis (ISR) and late thrombosis. Many modified stents have been developed to inhibit the hyperproliferation of vascular smooth muscle cells (SMCs) and protect vascular endothelial cells (VECs), thereby reducing such complications. Some modified stents, such as those infused with rapamycin, have improved in preventing acute thrombosis. However, ISR and late thrombosis, which are long-term complications, remain unavoidable. Panax notoginseng saponin (PNS), a traditional Chinese medicine consisting of various compounds, is beneficial in promoting the proliferation and migration of VECs and inhibiting the proliferation of SMCs. Herein, a 3D-printed polycaprolactone (PCL) stent loaded with PNS (PNS-PCL stent) was developed based on a previous study. In vitro studies confirmed that PNS promotes the migration and proliferation of VECs, which were damaged, by increasing the expression levels of microRNA-126, p-AKT, and endothelial nitric oxide synthase. In vivo, the PNS-PCL stents maintained the patency of the carotid artery in rabbits for up to three months, outperforming the PCL stents. The PNS-PCL stents may present a new solution for the EVT of cerebrovascular atherosclerotic stenosis in the future.

Recent research of peptide-based hydrogel in nervous regeneration

Neurological disorders exert significantly affect the quality of life for patients, necessitating effective strategies for nerve regeneration. Both traditional autologous nerve transplantation and emerging therapeutic approaches encounter scientific challenges due to the complex nature of the nervous system and the unsuitability of the surrounding environment for cell transplantation. Tissue engineering techniques offer a promising path for neurotherapy. Successful neural tissue engineering relies on modulating cell differentiation behavior and tissue repair by developing biomaterials that mimic the natural extracellular matrix (ECM) and establish a three-dimensional microenvironment. Peptide-based hydrogels have emerged as a potent option among these biomaterials due to their ability to replicate the structure and complexity of the ECM. This review aims to explore the diverse range of peptide-based hydrogels used in nerve regeneration with a specific focus on dipeptide hydrogels, tripeptide hydrogels, oligopeptide hydrogels, multidomain peptides (MDPs), and amphiphilic peptide hydrogels (PAs). Peptide-based hydrogels offer numerous advantages, including biocompatibility, structural diversity, adjustable mechanical properties, and degradation without adverse effects. Notably, hydrogels formed from self-assembled polypeptide nanofibers, derived from amino acids, show promising potential in engineering neural tissues, outperforming conventional materials like alginate, poly(ε-caprolactone), and polyaniline. Additionally, the simple design and cost-effectiveness of dipeptide-based hydrogels have enabled the creation of various functional supramolecular structures, with significant implications for nervous system regeneration. These hydrogels are expected to play a crucial role in future neural tissue engineering research. This review aims to highlight the benefits and potential applications of peptide-based hydrogels, contributing to the advancement of neural tissue engineering.

Peptide functionalized biomimetic gene complexes enhance specificity for vascular endothelial regeneration

Gene delivery presents great potential in endothelium regeneration and prevention of vascular diseases, but its outcome is inevitably limited by high shear stress and instable microenvironment. Highly efficient nanosystems may alleviate the problem with strong dual-specificity for diseased site and targeted cells. Hence, biomimetic coatings incorporating EC-targeting peptides were constructed by platelets and endothelial cells (ECs) for surface modification. A series of biomimetic gene complexes were fabricated by the biomimetic coatings to deliver pcDNA3.1-VEGF165 plasmid (pVEGF) for rapid recovery of endothelium. The gene complexes possessed good biocompatibility with macrophages, stability with serum and showed no evident cytotoxicity for ECs even at very high concentrations. Furthermore, the peptide modified gene complexes achieved selective internalization in ECs and significant accumulation in endothelium-injured site, especially the REDV-modified and EC-derived gene complexes. They substantially enhanced VEGF expression at mRNA and protein levels, thereby enabling a wound to heal completely within 24 h according to wound healing assay. In an artery endothelium-injured mouse model, the REDV-modified and EC-derived gene complexes presented efficient re-endothelialization with the help of enhanced specificity. The biomimetic gene complexes offer an efficient dual-targeting strategy for rapid recovery of endothelium, and hold potential in vascular tissue regeneration.

