Three-Dimensional Polydopamine Functionalized Coiled Microfibrous Scaffolds Enhance Human Mesenchymal Stem Cells Colonization and Mild Myofibroblastic Differentiation

3D cotton-type anisotropic biomimetic scaffold with low fiber motion electrospun via a sharply inclined array collector for induced osteogenesis

Electrospinning is an effective method to fabricate fibrous scaffolds that mimic the ECM of bone tissue on a nano- to macro-scale. However, a limitation of electrospun fibrous scaffolds for bone tissue engineering is the structure formed by densely compacted fibers, which significantly impedes cell infiltration and tissue ingrowth. To address this problem, several researchers have developed numerous techniques for fabricating 3D fibrous scaffolds with customized topography and pore size. Despite the success in developing various 3D electrospun scaffolds based on fiber repulsion, the lack of contact points between fibers in those scaffolds has been shown to hinder cell attachment, migration, proliferation, and differentiation due to excessive movement of the fibers. In this article, we introduce a Dianthus caryophyllus-inspired scaffold fabricated using SIAC-PE, a modified collector under specific viscosity conditions of PCL/LA solution. The developed scaffold mimicking the structural similarities of the nature-inspired design presented enhanced cell proliferation, infiltration, and increased expression of bone-related factors by reducing fiber movements, presenting high space interconnection, high porosity, and controlled fiber topography.

Fabrication of Customizable and Reproducible 3D Chondrocyte-Laden Nanofibrous Architectures: Effect of Specific Fiber Alignments and Porosities on Chondrocyte Response under Cyclic Compression

Electrospinning has been widely employed to fabricate complex extracellular matrix-like microenvironments for tissue engineering due to its ability to replicate structurally biomimetic micro- and nanotopographic cues. Nevertheless, these nanofibrous structures are typically either confined to bidimensional systems or confined to three-dimensional ones that are unable to provide controlled multiscale patterns. Thus, an electrospinning modality was used in this work to fabricate chondrocyte-laden nanofibrous scaffolds with highly customizable three-dimensional (3D) architectures in an automated manner, with the ultimate goal of recreating a suitable 3D scaffold for articular cartilage tissue engineering. Three distinct architectures were designed and fabricated by combining multiple nanofibrous and chondrocyte-laden hydrogel layers and tested in vitro in a compression bioreactor system. Results demonstrated that it was possible to precisely control the placement and alignment of electrospun polycaprolactone and gelatin nanofibers, generating three unique architectures with distinctive macroscale porosity, water absorption capacity, and mechanical properties. The architecture organized in a lattice-like fashion was highly porous with substantial pore interconnectivity, resulting in a high-water absorption capacity but a poor compression modulus and relatively weaker energy dissipation capacity. The donut-like 3D geometry was the densest, with lower swelling, but the highest compression modulus and improved energy dissipation ability. The third architecture combined a lattice and donut-like fibrous arrangement, exhibiting intermediary behavior in terms of porosity, water absorption, compression modulus, and energy dissipation capacity. The properties of the donut-like 3D architecture demonstrated great potential for articular cartilage tissue engineering, as it mimicked key topographic, chemical, and mechanical characteristics of chondrocytes' surrounding environment. In fact, the combination of these architectural features with a dynamically compressive mechanical stimulus triggered the best in vitro results in terms of viability and biosynthetic production.

A novel biomimetic nanofibrous cardiac tissue engineering scaffold with adjustable mechanical and electrical properties based on poly(glycerol sebacate) and polyaniline

Biomaterial tissue engineering scaffolds play a critical role in providing mechanical support, promoting cells growth and proliferation. However, due to the insulation and inappropriate stiffness of most biomaterials, there is an unmet need to engineer a biomimetic nanofibrous cardiac tissue engineering scaffold with tailorable mechanical and electrical properties. Here, we demonstrate for the first time the feasibility to generate a novel type of biocompatible fibrous scaffolds by blending elastic poly(glycerol sebacate) (PGS) and conductive polyaniline (PANI) with the help of a nontoxic carrier polymer, poly (vinyl alcohol) (PVA). Aligned and random PGS/PANI scaffolds are successfully obtained after electrospinning, cross-linking, water and ethanol wash. Incorporating of different concentrations of PANI into PGS fibers, the fibrous sheets show enhanced conductivity and slower degradation rates while maintaining the favorable hemocompatibility. The elastic modulus of the PGS/PANI scaffolds is in the range of 0.65-2.18 MPa under wet conditions, which is similar to that of natural myocardium. All of these fibrous mats show good cell viability and were able to promote adhesion and proliferation of H9c2 cells. Furthermore, the in vivo host responses of both random and aligned scaffolds confirm their good biocompatibility. Therefore, these PGS/PANI scaffolds have great potential for cardiac tissue engineering.

Engineered biomimetic micro/nano-materials for tissue regeneration

The incidence of tissue and organ damage caused by various diseases is increasing worldwide. Tissue engineering is a promising strategy of tackling this problem because of its potential to regenerate or replace damaged tissues and organs. The biochemical and biophysical cues of biomaterials can stimulate and induce biological activities such as cell adhesion, proliferation and differentiation, and ultimately achieve tissue repair and regeneration. Micro/nano materials are a special type of biomaterial that can mimic the microstructure of tissues on a microscopic scale due to its precise construction, further providing scaffolds with specific three-dimensional structures to guide the activities of cells. The study and application of biomimetic micro/nano-materials have greatly promoted the development of tissue engineering. This review aims to provide an overview of the different types of micro/nanomaterials, their preparation methods and their application in tissue regeneration.

