A Method for Preparation of an Internal Layer of Artificial Vascular Graft Co-Modified with Salvianolic Acid B and Heparin

Improving the hemocompatibility of a porohyperelastic layered vascular graft using luminal reversal microflows

Vascular graft thrombosis is a long-standing clinical problem. A myriad of efforts have been devoted to reducing thrombus formation following bypass surgery. Researchers have primarily taken a chemical approach to engineer and modify surfaces, seeking to make them more suitable for blood contacting applications. Using mechanical forces and surface topology to prevent thrombus formation has recently gained more attention. In this study, we have designed a bilayered porous vascular graft capable of repelling platelets and destabilizing absorbed protein layers from the luminal surface. During systole, fluid penetrates through the graft wall and is subsequently ejected from the wall into the luminal space (Luminal Reversal Flow - LRF), pushing platelets away from the surface during diastole. In-vitro hemocompatibility tests were conducted to compare platelet deposition in high LRF grafts with low LRF grafts. Graft material properties were determined and utilized in a porohyperelastic (PHE) finite element model to computationally predict the LRF generation in each graft type. Hemocompatibility testing showed significantly lower platelet deposition values in high versus low LRF generating grafts (median±IQR = 5,708 ± 987 and 23,039 ± 3,310 platelets per mm2, respectively, p=0.032). SEM imaging of the luminal surface of both graft types confirmed the quantitative blood test results. The computational simulations of high and low LRF generating grafts resulted in LRF values of -10.06 μm/s and -2.87 μm/s, respectively. These analyses show that a 250% increase in LRF is associated with a 75.2% decrease in platelet deposition. PHE vascular grafts with high LRF have the potential to improve anti-thrombogenicity and reduce thrombus-related post-procedure complications. Additional research is required to overcome the limitations of current graft fabrication technologies that further enhance LRF generation.

Improving hemocompatibility in tissue-engineered products employing heparin-loaded nanoplatforms

The enhancement of hemocompatibility through the use of nanoplatforms loaded with heparin represents a highly desirable characteristic in the context of emerging tissue engineering applications. The significance of employing heparin in biological processes is unquestionable, owing to its ability to interact with a diverse range of proteins. It plays a crucial role in numerous biological processes by engaging in interactions with diverse proteins and hydrogels. This review provides a summary of recent endeavors focused on augmenting the hemocompatibility of tissue engineering methods through the utilization of nanoplatforms loaded with heparin. This study also provides a comprehensive review of the various applications of heparin-loaded nanofibers and nanoparticles, as well as the techniques employed for encapsulating heparin within these nanoplatforms. The biological and physical effects resulting from the encapsulation of heparin in nanoplatforms are examined. The potential applications of heparin-based materials in tissue engineering are also discussed, along with future perspectives in this field.

Small-diameter vascular graft composing of core-shell structured micro-nanofibers loaded with heparin and VEGF for endothelialization and prevention of neointimal hyperplasia

Despite the significant progress made in recent years, clinical issues with small-diameter vascular grafts related to low mechanical strength, thrombosis, intimal hyperplasia, and insufficient endothelialization remain unresolved. This study aims to design and fabricate a core-shell fibrous small-diameter vascular graft by co-axial electrospinning process, which will mechanically and biologically meet the benchmarks for blood vessel replacement. The presented graft (PGHV) comprised polycaprolactone/gelatin (shell) loaded with heparin-VEGF and polycaprolactone (core). This study hypothesized that the shell structure of the fibers would allow rapid degradation to release heparin-VEGF, and the core would provide mechanical strength for long-term application. Physico-mechanical evaluation, in vitro biocompatibility, and hemocompatibility assays were performed to ensure safe in vivo applications. After 25 days, the PGHV group released 79.47 ± 1.54% of heparin and 86.25 ± 1.19% of VEGF, and degradation of the shell was observed but the core remained pristine. Both the control (PG) and PGHV groups demonstrated robust mechanical properties. The PGHV group showed excellent biocompatibility and hemocompatibility compared to the PG group. After four months of rat aorta implantation, PGHV exhibited smooth muscle cell regeneration and complete endothelialization with a patency rate of 100%. The novel core-shell structured graft could be pivotal in vascular tissue regeneration application.

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.

Multifunctional Asymmetric Bacterial Cellulose Membrane with Enhanced Anti-Bacterial and Anti-Inflammatory Activities for Promoting Infected Wound Healing

An asymmetric wound dressing acts as a skin-like structure serves as a protective barrier between a wound and its surroundings. It allows for the absorption of tissue fluids and the release of active substances at the wound site, thus speeding up the healing process. However, the production of such wound dressings requires the acquisition of specialized tools, expensive polymers, and solvents that contain harmful byproducts. In this study, an asymmetric bacterial cellulose (ABC) wound dressing using starch as a porogen has been developed. By incorporating silver-metal organic frameworks (Ag-MOF) and curcumin into the ABC membrane, the wound dressing gains antioxidant, reactive oxygen species (ROS) scavenging, and anti-bacterial activities. Compared to BC-based wound dressings, this dressing promotes efficient dissolution and controlled release of curcumin and silver ions. In a full-thickness skin defect model, wound dressing not only inhibits the growth of bacteria on infected wounds but also regulates the release of curcumin to reduce inflammation and promote the production of epithelium, blood vessels, and collagen. Consequently, this dressing provides superior wound treatment compared to BC-based dressing.

