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We engineered a textile-reinforced hydrogel vascular graft. The textile provides robustness while the hydrogel promotes endothelial cell attachment and growth. The composite enhanced macrophage activation, which increased endothelial cell migration.

The SARS-CoV-2 pandemic has increased the demand for antiviral technologies to mitigate or prevent the risk of viral transmission. Antiviral treated textiles have the potential to save lives, especially in healthcare settings that rely on reusable patient-care textiles and personal protective equipment. Currently, little is known about the role of textiles in cross-contamination and pathogen transmission, despite the wealth of information on hard surfaces and fomites harboring viruses that remain viable in certain circumstances. In addition, there is no international standard method for evaluating residual viral activity on textiles, which would allow a thorough investigation of the efficacy of antiviral textile products. Therefore, this pilot study aims to develop and refine a standardized protocol to quantitatively evaluate residual viral activity on antiviral textiles. Specifically, we focused on general textiles, such as bed linens, commonly used in healthcare settings for patient care. The Tissue Culture Infectious Dose 50 (TCID50) method is frequently used to quantitatively evaluate viral infectivity on textiles, but has not been established as a standard. This procedure involves observing the cytopathic effect of a given virus on cells grown in a 96-well plate after several days of incubation to determine the infectivity titer. We used HCoV-229E and Huh-7 human liver cancer cells for this investigation. We worked to improve the TCID50 method through variations of different steps within the protocol to attain reproducible results. Our proposed optimized hybrid protocol has shown evidence that the protocol is technically simpler and more efficient, and provides successful, consistent results. The analysis showed a significant difference between the treated fabric compared with controls.

Deficiency and dysfunction of corneal cells leads to the blindness observed in corneal diseases such as limbal stem cell deficiency (LSCD) and bullous keratopathy. Regenerative cell therapies and engineered corneal tissue are promising treatments for these diseases [1]. However, these treatments are not yet clinically feasible due to inadequate cell sources. The discovery of induced pluripotent stem cells (iPSCs) by Shinya Yamanaka has provided a multitude of opportunities in research because iPSCs can be generated from somatic cells, thus providing an autologous and unlimited source for corneal cells. Compared to other stem cell sources such as mesenchymal and embryonic, iPSCs have advantages in differentiation potential and ethical concerns, respectively. Efforts have been made to use iPSCs to model corneal disorders and diseases, drug testing [2], and regenerative medicine [1]. Autologous treatments based on iPSCs can be exorbitantly expensive and time-consuming, but development of stem cell banks with human leukocyte antigen (HLA)- homozygous cell lines can provide cost- and time-efficient allogeneic alternatives. In this review, we discuss the early development of the cornea because protocols differentiating iPSCs toward corneal lineages rely heavily upon recapitulating this development. Differentiation of iPSCs toward corneal cell phenotypes have been analyzed with an emphasis on feeder-free, xeno-free, and well-defined protocols, which have clinical relevance. The application, challenges, and potential of iPSCs in corneal research are also discussed with a focus on hurdles that prevent clinical translation.

Carbon nanotubes (CNTs) are known for their excellent conductive properties. Here, we present two novel methods, "sandwich" (sCNT) and dual deposition (DD CNT), for incorporating CNTs into electrospun polycaprolactone (PCL) and gelatin scaffolds to increase their conductance. Based on CNT percentage, the DD CNT scaffolds contain significantly higher quantities of CNTs than the sCNT scaffolds. The inclusion of CNTs increased the electrical conductance of scaffolds from 0.0 ± 0.00 kS (non-CNT) to 0.54 ± 0.10 kS (sCNT) and 5.22 ± 0.49 kS (DD CNT) when measured parallel to CNT arrays and to 0.25 ± 0.003 kS (sCNT) and 2.85 ± 1.12 (DD CNT) when measured orthogonally to CNT arrays. The inclusion of CNTs increased fiber diameter and pore size, promoting cellular migration into the scaffolds. CNT inclusion also decreased the degradation rate and increased hydrophobicity of scaffolds. Additionally, CNT inclusion increased Young's modulus and failure load of scaffolds, increasing their mechanical robustness. Murine fibroblasts were maintained on the scaffolds for 30 days, demonstrating high cytocompatibility. The increased conductivity and high cytocompatibility of the CNT-incorporated scaffolds make them appropriate candidates for future use in cardiac and neural tissue engineering.