Exploring the Potential of Saphenous Vein Grafts Ex Vivo: A Model for Intimal Hyperplasia and Re-Endothelialization

Coronary artery bypass grafting (CABG) utilizing saphenous vein grafts (SVGs) stands as a fundamental approach to surgically treating coronary artery disease. However, the long-term success of CABG is often compromised by the development of intimal hyperplasia (IH) and subsequent graft failure. Understanding the mechanisms underlying this pathophysiology is crucial for improving graft patency and patient outcomes. Objectives: This study aims to explore the potential of an ex vivo model utilizing SVG to investigate IH and re-endothelialization. Methods: A thorough histological examination of 15 surplus SVG procured from CABG procedures at Hospital Canselor Tuanku Muhriz, Malaysia, was conducted to establish their baseline characteristics. Results: SVGs exhibited a mean diameter of 2.65 ± 0.93 mm with pre-existing IH averaging 0.42 ± 0.13 mm in thickness, alongside an observable lack of luminal endothelial cell lining. Analysis of extracellular matrix components, including collagen, elastin, and glycosaminoglycans, at baseline and after 7 days of ex vivo culture revealed no significant changes in collagen but demonstrated increased percentages of elastin and glycosaminoglycans. Despite unsuccessful attempts at re-endothelialization with blood outgrowth endothelial cells, the established ex vivo SVG IH model underscores the multifaceted nature of graft functionality and patency, characterized by IH presence, endothelial impairment, and extracellular matrix alterations post-CABG. Conclusions: The optimized ex vivo IH model provides a valuable platform for delving into the underlying mechanisms of IH formation and re-endothelialization of SVG. Further refinements are warranted, yet this model holds promise for future research aimed at enhancing graft durability and outcomes for CAD patients undergoing CABG.

Redefining vascular repair: revealing cellular responses on PEUU-gelatin electrospun vascular grafts for endothelialization and immune responses on in vitro models

Tissue-engineered vascular grafts (TEVGs) poised for regenerative applications are central to effective vascular repair, with their efficacy being significantly influenced by scaffold architecture and the strategic distribution of bioactive molecules either embedded within the scaffold or elicited from responsive tissues. Despite substantial advancements over recent decades, a thorough understanding of the critical cellular dynamics for clinical success remains to be fully elucidated. Graft failure, often ascribed to thrombogenesis, intimal hyperplasia, or calcification, is predominantly linked to improperly modulated inflammatory reactions. The orchestrated behavior of repopulating cells is crucial for both initial endothelialization and the subsequent differentiation of vascular wall stem cells into functional phenotypes. This necessitates the TEVG to provide an optimal milieu wherein immune cells can promote early angiogenesis and cell recruitment, all while averting persistent inflammation. In this study, we present an innovative TEVG designed to enhance cellular responses by integrating a physicochemical gradient through a multilayered structure utilizing synthetic (poly (ester urethane urea), PEUU) and natural polymers (Gelatin B), thereby modulating inflammatory reactions. The luminal surface is functionalized with a four-arm polyethylene glycol (P4A) to mitigate thrombogenesis, while the incorporation of adhesive peptides (RGD/SV) fosters the adhesion and maturation of functional endothelial cells. The resultant multilayered TEVG, with a diameter of 3.0 cm and a length of 11 cm, exhibits differential porosity along its layers and mechanical properties commensurate with those of native porcine carotid arteries. Analyses indicate high biocompatibility and low thrombogenicity while enabling luminal endothelialization and functional phenotypic behavior, thus limiting inflammation in in-vitro models. The vascular wall demonstrated low immunogenicity with an initial acute inflammatory phase, transitioning towards a pro-regenerative M2 macrophage-predominant phase. These findings underscore the potential of the designed TEVG in inducing favorable immunomodulatory and pro-regenerative environments, thus holding promise for future clinical applications in vascular tissue engineering.

LY86 facilitates ox-LDL-induced lipid accumulation in macrophages by upregulating SREBP2/HMGCR expression

LY86, also known as MD1, has been implicated in various pathophysiological processes including inflammation, obesity, insulin resistance, and immunoregulation. However, the role of LY86 in cholesterol metabolism remains incompletely understood. Several studies have reported significant up-regulation of LY86 mRNA in atherosclerosis; nevertheless, the regulatory mechanism by which LY86 is involved in this disease remains unclear. In this study, we aimed to investigate whether LY86 affects ox-LDL-induced lipid accumulation in macrophages. Firstly, we confirmed that LY86 is indeed involved in the process of atherosclerosis and found high expression levels of LY86 in human atherosclerotic plaque tissue. Furthermore, our findings suggest that LY86 may mediate intracellular lipid accumulation induced by ox-LDL through the SREBP2/HMGCR pathway. This mechanism could be associated with increased cholesterol synthesis resulting from enhanced endoplasmic reticulum stress response.