Polycaprolactone Electrospun Nanofiber Membrane with Skin Graft Containing Collagen and Bandage Containing MgO Nanoparticles for Wound Healing Applications

The objective of this study was to create a nanofiber-based skin graft with an antimicrobial bandage that could accelerate the healing of an open wound while minimizing infection. To this end, we prepared a bi-layer construct where the top layer acts as bandage, and the bottom layer acts as a dermal equivalent graft. A collagen (CG) gel was combined without and with an electrospun polycaprolactone (PCL) membrane to prepare CG and CG-PCL dermal equivalent constructs. The antibacterial properties of PCL with and without an antibacterial agent (MgO nanoparticles) against Staphylococcus aureus (ATCC 6538) was also examined. Human dermal fibroblasts were cultured in each construct to make the dermal equivalent grafts. After culturing, keratinocytes were plated on top of the tissues to allow growth of an epidermis. Rheological and durability tests were conducted on in vitro dermal and skin equivalent cultures, and we found that PCL significantly affects CG-PCL graft biological and mechanical strength (rheology and durability). PCL presence in the dermal equivalent allowed sufficient tension generation to activate fibroblasts and myofibroblasts in the presence of transforming growth factor-beta. During culture of the skin equivalents, optical coherence tomography (OCT) showed layers corresponding to dermal and epidermal compartments in the presence or absence of PCL; this was confirmed after fixed specimens were histologically sectioned and stained. MgO added to PCL showed antibacterial activity against S. aureus. In vivo animal studies using a rat skin model showed that a polycaprolactone nanofiber bandage containing a type I collagen skin graft has potential for wound healing applications.

Is 3D Printing Promising for Osteochondral Tissue Regeneration?

Osteochondral tissue regeneration is quite difficult to achieve due to the complexity of its organization. In the design of these complex multilayer structures, a fabrication method, 3D printing, started to be employed, especially by using extrusion, stereolithography and inkjet printing approaches. In this paper, the designs are discussed including biphasic, triphasic, and gradient structures which aim to mimic the cartilage and the calcified cartilage and the whole osteochondral tissue closely. In the first section of the review paper, 3D printing of hydrogels including gelatin methacryloyl (GelMa), alginate, and polyethylene glycol diacrylate (PEGDA) are discussed. However, their physical and biological properties need to be augmented, and this generally is achieved by blending the hydrogel with other, more durable, less hydrophilic, polymers. These scaffolds are very suitable to carry growth factors, such as TGF-β1, to further stimulate chondrogenesis. The bone layer is mimicked by printing calcium phosphates (CaPs) or bioactive glasses together with the hydrogels or as a component of another polymer layer. The current research findings indicate that polyester (i.e. polycaprolactone (PCL), polylactic acid (PLA) and poly(lactide-co-glycolide) (PLGA)) reinforced hydrogels may more successfully mimic the complex structure of osteochondral tissue. Moreover, more recent printing methods such as melt electrowriting (MEW), are being used to integrate polyester fibers to enhance the mechanical properties of hydrogels. Additionally, polyester scaffolds that are 3D printed without hydrogels are discussed after the hydrogel-based scaffolds. In this review paper, the relevant studies are analyzed and discussed, and future work is recommended with support of tables of designed scaffolds. The outcome of the survey of the field is that 3D printing has significant potential to contribute to osteochondral tissue repair.

Fabrication of 3D Printed poly(lactic acid) strut and wet-electrospun cellulose nano fiber reinforced chitosan-collagen hydrogel composite scaffolds for meniscus tissue engineering

The main goal of the study was to produce chitosan-collagen hydrogel composite scaffolds consisting of 3D printed poly(lactic acid) (PLA) strut and nanofibrous cellulose for meniscus cartilage tissue engineering. For this purpose, first PLA strut containing microchannels was incorporated into cellulose nanofibers and then they were embedded into chitosan-collagen matrix to obtain micro- and nano-sized topographical features for better cellular activities as well as mechanical properties. All the hydrogel composite scaffolds produced by using three different concentrations of genipin (0.1, 0.3, and 0.5%) had an interconnected microporous structure with a swelling ratio of about 400% and water content values between 77 and 83% which is similar to native cartilage extracellular matrix. The compressive strength of all the hydrogel composite scaffolds was found to be similar (∼32 kPa) and suitable for cartilage tissue engineering applications. Besides, the hydrogel composite scaffold comprising 0.3% (w/v) genipin had the highest tan δ value (0.044) at a frequency of 1 Hz which is around the walking frequency of a person. According to the in vitro analysis, this hydrogel composite scaffold did not show any cytotoxic effect on the rabbit mesenchymal stem cells and enabled cells to attach, proliferate and also migrate through the inner area of the scaffold. In conclusion, the produced hydrogel composite scaffold holds great promise for meniscus tissue engineering.

Mussel‐Inspired Biomaterials: From Chemistry to Clinic

After several billions of years, nature still makes decisions on its own to identify, develop, and direct the most effective material for phenomena/challenges faced. Likewise, and inspired by the nature, we learned how to take steps in developing new technologies and materials innovations. Wet and strong adhesion by Mytilidae mussels (among which Mytilus edulis—blue mussel and Mytilus californianus—California mussel are the most well‐known species) has been an inspiration in developing advanced adhesives for the moist condition. The wet adhesion phenomenon is significant in designing tissue adhesives and surgical sealants. However, a deep understanding of engaged chemical moieties, microenvironmental conditions of secreted proteins, and other contributing mechanisms for outstanding wet adhesion mussels are essential for the optimal design of wet glues. In this review, all aspects of wet adhesion of Mytilidae mussels, as well as different strategies needed for designing and fabricating wet adhesives are discussed from a chemistry point of view. Developed muscle‐inspired chemistry is a versatile technique when designing not only wet adhesive, but also, in several more applications, especially in the bioengineering area. The applications of muscle‐inspired biomaterials in various medical applications are summarized for future developments in the field.

