Designing a MOF-functionalized Nanofibrous Aerogel via Vapor-Phase Synthesis

Designing 3D mechanically robust and high-surface-area substrates for uniform and high-density deposition of metal-organic frameworks (MOFs) provide a promising strategy to enhance surface accessibility and application of these highly functional materials. Nanofibrous aerogel (NFA) with its highly porous self-supported structure composed of interconnected nanofibrous network offers an ideal platform in this regard. Herein, a facile one-pot strategy is introduced, which utilizes direct deposition of MOF on the nanofibrous surface of the NFAs. NFAs are synthesized using electrospun polyacrylonitrile/polyvinylpyrrolidone (PAN/PVP) polymer nanofibers containing zinc acetate (Zn(Ac)2), which are subjected to freeze drying and thermal treatment. The latter converts Zn(Ac)2 to zinc oxide (ZnO), providing the sites for MOF growth while also adding mechanical integrity to the NFAs through cyclization of the PAN. Exposure of the NFA to the vapor-phase of organic ligand, 2-methylimidazole (2-MeIm) enables in situ growth of zeolitic imidazolate framework-8 (ZIF-8) MOF on the NFA. ZIF-8 loading on the NFAs is further improved by more than tenfold by synthesizing ZnO nanorods/protrusions on the nanofibers, which enables more sites for MOF growth. These findings underscore a significant advancement in designing MOF-based hybrid aerogels, offering a streamlined approach for their use in diverse applications, from catalysis to sensing and water purification.

Sheet-based extrusion bioprinting: a new multi-material paradigm providing mid-extrusion micropatterning control for microvascular applications

As bioprinting advances into clinical relevance with patient-specific tissue and organ constructs, it must be capable of multi-material fabrication at high resolutions to accurately mimick the complex tissue structures found in the body. One of the most fundamental structures to regenerative medicine is microvasculature. Its continuous hierarchical branching vessel networks bridge surgically manipulatable arteries (∼1-6 mm) to capillary beds (∼10µm). Microvascular perfusion must be established quickly for autologous, allogeneic, or tissue engineered grafts to survive implantation and heal in place. However, traditional syringe-based bioprinting techniques have struggled to produce perfusable constructs with hierarchical branching at the resolution of the arterioles (∼100-10µm) found in microvascular tissues. This study introduces the novel CEVIC bioprinting device (i.e.ContinuouslyExtrudedVariableInternalChanneling), a multi-material technology that breaks the current extrusion-based bioprinting paradigm of pushing cell-laden hydrogels through a nozzle as filaments, instead, in the version explored here, extruding thin, wide cell-laden hydrogel sheets. The CEVIC device adapts the chaotic printing approach to control the width and number of microchannels within the construct as it is extruded (i.e. on-the-fly). Utilizing novel flow valve designs, this strategy can produce continuous gradients varying geometry and materials across the construct and hierarchical branching channels with average widths ranging from 621.5 ± 42.92%µm to 11.67 ± 14.99%µm, respectively, encompassing the resolution range of microvascular vessels. These constructs can also include fugitive/sacrificial ink that vacates to leave demonstrably perfusable channels. In a proof-of-concept experiment, a co-culture of two microvascular cell types, endothelial cells and pericytes, sustained over 90% viability throughout 1 week in microchannels within CEVIC-produced gelatin methacryloyl-sodium alginate hydrogel constructs. These results justify further exploration of generating CEVIC-bioprinted microvasculature, such as pre-culturing and implantation studies.

Development of a hyaluronic acid-collagen bioink for shear-induced fibers and cells alignment

Human tissues are characterized by complex composition and cellular and extracellular matrix (ECM) organization at microscopic level. In most of human tissues, cells and ECM show an anisotropic arrangement, which confers them specific properties.In vitro, the ability to closely mimic this complexity is limited. However, in the last years, extrusion bioprinting showed a certain potential for aligning cells and biomolecules, due to the application of shear stress during the bio-fabrication process. In this work, we propose a strategy to combine collagen (col) with tyramine-modified hyaluronic acid (THA) to obtain a printable col-THA bioink for extrusion bioprinting, solely-based on natural-derived components. Collagen fibers formation within the hybrid hydrogel, as well as collagen distribution and spatial organization before and after printing, were studied. For the validation of the biological outcome, fibroblasts were selected as cellular model and embedded in the col-THA matrix. Cell metabolic activity and cell viability, as well as cell distribution and alignment, were studied in the bioink before and after bioprinting. Results demonstrated successful collagen fibers formation within the bioink, as well as collagen anisotropic alignment along the printing direction. Furthermore, results revealed suitable biological properties, with a slightly reduced metabolic activity at day 1, fully recovered within the first 3 d post-cell embedding. Finally, results showed fibroblasts elongation and alignment along the bioprinting direction. Altogether, results validated the potential to obtain collagen-based bioprinted constructs, with both cellular and ECM anisotropy, without detrimental effects of the fabrication process on the biological outcome. This bioink can be potentially used for a wide range of applications in tissue engineering and regenerative medicine in which anisotropy is required.