Fabrication of Vascular Grafts Using Poly(ε-Caprolactone) and Collagen-Encapsuled ADSCs for Interposition Implantation of Abdominal Aorta in Rhesus Monkeys

The production of small-diameter artificial vascular grafts continues to encounter numerous challenges, with concerns regarding the degradation rate and endothelialization being particularly critical. In this study, porous PCL scaffolds were prepared, and PCL vascular grafts were fabricated by 3D bioprinting of collagen materials containing adipose-derived mesenchymal stem cells (ADSCs) on the internal wall of the porous PCL scaffold. The PCL vascular grafts were then implanted in the abdominal aorta of Rhesus monkeys for up to 640 days to analyze the degradation of the scaffolds and regeneration of the aorta. Changes in surface morphology, mechanical properties, crystallization property, and molecular weight of porous PCL revealed a similar degradation process of PCL in PBS at pH 7.4 containing Thermomyces lanuginosus lipase and in situ in the abdominal aorta of rhesus monkeys. The contrast of in vitro and in vivo degradation provided valuable reference data for predicting in vivo degradation based on in vitro enzymatic degradation of PCL for further optimization of PCL vascular graft fabrication. Histological analysis through hematoxylin and eosin (HE) staining and fluorescence immunostaining demonstrated that the PCL vascular grafts successfully induced vascular regeneration in the abdominal aorta over the 640-day period. These findings provided valuable insights into the regeneration processes of the implanted vascular grafts. Overall, this study highlights the significant potential of PCL vascular grafts for the regeneration of small-diameter blood vessels.

Construction of tissue-engineered vascular grafts with enhanced patency by integrating heparin, cell-adhesive peptide, and carbon monoxide nanogenerators into acellular blood vessels

Small-diameter tissue-engineered vascular grafts (sdTEVGs) have garnered significant attention as a potential treatment modality for vascular bypass grafting and replacement therapy. However, the intimal hyperplasia and thrombosis are two major complications that impair graft patency during transplantation. To address this issue, we fabricated the covalent-organic framework (COF)-based carbon monoxide (CO) nanogenerator-and co-immobilized with LXW-7 peptide and heparin to establish a multifunctional surface on TEVGs constructed from acellular blood vessels for preventing thrombosis and stenosis. The cell-adhesive peptide LXW-7 could capture endothelial-forming cells (EFCs) to promote endothelialization, while the antithrombotic molecule heparin prevented thrombus formation. The reactive oxygen species (ROS)-triggered CO release suppressed the adhesion and activation of macrophages, leading to the reduction of ROS and inflammatory factors. As a result, the endothelial-to-mesenchymal transition (EndMT) triggered by inflammation was restricted, facilitating the maintenance of the homeostasis of the neo-endothelium and preventing pathological remodeling in TEVGs. When transplanted in vivo, these vascular grafts exhibited negligible intimal hyperplasia and remained patent for 3 months. This achievement provided a novel approach for constructing antithrombotic and anti-hyperplastic TEVGs.

Study on the Effect of Type III Recombinant Humanized Collagen on Human Vascular Endothelial Cells

The effect and mechanism of type III recombinant humanized collagen (hCOLIII) on human vascular endothelial EA.hy926 cells at the cellular and molecular levels were investigated. The impact of hCOLIII on the proliferation of EA.hy926 cells was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromid assay, the effect of hCOLIII on cell migration was investigated by scratch assay, the impact of hCOLIII on cell cycle and apoptosis was detected by flow cytometry, the ability of hCOLIII to induce angiogenesis of EA.hy926 cells was evaluated by angiogenesis assay, and the effect of hCOLIII on vascular endothelial growth factor (VEGF) expression was detected by real-time reverse transcription-polymerase chain reaction analysis. The hCOLIII at concentrations of 0.5, 0.25, and 0.125 mg/mL all showed specific effects on the proliferation and migration of human vascular endothelial cells. It could also affect the cell cycle, increase the proliferation index, and increase the expression level of VEGF in human vascular endothelial cells. In the meantime, hCOLIII at the concentration of 0.5 mg/mL also showed a promoting effect on vessel formation. hCOLIII can potentially promote the endothelization process of blood vessels, mainly by affecting the proliferation, migration, and vascular-like structure of human endothelial cells. At the same time, hCOLIII can promote the expression of VEGF. This collagen demonstrated its potential as a raw material for cardiovascular implants.