Surface polydopamine modification of bone defect repair materials: Characteristics and applications

Bone defects are a common challenge for clinical orthopedic surgeons. The existing bone defect repair materials are difficult to achieve satisfactory osseointegration between the material and the bone. Therefore, it is increasingly important to find effective methods to improve the integration of the materials with the bone and thus facilitate bone defect repair. Researchers have found that polydopamine (PDA) has a structure and properties similar to the adhesive proteins secreted by mussels in nature, with good biocompatibility, bioactivity, hydrophilicity, bio-adhesion and thermal stability. PDA is therefore expected to be used as a surface modification material for bone repair materials to improve the bonding of bone repair materials to the bone surface. This paper reviews research related to PDA-modified bone repair materials and looks at their future applications.

Application Progress of Modified Chitosan and Its Composite Biomaterials for Bone Tissue Engineering

In recent years, bone tissue engineering (BTE), as a multidisciplinary field, has shown considerable promise in replacing traditional treatment modalities (i.e., autografts, allografts, and xenografts). Since bone is such a complex and dynamic structure, the construction of bone tissue composite materials has become an attractive strategy to guide bone growth and regeneration. Chitosan and its derivatives have been promising vehicles for BTE owing to their unique physical and chemical properties. With intrinsic physicochemical characteristics and closeness to the extracellular matrix of bones, chitosan-based composite scaffolds have been proved to be a promising candidate for providing successful bone regeneration and defect repair capacity. Advances in chitosan-based scaffolds for BTE have produced efficient and efficacious bio-properties via material structural design and different modifications. Efforts have been put into the modification of chitosan to overcome its limitations, including insolubility in water, faster depolymerization in the body, and blood incompatibility. Herein, we discuss the various modification methods of chitosan that expand its fields of application, which would pave the way for future applied research in biomedical innovation and regenerative medicine.

The Bumpy Road to Stem Cell Therapies: Rational Design of Surface Topographies to Dictate Stem Cell Mechanotransduction and Fate

Cells sense and respond to a variety of physical cues from their surrounding microenvironment, and these are interpreted through mechanotransductive processes to inform their behavior. These mechanisms have particular relevance to stem cells, where control of stem cell proliferation, potency, and differentiation is key to their successful application in regenerative medicine. It is increasingly recognized that surface micro- and nanotopographies influence stem cell behavior and may represent a powerful tool with which to direct the morphology and fate of stem cells. Current progress toward this goal has been driven by combined advances in fabrication technologies and cell biology. Here, the capacity to generate precisely defined micro- and nanoscale topographies has facilitated the studies that provide knowledge of the mechanotransducive processes that govern the cellular response as well as knowledge of the specific features that can drive cells toward a defined differentiation outcome. However, the path forward is not fully defined, and the "bumpy road" that lays ahead must be crossed before the full potential of these approaches can be fully exploited. This review focuses on the challenges and opportunities in applying micro- and nanotopographies to dictate stem cell fate for regenerative medicine. Here, key techniques used to produce topographic features are reviewed, such as photolithography, block copolymer lithography, electron beam lithography, nanoimprint lithography, soft lithography, scanning probe lithography, colloidal lithography, electrospinning, and surface roughening, alongside their advantages and disadvantages. The biological impacts of surface topographies are then discussed, including the current understanding of the mechanotransductive mechanisms by which these cues are interpreted by the cells, as well as the specific effects of surface topographies on cell differentiation and fate. Finally, considerations in translating these technologies and their future prospects are evaluated.

Electrospun Nanofibers for Manipulating the Soft Tissue Regeneration

Soft tissue damage is a common clinical problem that affects the lives of a large number of patients all over the world. It is of great importance to develop functional...

Superhydrophilic Polyurethane/Polydopamine Nanofibrous Materials Enhancing Cell Adhesion for Application in Tissue Engineering

The use of nanofibrous materials in the field of tissue engineering requires a fast, efficient, scalable production method and excellent wettability of the obtained materials, leading to enhanced cell adhesion. We proposed the production method of superhydrophilic nanofibrous materials in a two-step process. The process is designed to increase the wettability of resulting scaffolds and to enhance the rate of fibroblast cell adhesion. Polyurethane (PU) nanofibrous material was produced in the solution blow spinning process. Then the PU fibers surface was modified by dopamine polymerization in water solution. Two variants of the modification were examined: dopamine polymerization under atmospheric oxygen (V-I) and using sodium periodate as an oxidative agent (V-II). Hydrophobic PU materials after the treatment became highly hydrophilic, regardless of the modification variant. This effect originates from polydopamine (PDA) coating properties and nanoscale surface structures. The modification improved the mechanical properties of the materials. Materials obtained in the V-II process exhibit superior properties over those from the V-I, and require shorter modification time (less than 30 min). Modifications significantly improved fibroblasts adhesion. The cells spread after 2 h on both PDA-modified PU nanofibrous materials, which was not observed for unmodified PU. Proposed technology could be beneficial in applications like scaffolds for tissue engineering.