Three‐dimensional nanofibrous and porous scaffolds of poly(ε‐caprolactone)‐chitosan blends for musculoskeletal tissue engineering

One of the established tissue engineering strategies relies on the fabrication of appropriate materials architectures (scaffolds) that mimic the extracellular matrix (ECM) and assist the regeneration of living tissues. Fibrous structures produced by electrospinning have been widely used as reliable ECM templates but their two-dimensional structure restricts, in part, cell infiltration and proliferation. A recent technique called thermally-induced self-agglomeration (TISA) allowed to alleviate this drawback by rearranging the 2D electrospun membranes into highly functional 3D porous-fibrous systems. Following this trend, the present research focused on preparing polycaprolactone/chitosan blends by electrospinning, to then convert them into 3D structures by TISA. By adding different amounts of chitosan, it was possible to accurately modulate the physicochemical properties of the obtained 3D nanofibrous scaffolds, leading to highly porous constructs with distinct morphologic and mechanical features. Viability and proliferation studies using adult human chondrocytes also revealed that the biocompatibility of the scaffolds was not impaired after 28 days of cell culture, highlighting their potential to be included into musculoskeletal tissue engineering applications, particularly cartilage repair.

Guiding cell migration in 3D with high-resolution photografting

Multi-photon lithography (MPL) has proven to be a suitable tool to precisely control the microenvironment of cells in terms of the biochemical and biophysical properties of the hydrogel matrix. In this work, we present a novel method, based on multi-photon photografting of 4,4′-diazido-2,2′-stilbenedisulfonic acid (DSSA), and its capabilities to induce cell alignment, directional cell migration and endothelial sprouting in a gelatin-based hydrogel matrix. DSSA-photografting allows for the fabrication of complex patterns at a high-resolution and is a biocompatible, universally applicable and straightforward process that is comparably fast. We have demonstrated the preferential orientation of human adipose-derived stem cells (hASCs) in response to a photografted pattern. Co-culture spheroids of hASCs and human umbilical vein endothelial cells (HUVECs) have been utilized to study the directional migration of hASCs into the modified regions. Subsequently, we have highlighted the dependence of endothelial sprouting on the presence of hASCs and demonstrated the potential of photografting to control the direction of the sprouts. MPL-induced DSSA-photografting has been established as a promising method to selectively alter the microenvironment of cells.

Preparation, properties and application of graphene-based materials in tissue engineering scaffolds

Tissue engineering has great application prospect as an effective treatment for tissue and organ injury, functional reduction or loss. Bioactive tissues are reconstructed and damaged organs are repaired by the three elements including cells, scaffold materials and growth factors. Graphene-based composites can be used as reinforcing auxiliary materials for tissue scaffold preparation because of their large specific surface area, and good mechanical support. Tissue engineering scaffolds with graphene-based composites have been widely studied. Part of research have focused on the application of graphene-based composites in single tissue engineering; The basic principles of graphene materials used in tissue engineering are summarized in some researches. Some studies emphasized the key problems and solutions urgently needed to be solved in the development of tissue engineering, and discussed their application prospect. Some related studies mainly focused on the conductivity of graphene, and discussed the application of electroactive scaffolds in tissue engineering. In this review, the composite materials for preparing tissue engineering scaffolds are briefly described, which emphasizes the preparation methods, biological properties and practical applications of graphene-based composite scaffolds. The synthetic techniques with stressing solvent casting, electrospinning and 3D printing are introduced in detail. The mechanical, cell-oriented and biocompatible properties of graphene-based composite scaffolds in tissue engineering are analyzed and summarized. Their applications in bone tissue engineering, nerve tissue engineering, cardiovascular tissue engineering and other tissue engineering are summarized systematically. In addition, this work also looks forward to the difficulties and challenges in the future research, providing some references for the follow-up research of graphene-based composites in tissue engineering scaffolds.

Electrospun microstructured PLA-based scaffolds featuring relevant anisotropic, mechanical and degradation characteristics for soft tissue engineering

Electrospun scaffolds combine suitable structural characteristics that make them strong candidates for their use in tissue engineering. These features can be tailored to optimize other physiologically relevant attributes (e.g. mechanical anisotropy and cellular affinity) while ensuring adequate degradation rates of the biomaterial. Here, we present the fabrication of microstructured scaffolds by using a combination of micropatterned electrospinning collectors (honeycomb- or square-patterned) and poly(lactic acid) (PLA)-based copolymers (linear or star-shaped). The resulting materials showed appropriate macropore size and fiber alignment that were key parameters to enhance their anisotropic properties in protraction. Moreover, their elastic modulus, which was initially similar to that of soft tissues, gradually changed in hydrolytic conditions, matching the degradation profile in a 2- to 3-month period. Finally, honeycomb-structured scaffolds exhibited enhanced cellular proliferation compared to standard electrospun mats, while cell colonization was shown to be guided by the macropore contour. Taking together, these results provide new insight into the rational design of microstructured materials that can mimic the progressive evolution of properties in soft tissue regeneration.