Development of pullulan/chitosan/salvianolic acid ternary fibrous membranes and their potential for chemotherapeutic applications

This study investigates the feasibility of centrifugal spinning for producing fibrous membranes containing pullulan, chitosan, and danshen extract. The danshen extract is composed of 20 wt% salvianolic acid B (SA). Citric acid was added to the mixture as a crosslinking agent to promote its use in the aqueous medium. The influence of the danshen concentration (25 wt% and 33 wt%) on fiber morphology, thermal behavior, and the biochemical effect was analyzed. Developed fiber-based membranes consist of long, continuous, and uniform fibers with a sparse scattering of beads. Fiber diameter analysis shows values ranging from 384 ± 123 nm to 644 ± 141 nm depending on the concentration of danshen. The nanofibers show adequate aqueous stability after crosslinking. Thermal analysis results prove that SA is loaded into nanofibers without compromising their structural integrity. Cell-based results indicate that the developed nanofiber membranes promote cell growth and are not detrimental to fibroblast cells. Anticancer studies reveal a promising inhibition to the proliferation of HCT116 colon cancer cells. The developed systems show potential as innovative systems to be used as a bioactive chemotherapeutic drug that could be placed on the removed tumor site to prevent development of colon cancer microdeposits.

Small diameter expanded polytetrafluoroethylene vascular graft with differentiated inner and outer biomacromolecules for collaborative endothelialization, anti-thrombogenicity and anti-inflammation

Without differentiated inner and outer biological function, expanded polytetrafluoroethylene (ePTFE) small-diameter (<6 mm) artificial blood vessels would fail in vivo due to foreign body rejection, thrombosis, and hyperplasia. In order to synergistically promote endothelialization, anti-thrombogenicity, and anti-inflammatory function, we modified the inner and outer surface of ePTFE, respectively, by grafting functional biomolecules, such as heparin and epigallocatechin gallate (EGCG), into the inner surface and polyethyleneimine and rapamycin into the outer surface via layer-by-layer self-assembly. Fourier-transform infrared spectroscopy showed the successful incorporation of EGCG, heparin, and rapamycin. The collaborative release profile of heparin and rapamycin lasted for 42 days, respectively. The inner surface promoted human umbilical vein endothelial cells (HUVECs) adhesion and growth and that the outer surface inhibited smooth muscle cells growth and proliferation. The modified ePTFE effectively regulated the differentiation behavior of RAW264.7, inhibited the expression of proinflammatory mediator TNF-α, and up-regulated the expression of anti-inflammatory genes Arg1 and Tgfb-1. The ex vivo circulation results indicated that the occlusions and total thrombus weight of modified ePTFE was much lower than that of the thrombus formed on the ePTFE, presenting good anti-thrombogenic properties. Hence, the straightforward yet efficient synergistic surface functionalization approach presented a potential resolution for the prospective clinical application of small-diameter ePTFE blood vessel grafts.

Optimizing the Porohyperelastic Response of a Layered Compliance Matched Vascular Graft to Promote Luminal Self-Cleaning

Thrombosis and intimal hyperplasia have remained the major failure mechanisms of small-diameter vascular grafts used in bypass procedures. While most efforts to reduce thrombogenicity have used a biochemical surface modification approach, the use of local mechanical phenomena to aid in this goal has received somewhat less attention. In this work, the mechanical, fluid transport, and geometrical properties of a layered and porous vascular graft are optimized within a porohyperelastic finite element framework to maximize self-cleaning via luminal reversal fluid velocity (into the lumen). This is expected to repel platelets as well as inhibit the formation of and/or destabilize adsorbed protein layers thereby reducing thrombogenic potential. A particle swarm optimization algorithm was utilized to maximize luminal reversal fluid velocity while also compliance matching our graft to a target artery (rat aorta). The maximum achievable luminal reversal fluid velocity was approximately 246 μm/s without simultaneously optimizing for host compliance. Simultaneous optimization of reversal flow and compliance resulted in a luminal reversal fluid velocity of 59 μm/s. Results indicate that a thick highly permeable compressible inner layer and a thin low permeability incompressible outer layer promote intraluminal reversal fluid velocity. Future research is needed to determine the feasibility of fabricating such a layered and optimized graft and verify its ability to improve hemocompatibility.

Tween-80 improves single/coaxial electrospinning of three-layered bioartificial blood vessel

Electrospinning is a promising technique for preparing bioartificial blood vessels. Nanofibers prepared by electrospinning can simulate the structure of extracellular matrix to promote cell adhesion and proliferation. However, thorn-like protrusions can appear as defects on electrospun scaffolds and coaxial electrospun nanofibers often have no clear core/shell structure, which can seriously affect the quality of bioartificial blood vessels. To address these problems, Tween 80 is added to the electrospinning solution, which results in a stable Taylor cone, eliminates the thorn-like protrusions on electrospun bioartificial blood vessels, and reduces interfacial effects due to different core/shell solutions during coaxial electrospinning. Simulations, biomechanical tests, and in vivo studies were performed. The results demonstrate the excellent mechanical properties and biocompatibility of the bioartificial blood vessel. This research provides a useful reference for optimizing the electrospinning process for fabricating bioartificial blood vessels.