Enhanced hemocompatibility and rapid magnetic anastomosis of electrospun small-diameter artificial vascular grafts

Background: Small-diameter (<6 mm) artificial vascular grafts (AVGs) are urgently required in vessel reconstructive surgery but constrained by suboptimal hemocompatibility and the complexity of anastomotic procedures. This study introduces coaxial electrospinning and magnetic anastomosis techniques to improve graft performance. Methods: Bilayer poly(lactide-co-caprolactone) (PLCL) grafts were fabricated by coaxial electrospinning to encapsulate heparin in the inner layer for anticoagulation. Magnetic rings were embedded at both ends of the nanofiber conduit to construct a magnetic anastomosis small-diameter AVG. Material properties were characterized by micromorphology, fourier transform infrared (FTIR) spectra, mechanical tests, in vitro heparin release and hemocompatibility. In vivo performance was evaluated in a rabbit model of inferior vena cava replacement. Results: Coaxial electrospinning produced PLCL/heparin grafts with sustained heparin release, lower platelet adhesion, prolonged clotting times, higher Young's modulus and tensile strength versus PLCL grafts. Magnetic anastomosis was significantly faster than suturing (3.65 ± 0.83 vs. 20.32 ± 3.45 min, p < 0.001) and with higher success rate (100% vs. 80%). Furthermore, magnetic AVG had higher short-term patency (2 days: 100% vs. 60%; 7 days: 40% vs. 0%) but similar long-term occlusion as sutured grafts. Conclusion: Coaxial electrospinning improved hemocompatibility and magnetic anastomosis enhanced implantability of small-diameter AVG. Short-term patency was excellent, but further optimization of anticoagulation is needed for long-term patency. This combinatorial approach holds promise for vascular graft engineering.

SEMA4D/VEGF surface enhances endothelialization by diminished-glycolysis-mediated M2-like macrophage polarization

Cardiovascular disease remains the leading cause of death and morbidity worldwide. Inflammatory responses after percutaneous coronary intervention led to neoathrosclerosis and in-stent restenosis and thus increase the risk of adverse clinical outcomes. In this work, a metabolism reshaped surface is engineered, which combines the decreased glycolysis promoting, M2-like macrophage polarization, and rapid endothelialization property. Anionic heparin plays as a linker and mediates cationic SEMA4D and VEGF to graft electronically onto PLL surfaces. The system composed by anticoagulant heparin, immunoregulatory SEMA4D and angiogenic VEGF endows the scaffold with significant inhibition of platelets, fibrinogen and anti-thrombogenic properties, also noteworthy immunometabolism reprogram, anti-inflammation M2-like polarization and finally leading to rapid endothelializaiton performances. Our research indicates that the immunometabolism method can accurately reflect the immune state of modified surfaces. It is envisioned immunometabolism study will open an avenue to the surface engineering of vascular implants for better clinical outcomes.

The Effect of Plasma Treatment on the Mechanical and Biological Properties of Polyurethane Artificial Blood Vessel

In recent years, the incidence of cardiovascular disease has increased annually, and the demand for artificial blood vessels has been increasing. Due to the formation of thrombosis and stenosis after implantation, the application of many materials in the human body has been inhibited. Therefore, the choice of surface modification process is very important. In this paper, small-diameter polyurethane artificial blood vessels were prepared through electrospinning, and their surfaces were treated with plasma to improve their biological properties. The samples before and after plasma treatment were characterized by SEM, contact angle, XPS, and tensile testing; meanwhile, the cell compatibility and blood compatibility were evaluated. The results show that there are no significant changes to the fiber morphology or diameter distribution on the surface of the sample before and after plasma treatment. Plasma treatment can increase the proportion of oxygen-containing functional groups on the surface of the sample and improve its wettability, thereby increasing the infiltration ability of cells and promoting cell proliferation. Plasma treatment can reduce the risk of hemolysis, and does not cause platelet adhesion. Due to the etching effect of plasma, the mechanical properties of the samples decreased with the extension of plasma treatment time, which should be used as a basis to balance the mechanical property and biological property of artificial blood vessels. But on the whole, plasma treatment has positive significance for improving the comprehensive performance of samples.