A biomimetic orthogonal-bilayer tubular scaffold for the co-culture of endothelial cells and smooth muscle cells

In blood vessels, endothelial cells (ECs) grow along the direction of blood flow, while smooth muscle cells (SMCs) grow circumferentially along the vessel wall. To mimic this structure, a polycaprolactone (PCL) tubular scaffold with orthogonally oriented bilayer nanofibers was prepared via electrospinning and winding. ECs were cultured on the inner layer of the scaffold with axial nanofibers and SMCs were cultured on the outer layer of the scaffold with circumferential nanofibers. Fluorescence images of the F-actin distribution of ECs and SMCs indicated that cells adhered, stretched, and proliferated in an oriented manner on the scaffold. Moreover, layers of ECs and SMCs formed on the scaffold after one month of incubation. The expression levels of platelet-endothelial cell adhesion molecule 1 (PECAM-1) and a contractile SMC phenotype marker in the EC/SMC co-culture system were much higher than those in individual culture systems, thus demonstrating that the proposed biomimetic scaffold promoted the intercellular junction of ECs and preserved the contractile phenotype of SMCs.

To mimic blood vessels, a polycaprolactone tubular scaffold was prepared via electrospinning and winding. Endothelial cells were cultured on the inner layer with axial nanofibers and smooth muscle cells were cultured on the outer layer with circumferential nanofibers.

Regulated Surface Morphology of Polyaniline/Polylactic Acid Composite Nanofibers via Various Inorganic Acids Doping for Enhancing Biocompatibility in Tissue Engineering

Conductive and degradable nanofibrous scaffolds have great potential in promoting cell growth, proliferation, and differentiation under an external electric field. Although the issue of inferior electrical conductivity in body fluids still exists, polyaniline (PANI)-based degradable nanofibers can promote cell adhesion, growth, and proliferation. To investigate whether the effect is caused by the PANI morphology, we selected three inorganic acids as dopants in the process of PANI in situ oxidative polymerization: hydrochloric acid, sulfuric acid, and perchloric acid. The obtained polyaniline/polylactic acid (PANI/PLA) composite nanofibers were characterized via SEM, FTIR, and XPS analysis, and we confirmed that the PLA nanofibers were successfully coated by PANI without any change to the porous structure of the PLA nanofibers. The in vitro mechanical properties and degradability indicated that the oxidation of acid dopants should be considered and that it was likely to have a higher oxidation degradation effect on PLA nanofibers. The contact angle test demonstrated that PANI/PLA composite nanofibers with different surface morphologies have good wettability, implying that they meet the requirements of bone tissue engineering scaffolds. The surface roughness and cell viability demonstrated that different PANI morphologies on the surface can promote cell proliferation. The higher the surface roughness of the PANI, the better the biocompatibility. Consequently, the regulated surface morphology of PANI/PLA composite nanofibers via different acids doping has positive effect on biocompatibility in tissue engineering.

Solvent Vapor Strengthened Polyimide Nanofiber-Based Aerogels with High Resilience and Controllable Porous Structure

Owing to the hierarchically three-dimensional (3D) network, ultralow density, and high porosity, nanofiber-based aerogels (NFAs) have drawn great attention recently. However, precise control of the porous structure and mechanical properties of NFAs, which have been proved to be extremely essential to the applications, still remains a major challenge. Herein, electrospun polyimide (PI) nanofibers were utilized as building blocks to construct NFAs through the solid-templating technique. The porous structure of PI nanofiber-based aerogels (PI-NFAs) could be adjusted by changing the processing parameters. By further welding the adjacent nanofibers at the contact sites with solvent vapor, high-resilience PI-NFAs were successfully prepared with comparable or higher recoverable, under compression, folding and torsion relative to other NFAs. The welded PI-NFAs showed ultralow density (minimum of 0.96 mg/cm³), high porosity (maximum of 99.93%), and tunable hierarchical structure. Therefore, this study brought a new perspective on the simple preparation of high-resilience nanofiber-based aerogels with tunable porous structures.