Electrospun nanofibrous membrane for biomedical application

Electrospinning is a simple, cost-effective, flexible, and feasible continuous micro-nano polymer fiber preparation technology that has attracted extensive scientific and industrial interest over the past few decades, owing to its versatility and ability to manufacture highly tunable nanofiber networks. Nanofiber membrane materials prepared using electrospinning have excellent properties suitable for biomedical applications, such as a high specific surface area, strong plasticity, and the ability to manipulate their nanofiber components to obtain the desired properties and functions. With the increasing popularity of nanomaterials in this century, electrospun nanofiber membranes are gradually becoming widely used in various medical fields. Here, the research progress of electrospun nanofiber membrane materials is reviewed, including the basic electrospinning process and the development of the materials as well as their biomedical applications. The main purpose of this review is to discuss the latest research progress on electrospun nanofiber membrane materials and the various new electrospinning technologies that have emerged in recent years for various applications in the medical field. The application of electrospun nanofiber membrane materials in recent years in tissue engineering, wound dressing, cancer diagnosis and treatment, medical protective equipment, and other fields is the main topic of discussion in this review. Finally, the development of electrospun nanofiber membrane materials in the biomedical field is systematically summarized and prospects are discussed. In general, electrospinning has profound prospects in biomedical applications, as it is a practical and flexible technology used for the fabrication of microfibers and nanofibers.

This review summarizes recent research on the application of electrospun nanofiber membranes as tissue engineering materials for the cardiovascular system, motor system, nervous system, and other clinical aspects.

Research on the application of electrospun nanofiber membrane materials as protective products is discussed in the context of the current epidemic situation.

Examples and analyses of recent popular applications in tissue engineering, wound dressing, protective products, and cancer sensors are presented.

Hyaluronic acid oligosaccharide-collagen mineralized product and aligned nanofibers with enhanced vascularization properties in bone tissue engineering

Considering the structural complexity of natural bone and the limitations of current treatment options, designing a biomimetic and functional tissue-engineered bone graft has been an urgent need for the replacement and regeneration of defected bone tissue. In light of the cell recruitment to the defect region, scaffold-guided bone tissue engineering has proven to be a viable strategy that is poised to deliver effective osseointegration and vascularization during bone remodeling. Herein, we provide an engineered bone scaffold based on aligned poly(lactic-co-glycolide) (PLGA) nanofibers incorporated with hyaluronic acid oligosaccharide-collagen mineralized microparticles (labeled oHA-Col/HAP) to guide the cell-specific orientation and osseointegration in bone healing. The aligned nanofibers were successfully prepared by a custom-made rotating mandrel with separating railings and HAs-Col/HAP mineralized microparticles were uniformly distributed in the composite scaffolds that acted as temporary templates for bone remodeling. The morphology, physicochemical properties and tensile strength of the scaffolds were characterized, the cell responses and in vivo biocompatibility and biodegradability of the scaffolds were also studied to evaluate the potential for bone tissue engineering. The experimental results illustrated that such anisotropic scaffolds loaded with oHA-Col/HAP microparticles mediated cell orderly arrangement conducive to the migration and recruitment of osseointegration-related cells and were stimulatory of cell proliferation. Those oHA-Col/HAP@PLGA scaffolds exhibited ideal biocompatibility and tissue regenerative capacity in vivo through a higher expression of vascularization-related genes. Overall, the novel engineered bone scaffold promises to serve as alternative candidates for bone tissue engineering applications.

Therapeutic Acellular Scaffolds for Limiting Left Ventricular Remodelling-Current Status and Future Directions

Myocardial infarction (MI) is one of the leading causes of heart-related deaths worldwide. Following MI, the hypoxic microenvironment triggers apoptosis, disrupts the extracellular matrix and forms a non-functional scar that leads towards adverse left ventricular (LV) remodelling. If left untreated this eventually leads to heart failure. Besides extensive advancement in medical therapy, complete functional recovery is never accomplished, as the heart possesses limited regenerative ability. In recent decades, the focus has shifted towards tissue engineering and regenerative strategies that provide an attractive option to improve cardiac regeneration, limit adverse LV remodelling and restore function in an infarcted heart. Acellular scaffolds possess attractive features that have made them a promising therapeutic candidate. Their application in infarcted areas has been shown to improve LV remodelling and enhance functional recovery in post-MI hearts. This review will summarise the updates on acellular scaffolds developed and tested in pre-clinical and clinical scenarios in the past five years with a focus on their ability to overcome damage caused by MI. It will also describe how acellular scaffolds alone or in combination with biomolecules have been employed for MI treatment. A better understanding of acellular scaffolds potentialities may guide the development of customised and optimised therapeutic strategies for MI treatment.

An Update on Mesoporous Silica Nanoparticle Applications in Nanomedicine

The efficient and safe delivery of therapeutic drugs, proteins, and nucleic acids are essential for meaningful therapeutic benefits. The field of nanomedicine shows promising implications in the development of therapeutics by delivering diagnostic and therapeutic compounds. Nanomedicine development has led to significant advances in the design and engineering of nanocarrier systems with supra-molecular structures. Smart mesoporous silica nanoparticles (MSNs), with excellent biocompatibility, tunable physicochemical properties, and site-specific functionalization, offer efficient and high loading capacity as well as robust and targeted delivery of a variety of payloads in a controlled fashion. Such unique nanocarriers should have great potential for challenging biomedical applications, such as tissue engineering, bioimaging techniques, stem cell research, and cancer therapies. However, in vivo applications of these nanocarriers should be further validated before clinical translation. To this end, this review begins with a brief introduction of MSNs properties, targeted drug delivery, and controlled release with a particular emphasis on their most recent diagnostic and therapeutic applications.

