Stiffness of Aligned Fibers Regulates the Phenotypic Expression of Vascular Smooth Muscle Cells

Development of an aligned nanofiber composite silk fibroin multilayer dressings: Accelerating wound healing and reducing scar formation

This study developed a novel three-layer composite dressing to accelerate wound healing and reduce hypertrophic scar formation. The dressing features an asymmetric wettability structure fabricated by electrospinning and consists of a hydrophilic outer layer of freeze-dried absorbent cotton, a silk fibroin (SF) transitional layer, and a hydrophobic inner layer of aligned poly(lactic acid) (PLA) nanofibers loaded with retinoic acid (RA). The SF transitional layer plays a critical role by bridging the outer and inner layers, establishing a smooth wettability gradient that facilitates efficient unidirectional fluid transport from the wound surface to the outer absorbent layer. This design not only manages wound exudate to maintain a moist yet non-wet microenvironment but also enhances cell adhesion, proliferation, and directional migration. In vitro evaluations demonstrated improved liquid flow and robust cellular responses, while in vivo tests revealed accelerated wound closure and significantly reduced scar formation in both burn and hypertrophic scar models. Overall, integrating the SF transitional layer with aligned RA-loaded PLA nanofibers offers a promising strategy for advanced wound management and scar minimization.

The Combination of Aligned PDA-Fe@PLCL Conduit with Aligned GelMA Hydrogel Promotes Peripheral Nerve Regeneration

Biomaterial-assisted therapeutic strategies enable precise modulation to direct endogenous cellular responses and harness regenerative capabilities for nerve repair. However, achieving effective cellular engagement during nerve remodeling remains challenging. Herein, a novel composite nerve guidance conduit (NGC), the GelMA/PLys@PDA-Fe@PLCL conduit is developed by combining aligned poly(l-lactide-co-caprolactone) (PLCL) nanofibers modified with polydopamine (PDA), ferrous iron (Fe3⁺), and polylysine (PLys) with aligned methacrylate-anhydride gelatin (GelMA) hydrogel nanofibers. PDA films exhibit strong adhesion and metal coordination properties, allowing Fe3⁺ irons to chelate with phenolic hydroxyl groups of dopamine derivatives, forming a metal-phenolic network on PLCL. PLys molecules are then grafted onto PDA-Fe3⁺ coating via Schiff base and Michael addition reactions. This multifunctional coating enhances surface roughness and zeta potential of PLCL nanofibers, imparts superhydrophilicity with anisotropic wetting behavior, and maintains wet tensile properties of substrates. In vitro studies show that the PLys@PDA-Fe coating significantly promotes aligned distribution of Schwann cells, improves cell adhesion and differentiation, and demonstrates notable antioxidant and anti-inflammatory properties. When implanted into nerve defects in rats, the multifunctional coating conduit combined with aligned GelMA hydrogel effectively accelerates axonal regeneration, remyelination, and angiogenesis, leading to enhanced motor function recovery. Overall, the GelMA/PLys@PDA-Fe@PLCL conduit presents a promising strategy for advancing peripheral nerve repair.

Multifunctional hybrid poly(ester-urethane)urea/resveratrol electrospun nanofibers for a potential vascularizing matrix

P/R-1.0 nanofiber with excellent antioxidant, blood and cell compatibility fibricated via electrospinning for a potential vascularizing matrix.

Sex-specific cardiovascular adaptations to simulated microgravity in Sprague-Dawley rats

Men and women have different cardiovascular responses to spaceflight; however, few studies have focused on direct comparisons between sexes. We investigated the mechanisms of aortic stiffening in socially and sexually mature 20-week-old male and female Sprague Dawley (SD) rats exposed to hindlimb unloading (HLU) for 14 days. Pulse wave velocity (PWV) was greater in the aortic arch of females after HLU versus control females (n = 6-8). HLU had no effect on aortic PWV in males (n = 5-6). Aortic α smooth muscle actin, myosin, collagen, elastin, and collagen-to-elastin ratio were not different in rats of either sex following HLU. The levels of G protein-coupled estrogen receptor (GPER) were lower in the aorta of SD females exposed to HLU compared with female controls but were not altered in males. HLU females also had lower aortic PPARγ, increased oxidative stress markers, and diastolic dysfunction compared with control females. GPER agonist G1 prevented the increase in PWV and 8-hydroxy-2'-deoxyguanosine without altering PPARγ or p47phox in HLU females (n = 4 in each group) suggesting that lower GPER may contribute to arterial stiffening in the setting of simulated microgravity. This study highlights sex-specific vascular adaptations to the state of simulated microgravity.

Multifunctional hybrid poly(ester-urethane)urea/resveratrol electrospun nanofibers for a potential vascularizing matrix

The challenges for clinical application of small-diameter vascular graft are mainly acute/chronic thrombosis, inadequate endothelialization, intimal hyperplasia caused by inflammation, oxidative stress, and the mismatch of mechanical compliance after transplantation. How to construct an effective regenerative microenvironment through a material with uniform dispersion of active components is the premise of maintaining patency of a vascular graft. In this study, we have compounded poly(ester-urethane)urea (PEUU) with various optimized concentrations of resveratrol (Res) by homogeneous emulsion blending, followed by electrospinning into the hybrid PEUU/Res nanofibers (P/R-0, P/R-0.5, P/R-1.0, and P/R-1.5). Then the microstructure, surface wettability, mechanical properties, degradation, Res sustained release properties, hemocompatibility, and cytocompatibility of P/R were evaluated comprehensively. The results indicate that Res can be gradually released from the P/R, and both the hydrophilicity and antioxidant ability of the nanofiber gradually increase with the increase of Res content. Moreover, with the increase of Res, the viability and proliferation behavior of HUVECs were significantly improved. Meanwhile, tube formation and migration experiments showed that Res promoted the formation of a neovascularization network. In brief, it is concluded that P/R-1.0 is the optimal candidate with a uniform microstructure, moderate wettability, optimized mechanical properties, reliable hemocompatibility and cytocompatibility, and strongest ability to promote endothelial growth for the vascularizing matrix.

Recent advances in coaxial electrospun nanofibers for wound healing

The skin is the body's primary immune barrier, defending it against pathogenic invasion. Skin injuries impose a significant physiological burden on patients, making effective wound management essential. Dressings are commonly employed in wound care, and electrospun nanofiber dressings are a research hotspot owing to their ease of fabrication, cost-effectiveness, and structural similarity to the extracellular matrix. Coaxial electrospinning offers considerable advantages in drug delivery, fiber structure transformation, and enhanced interaction with the host. These attributes make coaxial electrospun materials promising candidates for precision and personalized wound dressings in medical treatments. This review provides a comprehensive overview of wound healing and its influencing factors. It also outlines coaxial electrospinning's production principles and benefits in wound dressings. Guided by the factors affecting wound healing, coaxial electrospun nanofiber dressings have different application modalities. Furthermore, we discuss the current limitations and future directions for enhancing the current coaxial electrospun dressing technologies.