Electrospinning and emerging healthcare and medicine possibilities

Electrospinning forms fibers from either an electrically charged polymer solution or polymer melt. Over the past decades, it has become a simple and versatile method for nanofiber production. Hence, it has been explored in many different applications. Commonly used electrospinning assembles fibers from polymer solutions in various solvents, known as solution electrospinning, while melt and near-field electrospinning techniques enhance the versatility of electrospinning. Adaption of additive manufacturing strategy to electrospinning permits precise fiber deposition and predefining pattern construction. This manuscript critically presents the potential of electrospun nanofibers in healthcare applications. Research community drew impetus from the similarity of electrospun nanofibers to the morphology and mechanical properties of fibrous extracellular matrices (ECM) of natural human tissues. Electrospun nanofibrous scaffolds act as ECM analogs for specific tissue cells, stem cells, and tumor cells to realize tissue regeneration, stem cell differentiation, and in vitro tumor model construction. The large surface-to-volume ratio of electrospun nanofibers offers a considerable number of bioactive agents binding sites, which makes it a promising candidate for a number of biomedical applications. The applications of electrospinning in regenerative medicine, tissue engineering, controlled drug delivery, biosensors, and cancer diagnosis are elaborated. Electrospun nanofiber incorporations in medical device coating, in vitro 3D cancer model, and filtration membrane are also discussed.

Maneuvering the Migration and Differentiation of Stem Cells with Electrospun Nanofibers

Electrospun nanofibers have been extensively explored as a class of scaffolding materials for tissue regeneration, because of their unique capability to mimic some features and functions of the extracellular matrix, including the fibrous morphology and mechanical properties, and to a certain extent the chemical/biological cues. This work reviews recent progress in applying electrospun nanofibers to direct the migration of stem cells and control their differentiation into specific phenotypes. First, the physicochemical properties that make electrospun nanofibers well-suited as a supporting material to expand stem cells by controlling their migration and differentiation are introduced. Then various systems are analyzed in conjunction with mesenchymal, neuronal, and embryonic stem cells, as well as induced pluripotent stem cells. Finally, some perspectives on the challenges and future opportunities in combining electrospun nanofibers with stem cells are offered to address clinical issues.

Mussel-inspired polydopamine-mediated surface modification of freeze-cast poly (ε-caprolactone) scaffolds for bone tissue engineering applications

There are many methods used to fabricate the scaffolds for tissue regeneration, among which freeze casting has attracted a great deal of attention due to the capability to create a unidirectional structure. In this study, polycaprolactone (PCL) scaffolds were fabricated by freeze-casting technology in order to create porous microstructure with oriented open-pore channels. To induce biomineralization, and to improve hydrophilicity and cell interactions, mussel-inspired polydopamine (PDA) was coated on the surface of the freeze-cast PCL constructs. Then, the synergistic effects of oriented microstructure and deposited layer on efficient reconstruction of injured bone were studied. Microscopic observations demonstrated that, the coated layer did not show any special change in lamellar microstructure of the scaffolds. Water-scaffold interactions were evaluated by contact angle measurements, and they demonstrated strong enhancement in the hydrophilicity of the polymeric scaffolds after PDA coating. Biodegradation ratio and water uptake evaluation confirmed an increase in the measured values after PDA precipitation. The biomineralization of the PDA-coated scaffolds was characterized by field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD). Obtained results confirmed biomineralization of the constructs after a 28-day immersion in a simulated body fluid (SBF) solution. Mechanical analysis demonstrated higher compressive strength after PDA coating. L929 fibroblast cell viability and attachment illustrated that PDA-coated PCL scaffolds are able to support cell adhesion and proliferation. The increased secretion of alkaline phosphatase (ALP) after culturing osteosarcoma cell lines (MG-63) revealed the initial capability of scaffolds to induce bone regeneration. Therefore, the PDA-coated scaffolds introduce a promising approach for bone tissue engineering application.

A melt-electrowritten filter for capture and culture of circulating colon cancer cells

Metastasis is the major cause of death in cancer patients accounting for about 90% of the mortality. The detection and analysis of the hallmark of metastasis, circulating tumor cells (CTCs), have significant impact in cancer biology and clinical practice. However, the scarcity of CTCs in blood, particularly in that of colorectal cancer patients, is a serious bottleneck in the development of CTC-based precision medicine. Herein, the melt electrowriting (MEW) technology was used for reproductive fabrication of a biocompatible antibody-presenting polycaprolactone filter with tailored porous structure. It is demonstrated, for the first time, that such filter can be used not only to catch cancer cells spiked in whole blood but also to culture the cancer cells directly on site. Specifically, HT29 colon cancer cells can be captured with an efficiency of 85%, and when spiked into 4 mL of whole blood, 47% were captured on one Ø12mm filter. Furthermore, repeated capture and culture experiments have shown that as few as 20 HT29 colon cancer cells spiked into 4 mL of whole blood can be captured on the filter and within 2 weeks be expanded on site to become tumor bodies that are visible to the untrained eye. This filter allows for downstream analysis, such as flow cytometry, immunocytochemistry, Western blotting, and rt-qPCR. This technology represents a simple and cost-effective platform that potentially enables fast and efficient culture of rare CTCs from patients' blood. This provides non-invasive alternatives for solid biopsy tumor materials for treatment screening, with great potential to realize precision medicine for cancer treatment.

The effect of oxygen plasma pretreatment on the properties of mussel-inspired polydopamine-decorated polyurethane nanofibers

In this study, polyurethane (PU) scaffolds were fabricated by electrospinning technology and modified through the deposition of polydopamine (PDA) on the activated surface under oxygen plasma treatment. Herein, the effect of the modification process on the homogeneous surface coating and the changes in the physicochemical and biological properties were evaluated. Morphological observations demonstrated decoration of the nanofibrous microstructure with PDA, while the uniformity and homogeneity of the deposited layer increased after plasma oxygen treatment. Hydrophilicity measurements and swelling ratio indicated a remarkable improvement in the interaction of scaffolds with water molecules when the PDA coating is applied on the surface of the treated nanofibers. The biomineralization of the samples was characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) images. It was found that PDA has the capability for mineralization, and the amount of deposited hydroxyapatite increased as a function of PDA content. The in vitro evaluation of constructs indicated great improvement in cell-scaffold interactions, biocompatibility, and alkaline phosphatase activity after coating the PDA on the plasma-modified matrix. These results suggest that PDA coating, especially after oxygen plasma treatment, improves the physicochemical and in vitro properties of PU scaffolds for bone tissue engineering application.