An injectable peptide hydrogel with excellent self-healing ability to continuously release salvianolic acid B for myocardial infarction

Drug-loaded hydrogels can improve blood supply and inhibit extracellular matrix degradation after myocardial infarction. However, due to the continual dynamic motion of cardiac tissue, the hydrogel structure cannot be reconstructed in time, causing accelerated degradation and drug burst release. Here, a novel, superior, self-healing elastin-mimic peptide hydrogel (EMH) was fabricated for the local delivery of salvianolic acid B (SaB). The self-healing ability of EMH is enhanced by SaB-loaded polydopamine nanoparticles (SaB-PDA). In vitro, the pre-hydrogel (SaB-PDA/pre-EMH) is endowed with excellent biocompatibility and a low viscosity, making it suitable for intramyocardial injection. Once injected into the myocardial infarction (MI) region, SaB-PDA/pre-EMH can form SaB-PDA/EMH with great mechanical strength under the action of upregulated transglutaminase (TGase) in heart tissue post-MI. The superior self-healing ability of SaB-PDA/EMH allows for an increase in retention time in the beating ventricular wall. Therefore, with long-term release of SaB, SaB-PDA/EMH can inhibit ventricular remodeling and promote angiogenesis for MI treatment.

Design, Synthesis, and Biological Evaluation of Dexamethasone-Salvianolic Acid B Conjugates and Nanodrug Delivery against Cisplatin-Induced Hearing Loss

Cisplatin (CDDP) is an extensively used chemotherapeutic agent but has a high incidence of severe ototoxicity. Although a few molecules have entered clinical trials, none have been approved to prevent or treat CDDP-induced hearing loss by the Food and Drug Administration. In this study, an amphiphilic drug-drug conjugate was synthesized by covalently linking dexamethasone (DEX) and salvianolic acid B (SAL) through an ester or amide bond. The conjugates could self-assemble into nanoparticles (NPs) with ultrahigh drug loading capacity and favorable stability. Compared with DEX, SAL, or their physical mixture at the same concentrations, both conjugates and NPs showed enhanced otoprotection in vitro and in vivo. More importantly, the conjugates and NPs almost completely restored hearing in a guinea pig model with good biocompatibility. Immunohistochemical analyses suggested that conjugates and NPs activated the glucocorticoid receptor, which may work as one of the major mechanisms for their protective effects.

Evaluation of 3D Templated Synthetic Vascular Graft Compared with Standard Graft in a Rat Model: Potential Use as an Artificial Vascular Graft in Cardiovascular Disease

Although the number of vascular surgeries using vascular grafts is increasing, they are limited by vascular graft-related complications and size discrepancy. Current efforts to develop the ideal synthetic vascular graft for clinical application using tissue engineering or 3D printing are far from satisfactory. Therefore, we aimed to re-design the vascular graft with modified materials and 3D printing techniques and also demonstrated the improved applications of our new vascular graft clinically. We designed the 3D printed polyvinyl alcohol (PVA) templates according to the vessel size and shape, and these were dip-coated with salt-suspended thermoplastic polyurethane (TPU). Next, the core template was removed to obtain a customized porous TPU graft. The mechanical testing and cytotoxicity studies of the new synthetic 3D templated vascular grafts (3DT) were more appropriate compared with commercially available polytetrafluoroethylene (PTFE) grafts (ePTFE; standard graft, SG) for clinical use. Finally, we performed implantation of the 3DTs and SGs into the rat abdominal aorta as a patch technique. Four groups of the animal model (SG_7 days, SG_30 days, 3DT_7 days, and 3DT_30 days) were enrolled in this study. The abdominal aorta was surgically opened and sutured with SG or 3DT with 8/0 Prolene. The degree of endothelial cell activation, neovascularization, thrombus formation, calcification, inflammatory infiltrates, and fibrosis were analyzed histopathologically. There was significantly decreased thrombogenesis in the group treated with the 3DT for 30 days compared with the group treated with the SG for 7 and 30 days, and the 3DT for 7 days. In addition, the group treated with the 3DT for 30 days may also have shown increased postoperative endothelialization in the early stages. In conclusion, this study suggests the possibility of using the 3DT as an SG substitute in vascular surgery.

A novel polymeric fibrous microstructured biodegradable small-caliber tubular scaffold for cardiovascular tissue engineering

Increasing morbidity of cardiovascular diseases in modern society has made it crucial to develop artificial small-caliber cardiovascular grafts for surgical intervention of diseased natural arteries, as alternatives to the gold standard autologous implants. Synthetic small-caliber grafts are still not in use due to increased risk of restenosis, lack of lumen re-endothelialization and mechanical mismatch, leading sometimes either to graft failure or to unsuccessful remodeling and pathology of the distal parts of the anastomosed healthy vascular tissues. In this work, we aimed to synthesize small-caliber polymeric (polycaprolactone) tissue-engineered vascular scaffolds that mimic the structure and biomechanics of natural vessels. Electrospinning was implemented to prepare microstructured polymeric membranes with controlled axis-parallel fiber alignment. Consequently, we designed small-caliber multilayer anisotropic biodegradable nanofibrous tubular scaffolds, giving attention to their radial compliance. Polycaprolactone scaffold morphology and mechanical properties were assessed, quantified, and compared with those of native vessels and commercial synthetic grafts. Results showed a highly hydrophobic scaffold material with a three-layered tubular morphology, 4-mm internal diameter/0.25 ± 0.09-mm thickness, consisting of predominantly axially aligned thin (1.156 ± 0.447 μm), homogeneous and continuous microfibers, with adequate (17.702 ± 5.369 μm) pore size, potentially able to promote cell infiltration in vivo. In vitro accelerated degradation showed a 5% mass loss within 17-25 weeks. Mechanical anisotropy was attained as a result, almost one order of magnitude difference of the elastic modulus (18 ± 3 MPa axially/1 ± 0.3 MPa circumferentially), like that of natural arterial walls. Furthermore, a desirable radial compliance (5.04 ± 0.82%, within the physiological pressure range) as well as cyclic stability of the tubular scaffold was achieved. Finally, cytotoxicity evaluation of the polymeric scaffolds revealed that the materials were nontoxic and did not release substances harmful to living cells (over 80% cell viability achieved).