Electrospun "Hard-Soft" Interpenetrating Nanofibrous Tissue Scaffolds Facilitating Enhanced Mechanical Strength and Cell Proliferation

"Soft" hydrogel-based macroporous scaffolds have been widely used in tissue engineering and drug delivery applications due to their hydrated interfaces and macroporous structures, but have drawbacks related to their weak mechanics and often weak adhesion to cells. In contrast, "hard" poly(caprolactone) (PCL) electrospun fibrous networks have desirable mechanical strength and ductility but offer minimal interfacial hydration and thus limited capacity for cell proliferation. Herein, we demonstrate the fabrication of interpenetrating nanofibrous networks based on coelectrospun PCL and poly(oligoethylene glycol methacrylate) (POEGMA) nanofibers that exhibit the mechanical benefits of PCL but the interfacial hydration benefits of hydrogels. The electrospinning process results in partially aligned but interpenetrating fiber network with minimal internal phase separation, leading to anisotropic but strong mechanical properties even in the hydrated state; apparent ultimate tensile strengths of the swollen scaffolds ranged from 429 ± 39 kPa in the direction of fiber alignment (longitudinal) to 86 ± 25 kPa perpendicular to fiber alignment (cross-longitudinal), typical of PCL-based scaffolds and enabling efficient suture retention in different directions. However, contact angle measurements indicate hydrogel-like interfacial properties due to the presence of the interpenetrating POEGMA network. C2C12 myoblast proliferation in the PCL-POEGMA scaffolds was 50% higher than that observed on PCL-only scaffolds, a result attributed to the presence of the more hydrophilic POEGMA interpenetrating nanofiber network. Overall, this method is demonstrated to represent a facile single-step strategy to fabricate strong macroporous but still interfacially hydrophilic scaffolds for tissue engineering applications.

Vascular smooth muscle cells can be circumferentially aligned inside a channel using tunable gelatin microribbons

The gold standard to measure arterial health is vasodilation in response to nitric oxide. Vasodilation is generally measured via pressure myography of arteries isolated from animal models. However, animal arteries can be difficult to obtain and may have limited relevance to human physiology. It is, therefore, critical to engineer human cell-based arterial models capable of contraction. Vascular smooth muscle cells (SMCs) must be circumferentially aligned around the vessel lumen to contract the vessel, which is challenging to achieve in a soft blood vessel model. In this study, we used gelatin microribbons to circumferentially align SMCs inside a hydrogel channel. To accomplish this, we created tunable gelatin microribbons of varying stiffnesses and thicknesses and assessed how SMCs aligned along them. We then wrapped soft, thick microribbons around a needle and encapsulated them in a gelatin methacryloyl hydrogel, forming a microribbon-lined channel. Finally, we seeded SMCs inside the channel and showed that they adhered best to fibronectin and circumferentially aligned in response to the microribbons. Together, these data show that tunable gelatin microribbons can be used to circumferentially align SMCs inside a channel. This technique can be used to create a human artery-on-a-chip to assess vasodilation via pressure myography, as well as to align other cell types for 3Din vitromodels.

Preparing gelatin-containing polycaprolactone / polylactic acid nanofibrous membranes for periodontal tissue regeneration using side-by-side electrospinning technology

Electrospinning technology has recently attracted increased attention in the biomedical field, and preparing various cellulose nanofibril membranes for periodontal tissue regeneration has unique advantages. However, the characteristics of using a single material tend to make it challenging to satisfy the requirements for a periodontal barrier film, and the production of composite fibrous membranes frequently impacts the quality of the final fiber membrane due to the influence of miscibility between different materials. In this study, nanofibrous membranes composed of polylactic acid (PLA) and polycaprolactone (PCL) fibers were fabricated using side-by-side electrospinning. Different concentrations of gelatin were added to the fiber membranes to improve their hydrophilic properties. The morphological structure of the different films as well as their composition, wettability and mechanical characteristics were examined. The results show that PCL/PLA dual-fibrous composite membranes with an appropriate amount of gelatin ensures sufficient mechanical strength while obtaining improved hydrophilic properties. The viability of L929 fibroblasts was evaluated using CCK-8 assays, and cell adhesion on the scaffolds was confirmed by scanning electron microscopy and by immunofluorescence assays. The results demonstrated that none of the fibrous membranes were toxic to cells and the addition of gelatin improved cell adhesion to those membranes. Based on our findings, adding 30% gelatin to the membrane may be the most appropriate content for periodontal tissue regeneration, considering the scaffold's mechanical qualities, hydrophilic properties and biocompatibility. In addition, the PCL-gelatin/PLA-gelatin dual-fibrous membranes prepared using side-by-side electrospinning technology have potential applications for tissue engineering.

Pro-vasculogenic Fibers by PDA-Mediated Surface Functionalization Using Cell-Free Fat Extract (CEFFE)

Formation of adequate vascular network within engineered three-dimensional (3D) tissue substitutes postimplantation remains a major challenge for the success of biomaterials-based tissue regeneration. To better mimic the in vivo angiogenic and vasculogenic processes, nowadays increasing attention is given to the strategy of functionalizing biomaterial scaffolds with multiple bioactive agents. Aimed at engineering electrospun biomimicking fibers with pro-vasculogenic capability, this study was proposed to functionalize electrospun fibers of polycaprolactone/gelatin (PCL/GT) by cell-free fat extract (CEFFE or FE), a newly emerging natural "cocktail" of cytokines and growth factors extracted from human adipose tissue. This was achieved by having the electrospun PCL/GT fiber surface coated with polydopamine (PDA) followed by PDA-mediated immobilization of FE to generate the pro-vasculogenic fibers of FE-PDA@PCL/GT. It was found that the PDA-coated fibrous mat of PCL/GT exhibited a high FE-loading efficiency (∼90%) and enabled the FE to be released in a highly sustained manner. The engineered FE-PDA@PCL/GT fibers possess improved cytocompatibility, as evidenced by the enhanced cellular proliferation, migration, and RNA and protein expressions (e.g., CD31, vWF, VE-cadherin) in the human umbilical vein endothelial cells (huvECs) used. Most importantly, the FE-PDA@PCL/GT fibrous scaffolds were found to enormously stimulate tube formation in vitro, microvascular development in the in ovo chick chorioallantoic membrane (CAM) assay, and vascularization of 3D construct in a rat subcutaneous embedding model. This study highlights the potential of currently engineered pro-vasculogenic fibers as a versatile platform for engineering vascularized biomaterial constructs for functional tissue regeneration.

A multifunctional quercetin/polycaprolactone electrospun fibrous membrane for periodontal bone regeneration

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High-Performance Liquid-Repellent and Thermal-Wet Comfortable Membranes Using Triboelectric Nanostructured Nanofiber/Meshes

Skin-like functional membranes with liquid resistance and moisture permeability are in growing demand in various applications. However, the membranes have been facing a long-term dilemma in balancing waterproofness and breathability, as well as resisting internal liquid sweat transport, resulting in poor thermal-wet comfort. Herein, a novel electromeshing technique, based on manipulating the ejection and phase separation of charged liquids, is developed to create triboelectric nanostructured nano-mesh consisting of hydrophobic ferroelectric nanofiber/meshes and hydrophilic nanofiber/meshes. By combining the true nanoscale diameter (≈22 nm), small pore size, and high porosity, high waterproofness (129 kPa) and breathability (3736 g m-2 per day) for the membranes are achieved. Moreover, the membranes can break large water clusters into small water molecules to promote sweat absorption and release by coupling hydrophilic wicking and triboelectric field polarization, exhibiting a satisfactory water evaporation rate (0.64 g h-1 ) and thermal-wet comfort (0.7 °C cooler than the cutting-edge poly(tetrafluoroethylene) protective membranes). This work may shed new light on the design and development of advanced protective textiles.

Engineered muscle from micro-channeled PEG scaffold with magnetic Fe3O4 fixation towards accelerating esophageal muscle repair

Engineered scaffolds are used for repairing damaged esophagus to allow the precise alignment and movement of smooth muscle for peristalsis. However, most of these scaffolds focus solely on inducing cell alignment through directional apparatus, often overlooking the promotion of muscle tissue formation and causing reduced esophageal muscle repair effectiveness. To address this issue, we first introduced aligned nano-ferroferric oxide (Fe3O4) assemblies on a micropatterned poly(ethylene glycol) (PEG) hydrogel to form micro-/nano-stripes. Further modification using a gold coating was found to enhance cellular adhesion, orientation and organization within these micro-/nano-stripes, which consequently prevented excessive adhesion of smooth muscle cells (SMCs) to the thin PEG ridges, thereby effectively confining the cells to the Fe3O4-laid channels. This architectural design promotes the alignment of the cytoskeleton and elongation of actin filaments, leading to the organized formation of muscle bundles and a tendency for SMCs to adopt synthetic phenotypes. Muscle patches are harvested from the micro-/nano-stripes and transplanted into a rat esophageal defect model. In vivo experiments demonstrate the exceptional viability of these muscle patches and their ability to accelerate the regeneration of esophageal tissue. Overall, this study presents an efficient strategy for constructing muscle patches with directional alignment and muscle bundle formation of SMCs, holding significant promise for muscle tissue regeneration.