Microfluidic Technology for the Production of Well-Ordered Porous Polymer Scaffolds

Advances in tissue engineering (TE) have revealed that porosity architectures, such as pore shape, pore size and pore interconnectivity are the key morphological properties of scaffolds. Well-ordered porous polymer scaffolds, which have uniform pore size, regular geometric shape, high porosity and good pore interconnectivity, facilitate the loading and distribution of active biomolecules, as well as cell adhesion, proliferation and migration. However, these are difficult to prepare by traditional methods and the existing well-ordered porous scaffold preparation methods require expensive experimental equipment or cumbersome preparation steps. Generally, droplet-based microfluidics, which generates and manipulates discrete droplets through immiscible multiphase flows inside microchannels, has emerged as a versatile tool for generation of well-ordered porous materials. This short review details this novel method and the latest developments in well-ordered porous scaffold preparation via microfluidic technology. The pore structure and properties of microfluidic scaffolds are discussed in depth, laying the foundation for further research and application in TE. Furthermore, we outline the bottlenecks and future developments in this particular field, and a brief outlook on the future development of microfluidic technique for scaffold fabrication is presented.

Combination of electrospinning with other techniques for the fabrication of 3D polymeric and composite nanofibrous scaffolds with improved cellular interactions

The development of three-dimensional (3D) scaffolds with physical and chemical topological cues at the macro-, micro-, and nanometer scale is urgently needed for successful tissue engineering applications. 3D scaffolds can be manufactured by a wide variety of techniques. Electrospinning technology has emerged as a powerful manufacturing technique to produce non-woven nanofibrous scaffolds with very interesting features for tissue engineering products. However, electrospun scaffolds have some inherent limitations that compromise the regeneration of thick and complex tissues. By integrating electrospinning and other fabrication technologies, multifunctional 3D fibrous assemblies with micro/nanotopographical features can be created. The proper combination of techniques leads to materials with nano and macro-structure, allowing an improvement in the biological performance of tissue-engineered constructs. In this review, we focus on the most relevant strategies to produce electrospun polymer/composite scaffolds with 3D architecture. A detailed description of procedures involving physical and chemical agents to create structures with large pores and 3D fiber assemblies is introduced. Finally, characterization and biological assays including in vitro and in vivo studies of structures intended for the regeneration of functional tissues are briefly presented and discussed.

Accelerated Outgrowth of Neurites on Graphene Oxide-Based Hybrid Electrospun Fibro-Porous Polymeric Substrates

Fabrication of a surface-engineered electrospun scaffold having biomimetic properties like the extracellular matrix (ECM) is essential for neural tissue engineering. An electroconductive and elastomeric scaffold with aligned fibers acting as a substrate may have a great impact on the directional outgrowth of neurites. In this study, we have electrospun electrically conductive, polyurethane-based elastomeric and topographically aligned fibro-porous neural scaffolds. Adhesive proteins of the ECM are documented to have an important role in controlling neuronal cell behavior, including cell adhesion, proliferation, and neurite outgrowth. These bio-adhesion proteins or nanomaterials mimicking their action, if used for surface modification of neural scaffolds, may have the potential to accelerate the nerve repair process. Thus, electrospun scaffolds fabricated were surface-engineered using a unique and modified single-step electrospraying technique to coat the scaffold surface with an exploratory bio-adhesion agent, a thin layer of graphene oxide (GO) films. The study was then carried out to determine if the GO-coated electrospun electroconductive polycarbonate urethane (PCU) substrate can improve the bio-interface attributes of these scaffolds or may alter the neurite outgrowth of PC-12 cells like any other bio-adhesion proteins. Therefore, the hybrid scaffolds with GO coatings were compared with similar scaffolds coated with poly-l-lysine (PLL) for neural cell adhesion, proliferation, and neurite extension. Neurite outgrowth studies showed that although the average neurite length was comparable on both GO- and PLL-coated surfaces, the length profile of neurites, when categorized based on length, showed an increased number of lengthier neurites on the GO-coated hybrid scaffolds. In particular, the study brings out an innovative surface engineering technique for the coating of GO on polymeric scaffolds. It may be further put together in designing of hybrid surfaces with nanotopographical biophysical cues on three-dimensional neural scaffolds, which in turn may stimulate an accelerated neuronal regeneration via providing an enhanced ECM like milieu.

[Structural control and characterization of hierarchically structured fibrous scaffolds]

OBJECTIVE

To prepare hierarchically structured fibrous scaffolds with different morphologies, and to explore the additional dimensionality for tuning the physicochemical properties of the scaffolds and the effect of their hemocompatibility and cytocompatibility.

METHODS

Electrospinning poly (e-caprolactone) (PCL)/polyvinylpyrrolidone (PVP) bicomponent fibers (PCL∶PVP mass ratios were 8∶2 and 5∶5 respectively), and the surface porous fibrous scaffolds were prepared by extracting PVP components. The scaffolds were labeled PCL-P8 and PCL-P5 respectively according to the mass ratio of polymer. In addition, shish-kebab (SK) structured scaffolds with different kebab sizes were created by solution incubation method, which use electrospun PCL fibers as shish while PCL chains in solution crystallizes on the fiber surface. The PCL fibrous scaffolds with smooth surface was established as control group. The hierarchically structured fibrous scaffolds were characterized by field emission scanning electron microspore, water contact angle tests, and differential scanning calorimeter (DSC) experiments. The venous blood of New Zealand white rabbits was taken and hemolysis and coagulation tests were used to characterize the blood compatibility of the scaffolds. The proliferation of the pig iliac artery endothelial cell (PIEC) on the scaffolds was detected by cell counting kit 8 (CCK-8) method, and the biocompatibility of the scaffolds was evaluated.

