Mechanical Considerations of Electrospun Scaffolds for Myocardial Tissue and Regenerative Engineering

A Heart Rate Matched Patch for Mechano-Chemical Treatment of Myocardial Infarction: Optimal Design and Transspecies Application

After myocardial infarction (MI), ventricular dilation and the microscopic passive stretching of the infarcted border zone is the meaning contributor to the continuous expansion of myocardial fibrosis. Epicardial hydrogel patches have been demonstrated to alleviate this sequela of MI in small-animal models. However, these have not been successfully translated to humans or even large animals, in part because of challenges in attaining both the greater stiffness and slower viscoelastic relaxation that mathematical models predict to be optimal for application to larger, slower-beating hearts. Here, using borate-based dynamic covalent chemistry, we develop an injectable "heart rate matched" viscoelastic gelatin (VGtn) hydrogel with a gel point tunable across the stiffnesses and frequencies that are predicted to transspecies and cross-scale cardiac repair after MI. Small-animal experiments demonstrated that, compared to heart rate mismatched patches, the heart rate matched VGtn patches inhibited ventricular bulging and attenuated stress concentrations in the myocardium after MI. In particular, the viscoelastic patch can coordinate the microscopic strain at the infarction boundary. VGtn loaded with anti-fibrotic agents further reduced myocardial damage and promoted angiogenesis in the myocardium. The tuned heart rate matched patches demonstrated similar benefits in a larger-scale and lower heart rate porcine MI model. Results suggest that heart rate matched VGtn patches may hold potential for clinical translation.

Mechanical memory based biofabrication of hierarchical elastic cardiac tissue

Mimicking the multilayered, anisotropic, elastic structure of cardiac tissues for controlled guidiance of 3D cellular orientation is essential in designing bionic scaffolds for cardiac tissue biofabrication. Here, a hierarchically organized, anisotropic, wavy and conductive polycaprolactone/Au scaffold was created in a facile fashion based on mechanical memory during fabrication. The bionic 3D scaffold shows good biocompatibility, excellent biomimetic mechanical properties that guide myoblast alignment, support the hyperelastic behavior observed in native cardiac muscle tissue, and promote myotube maturation, which holds potential for cardiac muscle engineering and the establishment of anin vitroculture platform for drug screening.

Electroconductive cardiac patch based on bioactive PEDOT:PSS hydrogels

Engineering cardiac implants for treating myocardial infarction (MI) has advanced, but challenges persist in mimicking the structural properties and variability of cardiac tissues using traditional bioconstructs and conventional engineering methods. This study introduces a synthetic patch with a bioactive surface designed to swiftly restore functionality to the damaged myocardium. The patch combines a composite, soft, and conductive hydrogel-based on (3,4-ethylenedioxythiophene):polystyrene-sulfonate (PEDOT:PSS) and polyvinyl alcohol (PVA). This cardiac patch exhibits a reasonably high electrical conductivity (40 S/cm) and a stretchability up to 50% of its original length. Our findings reveal its resilience to 10% cyclic stretching at 1 Hz with no loss of conductivity over time. To mediate a strong cell-scaffold adhesion, we biofunctionalize the hydrogel with a N-cadherin mimic peptide, providing the cardiac patch with a bioactive surface. This modification promote increased adherence and proliferation of cardiac fibroblasts (CFbs) while effectively mitigating the formation of bacterial biofilm, particularly against Staphylococcus aureus, a common pathogen responsible for surgical site infections (SSIs). Our study demonstrates the successful development of a structurally validated cardiac patch possessing the desired mechanical, electrical, and biofunctional attributes for effective cardiac recovery. Consequently, this research holds significant promise in alleviating the burden imposed by myocardial infarctions.