A hernia is a pathological condition caused by a defect or opening in the muscle wall, which leads to organs pushing through the opening or defect. Hernia recurrence, seroma, persistent pain, tissue adhesions, and wound infection are common complications following hernia repair surgery. Infection after hernia mesh implantation is the third major complication leading to hernia recurrence. In order to reduce the incidence of late infections, we developed a polypropylene mesh with antibacterial properties. In this study, knitted polypropylene meshes were exposed to radio-frequency plasma to activate their surfaces. The antibacterial monomer diallyldimethylammonium chloride (DADMAC) was then grafted onto the mesh surface using pentaerythritol tetraacrylate as the cross-linker since it is able to engage all four functional groups to form a high-density cross-linked network. The subsequent antibacterial performance showed a 2.9 log reduction toward

To assure the long-term safety and functional performance after implantation, it is of critical importance to completely sterilize a biomaterial implant. Ineffective sterilization can cause severe inflammation and infection at the implant site, leading to detrimental events of morbidity and even mortality. Macrophages are pivotal players in the inflammatory and foreign body response after implanting a biomaterial in the body. However, the relationship between the sterilization procedure and macrophage response has not been established. In this study, three commonly used sterilization methods, including autoclaving, ethylene oxide gas and ethanol treatment, were used to sterilize a gelatin methacryloyl hydrogel. The impacts of different sterilization methods on the structure and physical properties of the hydrogel were compared. Macrophage responses to the sterilized hydrogel were analyzed based on their morphology, viability and in vitro gene expression. It was found that the sterilization methods only marginally altered the hydrogel morphology, swelling behavior and elastic modulus, but significantly impacted macrophage gene expression within 48 h and over 7 d in vitro. Therefore, when selecting sterilization methods for GelMA hydrogel, not only the sterility and hydrogel properties, such as material destruction and degradation caused by temperature and moisture, should be taken into consideration, but also the cellular responses to the sterilized material which could be substantially different.

Heart disease is the leading cause of death worldwide. Cardiac tissue engineering (CTE) aims to repair and replace heart tissue, offering a solution. Induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs) could revolutionize CTE due to their theoretical ability to supply limitless patient-specific CMs. However, iPSC-CMs are electrophysiologically immature compared to functional adult CMs, and therefore incapable of sustaining a heartbeat. Thus, a scaffold capable of electrophysiologically maturing iPSC-CMs is needed. My research increases the electroconductivity of electrospun (ES) scaffolds by incorporating carbon nanotubes (CNTs), which I hypothesize will mature iPSC-CMs seeded onto them due to their excellent electroconductive properties. Morphological, biocompatibility, and electrical analyses have been performed on ES polycaprolactone (PCL) and gelatin scaffolds with CNTs incorporated via a ‘sandwich’ and dual deposition method in order to increase electroconductivity. Morphological analyses were performed via ImageJ on SEM images. Fiber diameter and pore size quantification confirmed the ability to exert morphological control by modifying solution properties and ES parameters, which is crucial to achieve biomimicry of the cardiac extracellular matrix. Live/dead assays and immunofluorescence revealed the CNT scaffolds offer high biocompatibility for NIH 3T3 fibroblasts, which attach, proliferate, and migrate well. Electrical analysis performed with a multimeter and two-probe resistance measurement confirms that inclusion of CNTs significantly increases scaffold conductivity, moreso for dual deposition scaffolds than ‘sandwich’ ones, and moreso parallel to the CNT arrays than orthogonally. These results prove the feasibility of using such scaffolds as a method for in vitro electrophysiological iPSC-CM maturation. Next steps include optimization of scaffolds, analysis of iPSC-CM biocompatibility and response, and recapitulation and manipulation of the electrophysiology of cardiac tissue, including quantification of markers for cardiac function and maturity, and assessment of iPSC-CM + scaffold response to electrical pacing.