High-Performance Waterproof, Breathable, and Radiative Cooling Membranes Based on Nanoarchitectured Fiber/Meshworks

Smart membranes with protection and thermal-wet comfort are highly demanded in various fields. Nevertheless, the existing membranes suffer from a tradeoff dilemma of liquid resistance and moisture permeability, as well as poor thermoregulating ability. Herein, a novel strategy, based on the synchronous occurrence of humidity-induced electrospinning and electromeshing, is developed to synthesize a dual-network structured nanofiber/mesh for personal comfort management. Manipulating the ejection, deformation, and phase separation of spinning jets and charged droplets enables the creation of nanofibrous membranes composed of radiative cooling nanofibers and 2D nanostructured meshworks. With a combination of a true-nanoscale fiber (∼70 nm) in 2D meshworks, a small pore size (0.84 μm), and a superhydrophobic surface (151.9°), the smart membranes present high liquid repellency (95.6 kPa), improved breathability (4.05 kg m-2 d-1), and remarkable cooling performance (7.9 °C cooler than commercial cotton fabrics). This strategy opens up a pathway to the design of advanced smart textiles for personal protection.

A bio-inspired nanoparticle coating for vascular healing and immunomodulatory by cGMP-PKG and NF-kappa B signaling pathways

Drug-eluting stents (DESs) implantation is an effective method to tackle in-stent restenosis (ISR), which has been considered as an efficient treatment for coronary atherosclerosis. Although fruitful results have been achieved in treating coronary artery diseases (CAD), concern has arisen regarding the long-term safety and efficacy of DESs, primarily due to adverse events such as delayed re-endothelialization, persistent inflammatory response, and late stent thrombosis (LST). Taking inspiration from the immunomodulatory functions of camouflage strategies, this study designed a bio-inspired nanoparticle-coated stent. Briefly, the platelet membrane-coated poly (lactic-co-glycolic acid)/Rapamycin nanoparticles (PNP) were sprayed onto stents, forming a homogenous nanoparticle coating. The bilayer of poly (lactic-co-glycolic acid) (PLGA) and platelet membrane works synergistically to promote the sustained-release effect of rapamycin. In vitro studies revealed that the PNP-coated surfaces promoted the competitive adhesion of endothelia cells while inhibiting smooth muscle cells. Subsequent in vivo studies demonstrated that these surfaces expedite re-endothelialization and elicit immunomodulatory effects by regulating the cGMP-PKG and NF-kappa B signaling pathways, influencing the biosynthesis cofactors and immune system signaling. The study successfully deviced a novel and biomimetic drug-eluting stent system, unraveling its detailed functions and molecular mechanism of action for enhanced vascular healing.

Modulation of Smooth Muscle Cell Phenotype for Translation of Tissue-Engineered Vascular Grafts

Translation of small-diameter tissue-engineered vascular grafts (TEVGs) for the treatment of coronary artery disease (CAD) remains an unfulfilled promise. This is largely due to the limited integration of TEVGs into the native vascular wall-a process hampered by the insufficient smooth muscle cell (SMC) infiltration and extracellular matrix deposition, and low vasoactivity. These processes can be promoted through the judicious modulation of the SMC toward a synthetic phenotype to promote remodeling and vascular integration; however, the expression of synthetic markers is often accompanied by a decrease in the expression of contractile proteins. Therefore, techniques that can precisely modulate the SMC phenotypical behavior could have the potential to advance the translation of TEVGs. In this review, we describe the phenotypic diversity of SMCs and the different environmental cues that allow the modulation of SMC gene expression. Furthermore, we describe the emerging biomaterial approaches to modulate the SMC phenotype in TEVG design and discuss the limitations of current techniques. In addition, we found that current studies in tissue engineering limit the analysis of the SMC phenotype to a few markers, which are often the characteristic of early differentiation only. This limited scope has reduced the potential of tissue engineering to modulate the SMC toward specific behaviors and applications. Therefore, we recommend using the techniques presented in this review, in addition to modern single-cell proteomics analysis techniques to comprehensively characterize the phenotypic modulation of SMCs. Expanding the holistic potential of SMC modulation presents a great opportunity to advance the translation of living conduits for CAD therapeutics.

Biodegradable, Self-Reinforcing Vascular Grafts for In Situ Tissue Engineering Approaches

Clinically available small-diameter synthetic vascular grafts (SDVGs) have unsatisfactory patency rates due to impaired graft healing. Therefore, autologous implants are still the gold standard for small vessel replacement. Bioresorbable SDVGs may be an alternative, but many polymers have inadequate biomechanical properties that lead to graft failure. To overcome these limitations, a new biodegradable SDVG is developed to ensure safe use until adequate new tissue is formed. SDVGs are electrospun using a polymer blend composed of thermoplastic polyurethane (TPU) and a new self-reinforcing TP(U-urea) (TPUU). Biocompatibility is tested in vitro by cell seeding and hemocompatibility tests. In vivo performance is evaluated in rats over a period for up to six months. Autologous rat aortic implants serve as a control group. Scanning electron microscopy, micro-computed tomography (µCT), histology, and gene expression analyses are applied. TPU/TPUU grafts show significant improvement of biomechanical properties after water incubation and exhibit excellent cyto- and hemocompatibility. All grafts remain patent, and biomechanical properties are sufficient despite wall thinning. No inflammation, aneurysms, intimal hyperplasia, or thrombus formation are observed. Evaluation of graft healing shows similar gene expression profiles of TPU/TPUU and autologous conduits. These new biodegradable, self-reinforcing SDVGs may be promising candidates for clinical use in the future.

Nanofiber-based Stretchable Electrodes for Oriented Culture and Mechanotransduction Monitoring of Smooth Muscle Cells

Vascular smooth muscle cells (SMCs) are circumferentially oriented perpendicular to the blood vessel and maintain the contractile phenotype in physiological conditions. They can sense the mechanical forces of blood vessels expanding and contracting and convert them into biochemical signals to regulate vascular homeostasis. However, the real-time monitoring of mechanically evoked biochemical response while maintaining SMC oriented growth remains an important challenge. Herein, we developed a stretchable electrochemical sensor by electrospinning aligned and elastic polyurethane (PU) nanofibers on the surface of PDMS film and further modification of conductive polymer PEDOT:PSS-LiTFSI-CoPc (PPLC) on the nanofibers (denoted as PPLC/PU/PDMS). The aligned nanofibers on the electrode surface could guide the oriented growth of SMCs and maintain the contractile phenotype, and the modification of PPLC endowed the electrode with good electrochemical sensing performance and stability under mechanical deformation. By culturing cells on the electrode surface, the oriented growth of SMCs and real-time monitoring of stretch-induced H2O2 release were achieved. On this basis, the changes of H2O2 level released by SMCs under the pathology (hypertension) and intervention of natural product resveratrol were quantitatively monitored, which will be helpful to further understand the occurrence and development of vascular-related diseases and the mechanisms of pharmaceutical intervention.