RESULTS

Field emission scanning electron microscopy showed that porous morphology appeared on the surface of PCL/PVP bicomponent fibers after extracting PVP. In addition, SK structure with periodic arrangement was successfully prepared by solution induction, and the longer the crystallization time, the larger the lamellar size and periodic distance. The contact angle and DSC measurements showed that when compared with smooth PCL fiber scaffolds, the crystallinity of PCL surface porous fibrous scaffolds and PCL-SK fibrous scaffolds increased, while the hydrophobicity of PCL-SK fibrous scaffolds increased, but the hydrophobicity of PCL porous scaffolds did not change significantly. The hemolysis test showed that the hemolysis rate of PCL surface porous fibrous scaffolds and PCL-SK fibrous scaffolds was higher than that of PCL fibrous scaffolds. According to American Society of Materials and Tests (ASTM) F756-08 standard, all scaffolds were non-hemolytic materials and were suitable for blood contact materials. Coagulation test showed that the coagulation index of PCL surface porous fibrous scaffolds and PCL-SK fibrous scaffolds was higher than that of PCL fibrous scaffolds at 5 and 10 minutes of culture. CCK-8 assay showed that both hierarchically structured fibrous scaffolds were more conducive to PIEC proliferation than PCL fibrous scaffold.

CONCLUSION

Based on electrospinning technology, solution-induced and blend phase separation methods can be used to construct multi-scale fiber scaffolds with different morphologies, which can not only regulate the surface physicochemical properties of the scaffolds, but also have good blood compatibility and biocompatibility. The hierarchically structured fibrous scaffolds have high application potential in the field of tissue engineering.

Prefabricated and Self-Setting Cement Laminates

Polycaprolactone (PCL) fiber mats with defined pore architecture were shown to provide sufficient support for a premixed calcium phosphate cement (CPC) paste to serve as a flat and flexible composite material for the potential application in 2-dimensional, curved cranial defects. Fiber mats were fabricated by either melt electrospinning writing (MEW) or solution electrospinning (SES) with a patterned collector. While MEW processed fiber mats led to a deterioration of the cement bending strength by approximately 50%, due to a low fiber volume content in conjunction with a weak fiber-matrix interface, fiber mats obtained by solution electrospinning resulted in a mechanical reinforcement of the cement matrix in terms of both bending strength and absorbed fracture energy. This was attributed to a higher fiber volume content and a large contact area between nanosized fibers and cement matrix. Hydrophilization of the PCL scaffolds prior to lamination further improved composite strength and preserved the comparably higher fracture energy of 1.5 to 2.0 mJ/mm². The laminate composite approach from this study was successful in demonstrating the limitations and design options of such novel composite materials. However, fiber-cement compatibility remains an issue to be addressed, since a high degree of hydrophilicity does not necessarily provoke a stronger interface.

A facile low-temperature synthesis of hierarchical porous Co3O4 micro/nano structures derived from ZIF-67 assisted by ammonium perchlorate

Sub-micro hierarchical porous Co₃O₄ dodecahedra with a large specific surface area (106.11 m² g⁻¹) were synthesized by the thermolysis of ZIF-67 at a low temperature of 268 °C assisted by ammonium perchlorate (AP).

Tendon Fascicle-Inspired Nanofibrous Scaffold of Polylactic acid/Collagen with Enhanced 3D-Structure and Biomechanical Properties

Surgical treatment of tendon lesions still yields unsatisfactory clinical outcomes. The use of bioresorbable scaffolds represents a way forward to improve tissue repair. Scaffolds for tendon reconstruction should have a structure mimicking that of the natural tendon, while providing adequate mechanical strength and stiffness. In this paper, electrospun nanofibers of two crosslinked PLLA/Collagen blends (PLLA/Coll-75/25, PLLA/Coll-50/50) were developed and then wrapped in bundles, where the nanofibers are predominantly aligned along the bundles. Bundle morphology was assessed via SEM and high-resolution x-ray computed tomography (XCT). The 0.4-micron resolution in XCT demonstrated a biomimetic morphology of the bundles for all compositions, with a predominant nanofiber alignment and some scatter (50-60% were within 12° from the axis of the bundle), similar to the tendon microstructure. Human fibroblasts seeded on the bundles had increased metabolic activity from day 7 to day 21 of culture. The stiffness, strength and toughness of the bundles are comparable to tendon fascicles, both in the as-spun condition and after crosslinking, with moderate loss of mechanical properties after ageing in PBS (7 and 14 days). PLLA/Coll-75/25 has more desirable mechanical properties such as stiffness and ductility, compared to the PLLA/Coll-50/50. This study confirms the potential to bioengineer tendon fascicles with enhanced 3D structure and biomechanical properties.