The green production of textiles via an eco-friendly approach has recently gained considerable interest. As a derivative industry of silk manufacturing, spun silk utilizes waste materials generated in different processes of silk production, which is considered as the re-use of silk waste. The spun silk industry is facing several problems now, including environmental pollution, low production efficiency, increased labor intensity, significant material waste, and excessive energy consumption. This study presents an environment-friendly production route to produce mulberry spun silk yarns, by eliminating the gassing process that burns away surface hairs and neps. The gassing process not only generates odors, dust, and gas discharges but also results in significant material wastage and high production cost. The key is a modified ring spinning technology to achieve low yarn hairiness and neps; thus the yarn produced no longer requires gassing. The number of processing steps is also reduced to nine from twelve compared to the traditional silk spinning system. The modified 60 Nm mulberry spun silk yarns show a comparable tenacity of 26.33 cN/tex, evenness of 9.96%, neps (+200%) of 18 per 1 km, and a slightly worse hairiness S3 value of 74 per 100 m, compared with the conventional gassed ones. The plain knitted fabrics made by the modified yarns also reveal a 1.5 grade higher pilling resistance, similar mechanical and thermal properties, and a slightly hairier surface appearance than the conventional ones. The new processing route greatly reduces carbon footprint and achieves significant savings in materials, manpower, and energy, which may shed new light on the industrial manufacturing of mulberry spun silk yarns.

Insights into the expression of pacemaker-specific markers in human induced pluripotent stem cell (hiPSC)-derived cardiomyocyte subtypes can facilitate the enrichment and track differentiation and maturation of hiPSC-derived pacemaker-like cardiomyocytes. To date, no study has directly assessed gene expression in each pacemaker-, atria-, and ventricular-like cardiomyocyte subtype derived from hiPSCs since currently the subtypes of these immature cardiomyocytes can only be identified by action potential profiles. Traditional acquisition of action potentials using patch-clamp recordings renders the cells unviable for subsequent analysis. We circumvented these issues by acquiring the action potential profile of a single cell optically followed by assessment of protein expression through immunostaining in that same cell. Our same-single-cell analysis for the first time revealed expression of proposed pacemaker-specific markers—hyperpolarization-activated cyclic nucleotide-modulated (HCN)4 channel and Islet (Isl)1—at the protein level in all three hiPSC-derived cardiomyocyte subtypes. HCN4 expression was found to be higher in pacemaker-like hiPSC-derived cardiomyocytes than atrial- and ventricular-like subtypes but its downregulation over time in all subtypes diminished the differences. Isl1 expression in pacemaker-like hiPSC-derived cardiomyocytes was initially not statistically different than the contractile subtypes but did become statistically higher than ventricular-like cells with time. Our observations suggest that although HCN4 and Isl1 are differentially expressed in hiPSC-derived pacemaker-like relative to ventricular-like cardiomyocytes, these markers alone are insufficient in identifying hiPSC-derived pacemaker-like cardiomyocytes.

Within the past two decades polylactic-co-glycolic acid (PLGA) has gained considerable attention as a biocompatible and biodegradable polymer that is suitable for tissue engineering and regenerative medicine. In this present study, we have investigated the potential of PLGA, collagen I (ColI), and polyurethane (PU) scaffolds for ligament tissue regeneration. Two different ratios of PLGA (50:50 and 85:15) were used to determine the effects on mechanical tensile properties and cell adhesion. The Young's modulus, tensile stress at yield, and ultimate tensile strain of PLGA(50:50)-ColI-PU scaffolds demonstrated similar tensile properties to that of ligaments found in the knee. Whereas, scaffolds composed of PLGA(85:15)-ColI-PU had lower tensile properties than that of ligaments. Furthermore, we investigated the effect of fiber orientation on mechanical properties and our results indicate that aligned fiber scaffolds demonstrate higher tensile properties than scaffolds with random fiber orientation. Also, human fibroblasts attached and proliferated with no need for additional surface modifications to the presented electrospun scaffolds in both categories. Collectively, our investigation demonstrates the effectiveness of electrospun PLGA scaffolds as a suitable candidate for regenerative medicine, capable of being manipulated and combined with other polymers to create three-dimensional microenvironments with adjustable tensile properties to mimic native tissues. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 39–46, 2015.

