Peptide-modified PELCL electrospun membranes for regulation of vascular endothelial cells

Electrospun membranes of diselenide-containing poly(ester urethane)urea for in situ catalytic generation of nitric oxide

Nitric oxide (NO) plays an important role as a signalling molecule in the biological system. Organoselenium-coated or grafted biomaterials have the potential to achieve controlled NO release as they can catalyse decomposition of endogenous S-nitrosothiols to NO. However, such biomaterials are often challenged by the loss of the catalytic sites, which can affect the stability in tissue repair applications. In this work, we prepare a diselenide-containing poly(ester urethane)urea (SePEUU) polymer with Se-Se in the backbone, which is further electrospun into fibrous membranes by blending with poly(ester urethane)urea (PEUU) without diselenide bonds. The presence of catalytic sites in the main chain demonstrates stable and long-lasting NO catalytic activity, while the porous structure of the fibrous membranes ensures uniform distribution of the catalytic sites and better contact with the donor-containing solution. PEUU/SePEUU50 in 50/50 mass ratio has a physiologically adapted rate of NO release, with a sustained generation of NO after exposure to PBS at 37 °C for 30 d. PEUU/SePEUU50 has a low hemolysis and protein adsorption, with mechanical properties in the wet state matching those of natural vascular tissues. It can promote the adhesion and proliferation of human umbilical vein endothelial cells in vitro and control the proliferation of vascular smooth muscle cells in the presence of NO generation. This study exhibits the electrospun fibrous membranes have potential for utilizing as hemocompatible biomaterials for regeneration of blood-contacting tissues.

Functional electrospun nanofibers: fabrication, properties, and applications in wound-healing process

Electrostatic spinning as a technique for producing nanoscale fibers has recently attracted increasing attention due to its simplicity, versatility, and loadability. Nanofibers prepared by electrostatic spinning have been widely studied, especially in biomedical applications, because of their high specific surface area, high porosity, easy size control, and easy surface functionalization. Wound healing is a highly complex and dynamic process that is a crucial step in the body's healing process to recover from tissue injury or other forms of damage. Single-component nanofibers are more or less limited in terms of structural properties and do not fully satisfy various needs of the materials. This review aims to provide an in-depth analysis of the literature on the use of electrostatically spun nanofibers to promote wound healing, to overview the infinite possibilities for researchers to tap into their biomedical applications through functional composite modification of nanofibers for advanced and multifunctional materials, and to propose directions and perspectives for future research.

Zinc ions and ciprofloxacin-encapsulated chitosan/poly(ɛ-caprolactone) composite nanofibers promote wound healing via enhanced antibacterial and immunomodulatory

Antibacterial and anti-inflammatory nanofibrous membranes have attracted extensive attention, especially for the cutaneous wound treatment. In this study, zinc ions and ciprofloxacin-encapsulated chitosan/poly(ɛ-caprolactone) (CS/PCL) electrospun core-shell nanofibers were prepared by employing zinc ions-coordinated chitosan as the shell, and ciprofloxacin-functionalized PCL as the core. The morphology and core-shell structure of the as-prepared composite nanofibers were examined by SEM and TEM, respectively. The physical structure and mechanical property of the electrospun membrane were explored by FTIR, swelling, porosity and tensile test. Tensile strength of the zinc ions-coordinated CS/PCL composite nanofibers was enhanced to ca. 16 MPa. Meanwhile, the composite nanofibers can rapidly release of ciprofloxacin during 11 days and effectively suppress above 98 % of S. aureus proliferation. Moreover, the composite nanofibers exhibited excellent guide cell alignment and cyto-activity, as well as significantly down-regulated the inflammation factors, IL-6 and TNF-α in vitro. Animal experiments in vivo showed that the zinc ions-coordinated CS/PCL membrane by means of the synergistic effect of ciprofloxacin and active zinc ions, could significantly alleviate macrophage infiltration, promote collagen deposition and accelerate the healing process of wounds.