Multidrug-loaded electrospun micro/nanofibrous membranes: Fabrication strategies, release behaviors and applications in regenerative medicine

Electrospun micro/nanofibrous membranes (EFMs) have been widely investigated as local drug delivery systems. Multiple drugs can be simultaneously incorporated into one EFM to create synergistic effects, reduce side effects, and play their respective roles in the complex physiological processes of tissue regeneration and postoperative adhesion prevention. Due to the versatile electrospinning techniques, sustained and programmed release behaviors of multiple drugs could be achieved by modulating the structure of the EFMs and the location of the drugs. In this review, various multidrug incorporation approaches based on electrospinning are overviewed. In particular, the advantages and limitations of each drug incorporation technique, the methods to control drug release and the effect of one drug release on another are discussed. Then the applications of multidrug-loaded EFMs in regenerative medicine, including wound healing, bone regeneration, vascular tissue engineering, nerve regeneration, periodontal regeneration and adhesion prevention are comprehensively reviewed. Finally, the future perspectives and challenges in the research of multidrug-loaded EFMs are discussed.

Fabrication and assessment of chondroitin sulfate-modified collagen nanofibers for small-diameter vascular tissue engineering applications

Chondroitin sulfate (ChS) has shown promising results in promoting cell proliferation and antithrombogenic activity. To engineered develop a dual-function vascular scaffold with antithrombosis and endothelialization, ChS was tethered to collagen to accelerate the growth of endothelial cells and prevent platelet activation. First, ChS was used to conjugate with collagen to generate glycosylated products (ChS-COL) via reductive amination. Then, the fabricated ChS-COL conjugates were electrospun into nanofibers and their morphologies and physicochemical characteristics, cell-scaffold responses and platelet behaviors upon ChS-COL nanofibers were comprehensively characterized to evaluate their potential use for small-diameter vascular tissue-engineered scaffolds. The experimental results demonstrated that the ChS modified collagen electrospun nanofibers were stimulatory of endothelial cell behavior, alleviated thrombocyte activation and maintained an antithrombotic effect in vivo in 10-day post-transplantation. The ChS-COL scaffolds encouraged rapid endothelialization, thus probably ensuring the antithrombotic function in long-term implantation, suggesting their promise for small-diameter vascular tissue engineering applications.

Advanced fabrication for electrospun three-dimensional nanofiber aerogels and scaffolds

Electrospinning is a versatile strategy for creating nanofiber materials with various structures, which has broad application for a myriad of areas ranging from tissue engineering, energy harvesting, filtration and has become one of the most important academic and technical activities in the field of material science in recent years. In addition to playing a significant role in the construction of two-dimensional (2D) nanomaterials, electrospinning holds great promise as a robust method for producing three-dimensional (3D) aerogels and scaffolds. This article reviews and summarizes the recent advanced methods for fabricating electrospun three-dimensional nanofiber aerogels and scaffolds, including gas foaming, direct electrospinning of 3D nanofibrous scaffold, short nanofibers assembling into 3D aerogels/scaffolds, 3D printing, electrospray, origami and cell sheet engineering, centrifugal electrospinning, and other methods. Besides, intriguing formation process, crosslinking pathway, properties, and applications of 3D aerogels and scaffolds are also introduced. Taken together, these aerogels and scaffolds with various excellent features present tremendous potential in various fields.

Surface Engineering of Cardiovascular Devices for Improved Hemocompatibility and Rapid Endothelialization

Cardiovascular devices have been widely applied in the clinical treatment of cardiovascular diseases. However, poor hemocompatibility and slow endothelialization on their surface still exist. Numerous surface engineering strategies have mainly sought to modify the device surface through physical, chemical, and biological approaches to improve surface hemocompatibility and endothelialization. The alteration of physical characteristics and pattern topographies brings some hopeful outcomes and plays a notable role in this respect. The chemical and biological approaches can provide potential signs of success in the endothelialization of vascular device surfaces. They usually involve therapeutic drugs, specific peptides, adhesive proteins, antibodies, growth factors and nitric oxide (NO) donors. The gene engineering can enhance the proliferation, growth, and migration of vascular cells, thus boosting the endothelialization. In this review, the surface engineering strategies are highlighted and summarized to improve hemocompatibility and rapid endothelialization on the cardiovascular devices. The potential outlook is also briefly discussed to help guide endothelialization strategies and inspire further innovations. It is hoped that this review can assist with the surface engineering of cardiovascular devices and promote future advancements in this emerging research field.

Salvia bowleyana Dunn root is a novel source of salvianolic acid B and displays antitumor effects against gastric cancer cells

Salvianolic acid B (Sal-B) is widely used in China for the treatment of numerous diseases. Currently, Salvia miltiorrhiza Bunge is the main source of this compound, but Salvia bowleyana Dunn, a surrogate of S. miltiorrhiza Bge, may provide a novel source for obtaining more Sal-B. In the present study, a simple method for separation and purification of phenolic compounds from S. bowleyana Dunn roots was employed. Sal-B was subsequently purified and its inhibitory effect on the gastric cancer HGC-27 and AGS cell lines was investigated. Sal-B extracted from S. bowleyana Dunn displayed significant antitumor activity in proliferation and apoptosis assays. Overall, it was found that S. bowleyana Dunn has a higher Sal-B content than S. miltiorrhiza Bge and may be used as a novel source of this potential anti-gastric cancer compound.