We examined the effects of the microenvironment on vascular differentiation of murine cardiovascular progenitor cells (CPCs). We isolated CPCs and seeded them in culture exposed to the various extracellular matrix (ECM) proteins in both two-dimensional (2D) and 3D culture systems. To better understand the contribution of the microenvironment to vascular differentiation, we analyzed endothelial and smooth muscle cell differentiation at both day 7 and day 14. We found that laminin and vitronectin enhanced vascular endothelial cell differentiation while fibronectin enhanced vascular smooth muscle cell differentiation. We also observed that the effects of the 3D electrospun scaffolds were delayed and not noticeable until the later time point (day 14), which may be due to the amount of time necessary for the cells to migrate to the interior of the scaffold. The study characterized the contributions of both ECM proteins and the addition of a 3D culture system to continued vascular differentiation. Additionally, we demonstrated the capability bioengineer a CPC-derived vascular graft.

The relationship between stem cell niches in vivo and their surrounding microenvironment is still relatively unknown. Recent advances have indicated that extrinsic factors within the cardiovascular progenitor cell niche influence maintenance of a multipotent state as well as drive cell-fate decisions. We have previously shown the direct effects of extracellular matrix (ECM) proteins and have now investigated the effects of dimension on the induction of a cardiovascular progenitor cell (CPC) population. We have shown here that the three-dimensionality of a hyaluronan-based hydrogel greatly induces a CPC population, as marked by Flk-1. We have compared the effects of a 3D microenvironment to those of conventional 2D cell culture practices and have found that the 3D microenvironment potently induces a progenitor cell state.

Within the past two decades polylactic-co-glycolic acid (PLGA) has gained considerable attention as a biocompatible and biodegradable polymer that is suitable for tissue engineering and regenerative medicine. In this present study, we have investigated the potential of PLGA, collagen I (ColI), and polyurethane (PU) scaffolds for ligament tissue regeneration. Two different ratios of PLGA (50:50 and 85:15) were used to determine the effects on mechanical tensile properties and cell adhesion. The Young’s modulus, tensile stress at yield, and ultimate tensile strain of PLGA(50:50)-ColI-PU scaffolds demonstrated similar tensile properties to that of ligaments found in the knee. Whereas, scaffolds composed of PLGA(85:15)-ColI-PU had lower tensile properties than that of ligaments. Furthermore, we investigated the effect of fiber orientation on mechanical properties and our results indicate that aligned fiber scaffolds demonstrate higher tensile properties than scaffolds with random fiber orientation. Also, human fibroblasts attached and proliferated with no need for additional surface modifications to the presented electrospun scaffolds in both categories. Collectively, our investigation demonstrates the effectiveness of electrospun PLGA scaffolds as a suitable candidate for regenerative medicine, capable of being manipulated and combined with other polymers to create three-dimensional microenvironments with adjustable tensile properties to mimic native tissues.

Stem Cell Extracellular Matrix Interactions in Three- Dimensional System via Integrins Cells of all types interact with the extracellular matrix (ECM) through integrin-mediated interactions. Adhesion of embryonic stem (ES) cells is necessary for differentiation. We have characterized integrin expression of undifferentiated mES cells and established a system of evaluating the ECM-integrin interactions in three-dimension (3D) using electrospun scaffolds. We observed a higher proliferation rate at early time points in conventional 2D culture with various ECM proteins (collagen IV, laminin, fibronectin, vitronectin) as compared to 3D conditions. At later time points, we observed higher proliferations in 3D culture conditions compared to 2D culture conditions. We also detected the importance of α5, αV, β1, β5 and αVβ5 integrin subunits for cellular adhesion in 3D conditions using a cellular adhesion assay.