Applications of chitin and chitosan nanofibers in bone regenerative engineering

Promoting bone regeneration and repairing defects are urgent and critical challenges in orthopedic clinical practice. Research on bone substitute biomaterials is essential for improving the treatment strategies for bone regeneration. Chitin and its derivative, chitosan, are among the most abundant natural biomaterials and widely found in the shells of crustaceans. Chitin and chitosan are non-toxic, antibacterial, biocompatible, degradable, and have attracted significant attention in bone substitute biomaterials. Chitin/chitosan nanofibers and nanostructured scaffolds have large surface area to volume ratios and high porosities. These scaffolds can be fabricated by electrospinning, thermally induced phase separation and self-assembly, and are widely used in biomedical applications such as biological scaffolds, drug delivery, bacterial inhibition, and wound dressing. Recently, some chitin/chitosan-based nanofibrous scaffolds have been found structurally similar to bone's extracellular matrix and can assist in bone regeneration. This review outlines the biomedical applications and biological properties of chitin/chitosan-based nanofibrous scaffolds in bone tissue engineering.

Biomimetic Polymer-Based Engineered Scaffolds for Improved Stem Cell Function

Scaffolds are considered promising materials for tissue engineering applications due to their unique physiochemical properties. The high porosity and adequate mechanical properties of the scaffolds facilitate greater cell adhesion, proliferation, and differentiation. Stem cells are frequently applied in tissue engineering applications due to their excellent potential. It has been noted that cell functions are profoundly affected by the nature of the extracellular matrix (ECM). Naturally derived ECM contains the bioactive motif that also influences the immune response of the organism. The properties of polymer scaffolds mean they can resemble the native ECM and can regulate cellular responses. Various techniques such as electrospinning and 3D printing, among others, are frequently used to fabricate polymer scaffolds, and their cellular responses are different with each technique. Furthermore, enhanced cell viability, as well as the differentiation ability of stem cells on the surface of scaffolds, opens a fascinating approach to the formation of ECM-like environments for tissue engineering applications.

Bioadhesive anisotropic nanogrooved microfibers directing three-dimensional neurite extension

Neurodegenerative diseases and acute nerve injuries are becoming global clinical problems. Engineering three-dimensional (3D), anisotropic neural cellular structures in vitro is therefore desirable in the regenerative medicine research community. Here, we present, for the first time, a single-step, facile but delicate, fabrication of a 3D macroporous microfibrous scaffold with both anisotropic nanogrooved topography and in situ functionalization with a mussel inspired bioadhesive, poly(norepinephrine) (pNE). Specifically, immiscible blends of polycaprolactone (PCL) and polyethylene oxide (PEO) were electrospun into a grounded coagulation bath containing the precursor of pNE. Upon jet entrance in the bath, both phase-separation-driven longitudinal nanotopography and in situ pNE surface functionalization were introduced on individual microfibers that were packed into a 3D macroporous structure. The resulting scaffold significantly promoted 3D neurite extension capacity, 8-fold higher neurite extension over the isotropic counterpart, demonstrating that such a scaffold has great promise in 3D neural cell culture for nerve tissue modelling and engineering.

3D printing of hydrogel scaffolds for future application in photothermal therapy of breast cancer and tissue repair

Surgical removal remains the main clinical approach to treat breast cancer, although risks including high local recurrence of cancer and loss of breast tissues are the threats for the survival and quality of life of patients after surgery. In this study, bifunctional scaffold based on dopamine-modified alginate and polydopamine (PDA) was fabricated using 3D printing with an aim to treat breast cancer and fill the cavity, thereby achieving tissue repair. The as-prepared alginate-polydopamine (Alg-PDA) scaffold exhibited favorable photothermal effect both in vitro and in vivo upon 808 nm laser irradiation. Further, the Alg-PDA scaffold showed great flexibility and similar modulus with normal breast tissues and facilitated the adhesion and proliferation of normal breast epithelial cells. Moreover, the in vivo performance of the Alg-PDA scaffold could be tracked by magnetic resonance and photoacoustic dual-modality imaging. The scaffold that was fabricated using simple and biocompatible materials with individual-designed structure and macropores, as well as outstanding photothermal effect and enhanced cell proliferation ability, might be a potential option for breast cancer treatment and tissue repair after surgery. STATEMENT OF SIGNIFICANCE: In this study, a three-dimensional porous scaffold was developed using 3D printing for the treatment of local recurrence of breast cancer and the following tissue repair after surgery. In this approach, easily available materials (dopamine-modified alginate and PDA) with excellent biocompatibility were selected and prepared as printing inks. The fabricated scaffold showed effective photothermal effects for cancer therapy, as well as matched mechanical properties with breast tissues. Furthermore, the scaffold supported attachment and proliferation of normal breast cells, which indicates its potential ability for adipose tissue repair. Together, the 3D-printed scaffold might be a promising option for the treatment of locally recurrent breast cancer cells and the following tissue repair after surgery.