Vascular cells responses to controlled surface structure and properties of bacterial nanocellulose artificial blood vessel after mercerization

Therapeutic benefits of small caliber artificial blood vessels to cure cardio and cerebrovascular diseases are mainly limited by their low patency during long-term transplantation. Bacterial nanocellulose (BNC), as a natural polysaccharide mainly synthesized by a bacterium Komagataeibatacter xylinus, has shown great potential in small-caliber vascular graft applications due to its shape controllability, and furthermore its physical surface structure can be adjusted with different treatments. However, influences of physical surface structure and properties of BNC conduits on behaviors of vascular cells have not been investigated. In this work, mercerized BNC conduits (MBNC) with different surface roughness and stiffness were constructed by controlled alkali (NaOH) treatment. The changes of surface structures and properties significantly affected the behaviors of vascular cells and gene expression; meanwhile, the cell seeding density also affected the cell responses. After mercerization with NaOH concentration > 10 %, it was observed that the increased stiffness of MBNC decreased several functional gene expressions of human vascular endothelial cells, and the pathological transformation of smooth muscle cells was inhibited. This study demonstrates physical surface structure of MBNC conduits will critically regulate functions and behaviors of vascular cells and it also provides important designing parameters to improve the long-term patency of BNC-based conduits.

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.

Fabrication of Silk Hydrogel Scaffolds with Aligned Porous Structures and Tunable Mechanical Properties

The effectiveness of cell culture and tissue regeneration largely depends on the structural and physiochemical characteristics of tissue-engineering scaffolds. Hydrogels are frequently employed in tissue engineering because of their high-water content and strong biocompatibility, making them the ideal scaffold materials for simulating tissue structures and properties. However, hydrogels created using traditional methods have low mechanical strength and a non-porous structure, which severely restrict their application. Herein, we successfully developed silk fibroin glycidyl methacrylate (SF-GMA) hydrogels with oriented porous structures and substantial toughness through directional freezing (DF) and in situ photo-crosslinking (DF-SF-GMA). The oriented porous structures in the DF-SF-GMA hydrogels were induced by directional ice templates and maintained after photo-crosslinking. The mechanical properties, particularly the toughness, of these scaffolds were enhanced compared to the traditional bulk hydrogels. Interestingly, the DF-SF-GMA hydrogels exhibit fast stress relaxation and variable viscoelasticity. The remarkable biocompatibility of the DF-SF-GMA hydrogels was further demonstrated in cell culture. Accordingly, this work reports a method to prepare tough SF hydrogels with aligned porous structures, which can be extensively applied to cell culture and tissue engineering.

Scalable Fabrication of Electrospun True-Nanoscale Fiber Membranes for Effective Selective Separation

Electrospun fibers have received wide attention in various fields ranging from the environment and healthcare to energy. However, nearly all electrospun fibers suffer from a pseudonanoscale diameter, resulting in fabricated membranes with a large pore size and limited separation performance. Herein, we report a novel strategy based on manipulating the equilibrium of stretch deformation and phase separation of electrospun jets to develop true-nanoscale fibers for effective selective separation. The obtained fibers present true-nanoscale diameters (∼67 nm), 1 order of magnitude less than those of common electrospun fibers, which endows the resultant membranes with remarkable nanostructural characteristics and separation performances in areas of protective textiles (waterproofness of 113 kPa and breathability of 4.1 kg m^-2 d^-1), air filtration (efficiency of 99.3% and pressure drop of 127.4 Pa), and water purification (flux of 81.5 kg m^-2 h^-1 and salt rejection of 99.94%). This work may shed light on developing high-performance separation materials for various applications.

Esophageal wound healing by aligned smooth muscle cell-laden nanofibrous patch

The esophagus exhibits peristalsis via contraction of circularly and longitudinally aligned smooth muscles, and esophageal replacement is required if there is a critical-sized wound. In this study, we proposed to reconstruct esophageal tissues using cell electrospinning (CE), an advanced technique for encapsulating living cells into fibers that allows control of the direction of fiber deposition. After treatment with transforming growth factor-β, mesenchymal stem cell-derived smooth muscle cells (SMCs) were utilized for cell electrospinning or three-dimensional bioprinting to compare the effects of aligned micropatterns on cell morphology. CE resulted in SMCs with uniaxially arranged and elongated cell morphology with upregulated expression levels of SMC-specific markers, including connexin 43, smooth muscle protein 22 alpha (SM22α), desmin, and smoothelin. When SMC-laden nanofibrous patches were transplanted into a rat esophageal defect model, the SMC patch promoted regeneration of esophageal wounds with an increased number of newly formed blood vessels and enhanced the SMC-specific markers of SM22α and vimentin. Taken together, CE with its advantages, such as guidance of highly elongated, aligned cell morphology and accelerated SMC differentiation, can be an efficient strategy to reconstruct smooth muscle tissues and treat esophageal perforation.

Random and aligned electrostatically spun PLLA nanofibrous membranes enhance bone repair in mouse femur midshaft defects

Long-segment bone defects are a common clinical challenge and abstract biomaterials are a promising therapy. Poly-L-lactic acid (PLLA) nanofibrous membranes prepared by electrostatic spinning have a good bone repair potential. However, there are random and aligned surface morphologies of electrostatic spun PLLA nanofibrous membranes, which can affect the migration, proliferation, and differentiation ability of cells. The role of surface morphology in the repair of long bone defects in vivo is currently unknown. In this study, random and aligned electrostatically spun PLLA nanofibrous membranes were prepared, characterised, and implanted into a femur midshaft defect mouse model. The ability of electrostatically spun PLLA nanofibrous membranes to enhance bone repair was tested using X-ray photography, high-resolution micro-computed tomography (micro-CT), and pathological section specimens. The results showed that both random and aligned electrostatically spun PLLA nanofibrous membranes enhanced bone regeneration at bone defects, but the aligned ones exhibited superior results. These results provide a theoretical basis for engineering the surface morphology of bone repair materials.

Scalable fabrication, compartmentalization and applications of living microtissues

Living microtissues are used in a multitude of applications as they more closely resemble native tissue physiology, as compared to 2D cultures. Microtissues are typically composed of a combination of cells and materials in varying combinations, which are dictated by the applications' design requirements. Their applications range wide, from fundamental biological research such as differentiation studies to industrial applications such as cruelty-free meat production. However, their translation to industrial and clinical settings has been hindered due to the lack of scalability of microtissue production techniques. Continuous microfluidic processes provide an opportunity to overcome this limitation as they offer higher throughput production rates as compared to traditional batch techniques, while maintaining reproducible control over microtissue composition and size. In this review, we provide a comprehensive overview of the current approaches to engineer microtissues with a focus on the advantages of, and need for, the use of continuous processes to produce microtissues in large quantities. Finally, an outlook is provided that outlines the required developments to enable large-scale microtissue fabrication using continuous processes.

Tailoring micro/nano-fibers for biomedical applications

Nano/micro fibers have evoked much attention of scientists and have been researched as cutting edge and hotspot in the area of fiber science in recent years due to the rapid development of various advanced manufacturing technologies, and the appearance of fascinating and special functions and properties, such as the enhanced mechanical strength, high surface area to volume ratio and special functionalities shown in the surface, triggered by the nano or micro-scale dimensions. In addition, these outstanding and special characteristics of the nano/micro fibers impart fiber-based materials with wide applications, such as environmental engineering, electronic and biomedical fields. This review mainly focuses on the recent development in the various nano/micro fibers fabrication strategies and corresponding applications in the biomedical fields, including tissue engineering scaffolds, drug delivery, wound healing, and biosensors. Moreover, the challenges for the fabrications and applications and future perspectives are presented.