Surface Functionalization of Electrospun Scaffolds by QK-AG73 Peptide for Enhanced Interaction with Vascular Endothelial Cells

Rapid endothelialization still remains challenging for blood-contacting biomaterials, especially for long-term, functional, small-diameter vascular grafts. The vascular endothelial growth factor (VEGF)-mimicking QK peptide holds great promise in promoting vascular endothelial cellular activities such as adhesion, spreading, proliferation, and migration. Syndecans are transmembrane proteoglycans that are highly expressed on cell surfaces, including vascular endothelial cells, which can act as docking receptors to provide binding sites for a variety of cellular growth and signaling molecules. Herein, a novel peptide QK-AG73 that coupled the QK domain with the syndecan binding peptide AG73 was proposed, aiming to synergistically enhance the interaction with vascular endothelial cells. In addition, mechanically matched bioactive scaffolds based on poly(l-lactide-co-ε-caprolactone) were successfully prepared by surface functionalization of the covalently combined QK-AG73 peptide. The result showed that the adhesion of human umbilical vein endothelial cells (HUVECs) was increased by approximately 2-fold on QK-AG73-modified surface compared with those modified with a single QK or AG73 peptide. Moreover, surface functionalization of electrospun scaffolds by this QK-AG73 peptide was more efficient in specifically promoting the proliferation of HUVECs and allowing them to grow with an elongated cobblestone-like cell morphology. It was hypothesized that both VEGF receptors and transmembrane syndecan receptors were involved in cellular regulation by the QK-AG73 peptide, which resulted in synergistic improvement of the interactions with vascular endothelial cells and provided a promising strategy to promote endothelialization of small-diameter vascular grafts.

Amyloid Fibril and Clay Nanosheet Dual-Nanoengineered DNA Dynamic Hydrogel for Vascularized Bone Regeneration

Dynamic hydrogels have attracted enormous interest for bone tissue engineering as they demonstrate reversible mechanics to better mimic biophysical cues of natural extracellular matrix (ECM) compared to traditional static hydrogels. However, the facile development of therapeutic dynamic hydrogels that simultaneously recapitulate the filamentous architecture of the ECM of living tissues and induce both osteogenesis and angiogenesis to augment vascularized bone regeneration remains challenging. Herein, we report a dual nanoengineered DNA dynamic hydrogel developed through the supramolecular coassembly of amyloid fibrils and clay nanosheets with DNA strands. The nanoengineered ECM-like fibrillar hydrogel network is facilely formed without a complicated and tedious molecular synthesis. Amyloid fibrils together with clay nanosheets synergistically enhance the mechanical strength and stability of the dynamic hydrogel and, more remarkably, endow the matrix with an array of tunable features, including shear-thinning, injectability, self-healing, self-supporting, and 3D printable properties. The QK peptide is further chemically grafted onto amyloid fibrils, and its sustainable release from the hydrogel matrix stimulates the tube formation and migration with human umbilical vein endothelial cells. Meanwhile, the nanoengineered hydrogel matrix promotes osteogenic differentiation of bone marrow mesenchymal stem cells due to the sustainable release of Si4+ and Mg2+ derived from clay nanosheets. Furthermore, the manipulation of enhanced vascularized bone regeneration by the dynamic hydrogel is revealed in a rat cranial bone defect model. This dual nanoengineered strategy envisions great promise in developing therapeutic dynamic hydrogels for improved and customizable bone regeneration.

Red blood cell membrane-functionalized Nanofibrous tubes for small-diameter vascular grafts

The off-the-shelf small-diameter vascular grafts (SDVGs) have inferior clinical efficacy. Red blood cell membrane (Rm) has easy availability and multiple bioactive components (such as phospholipids, proteins, and glycoproteins), which can improve the clinic's availability and patency of SDVGs. Here we developed a facile approach to preparing an Rm-functionalized poly-ε-caprolactone/poly-d-lysine (Rm@PCL/PDL) tube by co-incubation and single-step rolling. The integrity, stability, and bioactivity of Rm on Rm@PCL/PDL were evaluated. The revascularization of Rm@PCL/PDL tubes was studied by implantation in the carotid artery of rabbits. Rm@PCL/PDL can be quickly prepared and showed excellent bioactivity with good hemocompatibility and great anti-inflammatory. Rm@PCL/PDL tubes as the substitute for the carotid artery of rabbits had good patency and quick remodeling within 21 days. Rm, as a "self" biomaterial with high biosafety, provides a new and facile approach to developing personalized or universal SDVGs for the clinic, which is of great significance in cardiovascular regenerative medicine and organ chip.