Cardiac tissue engineering: an emerging approach to the treatment of heart failure

Heart failure is a major health problem in which the heart is unable to pump enough blood to meet the body's needs. It is a progressive disease that becomes more severe over time and can be caused by a variety of factors, including heart attack, cardiomyopathy and heart valve disease. There are various methods to cure this disease, which has many complications and risks. The advancement of knowledge and technology has proposed new methods for many diseases. One of the promising new treatments for heart failure is tissue engineering. Tissue engineering is a field of research that aims to create living tissues and organs to replace damaged or diseased tissue. The goal of tissue engineering in heart failure is to improve cardiac function and reduce the need for heart transplantation. This can be done using the three important principles of cells, biomaterials and signals to improve function or replace heart tissue. The techniques for using cells and biomaterials such as electrospinning, hydrogel synthesis, decellularization, etc. are diverse. Treating heart failure through tissue engineering is still under development and research, but it is hoped that there will be no transplants or invasive surgeries in the near future. In this study, based on the most important research in recent years, we will examine the power of tissue engineering in the treatment of heart failure.

Fabrication of a tailor-made conductive polyaniline/ascorbic acid-coated nanofibrous mat as a conductive and antioxidant cell-free cardiac patch

Polyaniline (PANI) wasin-situpolymerized on nanofibrous polycaprolactone mats as cell-free antioxidant cardiac patches (CPs), providing electrical conductivity and antioxidant properties. The fabricated CPs took advantage of intrinsic and additive antioxidant properties in the presence of PANI backbone and ascorbic acid as a biocompatible dopant of PANI. The antioxidant nature of CPs may reduce the serious repercussions of oxidative stress, produced during the ischemia-reperfusion (I/R) process following myocardial infarction. The polymerization parameters were considered as aniline (60 mM, 90 mM, and 120 mM), ascorbic acid concentrations ([aniline]:[ascorbic acid] = 3:0, 3:0.5, 3:1, 3:3), and polymerization time (1 h and 3 h). Mainly, the more aniline concentrations and polymerization time, the less sheet resistance was obtained. 1,1 diphenyl-2-picrylhydrazyl (DPPH) assay confirmed the dual antioxidant properties of prepared samples. The advantage of the employedin-situpolymerization was confirmed by the de-doping/re-doping process. Non-desirable groups were excluded based on their electrical conductivity, antioxidant properties, and biocompatibility. The remained groups protected H9c2 cells against oxidative stress and hypoxia conditions. Selected CPs reduced the intracellular reactive oxygen species content and mRNA level of caspase-3 while the Bcl-2 mRNA level was improved. Also, the selected cardiac patch could attenuate the hypertrophic impact of hydrogen peroxide on H9c2 cells. Thein vivoresults of the skin flap model confirmed the CP potency to attenuate the harmful impact of I/R.

Pioneering a paradigm shift in tissue engineering and regeneration with polysaccharides and proteins-based scaffolds: A comprehensive review

In the realm of modern medicine, tissue engineering and regeneration stands as a beacon of hope, offering the promise of restoring form and function to damaged or diseased organs and tissues. Central to this revolutionary field are biological macromolecules-nature's own blueprints for regeneration. The growing interest in bio-derived macromolecules and their composites is driven by their environmentally friendly qualities, renewable nature, minimal carbon footprint, and widespread availability in our ecosystem. Capitalizing on these unique attributes, specific composites can be tailored and enhanced for potential utilization in the realm of tissue engineering (TE). This review predominantly concentrates on the present research trends involving TE scaffolds constructed from polysaccharides, proteins and glycosaminoglycans. It provides an overview of the prerequisites, production methods, and TE applications associated with a range of biological macromolecules. Furthermore, it tackles the challenges and opportunities arising from the adoption of these biomaterials in the field of TE. This review also presents a novel perspective on the development of functional biomaterials with broad applicability across various biomedical applications.

Optimization of Polycaprolactone and Type I Collagen Scaffold for Tendon Tissue Regeneration