3D Polycaprolactone/Gelatin-Oriented Electrospun Scaffolds Promote Periodontal Regeneration

Periodontitis is a worldwide chronic inflammatory disease, where surgical treatment still shows an uncertain prognosis. To break through the dilemma of periodontal treatment, we fabricated a three-dimensional (3D) multilayered scaffold by stacking and fixing electrospun polycaprolactone/gelatin (PCL/Gel) fibrous membranes. The biomaterial displayed good hydrophilic and mechanical properties. Besides, we found human periodontal ligament stem cell (hPDLSC) adhesion and proliferation on it. The following scanning electron microscopy (SEM) and cytoskeleton staining results proved the guiding function of fibers to hPDLSCs. Then, we further analyzed periodontal regeneration-related proteins and mRNA expression between groups. In vivo results in a rat acute periodontal defect model confirmed that the topographic cues of materials could directly guide cellular orientation and might provide the prerequisite for further differentiation. In the aligned scaffold group, besides new bone regeneration, we also observed that angular concentrated fiber regeneration in the root surface of the defect is similar to the normal periodontal tissue. To sum up, we have constructed electrospun membrane-based 3D biological scaffolds, which provided a new treatment strategy for patients undergoing periodontal surgery.

An overview of substrate stiffness guided cellular response and its applications in tissue regeneration

Cell-matrix interactions play a critical role in tissue repair and regeneration. With gradual uncovering of substrate mechanical characteristics that can affect cell-matrix interactions, much progress has been made to unravel substrate stiffness-mediated cellular response as well as its underlying mechanisms. Yet, as a part of cell-matrix interaction biology, this field remains in its infancy, and the detailed molecular mechanisms are still elusive regarding scaffold-modulated tissue regeneration. This review provides an overview of recent progress in the area of the substrate stiffness-mediated cellular responses, including 1) the physical determination of substrate stiffness on cell fate and tissue development; 2) the current exploited approaches to manipulate the stiffness of scaffolds; 3) the progress of recent researches to reveal the role of substrate stiffness in cellular responses in some representative tissue-engineered regeneration varying from stiff tissue to soft tissue. This article aims to provide an up-to-date overview of cell mechanobiology research in substrate stiffness mediated cellular response and tissue regeneration with insightful information to facilitate interdisciplinary knowledge transfer and enable the establishment of prognostic markers for the design of suitable biomaterials.

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Substrate stiffness physically determines cell fate and tissue development.

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Rational design of scaffolds requires the understanding of cell-matrix interactions.

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Substrate stiffness depends on scaffold molecular-constituent-structure interaction.

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Substrate stiffness-mediated cellular responses vary in different tissues.

Essential Oil—Loaded Nanofibers for Pharmaceutical and Biomedical Applications: A Systematic Mini-Review

Essential oils (EOs) have been widely exploited for their biological properties (mainly as antimicrobials) in the food industry. Encapsulation of EOs has opened the way to the utilization of EOs in the pharmaceutical and biomedical fields. Electrospinning (ES) has proved a convenient and versatile method for the encapsulation of EOs into multifunctional nanofibers. Within the last five years (2017–2022), many research articles have been published reporting the use of ES for the fabrication of essential oil—loaded nanofibers (EONFs). The objective of the present mini-review article is to elucidate the potential of EONFs in the pharmaceutical and biomedical fields and to highlight their advantages over traditional polymeric films. An overview of the conventional ES and coaxial ES technologies for the preparation of EONFs is also included. Even though EONFs are promising systems for the delivery of EOs, gaps in the literature can be recognized (e.g., stability studies) emphasizing that more research work is needed in this field to fully unravel the potential of EONFs.

Fabrication of a mimetic vascular graft using melt spinning with tailorable fiber parameters

Smooth muscle cells play a pivotal role in maintaining blood pressure and remodeling of the extracellular matrix. These cells have a characteristic spindle shape and are aligned in the radial direction to aid in the constriction of any artery. Tissue engineered grafts have the potential to recreate this alignment and offer a viable alternative to non-resorbable or autologous grafts. Specifically, with melt spinning small diameter fibers can be created that can align circumferentially on the scaffolds. In this study, a set of simplified equations were formulated to predict the final fiber parameters. Smooth muscle cell alignment was monitored on the fabricated scaffolds. Finally, a co-culture of smooth muscle cells in direct contact with endothelial cells was performed to assess the influence of the smooth muscle cell alignment on the morphology of the endothelial cells. The results show that the equations were able to accurately predict the fiber diameter, distance and angle. Primary vascular smooth muscle cells aligned according to the fiber direction mimicking the native orientation. The co-culture with endothelial cells showed that the aligned smooth muscle cells did not have an influence on the morphology of the endothelial cells. In conclusion, we formulated a series of equations that can predict the fiber parameters during melt spinning. Furthermore, the method described here can create a vascular graft with smooth muscle cells aligned circumferentially that morphologically mimics the native orientation.

Biomimetic Asymmetric Composite Dressing by Electrospinning with Aligned Nanofibrous and Micropatterned Structures for Severe Burn Wound Healing

The surface structure and topography of biomaterials play a crucial role in directing cell behaviors and fates. Meanwhile, asymmetric dressings that mimic the natural skin structure have been identified as an effective strategy for enhancing wound healing. Inspired by the skin structure and the superhydrophobic structure of the lotus leaf, an asymmetric composite dressing was obtained by constructing an asymmetric structure and wettability surface modification on both sides of the sponge based on electrospinning. Among them, the collagen and quaternized chitosan sponge was fabricated by freeze-drying, followed by an aligned poly(ε-caprolactone) (PCL)/gelatin nanofiber hydrophilic inner layer and hierarchical micronanostructure PCL/polystyrene microsphere highly hydrophobic outer layer constructed on each side of the sponge. The proposed asymmetric composite dressing combines topological morphology with the material's properties to effectively prevent bacterial colonization/infection and promote wound healing by directing cellular behavior. In vitro experimental results confirmed that the aligned nanofiber inner layer effectively promotes cell adhesion, proliferation, directed cell growth, and migration. Meanwhile, the sponge has good water absorption and antibacterial properties, while the biomimetic hydrophobic outer layer exhibits strong mechanical properties and resistance to bacterial adhesion. In vivo results showed that the composite dressing can reduce inflammatory response, prevent infection, accelerate angiogenesis and epithelial regeneration, and significantly accelerate the healing of severe burns. Thus, the proposed bionic asymmetric dressing is expected to be a promising candidate for severe burn wound healing.

Acute Elution of TGFβ2 Affects the Smooth Muscle Cells in a Compliance-Matched Vascular Graft

Transforming growth factor beta 2 (TGFβ2) is a pleiotropic growth factor that plays a vital role in smooth muscle cell (SMC) function. Our prior in vitro work has shown that SMC response can be modulated with TGFβ2 stimulation in a dose dependent manner. In particular, we have shown that increasing concentrations of TGFβ2 shift SMCs from a migratory to a synthetic behavior. In this work, electrospun compliance-matched and hypocompliant TGFβ2-eluting tissue engineered vascular grafts (TEVGs) were implanted into Sprague Dawley rats for 5 days to observe SMC population and collagen production. TEVGs were fabricated using a combined computational and experimental approach that varied the ratio of gelatin:polycaprolactone to be either compliance matched or twice as stiff as rat aorta (hypocompliant). TGFβ2 concentrations of 0, 10, 100 ng/mg were added to both graft types (n = 3 in each group) and imaged in vivo using ultrasound. Histological markers (SMC, macrophage, collagen, and elastin) were evaluated following explanation at 5 days. In vivo ultrasound showed that compliance-matched TEVGs became stiffer as TGFβ2 increased (100 ng/mg TEVGs compared to rat aorta, p < 0.01), while all hypocompliant grafts remained stiffer than control rat aorta. In vivo velocity and diameter were also not significantly different than control vessels. The compliance-matched 10 ng/mg group had an elevated SMC signal (myosin heavy chain) compared to the 0 and 100 ng/mg grafts (p = 0.0009 and 0.0006). Compliance-matched TEVGs containing 100 ng/mg TGFβ2 had an increase in collagen production (p < 0.01), general immune response (p < 0.05), and a decrease in SMC population to the 0 and 10 ng/mg groups. All hypocompliant groups were found to be similar, suggesting a lower rate of TGFβ2 release in these TEVGs. Our results suggest that TGFβ2 can modulate in vivo SMC phenotype over an acute implantation period, which is consistent with our prior in vitro work. To the author's knowledge, this is the first in vivo rat study that evaluates a TGFβ2-eluting TEVG. Impact statement TGFβ2 affects the SMCs in a vascular graft.