Spun Biotextiles in Tissue Engineering and Biomolecules Delivery Systems

Nowadays, tissue engineering is described as an interdisciplinary field that combines engineering principles and life sciences to generate implantable devices to repair, restore and/or improve functions of injured tissues. Such devices are designed to induce the interaction and integration of tissue and cells within the implantable matrices and are manufactured to meet the appropriate physical, mechanical and physiological local demands. Biodegradable constructs based on polymeric fibers are desirable for tissue engineering due to their large surface area, interconnectivity, open pore structure, and controlled mechanical strength. Additionally, biodegradable constructs are also very sought-out for biomolecule delivery systems with a target-directed action. In the present review, we explore the properties of some of the most common biodegradable polymers used in tissue engineering applications and biomolecule delivery systems and highlight their most important uses.

Artificial small-diameter blood vessels: materials, fabrication, surface modification, mechanical properties, and bioactive functionalities

Cardiovascular diseases, especially ones involving narrowed or blocked blood vessels with diameters smaller than 6 millimeters, are the leading cause of death globally. Vascular grafts have been used in bypass surgery to replace damaged native blood vessels for treating severe cardio- and peripheral vascular diseases. However, autologous replacement grafts are not often available due to prior harvesting or the patient's health. Furthermore, autologous harvesting causes secondary injury to the patient at the harvest site. Therefore, artificial blood vessels have been widely investigated in the last several decades. In this review, the progress and potential outlook of small-diameter blood vessels (SDBVs) engineered in vitro are highlighted and summarized, including material selection and development, fabrication techniques, surface modification, mechanical properties, and bioactive functionalities. Several kinds of natural and synthetic polymers for artificial SDBVs are presented here. Commonly used fabrication techniques, such as extrusion and expansion, electrospinning, thermally induced phase separation (TIPS), braiding, 3D printing, hydrogel tubing, gas foaming, and a combination of these methods, are analyzed and compared. Different surface modification methods, such as physical immobilization, surface adsorption, plasma treatment, and chemical immobilization, are investigated and are compared here as well. Mechanical requirements of SDBVs are also reviewed for long-term service. In vitro biological functions of artificial blood vessels, including oxygen consumption, nitric oxide (NO) production, shear stress response, leukocyte adhesion, and anticoagulation, are also discussed. Finally, we draw conclusions regarding current challenges and attempts to identify future directions for the optimal combination of materials, fabrication methods, surface modifications, and biofunctionalities. We hope that this review can assist with the design, fabrication, and application of SDBVs engineered in vitro and promote future advancements in this emerging research field.

Development of Tripolymeric Triaxial Electrospun Fibrous Matrices for Dual Drug Delivery Applications

Since the first work by Laurencin and colleagues on the development of polymeric electrospinning for biomedical purposes, the use of electrospinning technology has found broad applications in such areas of tissue regeneration and drug delivery. More recently, coaxial electrospinning has emerged as an important technique to develop scaffolds for regenerative engineering incorporated with drug(s). However, the addition of a softer core layer leads to a reduction in mechanical properties. Here, novel robust tripolymeric triaxially electrospun fibrous scaffolds were developed with a polycaprolactone (PCL) (core layer), a 50:50 poly (lactic-co-glycolic acid) (PLGA) (sheath layer) and a gelatin (intermediate layer) with a dual drug delivery capability was developed through modified electrospinning. A sharp increase in elastic modulus after the incorporation of PCL in the core of the triaxial fibers in comparison with uniaxial PLGA (50:50) and coaxial PLGA (50:50) (sheath)-gelatin (core) fibers was observed. Thermal analysis of the fibrous scaffolds revealed an interaction between the core-intermediate and sheath-intermediate layers of the triaxial fibers contributing to the higher tensile modulus. A simultaneous dual release of model small molecule Rhodamine B (RhB) and model protein Fluorescein isothiocynate (FITC) Bovine Serum Albumin (BSA) conjugate incorporated in the sheath and intermediate layers of triaxial fibers was achieved. The tripolymeric, triaxial electrospun systems were seen to be ideal for the support of mesenchymal stem cell growth, as shrinkage of fibers normally found with conventional electrospun systems was minimized. These tripolymeric triaxial electrospun fibers that are biomechanically competent, biocompatible, and capable of dual drug release are designed for regenerative engineering and drug delivery applications.

Reduction of thrombotic and inflammatory complications of polystyrene-block-polyisoprene-block-polystyrene (SIS) with one-step electrospinning

Polystyrene-block-polyisoprene-block-polystyrene (SIS) has been used as biomaterials due to its soft and stable properties under physiological conditions. However, the thrombotic and inflammatory complications caused by SIS restrain its application as blood-contacting implant. To overcome this problem, the hydrophilic core-shell structured SIS-based microfiber with antioxidant encapsulation is fabricated with one-step reactive electrospinning. We demonstrate that the phase separation of SIS and acylated Pluronic F127 (F127-DA) components and crosslinking during electrospinning renders the microfiber blood compatible and stable under physiological condition; the encapsulation of 2-O-d-glucopyranosyl-l-ascorbic acid (AA-2G) in microfiber and subsequent release of AA-2G detoxifies the excess reactive oxygen species (ROS). The microfibers are nontoxic to cells and promote the fast growth and proliferation of human umbilical vein endothelial cells (HUVECs) in the presence of ROS; the thrombotic and inflammatory complications are effectively reduced with implant evaluation in vivo. Therefore, our work paves a new way to improve the biocompatibility of SIS, making it a promising candidate for blood contact materials.