Tailoring weight ratio of PCL/PLA in electrospun three-dimensional nanofibrous scaffolds and the effect on osteogenic differentiation of stem cells

Three-dimensional (3D) scaffolds as artificial ECMs have been extensively studied to mimic the critical features of natural ECMs. To develop more clinically relevant 3D scaffolds, electrospun nanofibrous scaffolds with different weight ratios of PCL/PLA (i.e., 100/0, 60/40, and 20/80) were fabricated via the thermally induced (nanofiber) self-agglomeration (TISA) method. The hypothesis was that, with the weight ratio increase of stiffer and more bioactive PLA in the 3D PCL/PLA blend scaffolds, the osteogenic differentiation of human mesenchymal stem cells (hMSCs) would be enhanced. The results indicated that, all of the 3D scaffolds were elastic/resilient and possessed interconnected and hierarchical pores with sizes from sub-microns to ∼300 μm; therefore, the morphological structures of these scaffolds were similar to those of natural ECMs. The PLA80 scaffolds exhibited the best overall properties in terms of density, porosity, water absorption capacity, mechanical properties, bioactivity, and cell viability. Furthermore, with increasing the PLA weight ratio, the alkaline phosphatase (ALP) activity, calcium content, and gene expression level were also increased, probably due to the improved stiffness/bioactivity of scaffold. Hence, the novel 3D electrospun PLA80 nanofibrous scaffold might be desired/favorable for the osteogenic differentiation of hMSCs.

Electroactive biomaterial surface engineering effects on muscle cells differentiation

Even though skeletal muscle cells can naturally regenerate as a response to insignificant tissue damages, more severe injuries can cause irreversible loss of muscle cells mass and/or function. Until now, cell therapies are not a good approach to treat those injuries. Biomaterials such as poly(vinylidene fluoride), PVDF, can improve muscle regeneration by presenting physical cues to muscle cells that mimic the natural regeneration environment. In this way, the ferroelectric and piezoelectric properties of PVDF offer new opportunities for skeletal muscle tissue engineering once the piezoelectricity is an electromechanical effect that can be used to provide electrical signals to the cells, upon mechanical solicitations, similar to the ones found in several body tissues. Thus, previous to dynamic experiments, it is important to determine how the surface properties of the material, both in terms of the poling state (positive or negative net surface charge) and of the morphology (films or fibers) influence myoblast differentiation. It was observed that PVDF promotes myogenic differentiation of C2C12 cells as evidenced by quantitative analysis of myotube fusion, maturation index, length, diameter and number. Charged surfaces improve the fusion of muscle cells into differentiated myotubes, as demonstrated by fusion and maturation index values higher than the control samples. Finally, the use of random and oriented β-PVDF electrospun fibers scaffolds has revealed differences in cell morphology. Contrary to the randomly oriented fibers, oriented PVDF electrospun fibers have promoted the alignment of the cells. It is thus demonstrated that the use of this electroactive polymer represents a suitable approach for the development of electroactive microenvironments for effective muscle tissue engineering.

Ultraporous, Compressible, Wettable Polylactide/Polycaprolactone Sponges for Tissue Engineering

Ultraporous, degradable sponges made of either polylactide or of blends of polylactide/poly(ε-caprolactone) are prepared by freeze-drying of dispersions of short electrospun fibers and subsequent thermal annealing. The sponges feature ultrahigh porosity (99.6%), a hierarchical cellular structure, and high reversible compressibility with fast recovery from deformation in the dry as well as in the wet state. The sponge properties depend on the fiber dispersion concentration and the annealing temperature. Sponge characteristics like fiber density (2.5-20 mg/cm³), size, shape, crystallinity, mechanical strength, wetability, and structural integrity are user adjustable. Cell culture experiments were successfully performed with Jurkat cells with Confocal Laser Scanning Microscopy and MTT staining showing rapid cell proliferation. Live/Dead staining demonstrated high viability of the seeded cells. The sponge characteristics and modifications investigated and presented here reveal that these sponges are highly promising for tissue engineering applications.