Step-wise CAG@PLys@PDA-Cu2+ modification on micropatterned nanofibers for programmed endothelial healing

Native-like endothelium regeneration is a prerequisite for material-guided small-diameter vascular regeneration. In this study, a novel strategy is proposed to achieve phase-adjusted endothelial healing by step-wise modification of parallel-microgroove-patterned (i.e., micropatterned) nanofibers with polydopamine-copper ion (PDA-Cu²⁺) complexes, polylysine (PLys) molecules, and Cys-Ala-Gly (CAG) peptides (CAG@PLys@PDA-Cu²⁺). Using electrospun poly(l-lactide-co-caprolactone) random nanofibers as the demonstrating biomaterial, step-wise modification of CAG@PLys@PDA-Cu²⁺ significantly enhanced substrate wettability and protein adsorption, exhibited an excellent antithrombotic surface and outstanding phase-adjusted capacity of endothelium regeneration involving cell adhesion, endothelial monolayer formation, and the regenerated endothelium maturation. Upon in vivo implantation for segmental replacement of rabbit carotid arteries, CAG@PLys@PDA-Cu²⁺ modified grafts (2 mm inner diameter) with micropatterns on inner surface effectively accelerated native-like endothelium regeneration within 1 week, with less platelet aggregates and inflammatory response compared to those on non-modified grafts. Prolonged observations at 6- and 12-weeks post-implantation demonstrated a positive vascular remodeling with almost fully covered endothelium and mature smooth muscle layer in the modified vascular grafts, accompanied with well-organized extracellular matrix. By contrast, non-modified vascular grafts induced a disorganized tissue formation with a high risk of thrombogenesis. In summary, step-wise modification of CAG@PLys@PDA-Cu²⁺ on micropatterned nanofibers can significantly promote endothelial healing without inflicting thrombosis, thus confirming a novel strategy for developing functional vascular grafts or other blood-contacting materials/devices.

The substrate stiffness at physiological range significantly modulates vascular cell behavior

Changes in the stiffness of the cellular microenvironment are involved in many pathological processes of blood vessels. Substrate stiffness has been shown to have extensive effects on vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs). However, the material stiffness of most previously reported in-vitro models is ranging from ~100 kPa to the magnitude of MPa, which does not match the mechanical properties of natural vascular tissue (10-100 kPa). Herein, we constructed hydrogel substrates with the stiffness of 18-86 kPa to explore the effect of physiological stiffness on vascular cells. Our findings show that, with the increase of stiffness at the physiological range, the cell adhesion and proliferation behaviors of VECs and VSMCs are significantly enhanced. On the soft substrate, VECs express more nitric oxide (NO), and VSMCs tend to maintain a healthy contraction phenotype. More importantly, we find that the number of differentially expressed genes in cells cultured between 18 kPa and 86 kPa substrates (560 in VECs, 243 in VSMCs) is significantly higher than that between 86 kPa and 333 kPa (137 in VECs, 172 in VSMCs), indicating that a small increase in stiffness within the physiological range have a higher impact on vascular cell behaviors. Overall, our results expanded the exploration of how stiffness affects the behavior of vascular cells at the physiological range.

Engineering a Mechanoactive Fibrous Substrate with Enhanced Efficiency in Regulating Stem Cell Tenodifferentiation

Electrospun-aligned fibers in ultrathin fineness have previously demonstrated a limited capacity in driving stem cells to differentiate into tendon-like cells. In view of the tendon's mechanoactive nature, endowing such aligned fibrous structure with mechanoactivity to exert in situ mechanical stimulus by itself, namely, without any forces externally applied, is likely to potentiate its efficiency of tenogenic induction. To test this hypothesis, in this study, a shape-memory-capable poly(l-lactide-co-caprolactone) (PLCL) copolymer was electrospun into aligned fibrous form followed by a "stretching-recovery" shape-programming procedure to impart shape memory capability. Thereafter, in the absence of tenogenic supplements, human adipose-derived stem cells (ADSCs) were cultured on the programmed fibrous substrates for a duration of 7 days, and the effects of constrained recovery resultant stress-stiffening on cell morphology, proliferation, and tenogenic differentiation were examined. The results indicate that the in situ enacted mechanical stimulus due to shape memory effect (SME) did not have adverse influence on cell viability and proliferation, but significantly promoted cellular elongation along the direction of fiber alignment. Moreover, it revealed that tendon-specific protein markers such as tenomodulin (TNMD) and tenascin-C (TNC) and gene expression of scleraxis (SCX), TNMD, TNC, and collagen I (COL I) were significantly upregulated on the mechanoactive fibrous substrate with higher recovery stress compared to the counterparts. Mechanistically, the Rho/ROCK signaling pathway was identified to be involved in the substrate self-actuation-induced enhancement in tenodifferentiation. Together, these results suggest that constrained shape recovery stress may be employed as an innovative loading modality to regulate the stem cell tenodifferentiation by presenting the fibrous substrate with an aligned tendon-like topographical cue and an additional mechanoactivity. This newly demonstrated paradigm in modulating stem cell tenodifferentiation may improve the efficacy of tendon tissue engineering strategy for tendon healing and regeneration.

Scaffold Engineering with Flavone-Modified Biomimetic Architecture for Vascular Tissue Engineering Applications

BACKGROUND

Vascular intimal hyperplasia (IH) is one of the key challenges in the clinical application of small-diameter vascular grafts. Current tissue engineering strategies focus on vascularization and antithrombotics, yet few approaches have been developed to treat IH. Here, we designed a tissue-engineered vascular scaffold with portulaca flavonoid (PTF) composition and biomimetic architecture.

METHOD

By electrospinning, PTF is integrated with biodegradable poly(ε-caprolactone) (PCL) into a bionic vascular scaffold. The structure and functions of the scaffolds were evaluated based on material characterization and cellular biocompatibility. Human vascular smooth muscle cells (HVSMCs) were cultured on scaffolds for up to 14 days.

RESULTS

The incorporation of PTF and preparation parameters during fabrication influences the morphology of the scaffold, including fibre diameter, structure, and orientation. Compared to the PCL scaffold, the scaffolds integrated with bioactive PTF show better hydrophilicity and degradability. HVSMCs seeded on the scaffold alongside the fibres exhibit fusiform-like shapes, indicating that the scaffold can provide contact guidance for cell morphology alterations. This study demonstrates that the PCL/PTF (9.1%) scaffold inhibits the excessive proliferation of HVSMCs without causing cytotoxicity.

CONCLUSION

The study provides insights into the problem of restenosis caused by IH. This engineered vascular scaffold with complex function and preparation is expected to be applied as a substitute for small-diameter vascular grafts.

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

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

Cryogenic Coaxial Printing for 3D Shell/Core Tissue Engineering Scaffold with Polymeric Shell and Drug-Loaded Core

For decades, coaxial printing has been widely applied in 3D tissue engineering scaffold fabrication. However, there are few reports regarding polymeric materials application in shell production due to fabrication constraints. In this study, a combination of cryogenic printing and coaxial printing aims to approach the challenge. Polycaprolactone (PCL) and sodium alginate (SA) were selected as the representative shell and core materials to test the feasibility of the coaxial cryogenic printing by optimizing key parameters, including working temperature, air pressure, PCL, and SA concentration. According to the optical and SEM images, the SA core contracts a string inside the PCL shell, illustrating the shell/core structure of the 3D coaxial PCL/SA scaffolds. Besides, the shell/core 3D scaffold possesses a 38.39 MPa Young’s modulus in mechanical tests; the PCL shell could retain at least 8 h in 5 mol/L HCl solution, leading to a fabricated drug-loaded PCL/SA shell/core “responsive” to acidic pH. In summary, coaxial cryogenic printing was developed to fabricate 3D scaffolds with a PCL/SA shell/core scaffold, broadening the material range of coaxial printing and providing promising applications in drug release.