Biomimetic-modified bioprosthetic heart valves with Cysteine-Alanine-Glycine peptide for anti-thrombotic, endothelialization and anti-calcification

In recent years, bioprosthetic heart valves (BHVs) prepared by cross-linking porcine or bovine pericardium with glutaraldehyde (Glut) have received widespread attention due to their excellent hemocompatibility and hydrodynamic properties. However, the failure of BHVs induced by thrombosis and difficulty in endothelialization still exists in clinical practice. Improving the biocompatibility and endothelialization potential of BHVs is conducive to promoting their anti-thrombosis properties and prolonging their service life. Herein, Cysteine-Alanine-Glycine (CAG) peptide was introduced into the biomimetic BHV materials modified by 2-methacryloyloxyethyl phosphorylcholine (MPC) to improve their anti-thrombosis and promoting-endothelialization performances. MPC can improve the anti-adsorption performance of BHV materials, as well as, CAG contributes to the adhesion and proliferation of endothelial cells on the surface of BHV materials. The results of experiments showed that the biomimetic modification strategy with MPC and CAG reduce the thrombosis of BHV materials and improve their endothelialization in vitro. More importantly, the calcification of BHV significantly reduced by inhibiting the expression of M1 macrophage-related factors (IL-6, iNOS) and promoting the expression of M2 macrophage-related factors (IL-10, CD206). We believe that the valve-modified strategy is expected to provide effective solutions to clinical valve problems.

Polymer Complex Multilayers for Drug Delivery and Medical Devices

Polymer complex multilayers (PCMs) can be engineered into various structures with tunable properties via layer-by-layer (LBL) assembly driven by noncovalent forces. Due to their ease of preparation, capability of integrating multiple functional components, and excellent substrate compliance, biocompatible PCMs as coating materials or individual entities have attracted extensive attention in biomedical applications. This Spotlight on Applications presents recent progress on PCMs applied for drug delivery and medical devices. We provide several examples to address the importance of using PCM platforms to achieve controlled drug delivery including stimuli-triggered release, sustained release, and spatiotemporal sequential release. The effects of PCM coatings on the bioresponse regulation and performance enhancement of implantable devices are also highlighted. Moreover, the design and fabrication of flexible electrical and optical elements modified with LBL PCMs have been discussed, which demonstrates the great potential to advance emerging wearable devices for disease monitoring and health management.

Stent-Graft Fabrics Incorporating a Specific Corona Ready to Fenestrate

In situ fenestration of endovascular stent-grafts has become a mainstream bailout technique to treat complex emergent aneurysms while maintaining native anatomical visceral and aortic arch blood supplies. Fabric tearing from creating the in situ fenestration using balloon angioplasty may extend beyond the intended diameter over time. Further tearing may result from the physiologic pulsatile motion at the branching site. A resultant endoleak at the fenestrated sites in stent-grafts could ultimately lead to re-pressurization of the aortic sac and, eventually, rupture. In an attempt to address this challenge, plain woven fabrics were designed. They hold a specific corona surrounding a square-shaped cluster with a plain weave fabric structure, a 2/2 twill, or a honeycomb. The corona was designed to stop potential further tearing of the fabric caused by the initial balloon angioplasty and stent or later post-implantation motion. The cluster within the corona was designed with relatively loose fabric structures (plain weave, 2/2 twill weave, and honeycomb) to facilitate the laser fenestration. Two commercial devices, Anaconda (Vascutek, Terumo Aortic) and Zenith TX2 (Cook), were selected as controls for comparison against this new design. All the specimens were characterized by morphology, thickness, and water permeability. The results demonstrated that all specimens with a low thickness and water permeability satisfied the requirements for a stent graft material that would be low profile and resistant to endoleaks. The in situ fenestrations were performed on all fabrics utilizing an Excimer laser followed by balloon angioplasty. The fabrics were further observed by light microscopy and scanning electron microscopy. The dimension of the fenestrated apertures was smaller than the balloon's diameter. The tearing was effectively confined within the corona. The clinical acceptability of this concept deserves additional bench testing and animal experimentation.