Introduction Collagen synthesis is vital for restoring musculoskeletal tissues, particularly in tendon and ligamentous structures. Tissue engineering utilizes scaffolds for cell adhesion and differentiation. Although synthetic scaffolds offer initial strength, their long-term stability is surpassed by biological scaffolds. Combining polycaprolactone (PCL) toughness with collagen in scaffold design, this study refines fabrication via electrospinning, aiming to deliver enduring biomimetic matrices for widespread applications in musculoskeletal repair. Methods Electrospinning employed four solutions with varied collagen and PCL concentrations, dissolved in chloroform, methanol, and hexafluoro-2-propanol. Solutions were combined to yield 60 mg/mL concentrations with different collagen/PCL ratios. Electrospinning at 12-14kV voltage produced scaffolds, followed by vacuum-drying. Collagen coating was applied to PCL and 15% collagen/PCL scaffolds using a 0.1% collagen solution. SEM characterized fiber morphology, tensile testing was conducted to determine the mechanical properties of the scaffold, and Fourier-transform infrared (FTIR) spectroscopy analyzed scaffold composition. Atomic force microscopy (AFM) analyzed the stiffness properties of individual fibers, and a finite element model was developed to predict the mechanical properties. Cell culture involved seeding human bone marrow mesenchymal stem cells onto scaffolds, which were assessed through Alamar Blue assay and confocal imaging. Results Various scaffolds (100% PCL, PCL-15% collagen, PCL-25% collagen, PCL-35% collagen) were fabricated to emulate the extracellular matrix, revealing collagen's impact on fiber diameter reduction with increasing concentration. Tensile testing highlighted collagen's initial enhancement of mechanical strength, followed by a decline beyond PCL-15% collagen. FTIR spectroscopy detected potential hydrogen bonding between collagen and PCL. A finite element model predicted scaffold response to external forces which was validated by the tensile test data. Cell viability and proliferation assays demonstrated successful plating on all scaffolds, with optimal proliferation observed in PCL-25% collagen. Confocal imaging confirmed stem cell integration into the three-dimensional material. Collagen coating preserved nanofiber morphology, with no significant changes in diameter. Coating of collagen significantly altered the tensile strength of the scaffolds at the macro scale. AFM highlighted stiffness differences between PCL and collagen-coated PCL mats at the single fiber scale. The coating process did not significantly enhance initial cell attachment but promoted increased proliferation on collagen-coated PCL scaffolds. Conclusion The study reveals collagen-induced mechanical and morphological alterations, influencing fiber alignment, diameter, and chemical composition while emphasizing scaffolds' vital role in providing a controlled niche for stem cell proliferation and differentiation. The optimization of each of these scaffold characteristics and subsequent finite element modeling can lead to highly repeatable and ideal scaffold properties for stem cell integration and proliferation.

Exploring Electrospun Scaffold Innovations in Cardiovascular Therapy: A Review of Electrospinning in Cardiovascular Disease

Cardiovascular disease (CVD) remains the leading cause of mortality worldwide. In particular, patients who suffer from ischemic heart disease (IHD) that is not amenable to surgical or percutaneous revascularization techniques have limited treatment options. Furthermore, after revascularization is successfully implemented, there are a number of pathophysiological changes to the myocardium, including but not limited to ischemia-reperfusion injury, necrosis, altered inflammation, tissue remodeling, and dyskinetic wall motion. Electrospinning, a nanofiber scaffold fabrication technique, has recently emerged as an attractive option as a potential therapeutic platform for the treatment of cardiovascular disease. Electrospun scaffolds made of biocompatible materials have the ability to mimic the native extracellular matrix and are compatible with drug delivery. These inherent properties, combined with ease of customization and a low cost of production, have made electrospun scaffolds an active area of research for the treatment of cardiovascular disease. In this review, we aim to discuss the current state of electrospinning from the fundamentals of scaffold creation to the current role of electrospun materials as both bioengineered extracellular matrices and drug delivery vehicles in the treatment of CVD, with a special emphasis on the potential clinical applications in myocardial ischemia.

Improving rodents and humans cardiac cell maturityin vitrothrough polycaprolactone and polyurethane nanofibers

Currently, numerous studies are conducted using nanofibers as a scaffold for culture cardiac cells; however, there still needs to be more research evaluating the impact of the physicochemical properties of polymer nanofibers on the structure and function of cardiac cells. We have studied how poly(ϵ-caprolactone) and polyurethane nanofibrous mats with different physicochemical properties influence the viability, morphology, orientation, and maturation of cardiac cells. For this purpose, the cells taken from different species were used. They were rat ventricular cardiomyoblasts (H9c2), mouse atrial cardiomyocytes (CMs) (HL-1), and human ventricular CMs. Based on the results, it can be concluded that cardiac cells cultured on nanofibers exhibit greater maturity in terms of orientation, morphology, and gene expression levels compared to cells cultured on polystyrene plates. Additionally, the physicochemical properties of nanofibers affecting the functionality of cardiac cells from different species and different parts of the heart were evaluated. These studies can support research on understanding and explaining mechanisms leading to cellular maturity present in the heart and the selection of nanofibers that will effectively help the maturation of CMs.