Gelatin Blends Enhance Performance of Electrospun Polymeric Scaffolds in Comparison to Coating Protocols

The electrospinning of hybrid polymers is a versatile fabrication technique which takes advantage of the biological properties of natural polymers and the mechanical properties of synthetic polymers. However, the literature is scarce when it comes to comparisons of blends regarding coatings and the improvements offered thereby in terms of cellular performance. To address this, in the present study, nanofibrous electrospun scaffolds of polycaprolactone (PCL), their coating and their blend with gelatin were compared. The morphology of nanofibrous scaffolds was analyzed under field emission scanning electron microscopy (FE-SEM), indicating the influence of the presence of gelatin. The scaffolds were mechanically tested with tensile tests; PCL and PCL gelatin coated scaffolds showed higher elastic moduli than PCL/gelatin meshes. Viability of mouse embryonic fibroblasts (MEF) was evaluated by MTT assay, and cell proliferation on the scaffold was confirmed by fluorescence staining. The positive results of the MTT assay and cell growth indicated that the scaffolds of PCL/gelatin excelled in comparison to other scaffolds, and may serve as good candidates for tissue engineering applications.

Comparative Study of Traditional Single-Needle Electrospinning and Novel Spiral-Vane Electrospinning: Influence on the Properties of Poly(caprolactone)/Gelatin Nanofiber Membranes

Spiral-vane electrospinning (SVE), a novel needleless electrospinning, was proven effective in obtaining high-throughput production of nanofibers. However, the properties of the electrospun nanofibers produced by SVE remain relatively underexplored, especially in comparison with those made by traditional single-needle electrospinning (SNE). Hence, for the comparative study of SNE and SVE in this study, the difference in the preparation mechanism was first analyzed using numerical simulation, followed by the experimental analysis of the effects of spinneret types on the quality and biocompatibility of electrospun poly(caprolactone)/gelatin (PCL/Gel) nanofibers. The values predicted by the electric field results were consistent with the experimental data, showing that the PCL/Gel nanofibers prepared by SVE have higher yields than SNE. Although the different spinnerets (i.e., needle and spiral vane) had little effect on the surface chemistry, thermal stability, and composition of the PCL/Gel nanofibers, they had great effects on the fiber diameter distribution and mechanical properties in which SVE-electrospun nanofibers have the wider diameter distribution and higher softness. Furthermore, the SVE-electrospun nanofibers were also proven to exhibit good biocompatibility for cell growth of human adipose-derived stem cells (hADSCs) and cell-fiber interactions. Summarily, compared to the traditional SNE, SVE-electrospun nanofibers exhibited many merits including high-throughput yield, good air permeability, and compliance, which provide a facile and effective platform for the improvement of nanofiber applications in biomedical fields (e.g., tissue engineering, cosmetic, and medical textiles).

Electrospun strong, bioactive, and bioabsorbable silk fibroin/poly (L-lactic-acid) nanoyarns for constructing advanced nanotextile tissue scaffolds

Bio-textiles have aroused attractive attentions in tissue engineering and regenerative medicine, and developing robust, bio-absorbable, and extracellular matrix (ECM) fibril-mimicking nanofibrous textiles is urgently required for the renewal of existing microfibrous textile-based scaffolds and grafts. In this study, an integrated electrospinning system consisting of one nanoyarn-forming unit and one hot stretching unit is reported to fabricate silk fibroin (SF)/poly (L-lactic-acid) (PLLA) nanofibrous yarns (nanoyarns). The hot stretching process is demonstrated to significantly improve the fiber alignment, crystallinity, and mechanical properties of SF/PLLA nanoyarns, compared to the unstretched controls. For instance, the fiber alignment degree of hot stretched 50/50 SF/PLLA nanoyarn has increased by 25%, and the failure strength has increased by 246.5%, compared with the corresponding un-stretched control. Increasing the SF/PLLA mass ratio is found to significantly decrease the crystallinity and mechanical properties, but notably increase the degradation rate and surface hydrophilicity of SF/PLLA nanoyarns. Different SF/PLLA nanoyarns are further meticulously interwoven with warp and weft directions to obtain several nanofibrous woven textiles. The results from in vitro cell characterization and in vivo subcutaneous implantation show that increasing the SF/PLLA mass ratio significantly improves the biological properties and effectively reduces the inflammatory response of nanoyarn-constructed textiles. Overall, this study demonstrates that our SF/PLLA nanoyarns with controllable physical, mechanical and biological performances are fantastic candidates for the designing and development of advanced nanoarchitectured textile tissue scaffolds.

Cellular modulation by the mechanical cues from biomaterials for tissue engineering

Mechanical cues from the extracellular matrix (ECM) microenvironment are known to be significant in modulating the fate of stem cells to guide developmental processes and maintain bodily homeostasis. Tissue engineering has provided a promising approach to the repair or regeneration of damaged tissues. Scaffolds are fundamental in cell-based regenerative therapies. Developing artificial ECM that mimics the mechanical properties of native ECM would greatly help to guide cell functions and thus promote tissue regeneration. In this review, we introduce various mechanical cues provided by the ECM including elasticity, viscoelasticity, topography, and external stimuli, and their effects on cell behaviours. Meanwhile, we discuss the underlying principles and strategies to develop natural or synthetic biomaterials with different mechanical properties for cellular modulation, and explore the mechanism by which the mechanical cues from biomaterials regulate cell function toward tissue regeneration. We also discuss the challenges in multimodal mechanical modulation of cell behaviours and the interplay between mechanical cues and other microenvironmental factors.

Use of Electrospun Phenylalanine/Poly-ε-Caprolactone Chiral Hybrid Scaffolds to Promote Endothelial Remodeling

The fabrication of tissue-engineered vascular grafts to replace damaged vessels is a promising therapy for cardiovascular diseases. Endothelial remodeling in the lumen of TEVGs is critical for successful revascularization. However, the construction of well-functioning TEVGs remains a fundamental challenge. Herein, chiral hybrid scaffolds were prepared by electrospinning using D/L-phenylalanine based gelators [D(L)PHEG] and poly-ε-caprolactone (PCL). The chirality of scaffolds significantly affected the endothelial remodeling progress of TEVGs. Compared with L-phenylalanine based gelators/poly-ε-caprolactone (L/PCL) and PCL, D-phenylalanine based gelators/poly-ε-caprolactone (D/PCL) scaffolds enhanced cell adhesion, and proliferation and upregulated the expression of fibronectin-1, and vinculin. These results suggests that chiral hybrid scaffolds can promote endothelial remodeling of TEVGs by upregulating adhesion-associated protein levels. This study offers an innovative strategy for endothelial remodeling of TEVGs by fabricating chiral hybrid scaffolds, and provides new insight for the treatment of cardiovascular diseases.

Isotropic and Anisotropic Scaffolds for Tissue Engineering: Collagen, Conventional, and Textile Fabrication Technologies and Properties

In this review article, tissue engineering and regenerative medicine are briefly explained and the importance of scaffolds is highlighted. Furthermore, the requirements of scaffolds and how they can be fulfilled by using specific biomaterials and fabrication methods are presented. Detailed insight is given into the two biopolymers chitosan and collagen. The fabrication methods are divided into two categories: isotropic and anisotropic scaffold fabrication methods. Processable biomaterials and achievable pore sizes are assigned to each method. In addition, fiber spinning methods and textile fabrication methods used to produce anisotropic scaffolds are described in detail and the advantages of anisotropic scaffolds for tissue engineering and regenerative medicine are highlighted.