Core-Shell Fibers: Design, Roles, and Controllable Release Strategies in Tissue Engineering and Drug Delivery

The key attributes of core-shell fibers are their ability to preserve bioactivity of incorporated-sensitive biomolecules (such as drug, protein, and growth factor) and subsequently control biomolecule release to the targeted microenvironments to achieve therapeutic effects. Such qualities are highly favorable for tissue engineering and drug delivery, and these features are not able to be offered by monolithic fibers. In this review, we begin with an overview on design requirement of core-shell fibers, followed by the summary of recent preparation methods of core-shell fibers, with focus on electrospinning-based techniques and other newly discovered fabrication approaches. We then highlight the importance and roles of core-shell fibers in tissue engineering and drug delivery, accompanied by thorough discussion on controllable release strategies of the incorporated bioactive molecules from the fibers. Ultimately, we touch on core-shell fibers-related challenges and offer perspectives on their future direction towards clinical applications.

Co-immobilization of ACH11 antithrombotic peptide and CAG cell-adhesive peptide onto vascular grafts for improved hemocompatibility and endothelialization

Surface modification by conjugating biomolecules has been widely proved to enhance biocompatibility of small-caliber artificial vascular grafts. In this study, we aimed at developing a multifunctional vascular graft that provides not only good hemocompatibility but also in situ rapid endothelialization. Herein, a vascular graft (inner diameter ∼2 mm) was fabricated by electrospinning with poly(lactic acid-co-caprolactone) and gelatin, and then biofunctionalized with antithrombotic peptide with sequence LTFPRIVFVLG (ACH₁₁) and cell adhesion peptide with sequence CAG through adhesive poly(dopamine) coating. We developed this graft with the synergistic properties of low thrombogenicity and rapid endothelialization. The successful grafting of both CAG and ACH₁₁ peptides was confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The surface micromorphology of the modified surfaces was observed by field emission scanning electron microscopy. Our results demonstrated that the multifunctional surface suppressed the denaturation of absorbed fibrinogen, hindered coagulation factor Xa activation, and inhibited platelet adhesion and aggregation. Importantly, this modified surface could selectively enhance endothelial cells adhesion, proliferation and release of nitric oxide. Upon in vivo implantation of 6 weeks, the multifunctional vascular graft showed improved patency and superior vascular endothelialization. Overall, the results effectively demonstrated that the co-immobilization of ACH₁₁ and CAG provided a promising method for the improvement of hemocompatibility and endothelialization of vascular grafts. STATEMENT OF SIGNIFICANCE: Electrospun small-caliber vascular grafts are increasingly used to treat cardiovascular diseases. Despite their success related to their good biodegradation and mechanical strength, they have some drawbacks, such as low hemocompatibility and endothelialization. The single-function ligands are insufficient to modify surface with both good hemocompatibility and rapid endothelialization simultaneously. Therefore, we functionalized electrospun vascular graft by novel antithrombotic peptide and cell-adhesive peptide to construct superior anticoagulation and ECs-selective adhesion surface in present study. The multifunctional vascular grafts benefit for high long-term patency and rapid endothelialization.

Programmed Release of Multimodal, Cross-Linked Vascular Endothelial Growth Factor and Heparin Layers on Electrospun Polycaprolactone Vascular Grafts

Viable tissue-engineering small-diameter vascular grafts should support rapid growth of an endothelial cell layer and exhibit long-term antithrombogenic property. In this study, multiple layers of various bioactive molecules, such as vascular endothelial growth factor (VEGF) and heparin, on an electrospun polycaprolactone scaffold have been developed through repeated electrostatic adsorption self-assembly (up to 20 layers), followed by genipin cross-linking. Programmed and sustained release of biomolecules embedded within the multilayered structure can be triggered by matrix metallopeptidase 2 enzyme in vitro. The result is an early and full release of VEGF to promote rapid endothelialization on the intended vascular grafts, followed by a gradual but sustained release of heparin for long-term anticoagulation and antithrombogenicity. This method of forming a biologically responsive, multimodal delivery of VEGF and heparin is highly suitable for all hydrophobic surfaces and provides a promising way to meet the critical requirements of engineered small-diameter vascular grafts.

Mesoporous silica nanoparticles for tissue-engineering applications

Mesoporous silica nanoparticles (MSNs) have been widely investigated as a nanocarrier for the delivery of various cargoes in nanomedicine. The application of MSNs in tissue engineering is a relatively newly emerged field that has gained much research interest. In this review, the recent advances in the tissue-engineering application of MSNs are summarized. The controlled synthesis of MSNs is delineated first in terms of tuning the morphology, pore size of MSNs, and its surface chemistry, as well as biodegradability. Then, the different roles of MSNs in tissue engineering are successively introduced, which mainly comprise the delivery of bioactive factors, the inherent bioactivity of MSNs, stem cells labelling, and the impacts of incorporated MSNs on scaffolds. Furthermore, the recent progress in the applications of MSNs for tissue engineering, particularly bone tissue engineering, is summarized in detail. Finally, the challenges or potential trends for the further applications of MSNs in tissue engineering are also discussed. This article is categorized under: Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement Implantable Materials and Surgical Technologies > Nanomaterials and Implants.