Bioadhesive Technology Platforms

Bioadhesives have emerged as transformative and versatile tools in healthcare, offering the ability to attach tissues with ease and minimal damage. These materials present numerous opportunities for tissue repair and biomedical device integration, creating a broad landscape of applications that have captivated clinical and scientific interest alike. However, fully unlocking their potential requires multifaceted design strategies involving optimal adhesion, suitable biological interactions, and efficient signal communication. In this Review, we delve into these pivotal aspects of bioadhesive design, highlight the latest advances in their biomedical applications, and identify potential opportunities that lie ahead for bioadhesives as multifunctional technology platforms.

Three-Dimensionally Printed Hydrogel Cardiac Patch for Infarct Regeneration Based on Natural Polysaccharides

Myocardial infarction is one of the more common cardiovascular diseases, and remains the leading cause of death, globally. Hydrogels (namely, those using natural polymers) provide a reliable tool for regenerative medicine and have become a promising option for cardiac tissue regeneration due to their hydrophilic character and their structural similarity to the extracellular matrix. Herein, a functional ink based on the natural polysaccharides Gellan gum and Konjac glucomannan has, for the first time, been applied in the production of a 3D printed hydrogel with therapeutic potential, with the goal of being locally implanted in the infarcted area of the heart. Overall, results revealed the excellent printability of the bioink for the development of a stable, porous, biocompatible, and bioactive 3D hydrogel, combining the specific advantages of Gellan gum and Konjac glucomannan with proper mechanical properties, which supports the simplification of the implantation process. In addition, the structure have positive effects on endothelial cells' proliferation and migration that can promote the repair of injured cardiac tissue. The results presented will pave the way for simple, low-cost, and efficient cardiac tissue regeneration using a 3D printed hydrogel cardiac patch with potential for clinical application for myocardial infarction treatment in the near future.

Recent Advances in Tissue-Engineered Cardiac Scaffolds-The Progress and Gap in Mimicking Native Myocardium Mechanical Behaviors

Heart failure is the leading cause of death in the US and worldwide. Despite modern therapy, challenges remain to rescue the damaged organ that contains cells with a very low proliferation rate after birth. Developments in tissue engineering and regeneration offer new tools to investigate the pathology of cardiac diseases and develop therapeutic strategies for heart failure patients. Tissue -engineered cardiac scaffolds should be designed to provide structural, biochemical, mechanical, and/or electrical properties similar to native myocardium tissues. This review primarily focuses on the mechanical behaviors of cardiac scaffolds and their significance in cardiac research. Specifically, we summarize the recent development of synthetic (including hydrogel) scaffolds that have achieved various types of mechanical behavior-nonlinear elasticity, anisotropy, and viscoelasticity-all of which are characteristic of the myocardium and heart valves. For each type of mechanical behavior, we review the current fabrication methods to enable the biomimetic mechanical behavior, the advantages and limitations of the existing scaffolds, and how the mechanical environment affects biological responses and/or treatment outcomes for cardiac diseases. Lastly, we discuss the remaining challenges in this field and suggestions for future directions to improve our understanding of mechanical control over cardiac function and inspire better regenerative therapies for myocardial restoration.

Recent Tissue Engineering Approaches to Mimicking the Extracellular Matrix Structure for Skin Regeneration

Inducing tissue regeneration in many skin defects, such as large traumatic wounds, burns, other physicochemical wounds, bedsores, and chronic diabetic ulcers, has become an important clinical issue in recent years. Cultured cell sheets and scaffolds containing growth factors are already in use but have yet to restore normal skin tissue structure and function. Many tissue engineering materials that focus on the regeneration process of living tissues have been developed for the more versatile and rapid initiation of treatment. Since the discovery that cells recognize the chemical-physical properties of their surrounding environment, there has been a great deal of work on mimicking the composition of the extracellular matrix (ECM) and its three-dimensional network structure. Approaches have used ECM constituent proteins as well as morphological processing methods, such as fiber sheets, sponges, and meshes. This review summarizes material design strategies in tissue engineering fields, ranging from the morphology of existing dressings and ECM structures to cellular-level microstructure mimicry, and explores directions for future approaches to precision skin tissue regeneration.