Milestones and current achievements in development of multifunctional bioscaffolds for medical application

Tissue engineering (TE) is a rapidly growing interdisciplinary field, which aims to restore or improve lost tissue function. Despite that TE was introduced more than 20 years ago, innovative and more sophisticated trends and technologies point to new challenges and development. Current challenges involve the demand for multifunctional bioscaffolds which can stimulate tissue regrowth by biochemical curves, biomimetic patterns, active agents and proper cell types. For those purposes especially promising are carefully chosen primary cells or stem cells due to its high proliferative and differentiation potential. This review summarized a variety of recently reported advanced bioscaffolds which present new functions by combining polymers, nanomaterials, bioactive agents and cells depending on its desired application. In particular necessity of study biomaterial-cell interactions with in vitro cell culture models, and studies using animals with in vivo systems were discuss to permit the analysis of full material biocompatibility. Although these bioscaffolds have shown a significant therapeutic effect in nervous, cardiovascular and muscle, tissue engineering, there are still many remaining unsolved challenges for scaffolds improvement.

Micro- and nanoscale biophysical cues for cardiovascular disease therapy

After cardiovascular injury, numerous pathological processes adversely impact the homeostatic function of cardiomyocyte, macrophage, fibroblast, endothelial cell, and vascular smooth muscle cell populations. Subsequent malfunctioning of these cells may further contribute to cardiovascular disease onset and progression. By modulating cellular responses after injury, it is possible to create local environments that promote wound healing and tissue repair mechanisms. The extracellular matrix continuously provides these mechanosensitive cell types with physical cues spanning the micro- and nanoscale to influence behaviors such as adhesion, morphology, and phenotype. It is therefore becoming increasingly compelling to harness these cell-substrate interactions to elicit more native cell behaviors that impede cardiovascular disease progression and enhance regenerative potential. This review discusses recent in vitro and preclinical work that have demonstrated the therapeutic implications of micro- and nanoscale biophysical cues on cell types adversely affected in cardiovascular diseases - cardiomyocytes, macrophages, fibroblasts, endothelial cells, and vascular smooth muscle cells.

Progress in the mechanical modulation of cell functions in tissue engineering

In mammals, mechanics at multiple stages-nucleus to cell to ECM-underlie multiple physiological and pathological functions from its development to reproduction to death. Under this inspiration, substantial research has established the role of multiple aspects of mechanics in regulating fundamental cellular processes, including spreading, migration, growth, proliferation, and differentiation. However, our understanding of how these mechanical mechanisms are orchestrated or tuned at different stages to maintain or restore the healthy environment at the tissue or organ level remains largely a mystery. Over the past few decades, research in the mechanical manipulation of the surrounding environment-known as substrate or matrix or scaffold on which, or within which, cells are seeded-has been exceptionally enriched in the field of tissue engineering and regenerative medicine. To do so, traditional tissue engineering aims at recapitulating key mechanical milestones of native ECM into a substrate for guiding the cell fate and functions towards specific tissue regeneration. Despite tremendous progress, a big puzzle that remains is how the cells compute a host of mechanical cues, such as stiffness (elasticity), viscoelasticity, plasticity, non-linear elasticity, anisotropy, mechanical forces, and mechanical memory, into many biological functions in a cooperative, controlled, and safe manner. High throughput understanding of key cellular decisions as well as associated mechanosensitive downstream signaling pathway(s) for executing these decisions in response to mechanical cues, solo or combined, is essential to address this issue. While many reports have been made towards the progress and understanding of mechanical cues-particularly, substrate bulk stiffness and viscoelasticity-in regulating the cellular responses, a complete picture of mechanical cues is lacking. This review highlights a comprehensive view on the mechanical cues that are linked to modulate many cellular functions and consequent tissue functionality. For a very basic understanding, a brief discussion of the key mechanical players of ECM and the principle of mechanotransduction process is outlined. In addition, this review gathers together the most important data on the stiffness of various cells and ECM components as well as various tissues/organs and proposes an associated link from the mechanical perspective that is not yet reported. Finally, beyond addressing the challenges involved in tuning the interplaying mechanical cues in an independent manner, emerging advances in designing biomaterials for tissue engineering are also explored.

An in-silico Investigation Into the Role of Strain and Structure on Vascular Smooth Muscle Cell Growth

The orientation of vascular cells can greatly influence the in vivo mechanical properties and functionality of soft vascular tissues. How cell orientation mediates the growth response of cells is of critical importance in understanding the response of soft tissues to mechanical stimuli or injury. To date, considerable evidence has shown that cells align with structural cues such as collagen fibers. However, in the presence of uniaxial cyclic strain on unstructured substrates, cells generally align themselves perpendicularly to the mechanical stimulus, such as strain, a phenomenon known as “strain avoidance.” The cellular response to this interplay between structural cues and a mechanical stimulus is poorly understood. A recent in vitro experimental study in our lab has investigated both the individual and collective response of rat aortic smooth muscle cells (RASMC) to structural (collagenous aligned constructs) and mechanical (cyclic strain) cues. In this study, a 2D agent-based model (ABM) is developed to simulate the collective response of RASMC to varying amplitudes of cyclic strain (0–10%, 2–8%, 4–6%) when seeded on unstructured (PDMS) and structured (decellularized collagenous tissue) constructs. An ABM is presented that is fit to the experimental outcomes in terms of cellular alignment and cell growth on PDMS substrates, under cyclic strain amplitudes of (4–6%, 2–8%, 0–10%) at 24 and 72 h timepoints. Furthermore, the ABM can predict RASMC alignment and change in cell number on a structured construct at a cyclic strain amplitude of 0–10% after 10 days. The ABM suggests that strain avoidance behavior observed in cells is dominated by selective cell proliferation and apoptosis at these early time points, as opposed to cell re-orientation, i.e., cells perpendicular to the strain increase their rate of proliferation, whilst the rate of apoptosis simultaneously increases in cells parallel to the strain direction. The development of in-silico modeling platforms, such as that presented here, allow for further understanding of the response of cells to changes in their mechanical environment. Such models offer an efficient and robust means to design and optimize the compliance and topological structure of implantable devices and could be used to aid the design of next-generation vascular grafts and stents.

In-vivo assessment of a tissue engineered vascular graft computationally optimized for target vessel compliance

Tissue engineered vascular grafts (TEVGs) have the ability to be tuned to match a target vessel's compliance, diameter, wall thickness, and thereby prevent compliance mismatch. In this work, TEVG compliance was manipulated by computationally tuning its layered composition or by manipulating a crosslinking agent (genipin). In particular, these three acelluluar TEVGs were compared: a compliance matched graft (CM_gel - high gelatin content); a hypocompliant PCL graft (HYPO_pcl - high polycaprolactone content); and a hypocompliant genipin graft (HYPO_gen - equivalent composition as CM_gel but hypocompliant via increased genipin crosslinking). All constructs were implanted interpositionally into the abdominal aorta of 21 Sprague Dawley rats (n=7, males=11, females=10) for 28 days, imaged in-vivo using ultrasound, explanted, and assessed for remodeling using immunofluorescence and two photon excitation fluorescence imaging. Compliance matched grafts remained compliance-matched in-vivo compared to the hypocompliant grafts through 4 weeks (p<0.05). Construct degradation and cellular infiltration was increased in the CM_gel and HYPO_gen TEVGs. Contractile smooth muscle cell markers in the proximal anastomosis of the graft were increased in the CM_gel group compared to the HYPO_pcl (p=0.007) and HYPO_gen grafts (p=0.04). Both hypocompliant grafts also had an increased pro-inflammatory response (increased ratio of CD163 to CD86 in the mid-axial location) compared to the CM_gel group. Our results suggest that compliance matching using a computational optimization approach leads to the improved acute (28 day) remodeling of TEVGs. To the authors' knowledge, this is the first in-vivo rat study investigating TEVGs that have been computationally optimized for target vessel compliance.