Restoring endothelial function: shedding light on cardiovascular stent development

Complete endothelialization is highly important for maintaining long-term patency and avoiding subsequent complications in implanting cardiovascular stents. It not only refers to endothelial cells (ECs) fully covering the inserted stents, but also includes the newly formed endothelium, which could exert physiological functions, such as anti-thrombosis and anti-stenosis. Clinical outcomes have indicated that endothelial dysfunction, especially the insufficiency of antithrombotic and barrier functions, is responsible for stent failure. Learning from vascular pathophysiology, endothelial dysfunction on stents is closely linked to the microenvironment of ECs. Evidence points to inflammatory responses, oxidative stress, altered hemodynamic shear stress, and impaired endothelial barrier affecting the normal growth of ECs, which are the four major causes of endothelial dysfunction. The related molecular mechanisms and efforts dedicated to improving the endothelial function are emphasized in this review. From the perspective of endothelial function, the design principles, advantages, and disadvantages behind current stents are introduced to enlighten the development of new-generation stents, aiming to offer new alternatives for restoring endothelial function.

Nitric oxide releasing poly(vinyl alcohol)/S-nitrosated keratin film as a potential vascular graft

Nitric oxide (NO) releasing vascular graft is promising due to its merits of thromboembolism reduction and endothelialization promotion. In this study, keratin-based NO donor of S-nitrosated keratin (KSNO) was blended with poly(vinyl alcohol) (PVA) and further crosslinked with sodium trimetaphosphate (STMP) to afford PVA/KSNO biocomposite films. These films could release NO sustainably for up to 10 days, resulting in the promotion of HUVECs growth and the inhibition of HUASMCs growth. In addition, these films displayed good blood compatibility and antibacterial activity. Taken together, these films have potential applications in vascular grafts.

Poly(ferulic acid)-hybrid nanofibers for reducing thrombosis and restraining intimal hyperplasia in vascular tissue engineering

Small-diameter blood vascular transplantation failure is mainly caused by the vascular materials' unreliable hemocompatibility and histocompatibility and the unmatched mechanical properties, which will cause unstable blood flow. How to solve the problems of coagulation and intimal hyperplasia caused by the above factors is formidable in vascular replacement. In this work, we have synthesized poly(ferulic acid) (PFA) and prepared poly(ester-urethane)urea (PEUU)/silk fibroin (SF)/poly(ferulic acid) (PFA) hybrid nanofibers vascular graft (PSPG) by random electrospinning and post-double network bond crosslinking for process optimization. The results in vitro demonstrated that the graft is of significant anti-oxidation, matched mechanical properties, reliable cytocompatibility, and blood compatibility. Replacing resected rat abdominal aorta and rabbit carotid artery models with PSPG vascular grafts indicated that the grafts are capable of homogeneous hybrid PFA significantly promoted the stabilization of endothelial cells and the ingrowth of smooth muscle cells, meanwhile stabilizing the immune microenvironment. This research demonstrates the PSPG vascular graft with substantial patency, indicating their potential for injured vascular healing.

Facile fabrication of copper-incorporating poly(ε-caprolactone)/keratin mats for tissue-engineered vascular grafts with the potential of catalytic nitric oxide generation

Tissue-engineered vascular grafts (TEVGs) provide a new alternative for vascular construction. Nitric oxide (NO) is capable of promoting vascular tissue regeneration and reducing restenosis caused by vascular implantation. Therefore, in situ production of NO by catalytic decomposition of the endogenous donor is a promising strategy to fabricate a TEVG. In this study, poly(ε-caprolactone) (PCL) was first electrospun with keratin (Ker) to afford PCL/Ker mats and then incorporated with Cu(II) ions through multiple interactions. This strategy is very simple, green, and facile. Particularly, the incorporated Cu(II) ions were partially reduced to Cu(I) ions due to the reducibility of keratin. The chelated copper ions were expected to catalyze the generation of NO from endogenous S-nitrosothiol (RSNO). As a result, PCL/Ker-Cu mats selectively accelerated the adhesion, migration, and growth of human umbilical vein endothelial cells (HUVECs), while inhibiting the proliferation of human umbilical artery smooth muscle cells (HUASMCs). Furthermore, these mats exhibited excellent blood compatibility and significant antibacterial activity. Vascular implantation in vivo indicated that the tubular mats could inhibit thrombus formation and retain patency for 3 months after implantation in the rabbit carotid artery. More importantly, vascular remodeling was observed during follow-up, including a complete endothelium and smooth muscle layer. Taken together, the PCL/Ker-Cu mats have great potential application in vascular tissue regeneration.