Curcumin Functionalized Electrospun Fibers with Efficient pH Real-Time Monitoring and Antibacterial and Anti-inflammatory Properties

Wound infection has threatened the health of humans, and developing novel dressings by integrating infection detection and wound treatment in biomaterials is urgently required in the medical industry. In this study, we report a facile strategy to develop curcumin functionalized poly(ε-caprolactone) and gelatin composite fibrous membranes with pH real-time monitoring and antibacterial and anti-inflammatory properties. The developed curcumin-functionalized composite fibers displayed highly sensitive and visible response to the variation of the pH value of a buffer solution in the range of 5.6-8.6. In addition, the resultant fibrous membrane showed obviously enhanced antibacterial efficiency against both E. coli and S. aureus and no obvious cytotoxicity to human dermal fibroblasts when the curcumin content was less than 5 wt %. More importantly, 3 wt % curcumin-functionalized composite membrane exhibited excellent anti-inflammatory activities, good antioxidant activity of ca. 82%, and significantly decreased expression levels of pro-inflammatory cytokines like TNF-α and IL-6 in vitro (p < 0.001). Furthermore, subcutaneous embedding experiments showed that the 3 wt % curcumin-functionalized membrane significantly promoted cell penetration, recruited less macrophages, and facilitated collage deposition. Therefore, the curcumin-functionalized composite fibers could be employed to fabricate multifunctional dressings for the future treatment of chronic wounds.

Endothelialization strategy of implant materials surface: The newest research in recent 5 years

In recent years, more and more metal or non-metal materials have been used in the treatment of cardiovascular diseases, but the vascular complications after transplantation are still the main factors restricting the clinical application of most grafts, such as acute thrombosis and graft restenosis. Implant materials have been extensively designed and surface optimized by researchers, but it is still too difficult to avoid complications. Natural vascular endodermis has excellent function, anti-coagulant and anti-intimal hyperplasia, and it is also the key to maintaining the homeostasis of normal vascular microenvironment. Therefore, how to promote the adhesion of endothelial cells (ECs) on the surface of cardiovascular materials to achieve endothelialization of the surface is the key to overcoming the complications after implant materialization. At present, the surface endothelialization design of materials based on materials surface science, bioactive molecules, and biological function intervention and feedback has attracted much attention. In this review, we summarize the related research on the surface modification of materials by endothelialization in recent years, and analyze the advantages and challenges of current endothelialization design ideas, explain the relationship between materials, cells, and vascular remodeling in order to find a more ideal endothelialization surface modification strategy for future researchers to meet the requirements of clinical biocompatibility of cardiovascular materials.

Peptide grafting strategies before and after electrospinning of nanofibers

Nanofiber films produced by electrospinning currently provide a promising platform for different applications. Although nonfunctionalized nanofiber films from natural or synthetic polymers are extensively used, electrospun materials combined with peptides are gaining more interest. In fact, the selection of specific peptides improves the performance of the material for biological applications and mainly for tissue engineering, mostly by maintaining similar mechanical properties with respect to the simple polymer. The main drawback in using peptides blended with a polymer is the quick release of the peptides. To avoid this problem, covalent linking of the peptide is more beneficial. Here, we reviewed synthetic protocols that enable covalent grafting of peptides to polymers before or after the electrospinning procedures to obtain more robust electrospun materials. Applications and the performance of the new material compared to that of the starting polymer are discussed.