Fabrication of transparent hemispherical 3D nanofibrous scaffolds with radially aligned patterns via a novel electrospinning method

Tissue engineering has significantly contributed to the development of optimal treatments for individual injury sites based on their unique functional and histologic properties. Human organs and tissue have three-dimensional (3D) morphologies; for example, the morphology of the eye is a spherical shape. However, most conventional electrospinning equipment is only capable of fabricating a two-dimensional (2D) structured fibrous scaffold and no report is available on a 3D electrospinning method to fabricate a hemispherical scaffold to mimic the native properties of the cornea, including microscopic to macroscopic morphology and transparency. We proposed a novel electrospinning method using a single nonconductive hemispherical device and a metal pin. A designed peg-top shaped collector, a hemispherical nonconductive device with a metal pin in the center and copper wire forming a circle around at the edge was attached to a conventional conductive collector. A 3D hemispherical transparent scaffold with radially aligned nanofibers was successfully fabricated with the designed peg-top collector. In summary, our fabricated 3D electrospun scaffold is expected to be suitable for the treatment of injuries of ocular tissues owing to the hemispherical shape and radially aligned nanofibers which can guide the direction of the main collagen and cellular actin filament in the extracellular matrix.

Harnessing Nanotopography of Electrospun Nanofibrous Nerve Guide Conduits (NGCs) for Neural Tissue Engineering

The anatomical recovery of nerve defects with their neurological functions after an injury caused by diseases or accidents is an important clinical issue. The most efficient surgical technique so far to the nerve defects, which are unrepairable by direct end-to-end suture, can be autograft transplantation. The autograft transplantation, however, has disadvantages including multiple rounds of surgery, a shortage of nerve donor, and function loss at the donor site. Tissue-engineered nerve guide conduits (TENGCs) have emerged as a potential alternative to autologous nerve grafts for nerve regeneration and functional recovery. Various TENGCs researches are being carried out to improve characteristics and enhance functionality such as material selection, biomimetic, topography, and enhancement by the biomolecules additions. Among them, the customizable surface nanotopography of aligned fibrous TENGCs foster neural repair by providing a cell-friendly environment, permissiveness, guidance cues, and directional growth of the cells. Fibrous nerve guide conduits (NGCs) made of longitudinally ordered fibers is a promising candidate for nerve tissue engineering.

The influence of bubble size on chondrogenic differentiation of adipose-derived stem cells in gelatin microbubble scaffolds

In human bodies, cartilage tissue lacks the ability to heal when it encounters trauma or lesions.

Alignment of Multiple Electrospun Piezoelectric Fiber Bundles Across Serrated Gaps at an Incline: A Method to Generate Textile Strain Sensors

In this paper, we report a new type of electrospinning collector that allows simultaneous collection and alignment of multiple poly(vinylidene fluoride-trifluoroethylene) piezoelectric fiber bundles with a controlled separation. The key enabling feature is the serrated teeth along the edges across an inclined gap as a part of the conductive collector. As a result, the electrical field across the gap is shaped to direct the electrospun fibers to merge into multiple bundles. The sharp points on the serrated teeth provide favorable charge dissipation points and thus fibers are preferentially formed bridging two closest sharp points across the gap. To investigate the effectiveness of serrated teeth on the formation of multiple fiber bundles, three-dimensional finite element simulations are conducted. The corresponding collectors are implemented to experimentally study the resulting electrospun fibers. Both simulation and experimental results suggest that multiple fiber bundles can be formed under the condition of a low teeth pitch to gap distance ratio. Furthermore, a sharper tooth angle results in a higher preferential formation of fiber bundles. Finally, the total electrospinning time should be less than 60 seconds to maintain favorable electric field profile. We also demonstrate that these piezoelectric fiber bundles can serve as ultra-flexible textile sensors.

Three-Dimensional Au-Coated Electrosprayed Nanostructured BODIPY Films on Aluminum Foil as Surface-Enhanced Raman Scattering Platforms and Their Catalytic Applications

The design and development of three-dimensional (3D) nanostructures with high surface-enhanced Raman scattering (SERS) performances have attracted considerable attention in the fields of chemistry, biology, and materials science. Nevertheless, electrospraying of organic small molecules on low-cost flexible substrates has never been studied to realize large-scale SERS-active platforms. Here, we report the facile, efficient, and low-cost fabrication of stable and reproducible Au-coated electrosprayed organic semiconductor films (Au@BDY-4T-BDY) on flexible regular aluminum foil at a large scale (5 cm × 5 cm) for practical SERS and catalytic applications. To this end, a well-designed acceptor-donor-acceptor-type solution-processable molecular semiconductor, BDY-4T-BDY, developed by our group, is used because of its advantageous structural and electrical properties. The morphology of the electrosprayed organic film changes by solution concentration, and two different 3D morphologies with out-of-plane features are obtained. Highly uniform dendritic nanoribbons with sharp needle-like tips and vertically oriented nanoplates (∼50 nm thickness) are achieved when electrospraying solution concentrations of 240 and 253% w/v (mg/mL) are, respectively, used. When these electrosprayed organic films are coated with a nanoscopic thin (30 nm) Au layer, the resulting Au@BDY-4T-BDY platforms demonstrate remarkable SERS enhancement factors up to 1.7 × 10⁶ with excellent Raman signal reproducibility (relative standard deviation ≤ 0.13) for methylene blue over the entire film. Finally, Au@BDY-4T-BDY films showed good catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol with rate constants of 1.3 × 10^-2 and 9.2 × 10^-3 min^-1. Our results suggest that electrospraying of rationally designed organic semiconductor molecules on flexible substrates holds great promise to enable low-cost, solution-processed, SERS-active platforms.