Electrospinning and Electrospun Nanofibers: Methods, Materials, and Applications

Electrospinning is a versatile and viable technique for generating ultrathin fibers. Remarkable progress has been made with regard to the development of electrospinning methods and engineering of electrospun nanofibers to suit or enable various applications. We aim to provide a comprehensive overview of electrospinning, including the principle, methods, materials, and applications. We begin with a brief introduction to the early history of electrospinning, followed by discussion of its principle and typical apparatus. We then discuss its renaissance over the past two decades as a powerful technology for the production of nanofibers with diversified compositions, structures, and properties. Afterward, we discuss the applications of electrospun nanofibers, including their use as "smart" mats, filtration membranes, catalytic supports, energy harvesting/conversion/storage components, and photonic and electronic devices, as well as biomedical scaffolds. We highlight the most relevant and recent advances related to the applications of electrospun nanofibers by focusing on the most representative examples. We also offer perspectives on the challenges, opportunities, and new directions for future development. At the end, we discuss approaches to the scale-up production of electrospun nanofibers and briefly discuss various types of commercial products based on electrospun nanofibers that have found widespread use in our everyday life.

Redox State of PDA Directs Cellular Responses through Preadsorbed Protein

Polydopamine (PDA) is capable of adhering on nearly all kinds of surfaces and shows good biocompatibility. Moreover, its surface state could be switched between oxidation and reduction states under different electrical stimulation. In this work, the effects of PDA redox states on protein adsorption, as well as the subsequent effects on cellular responses were characterized and evaluated. It was found that the electrical treatment changed the redox states of PDA, which in turn changed the state of preadsorbed protein molecules and eventually affected the cellular responses. BSA preadsorbed PDA film was found to be beneficial for cell proliferation when PDA was changed into reduction state (RPDA), while BMP-2 preadsorbed PDA film showed promotion on cell differentiation when PDA was changed into oxidation state (OPDA). It was found that the transitions of PDA to RPDA and OPDA greatly changed the secondary structure of protein preadsorbed on it. This work provides a deeper insight on changes of protein molecules between cells and PDA surfaces with different redox states, which is important for both optimization of cell-material interactions and application of PDA as a functional coating for biomedical engineering.

Novel Hierarchical Nitrogen-Doped Multiwalled Carbon Nanotubes/Cellulose/Nanohydroxyapatite Nanocomposite As an Osteoinductive Scaffold for Enhancing Bone Regeneration

Nanomaterials based on hybrid scaffolds have shown a high potential to promote osteointegration and bone regeneration. In this study, a novel nanocomposite scaffold was synthesized via a cross-linking/hydrothermal/freeze-drying method, resulting in layer-by-layer structures with functional and structural properties mimicking the natural bone. The hierarchical structures of the scaffold were reinforced with nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs), cellulose, and nanohydroxyapatite. The N-MWCNT/Cel/nHA scaffolds were characterized and evaluated in terms of structure, morphology, biocompatibility, cellular responses, and bone repair efficiency in vivo. The resulting scaffolds showed that incorporation of 1 wt % N-MWCNTs into the hybrid scaffold with micropores (∼5 μm) significantly improved its mechanical properties, although the surface morphology of the scaffold tended to be rough and porous. Importantly, the resulting scaffolds supported in vitro cellular attachment, proliferation, viability, and mineralization of bone mesenchymal stem cells (BMSCs). On the other hand, incorporation of N-MWCNTs into the scaffold induced preferential differentiation of BMSCs to osteogenic lineage accompanied by increased alkaline phosphatase activity and expression of key osteogenic genes. Furthermore, 12 weeks after implantation, the 1%N-MWCNT/Cel/nHA porous scaffolds successfully cicatrized a distal femoral condyle critical size defect in rabbit without obvious inflammatory responses, as indicated by the results of the Micro-CT and histological analyses. In vitro and in vivo experiments confirmed that the scaffolds not only improved the interface bonding with bone tissue but also accelerated the new bone formation and regeneration by up-regulating signaling molecules that are involved in cell proliferation and differentiation. These results indicated that the novel N-MWCNT/Cel/nHA scaffold is an efficient platform for osteogenesis research and bone regeneration medicine.

Encapsulating Microorganisms inside Electrospun Microfibers as a Living Material Enables Room-Temperature Storage of Microorganisms

Room-temperature storage and transportation of microorganisms maximize the power of microorganisms in healthcare, energy, and environment. Recently, paper-based biotechnologies have been developed to enable room-temperature storage of a variety of nonliving biosystems such as diagnostic devices and cell-free systems. Herein, room-temperature storage of living microorganisms is realized by an electrospun nonwoven paper containing convex region, which is composed of coiled microfibers with dense distribution of microorganisms. Microorganisms are encapsulated into the microfibers and remain intact after electrospinning. Poly(ethylene oxide) is used as polymer matrix, and glycerol and dextran are used as additives. When the contents of glycerol and dextran are optimized as 5 and 0.4%, the room-temperature time is prolonged to 2 days, more than 8 folds as compared with the control group. Upon demand, the microorganisms can be activated by adding water and used for culturing microorganisms directly. Furthermore, mechanisms which account for microbial activity and storage are studied. Our microfiber-based strategy is universal for the room-temperature storage of prokaryotic and eukaryotic microorganisms in the solid formulation. Besides, our microorganism/polymer complex structures represent novel living materials via a bottom-up strategy, which are of great potential for new biomedical applications.

Why the impact of mechanical stimuli on stem cells remains a challenge

Mechanical stimulation affects growth and differentiation of stem cells. This may be used to guide lineage-specific cell fate decisions and therefore opens fascinating opportunities for stem cell biology and regenerative medicine. Several studies demonstrated functional and molecular effects of mechanical stimulation but on first sight these results often appear to be inconsistent. Comparison of such studies is hampered by a multitude of relevant parameters that act in concert. There are notorious differences between species, cell types, and culture conditions. Furthermore, the utilized culture substrates have complex features, such as surface chemistry, elasticity, and topography. Cell culture substrates can vary from simple, flat materials to complex 3D scaffolds. Last but not least, mechanical forces can be applied with different frequency, amplitude, and strength. It is therefore a prerequisite to take all these parameters into consideration when ascribing their specific functional relevance-and to only modulate one parameter at the time if the relevance of this parameter is addressed. Such research questions can only be investigated by interdisciplinary cooperation. In this review, we focus particularly on mesenchymal stem cells and pluripotent stem cells to discuss relevant parameters that contribute to the kaleidoscope of mechanical stimulation of stem cells.