Development of Scaffolds from Bio-Based Natural Materials for Tissue Regeneration Applications: A Review

Tissue damage and organ failure are major problems that many people face worldwide. Most of them benefit from treatment related to modern technology's tissue regeneration process. Tissue engineering is one of the booming fields widely used to replace damaged tissue. Scaffold is a base material in which cells and growth factors are embedded to construct a substitute tissue. Various materials have been used to develop scaffolds. Bio-based natural materials are biocompatible, safe, and do not release toxic compounds during biodegradation. Therefore, it is highly recommendable to fabricate scaffolds using such materials. To date, there have been no singular materials that fulfill all the features of the scaffold. Hence, combining two or more materials is encouraged to obtain the desired characteristics. To design a reliable scaffold by combining different materials, there is a need to choose a good fabrication technique. In this review article, the bio-based natural materials and fine fabrication techniques that are currently used in developing scaffolds for tissue regeneration applications, along with the number of articles published on each material, are briefly discussed. It is envisaged to gain explicit knowledge of developing scaffolds from bio-based natural materials for tissue regeneration applications.

Biomechanics Assist Measurement, Modeling, Engineering Applications, and Clinical Decision Making in Medicine

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Biomimetic design of bioartificial scaffolds for the in vitro modelling of human cardiac fibrosis

In vitro models of pathological cardiac tissue have attracted interest as predictive platforms for preclinical validation of therapies. However, models reproducing specific pathological features, such as cardiac fibrosis size (i.e., thickness and width) and stage of development are missing. This research was aimed at engineering 2D and 3D models of early-stage post-infarct fibrotic tissue (i.e., characterized by non-aligned tissue organization) on bioartificial scaffolds with biomimetic composition, design, and surface stiffness. 2D scaffolds with random nanofibrous structure and 3D scaffolds with 150 µm square-meshed architecture were fabricated from polycaprolactone, surface-grafted with gelatin by mussel-inspired approach and coated with cardiac extracellular matrix (ECM) by 3 weeks culture of human cardiac fibroblasts. Scaffold physicochemical properties were thoroughly investigated. AFM analysis of scaffolds in wet state, before cell culture, confirmed their close surface stiffness to human cardiac fibrotic tissue. Following 3 weeks culture, biomimetic biophysical and biochemical scaffold properties triggered the activation of myofibroblast phenotype. Upon decellularization, immunostaining, SEM and two-photon excitation fluorescence microscopy showed homogeneous decoration of both 2D and 3D scaffolds with cardiac ECM. The versatility of the approach was demonstrated by culturing ventricular or atrial cardiac fibroblasts on scaffolds, thus suggesting the possibility to use the same scaffold platforms to model both ventricular and atrial cardiac fibrosis. In the future, herein developed in vitro models of cardiac fibrotic tissue, reproducing specific pathological features, will be exploited for a fine preclinical tuning of therapies.

Bioengineering lungs: An overview of current methods, requirements, and challenges for constructing scaffolds

Chronic respiratory diseases remain a significant health burden worldwide. The only option for individuals with end-stage lung failure remains Lung Transplantation. However, suitable organ donor shortages and immune rejection following transplantation remain a challenge. Since alternative options are urgently required to increase tissue availability for lung transplantation, researchers have been exploring lung bioengineering extensively, to generate functional, transplantable organs and tissue. Additionally, the development of physiologically-relevant artificial tissue models for testing novel therapies also represents an important step toward finding a definite clinical solution for different chronic respiratory diseases. This mini-review aims to highlight some of the most common methodologies used in bioengineering lung scaffolds, as well as the benefits and disadvantages associated with each method in conjunction with the current areas of research devoted to solving some of these challenges in the area of lung bioengineering.