Strategies to Improve Nanofibrous Scaffolds for Vascular Tissue Engineering

The biofabrication of biomimetic scaffolds for tissue engineering applications is a field in continuous expansion. Of particular interest, nanofibrous scaffolds can mimic the mechanical and structural properties (e.g., collagen fibers) of the natural extracellular matrix (ECM) and have shown high potential in tissue engineering and regenerative medicine. This review presents a general overview on nanofiber fabrication, with a specific focus on the design and application of electrospun nanofibrous scaffolds for vascular regeneration. The main nanofiber fabrication approaches, including self-assembly, thermally induced phase separation, and electrospinning are described. We also address nanofibrous scaffold design, including nanofiber structuring and surface functionalization, to improve scaffolds' properties. Scaffolds for vascular regeneration with enhanced functional properties, given by providing cells with structural or bioactive cues, are discussed. Finally, current in vivo evaluation strategies of these nanofibrous scaffolds are introduced as the final step, before their potential application in clinical vascular tissue engineering can be further assessed.

Local Delivery of Dual MicroRNAs in Trilayered Electrospun Grafts for Vascular Regeneration

Globally growing problems related to cardiovascular diseases lead to a considerable need for synthetic vascular grafts. For small-caliber vascular prosthesis, it remains essential to fulfill rapid endothelialization, inhibit intimal hyperplasia, and prevent calcification for keeping patency. To modulate vascular regeneration, herein, we developed a bioactive trilayered tissue-engineered vascular graft encapsulating both microRNA-126 and microRNA-145 in the fibrous inner and middle layers, respectively. In vitro cell activities demonstrated that the trilayered electrospun membranes had significant biological advantages in enhanced growth and intracellular nitric oxide production of vascular endothelial cells, modulation of phenotypes of vascular smooth muscle cells (SMCs), and restraint of calcium deposition through fast-releasing microRNA-126 and slow-releasing microRNA-145. Histological and immunofluorescent analyses of in vivo implantation in a rat abdominal aorta interposition model suggested that the dual-microRNA-loading trilayered electrospun graft exerted a positive effect on accelerating endothelialization, improving contractile SMC regeneration, and promoting normal extracellular matrix formation. Meanwhile, the local bioactivity of microRNA-126 and microRNA-145 in the trilayered vascular graft could regulate inflammation and depress calcification possibly by facilitating transformation of macrophages into the anti-inflammatory M2 phenotype. These findings indicated that the trilayered electrospun graft by local delivery of dual microRNAs could be possibly used as a bioactive substitute for replacement of artificial small-caliber blood vessels.

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.

Combinatorial functionalization with bisurea-peptides and antifouling bisurea additives of a supramolecular elastomeric biomaterial

The bioactive additive toolbox to functionalize supramolecular elastomeric materials expands rapidly. Here we have set an explorative step toward screening of complex combinatorial functionalization with antifouling and three peptide-containing additives in a bisurea-based supramolecular system. Thorough investigation of surface properties of thin films with contact angle measurements, X-ray photoelectron spectroscopy and atomic force microscopy, was correlated to cell-adhesion of endothelial and smooth muscle cells to apprehend their respective predictive values for functional biomaterial development. Peptides were presented at the surface alone, and in combinatorial functionalization with the oligo(ethylene glycol)-based non-cell adhesive additive. The bisurea-RGD additive was cell-adhesive in all conditions, whereas the endothelial cell-specific bisurea-REDV showed limited bioactive properties in all chemical nano-environments. Also, aspecific functionality was observed for a bisurea-SDF1α peptide. These results emphasize that special care should be taken in changing the chemical nano-environment with peptide functionalization. © 2019 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1725-1735.

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.

Immobilization of Enzymes on a Phospholipid Bionically Modified Polysulfone Gradient-Pore Membrane for the Enhanced Performance of Enzymatic Membrane Bioreactors