Facile fabrication of hypericin-entrapped glyconanoparticles for targeted photodynamic therapy

BACKGROUND

Photodynamic therapy is a safe, noninvasive modality for cancer therapy, in which the photosensitizer (PS) is a crucial component. Hypericin (Hy) is a promising PS; however, its clinical application is significantly limited by its poor hydrophilicity.

MATERIALS AND METHODS

To overcome the clinical application limitation of Hy, a novel strategy is developed here by entrapping Hy into polydopamine (PDA) film formed on the surface of magnetic iron oxide nanoparticles (MNPs) through the self-polymerization of dopamine under alkaline condition. The amount of Hy in the Hy-entrapped PDA-MNP composite nanoparticles (denoted as PHMs) was measured by spectrophotometry. Furthermore, lactose, as the targeting ligand to asialoglycoprotein receptors, was conjugated to the surface of the PHMs by taking advantage of the spontaneous reaction of PDA with amino groups.

RESULTS

Spectrophotometry analysis revealed that the amount of Hy in the PHMs was 72 μmol g-1 PHMs. The fabricated Hy-entrapped glyconanoparticle (Lac-PHM) exhibited excellent water dispersibility, stability, and selectivity for asialoglycoprotein receptors overexpressing HepG2 cells. Atomic absorption spectroscopy analysis showed that the amount of the Lac-PHMs taken in HepG2 cells was 2.1-fold higher than that of the triethylene glycol-modified PHMs. The results of intracellular reactive oxygen species generation detection, cytotoxicity study, and apoptosis detection indicated that the Lac-PHMs had a satisfying photodynamic effect to HepG2 cells.

CONCLUSION

The strategy developed in this work offers great potential for delivery of a variety of hydrophobic PSs.

Wet electrospun alginate/gelatin hydrogel nanofibers for 3D cell culture

Convergence of biological and biofabrication approaches is necessary to progress new biomaterials promoting three-dimensional (3D) cell growth and maturation towards tissue regeneration and integration. Here, we have developed a novel approach to fabricate 3D macroporous, alginate/gelatin hydrogel nanofibers (Alg/GelF-MA), which provide superior cell adhesion, motility, proliferation and maturation. The electrospinning process greatly depends on the ionic strength and viscoelastic behavior of the solution. The polyelectrolyte nature of alginate favors intramolecular bundles over intermolecular entanglement, which hinders its electrospinnability. Electrospinning of alginate was achieved by the aid of a supporting polymer, polyethylene oxide and a surfactant, Pluronic®F127. Furthermore, the Ca²⁺-mediated coagulation process of alginate was realized in situ during wet electrospinning, where the rapid physical crosslink-ability of alginate was applied in conjunction with the jet entrance into the wet electrospinning collector, a coagulation bath. Consequently, the rapid formation of Ca²⁺-alginate complex stabilized the nanofiber morphology. The low surface tension of the non-solvent ethanol used in the bath prevented fibers from dense packing, thus allowing the generation of 3D macroporous structure favoring cell motility. The subsequent UV-mediated chemical crosslinking further stabilized the gelatin content in the Alg/GelF-MA hydrogel nanofibers. It is demonstrated that the Alg/GelF-MA nanofibers with low cytotoxicity (below 10%) supported an over 8-fold proliferation of mesenchymal stem cells over 5 weeks and supported the maturation of human iPSC-derived ventricular cardiomyocytes, which significantly outperform the cell encapsulated bulk GelF-MA hydrogel. The work provides an insight for rational design and development of 3D cell culture matrix for advancement of stem cell therapy and tissue regeneration.

Electrospun Fibers for Recruitment and Differentiation of Stem Cells in Regenerative Medicine

Electrospinning is a popular technique used to mimic the natural sub-micron features of the native tissue. The ultra-fine fibers provide a favorable extracellular matrix-like environment for regulation of cellular functions. This article summarizes and reviews the current advances in electrospun fiber application and focuses on the novel strategies applied for tissue regeneration and repair. It explores the different factors affecting the attachment and proliferation of mesenchymal stem cells (MSCs) on the electrospun substrates. The influence of different features of electrospun fibers in the differentiation of MSCs into specific lineages (bone, cartilage, tendon/ligament, and nerves) has been elaborated. In addition, the different techniques to mimic the hierarchical features of tissues and its effect on cellular functions are reviewed. Additionally, the new developments like three-dimensional (3D) electrospinning, 3D spheroid double strategy and the comparative analysis of dynamic and static culture on electrospun scaffolds are discussed. With the intricate understanding of the interaction between the cells and the electrospun fiber matrix we can aim to combine the newer strategies to overcome the existing challenges and improve the potential application of electrospun fibers in the field of tissue regeneration and repair.