Artificial Scaffolds in Cardiac Tissue Engineering

Cardiovascular diseases are a leading cause of death worldwide. Current treatments directed at heart repair have several disadvantages, such as a lack of donors for heart transplantation or non-bioactive inert materials for replacing damaged tissue. Because of the natural lack of regeneration of cardiomyocytes, new treatment strategies involve stimulating heart tissue regeneration. The basic three elements of cardiac tissue engineering (cells, growth factors, and scaffolds) are described in this review, with a highlight on the role of artificial scaffolds. Scaffolds for cardiac tissue engineering are tridimensional porous structures that imitate the extracellular heart matrix, with the ability to promote cell adhesion, migration, differentiation, and proliferation. In the heart, there is an important requirement to provide scaffold cellular attachment, but scaffolds also need to permit mechanical contractility and electrical conductivity. For researchers working in cardiac tissue engineering, there is an important need to choose an adequate artificial scaffold biofabrication technique, as well as the ideal biocompatible biodegradable biomaterial for scaffold construction. Finally, there are many suitable options for researchers to obtain scaffolds that promote cell-electrical interactions and tissue repair, reaching the goal of cardiac tissue engineering.

Recreating the heart's helical structure-function relationship with focused rotary jet spinning

Helical alignments within the heart's musculature have been speculated to be important in achieving physiological pumping efficiencies. Testing this possibility is difficult, however, because it is challenging to reproduce the fine spatial features and complex structures of the heart's musculature using current techniques. Here we report focused rotary jet spinning (FRJS), an additive manufacturing approach that enables rapid fabrication of micro/nanofiber scaffolds with programmable alignments in three-dimensional geometries. Seeding these scaffolds with cardiomyocytes enabled the biofabrication of tissue-engineered ventricles, with helically aligned models displaying more uniform deformations, greater apical shortening, and increased ejection fractions compared with circumferential alignments. The ability of FRJS to control fiber arrangements in three dimensions offers a streamlined approach to fabricating tissues and organs, with this work demonstrating how helical architectures contribute to cardiac performance.

Pro-angiogenic Potential of Mesenchymal Stromal Cells Regulated by Matrix Stiffness and Anisotropy Mimicking Right Ventricles

Capillary rarefaction is a hallmark of right ventricle (RV) failure. Mesenchymal stromal cell (MSC)-based therapy offers a potential treatment due to its pro-angiogenic function. However, the impact of RV tissue mechanics on MSC behavior is unclear, especially when referring to RV end-diastolic stiffness and mechanical anisotropy. In this study, we assessed MSC behavior on electrospun scaffolds with varied stiffness (normal vs failing RV) and anisotropy (isotropic vs anisotropic). In individual MSCs, we observed the highest vascular endothelial growth factor (VEGF) production and total tube length in the failing, isotropic group (2.00 ± 0.37, 1.53 ± 0.24), which was greater than the normal, isotropic group (0.70 ± 0.15, 0.55 ± 0.07; p < 0.05). The presence of anisotropy led to trends of increased VEGF production on normal groups (0.75 ± 0.09 vs 1.20 ± 0.17), but this effect was absent on failing groups. Our findings reveal synergistic effects of RV-like stiffness and anisotropy on MSC pro-angiogenic function and may guide MSC-based therapies for heart failure.

Multiscale Contrasts Between the Right and Left Ventricle Biomechanics in Healthy Adult Sheep and Translational Implications