Enzymatic membrane bioreactors (EMBRs), with synergistic catalysis-separation performance, have increasingly been used for practical applications. Generally, the membrane properties, particularly the pore structures and interface interactions, have a significant impact on the catalytic efficiency of the EMBR. Therefore, a biomimetic interface based on a phospholipid assembled onto a polysulfone hollow-fiber membrane with perfect radial gradient pores (RGM-PSF) has been prepared in this work to construct a highly efficient and stable EMBR. On account of the special pore structure of the RGM-PSF with the apertures decreasing gradually from the inner side to the outer side, the enzyme molecules could be evenly distributed on the three-dimensional skeleton of the membrane. In addition, the supported phospholipid layer in the membrane, prepared by physical adsorption, was used for the immobilization of the enzymes, which provides sufficient linkage to prevent the enzymes from leaching but also accommodates as many enzyme molecules as possible to retain high bioactivity. The properties of the EMBR were studied by using lipase from Candida rugosa for the hydrolysis of glycerol triacetate as a model. Energy-dispersive X-ray and circular dichroism spectroscopy were employed to observe the effect of lecithin on the membrane and structure changes in the enzyme, respectively. The operational conditions were investigated to optimize the performance of the EMBR by testing substrate concentrations from 0.05 to 0.25 M, membrane fluxes from 25.5 to 350.0 L·m-2·h-1, and temperatures from 15 to 55 °C. As a result, the obtained EMBR showed a desirable performance with 42% improved enzymatic activity and 78% improved catalytic efficiency relative to the unmodified membrane.

Introduction of Nature's Complexity in Engineered Blood-compatible Biomaterials

Biomaterials with excellent blood-compatibility are needed for applications in vascular replacement therapies, such as vascular grafts, heart valves and stents, and in extracorporeal devices such as hemodialysis machines and blood-storage bags. The modification of materials that are being used for blood-contacting devices has advanced from passive surface modifications to the design of more complex, smart biomaterials that respond to relevant stimuli from blood to counteract coagulation. Logically, the main source of inspiration for the design of new biomaterials has been the endogenous endothelium. Endothelial regulation of hemostasis is complex and involves a delicate interplay of structural components and feedback mechanisms. Thus, challenges to develop new strategies for blood-compatible biomaterials now lie in incorporating true feedback controlled mechanisms that can regulate blood compatibility in a dynamic way. Here, supramolecular material systems are highlighted as they provide a promising platform to introduce dynamic reciprocity, due to their inherent dynamic nature.

Surface Coating of Polytetrafluoroethylene with Extracellular Matrix and Anti-CD34 Antibodies Facilitates Endothelialization and Inhibits Platelet Adhesion Under Sheer Stress

Expanded polytetrafluoroethylene (ePTFE) polymers do not support endothelialization because of nonconductive characteristics towards cellular attachment. Inner surface modification of the grafts can improve endothelialization and increase the long-term patency rate of the ePTFE vascular grafts. Here we reported a method of inner-surface modification of ePTFE vascular graft with extracellular matrix (ECM) and CD34 monoclonal antibodies (CD34 mAb) to stimulate the adhesion and proliferation of circulating endothelial progenitor cells on ePTFE graft to enhance graft endothelialization. The inner surface of ECM-coated ePTFE grafts were linked with CD34 mAb in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide (EDC/NHS) solution and the physicochemical properties, surface morphology, biocompatibility, and hemocompatibility of the grafts were studied. The hydrophilicity of CD34 mAb-coated graft inner surface was significantly improved. Fourier transform infrared spectroscopy analysis confirmed ECM and CD34 mAb cross-linking in the ePTFE vascular grafts with our method. Scanning electron microscopy analysis showed protein layer covering uniformly on the inner surface of the modified grafts. The cell-counting kit-8 (CCK-8) assay confirmed that the modified graft has no obvious cytotoxicity. The modified graft showed a low hemolytic rate (0.9%) in the direct contact hemolysis test, suggesting the modification improved hemocompatibility of biopolymers. The modification also decreased adhesion of platelets, while significantly increased the adhesion of endothelial cells on the grafts. We conclude that our method enables ePTFE polymers modification with ECM and CD34 mAb, facilitates endothelialization, and inhibits platelet adhesion on the grafts, thus may increase the long-term patency rate of the prosthetic bypass grafts.

Functional electrospun fibrous scaffolds with dextran-g-poly(l-lysine)-VAPG/microRNA-145 to specially modulate vascular SMCs

Functional electrospun membranes loaded with Dex-g-PLL-VAPG/miR-145 complexes exhibit the excellent ability to modulate SMC phenotype and proliferation locally.

Multi-targeting peptides for gene carriers with high transfection efficiency

Non-viral gene carriers for gene therapy have been developed for many years.