While stem cell niches in vivo are complex three-dimensional (3D) microenvironments, the relationship between the dimensionality of the niche to its function is unknown. We have created a 3D microenvironment through electrospinning to study the impact of geometry and different extracellular proteins on the development of cardiac progenitor cells (Flk-1(+)) from resident stem cells and their differentiation into functional cardiovascular cells. We have investigated the effect of collagen IV, fibronectin, laminin and vitronectin on the adhesion and proliferation of murine ES cells as well as the effects of these proteins on the number of Flk-1(+) cells cultured in 2D conditions compared to 3D system in a feeder free condition. We found that the number of Flk-1(+) cells was significantly higher in 3D scaffolds coated with laminin or vitronectin compared to colIV-coated scaffolds. Our results show the importance of defined culture systems in vitro for studying the guided differentiation of pluripotent embryonic stem cells in the field of cardiovascular tissue engineering and regenerative medicine.

Electrospinning using synthetic and natural polymers is a promising technique for the fabrication of scaffolds for tissue engineering. Numerous synthetic polymers are available to maximize durability and mechanical properties (polyurethane) versus degradability and cell adhesion (polycaprolactone). In this study, we explored the feasibility of creating scaffolds made of bicomponent nanofibers from both polymers using a coaxial electrospinning system. We used a core of poly(urethane) and a sheath of a mixture of poly(e-caprolactone) and gelatin, all dissolved in 1,1,1,3,3,3-hexafluror-2-propanol. These nanofibrous scaffolds were then evaluated to confirm their core-sheath nature and characterize their morphology and mechanical properties under static and dynamic conditions. Furthermore, the antigenicity of the scaffolds was studied to confirm that there is no significant foreign body response to the scaffold itself that would preclude its use in vivo. The results show the advantages of combining both natural and synethic polymers to create a coaxial scaffold capable of withstanding dynamic culture conditions and encourage cellular migration to the interior of the scaffold for tissue-engineering applications. Also, the results show that there is no significant immunoreactivity in vivo to the components of the scaffolds.

Stem or progenitor cell populations are often established in unique niche microenvironments that regulate cell fate decisions. Although niches have been shown to be critical for the normal development of several tissues, their role in the cardiovascular system is poorly understood. In this study, we characterized the cardiovascular progenitor cell (CPC) niche in developing human and mouse hearts, identifying signaling pathways and extracellular matrix (ECM) proteins that are crucial for CPC maintenance and expansion. We demonstrate that collagen IV (ColIV) and β-catenin-dependent signaling are essential for maintaining and expanding undifferentiated CPCs. Since niches are three-dimensional (3D) structures, we investigated the impact of a 3D microenvironment that mimics the in vivo niche ECM. Employing electrospinning technologies, 3D in vitro niche substrates were bioengineered to serve as culture inserts. The three-dimensionality of these structures increased mouse embryonic stem cell differentiation into CPCs when compared to 2D control cultures, which was further enhanced by incorporation of ColIV into the substrates. Inhibiting p300-dependent β-catenin signals with the small molecule IQ1 facilitated further expansion of CPCs. Our study represents an innovative approach to bioengineer cardiac niches that can serve as unique 3D in vitro systems to facilitate CPC expansion and study CPC biology.

Synthetic polymers or naturally-derived extracellular matrix (ECM) proteins have been used to create tissue engineering scaffolds; however, the need for surface modification in order to achieve polymer biocompatibility and the lack of biomechanical strength of constructs built using proteins alone remain major limitations. To overcome these obstacles, we developed novel hybrid constructs composed of both strong biosynthetic materials and natural human ECM proteins. Taking advantage of the ability of cells to produce their own ECM, human foreskin fibroblasts were grown on silicon-based nanostructures exhibiting various surface topographies that significantly enhanced ECM protein production. After 4 weeks, cell-derived sheets were harvested and histology, immunochemistry, biochemistry and multiphoton imaging revealed the presence of collagens, tropoelastin, fibronectin and glycosaminoglycans. Following decellularization, purified sheet-derived ECM proteins were mixed with poly(epsilon-caprolactone) to create fibrous scaffolds using electrospinning. These hybrid scaffolds exhibited excellent biomechanical properties with fiber and pore sizes that allowed attachment and migration of adipose tissue-derived stem cells. Our study represents an innovative approach to generate strong, non-cytotoxic scaffolds that could have broad applications in tissue regeneration strategies.