Cardiac biomechanics play a significant role in the progression of structural heart diseases (SHDs). SHDs alter baseline myocardial biomechanics leading to single or bi-ventricular dysfunction. But therapies for left ventricle (LV) failure patients do not always work well for right ventricle (RV) failure patients. This is partly because the basic knowledge of baseline contrasts between the RV and LV biomechanics remains elusive with limited discrepant findings. The aim of the study was to investigate the multiscale contrasts between LV and RV biomechanics in large animal species. We hypothesize that the adult healthy LV and RV have distinct passive anisotropic biomechanical properties. Ex vivo biaxial tests were performed in fresh sheep hearts. Histology and immunohistochemistry were performed to measure tissue collagen. The experimental data were then fitted to a Fung type model and a structurally informed model, separately. We found that the LV was stiffer in the longitudinal (outflow tract) than circumferential direction, whereas the RV showed the opposite anisotropic behavior. The anisotropic parameter K from the Fung type model accurately captured contrasting anisotropic behaviors in the LV and RV. When comparing the elasticity in the same direction, the LV was stiffer than the RV longitudinally and the RV was stiffer than the LV circumferentially, suggesting different filling patterns of these ventricles during diastole. Results from the structurally informed model suggest potentially stiffer collagen fibers in the LV than RV, demanding further investigation. Finally, type III collagen content was correlated with the low-strain elastic moduli in both ventricles. In summary, our findings provide fundamental biomechanical differences between the chambers. These results provide valuable insights for guiding cardiac tissue engineering and regenerative studies to implement chamber-specific matrix mechanics, which is particularly critical for identifying biomechanical mechanisms of diseases or mechanical regulation of therapeutic responses. In addition, our results serve as a benchmark for image-based inverse modeling technologies to non-invasively estimate myocardial properties in the RV and LV.

Optimization of Salt-Leaching Parameters for Gelatin/Na2Ti3O7 Scaffolds Using a Mixture Design Experiment

The purpose of this research was to learn the formation of biomedical scaffold material from gelatin by using titanate (Na₂Ti₃O₇), which is a newly synthesized derivative of titanium dioxide (TiO₂) with gelatin. It was prepared by mixed several solutions and cross-linked molecules by heating and salt-leaching. The biomedical scaffold was formed, and its porosity depended on the size of the salt crystal. The mixture was designed by using a mixture design with three factors: gelatin, titanate, and deionized water to determine the optimal mixture for the tensile strength of the biomedical scaffold. The microstructure of the biomedical scaffold was studied using scanning electron microscopy (SEM). The findings revealed that Na₂Ti₃O₇ thoroughly pen-extracted the biomedical scaffold, and the tensile strength of the gelatin/titanate scaffold was higher than the biomedical scaffold, which was formed using pure gelatin. By using the mixture design technique, the 14.73% gelatin, 0.2% Na₂Ti₃O₇, and 85.07% DI water got the highest yield of tensile strength (1508.15 kP). This was an about 4.88% increase in the tensile strength property when compared with using TiO₂.

Passive myocardial mechanical properties: meaning, measurement, models

Passive mechanical tissue properties are major determinants of myocardial contraction and relaxation and, thus, shape cardiac function. Tightly regulated, dynamically adapting throughout life, and affecting a host of cellular functions, passive tissue mechanics also contribute to cardiac dysfunction. Development of treatments and early identification of diseases requires better spatio-temporal characterisation of tissue mechanical properties and their underlying mechanisms. With this understanding, key regulators may be identified, providing pathways with potential to control and limit pathological development. Methodologies and models used to assess and mimic tissue mechanical properties are diverse, and available data are in part mutually contradictory. In this review, we define important concepts useful for characterising passive mechanical tissue properties, and compare a variety of in vitro and in vivo techniques that allow one to assess tissue mechanics. We give definitions of key terms, and summarise insight into determinants of myocardial stiffness in situ. We then provide an overview of common experimental models utilised to assess the role of environmental stiffness and composition, and its effects on cardiac cell and tissue function. Finally, promising future directions are outlined.

Revealing Electrical and Mechanical Performances of Highly Oriented Electrospun Conductive Nanofibers of Biopolymers with Tunable Diameter

The present study outlines a reliable approach to determining the electrical conductivity and elasticity of highly oriented electrospun conductive nanofibers of biopolymers. The highly oriented conductive fibers are fabricated by blending a high molar mass polyethylene oxide (PEO), polycaprolactone (PCL), and polylactic acid (PLA) with polyaniline (PANi) filler. The filler-matrix interaction and molar mass (M) of host polymer are among governing factors for variable fiber diameter. The conductivity as a function of filler fraction (φ) is shown and described using a McLachlan equation to reveal the electrical percolation thresholds (φ_c) of the nanofibers. The molar mass of biopolymer, storage time, and annealing temperature are significant factors for φ_c. The Young’s modulus (E) of conductive fibers is dependent on filler fraction, molar mass, and post-annealing process. The combination of high orientation, tunable diameter, tunable conductivity, tunable elasticity, and biodegradability makes the presented nanofibers superior to the fibers described in previous literature and highly desirable for various biomedical and technical applications.