Salvianolic Acid B Attenuates Apoptosis of HUVEC Cells Treated with High Glucose or High Fat via Sirt1 Activation

High glucose and high fat are important inducements for the development and progression of diabetic cardiopathy. Salvianolic acid B (SAB), which is the most abundant and bioactive compound in Danshen, attenuates oxidative stress-related disorders, such as cardiovascular diseases, cerebral ischemia, and diabetes. However, the effect of SAB on diabetic cardiopathy is not clear. The aim of study was to investigate the effect and the underlying molecular mechanisms of SAB on diabetic cardiopathy in vitro model. The human umbilical vein endothelial (HUVEC) cells were treated with high glucose (HG, 30 mM) or high fat (palmitic acid, PA, 0.75 mM) in the presence or absence of SAB (100, 200, and 400 mg/L) and incubated for 24 h. We found that HG or PA induced apoptosis of HUVEC cells, while treatment with SAB inhibited the apoptosis. We also found that SAB reversed HG- or PA-induced oxidative stress, apoptosis cell cytokines production, and expression of thioredoxin-interacting protein (TXNIP). Moreover, SAB increased HG- or PA-induced expression of Sirtuin 1 (Sirt1), a nicotinamide adenine dinucleotide- (NAD⁺-) dependent histone deacetylase. Exposure of HUVEC cells to Ex527 (Sirt1 inhibitor) suppressed the effect of SAB on acetyl-p53 and procaspase-3 expressions. In conclusion, the results suggested that SAB could attenuate HUVEC cells damage treated with HG or PA via Sirt1 and might be a potential therapy agent for the diabetic cardiopathy treatment.

Electrospun Nanofibers for Tissue Engineering with Drug Loading and Release

Electrospinning technologies have been applied in the field of tissue engineering as materials, with nanoscale-structures and high porosity, can be easily prepared via this method to bio-mimic the natural extracellular matrix (ECM). Tissue engineering aims to fabricate functional biomaterials for the repairment and regeneration of defective tissue. In addition to the structural simulation for accelerating the repair process and achieving a high-quality regeneration, the combination of biomaterials and bioactive molecules is required for an ideal tissue-engineering scaffold. Due to the diversity in materials and method selection for electrospinning, a great flexibility in drug delivery systems can be achieved. Various drugs including antibiotic agents, vitamins, peptides, and proteins can be incorporated into electrospun scaffolds using different electrospinning techniques and drug-loading methods. This is a review of recent research on electrospun nanofibrous scaffolds for tissue-engineering applications, the development of preparation methods, and the delivery of various bioactive molecules. These studies are based on the fabrication of electrospun biomaterials for the repair of blood vessels, nerve tissues, cartilage, bone defects, and the treatment of aneurysms and skin wounds, as well as their applications related to oral mucosa and dental fields. In these studies, due to the optimal selection of drugs and loading methods based on electrospinning, in vitro and in vivo experiments demonstrated that these scaffolds exhibited desirable effects for the repair and treatment of damaged tissue and, thus, have excellent potential for clinical application.

Bi-layered electrospun nanofibrous membrane with osteogenic and antibacterial properties for guided bone regeneration

Guided bone regeneration (GBR) membranes have the potential to prevent the invasion of epithelial and connective tissues as well as to maintain a stable space for facilitating the ingrowth of regenerative bone tissue. However, the bioactivity and regeneration potential of currently available membranes still need to be improved. In this study, a novel bi-layered membrane with both osteogenic and antibacterial functions was developed for GBR applications. The loose layer (LL) of the membrane was composed of conjugated electrospun poly (lactic-co-glycolic acid) (PLGA)/gelatin nanofibers incorporating dexamethasone-loaded mesoporous silica nanoparticles (DEX@MSNs), while the dense layer (DL) of the membrane consisted of traditionally electrospun PLGA nanofibers loaded with the broad-spectrum antibiotic doxycycline hyclate (DCH). Morphological results showed that the LL (DEX@MSNs/PLGA/Gel) membrane exhibited a porous and loosely packed structure, which was beneficial for cell adhesion and infiltration, while the DL (DCH/PLGA) membrane remained dense enough to act as a barrier. In vitro drug release tests indicated that both DEX and DCH followed a favorable sustained release profile. The cell viability evaluation suggested that the electrospun membranes possessed good cytocompatibility. Furthermore, in vitro osteogenesis analyses demonstrated that the DEX@MSNs/PLGA/Gel composite membrane possessed an enhanced osteoinductive capacity for rat bone marrow stem cells (BMSCs), which was verified by the increased alkaline phosphatase (ALP) activity, the enhanced calcium deposition, and the upregulated osteocalcin (OCN) expression. In vitro antimicrobial experiments revealed the effective antibacterial potency of the DCH/PLGA membrane. In conclusion, the prepared nanocarrier-incorporated bi-layered composite membrane with combined osteogenic and antibacterial properties may be a promising candidate for GBR application.

Facile preparation of a controlled-release tubular scaffold for blood vessel implantation

Salvianic acid-loaded mesoporous silica nanoparticles into gelatin/polyurethane bilayered small-diameter tubular scaffold were prepared by thermally induced phase separation (TIPS) and electrospinning. Mesoporous silica nanoparticles (MSNs) were selected as carriers to load salvianic acid (SAL). The SAL-loaded MSNs (SAL@MSNs) with an optimized SAL loading efficiency of 10% was initially dispersed in gelatin solution and under a vacuum freeze-drying process as an inner layer of vascular scaffolds. Then, poly(ester-urethane)urea (C-PEEUU) nanofibers were electrospun outside the SAL@MSNs/Gelatin vascular scaffold to strengthen the spongy matrix. The loaded SAL within the MSNs/Gelatin/C-PEEUU bilayered small-diameter tubular scaffold showed a sustained release profile and good mechanical properties. In addition, the drug-loaded composite scaffold showed no unfavorable effects on the adhesion and proliferation of endothelial cells. Moreover, no intimal hyperplasia and acute thrombosis was observed in the short-term implantation in rabbit's carotid artery. We believe the SAL@MSNs/Gelatin/C-PEEUU bilayered vascular scaffolds have promise for vascular tissue engineering applications.