Preparation and biocompatibility of electrospinning PDLLA/β-TCP/collagen for peripheral nerve regeneration

A unique nerve conduit composed of poly(d,l-lactic acid) (PDLLA), β-tricalcium phosphate (β-TCP) and collagen was prepared by electrospinning for the first time.

Colorful Hydrophobic Poly(Vinyl Butyral)/Cationic Dye Fibrous Membranes via a Colored Solution Electrospinning Process

Colorful nanofibrous membranes have attracted much attention for their visual varieties and various functionalities. In this article, a colored solution electrospinning process was used to fabricate colorful hydrophobic poly(vinyl butyral) (PVB)/cationic dye nanofibrous membranes (NFMs) successfully. The color and morphology of these as-spun nanofibrous membranes have been analyzed by colorimetry, spectroscopy, and scanning electron microscopy (SEM). It is shown that the as-spun colorful PVB-based membranes exhibit excellent level-dyeing property and color stability. Furthermore, the doping of cationic dye and the increase of dye concentration can decrease the diameter of the as-spun colored fibers, which results in better level-dyeing property and higher water contact angle more than 140°. The stained PVB fibrous membranes with excellent level-dyeing property and hydrophobicity are promising in some applications such as textiles, wallpapers, and anticorrosive coating/painting.

Electrospinning of Nanodiamond-Modified Polysaccharide Nanofibers with Physico-Mechanical Properties Close to Natural Skins

Electrospinning of biopolymers has gained significant interest for the fabrication of fibrous mats for potential applications in tissue engineering, particularly for wound dressing and skin regeneration. In this study, for the first time, we report successful electrospinning of chitosan-based biopolymers containing bacterial cellulous (33 wt %) and medical grade nanodiamonds (MND) (3 nm; up to 3 wt %). Morphological studies by scanning electron microscopy showed that long and uniform fibers with controllable diameters from 80 to 170 nm were prepared. Introducing diamond nanoparticles facilitated the electrospinning process with a decrease in the size of fibers. Fourier transform infrared spectroscopy determined hydrogen bonding between the polymeric matrix and functional groups of MND. It was also found that beyond 1 wt % MND, percolation networks of nanoparticles were formed which affected the properties of the nanofibrous mats. Uniaxial tensile testing of the woven mats determined significant enhancement of the strength (from 13 MPa to 25 MP) by dispersion of 1 wt % MND. The hydrophilicity of the mats was also remarkably improved, which was favorable for cell attachment. The water vapor permeability was tailorable in the range of 342 to 423 µg·Pa(-1)·s(-1)·m(-1). The nanodiamond-modified mats are potentially suitable for wound healing applications.

Engineering Porous Poly(lactic acid) Scaffolds with High Mechanical Performance via a Solid State Extrusion/Porogen Leaching Approach

A knotty issue concerning the poor mechanical properties exists in the porogen leaching approach to porous scaffolds, despite its advantage in tuning pore structure. To address this hurdle, solid state extrusion (SSE) combined with porogen leaching was utilized to engineer porous scaffolds of poly(lactic acid) (PLA). Advances introduced by poly(ethylene glycol) (PEG) caused the PLA ductile to be processed and, on the other hand, enabled the formation of interconnected pores. Thus, a well-interconnected porous architecture with high connectivity exceeding 97% and elevated porosity over 60% was obtained in the as-prepared PLA scaffolds with the composition of NaCl higher than 75.00 wt % and PEG beyond 1.25 wt %. More strikingly, the pore walls of macropores encompassed countless micropores and rough surface topography, in favor of transporting nutrients and metabolites as well as cell attachment. The prominent compressive modulus of the PLA scaffolds was in the range of 85.7⁻207.4 MPa, matching the normal modulus of human trabecular bone (50⁻250 MPa). By means of alkaline modification to improve hydrophilicity, biocompatible porous PLA scaffolds exhibited good cell attachment. These results suggest that the SSE/porogen leaching approach provides an eligible clue for fabricating porous scaffolds with high mechanical performance for use as artificial extracellular matrices.

A structurally self-assembled peptide nano-architecture by one-step electrospinning

Peptide self-assembly during electrospinning while the solvent is evaporating and the fibres are forming.

Nanofibrous polylactide composite scaffolds with electroactivity and sustained release capacity for tissue engineering

A conveniently fabricated electroactive nanofibrous composite scaffold serves as a sustained drug release system and promotes myoblast differentiation.

Understanding cell homing-based tissue regeneration from the perspective of materials

The triad of cell homing-based tissue engineering.