Electrospun nanofibers promote wound healing: theories, techniques, and perspectives

At present, the clinical strategies for treating chronic wounds are limited, especially when it comes to pain relief and rapid wound healing. Therefore, there is an urgent need to develop alternative treatment methods. This paper provides a systematic review on recent researches on how electrospun nanofiber scaffolds promote wound healing and how the electrospinning technology has been used for fabricating multi-dimensional, multi-pore and multi-functional nanofiber scaffolds that have greatly promoted the development of wound healing dressings. First, we provide a review on the four stages of wound healing, which is followed by a discussion on the evolvement of the electrospinning technology, what is involved in electrospinning devices, and factors affecting the electrospinning process. Finally, we present the possible mechanisms of electrospun nanofibers to promote wound healing, the classification of electrospun polymers, cell infiltration favoring fiber scaffolds, antibacterial fiber scaffolds, and future multi-functional scaffolds. Although nanofiber scaffolds have made great progress as a type of multi-functional biomaterial, major challenges still remain for commercializing them in a way that fully meets the needs of patients.

Nanofiber Scaffolds by Electrospinning for Rotator Cuff Tissue Engineering

Rotator cuff tears continue to be at risk of retear or failure to heal after surgical repair, despite the use of various surgical techniques, which stimulate development of novel scaffolding strategies. They should be able to address the known causes of failure after the conventional rotator cuff repair: (1) failure to reproduce the normal tendon healing process, (2) resultant failure to reproduce four zones of the enthesis, and (3) failure to attain sufficient mechanical strength after repair. Nanofiber scaffolds are suited for this application because they can be engineered to mimic the ultrastructure and properties of the native rotator cuff tendon. Among various methods for tissue-engineered nanofibers, electrospinning has recently been highlighted in the rotator cuff field. Electrospinning can create fibrous and porous structures that resemble natural tendon's extracellular matrix. Other advantages include the ability to create relatively large surface-to-volume ratios, the ability to control fiber size from the micro to the nano scale, and the flexibility of material choices. In this review, we will discuss the anatomical and mechanical features of the rotator cuff tendon, their potential impacts on improper healing after repair, and the current knowledge of the use of electrospinning for rotator cuff tissue engineering.

Use of Stacked Layers of Electrospun L-Lactide/Glycolide Co-Polymer Fibers for Rapid Construction of Skin Sheets

This paper describes a novel method for the rapid construction of skin, using multiple layers of aligned electrospun fibers as starting scaffolds. Scaffolds were spun from biodegradable L-lactide/glycolide (molar ratio 10:90) with predominantly parallel arrays of fibers attached peripherally to thin 304 stainless steel layer frames. Each layer frame was held between two thicker support frames. Human skin cells were seeded onto multiple (three–nine) scaffolds. Dermal fibroblasts were seeded on both sides of each scaffold except for one on which keratinocytes were seeded on one side only. Following 48 h of culture, the scaffolds and layer frames were unmounted from their support frames, stacked, with keratinocytes uppermost, and securely held in place by upper and lower support frames to instantly form a multilayered “dermis” and a nascent epidermis. The stack was cultured for a further 5 days during which time the cells proliferated and then adhered to form, in association with the spun fibers, a mechanically coherent tissue. Fibroblasts preferentially elongated in the dominant fiber direction and a two-dimensional weave of alternating fiber and cell alignments could be constructed by selected placement of the layer frames during stacking. Histology of the 7-day tissue stacks showed the organized layers of fibroblasts and keratinocytes immuno-positive for keratin. Electron microscopy showed attachment of fibroblasts to the lactide/glycolide fibers and small-diameter collagen fibers in the extracellular space. This novel approach could be used to engineer a range of tissues for grafting where rapid construction of tissues with aligned or woven layers would be beneficial.