Fabrication of dopamine modified polylactide-poly(ethylene glycol) scaffolds with adjustable properties

Bio-based polymers have been widely used to be as scaffolds for repairing the bone defects. However, the polymer scaffolds are generally lack of bioactivity and cell recognition site. Seeking effective ways to improve the bioactivity and interaction between materials and tissue or cells is clinically important for long-term performance of bone repair materials. In this work, polylactide-b-poly(ethylene glycol)-b-polylactide (PLA-PEG-PLA, PLEL) tri-block copolymers were firstly synthesized by ring-opening polymerization of lactide using PEG with various molecular weights. Inspired by excellent adhesion of dopamine (DA), a facile and effective method was developed to fabricate polydopamine (PDA) and polydopamine/nano-hydroxyapatite (PDA/n-HA) modified PLEL scaffolds by deposition of PDA and PDA/n-HA coating. The surface structure, degradation rates and mineralization of the modified PLEL scaffolds were investigated, and obviously improved after immobilization of PDA and PDA/n-HA coatings. Moreover, the biocompatible results showed a significant increase in cells viability and adhesion. Therefore, the surface modification with PDA and PDA/n-HA could not only adjust the properties of scaffolds, but also reinforce the interfacial adhesion between the PLEL and cells.

Nanotopography featured polycaprolactone/polyethyleneoxide microfibers modulate endothelial cell response

Among many physical properties, surface nanotopography has been found to strongly affect cell adhesion, migration and other functions. Accurate biological interpretation requires the nanotopography to be presented in a three-dimensional (3D) micro-environment. Herein, immiscible blends of polycaprolactone (PCL)/polyethyleneoxide (PEO) were electrospun into a grounded coagulation bath, resulting in macroporous microfibers with nanotopography featured surfaces. Variations in PCL/PEO ratios enabled tunable surface nanotopographic structures, from longitudinal submicron grooves to transverse nano-lamellae. Chemical composition, crystallinity and quantitative nanomechanical analysis confirmed that the interplay of the two semi-crystalline immiscible polymers and the pairing of miscible solvents/non-solvents in both the electrospinning solution and the bath solution were critical for the formation of the secondary structure. It was found that the nanotopography features promoted the proliferation of human umbilical vein endothelial cells (HUVECs) compared with their smooth film counterparts. An analysis of the cell adhesion related markers, vinculin and phosphorylated focal adhesion kinase (pFAK), further revealed that the nanotopographies enhanced the nascent adhesion complex formation compared with smooth PCL fibers, even in the scaffolds with a high PEO content, which is often considered as a non-adhesive material.

A polydopamine peptide coating enables adipose-derived stem cell growth on the silicone surface of cochlear implant electrode arrays

The simultaneous application of neurotrophic factors with cochlear implantation is proposed to enhance the bioelectrical interface between electrodes and auditory neurons, and thus improve speech intelligibility in patients with cochlear implants (CIs). In cell-based approaches, the goal is to colonize CIs with cells producing neurotrophic factors. This study aims to evaluate whether a polydopamine (PD) functionalization of the hydrophobic silicone surface of the electrode carrier enables colonization of adipose-derived stem cells known to deliver neurotrophic factors. Surface characteristics of PD-coated silicone samples and electrode carriers were determined, and the proliferation and viability of adipose-derived stem cells (ASCs) on these surfaces were subsequently analyzed. A homogenous PD coating and cell growth with regular morphology was observed on coated silicone samples and electrode arrays. Hydrophilicity and cell viability was significantly enhanced by PD surface modification. Insertion forces of coated electrode arrays did not increase compared with untreated CIs. Hence, PD coating of the silicone surface of CIs might allow for sufficient colonization with ASCs as a continuous source of neurotrophic factors. © 2017 Wiley Periodicals, Inc. J Biomater Res Part A: 106B: 1431-1438, 2018.

Responses of MSCs to 3D Scaffold Matrix Mechanical Properties under Oscillatory Perfusion Culture

Both fluid shear stress and matrix stiffness are implicated in bone metabolism and functional adaptation, but the synergistic action of these mechanical cues on the biological behaviors of mesenchymal stem cells (MSCs) is still not well-known. In the present work, a homemade oscillatory flow device was applied to investigate the effects of matrix stiffness on MSCs survival, distribution, and osteogenic differentiation in three-dimensional (3D) conditions. Furthermore, the flow field and cell growth in this bioreactor were theoretically simulated. The results demonstrated that oscillatory shear stress significantly increased the viability and distribution uniformity of MSCs throughout the scaffold after culture for 3 weeks. Compared to static culture, oscillatory shear stress could promote the collagen secretion, mineral deposits, and osteogenic differentiation of MSCs. The findings obtained from this work indicate that the oscillatory perfusion not only provides a higher survival rate and a more uniform distribution of cells but also facilitates osteogenic differentiation of MSCs. Oscillating perfusion bioreactor culture of MSCs in 3D scaffold with optimal matrix stiffness could offer an easy-to-use but efficient bioreactor for bone tissue engineering.

Bioinspired Design of Polycaprolactone Composite Nanofibers as Artificial Bone Extracellular Matrix for Bone Regeneration Application

The design and development of functional biomimetic systems for programmed stem cell response is a field of topical interest. To mimic bone extracellular matrix, we present an innovative strategy for constructing drug-loaded composite nanofibrous scaffolds in this study, which could integrate multiple cues from calcium phosphate mineral, bioactive molecule, and highly ordered fiber topography for the control of stem cell fate. Briefly, inspired by mussel adhesion mechanism, a polydopamine (pDA)-templated nanohydroxyapatite (tHA) was synthesized and then surface-functionalized with bone morphogenetic protein-7-derived peptides via catechol chemistry. Afterward, the resulting peptide-loaded tHA (tHA/pep) particles were blended with polycaprolactone (PCL) solution to fabricate electrospun hybrid nanofibers with random and aligned orientation. Our research demonstrated that the bioactivity of grafted peptides was retained in composite nanofibers. Compared to controls, PCL-tHA/pep composite nanofibers showed improved cytocompatibility. Moreover, the incorporated tHA/pep particles in nanofibers could further facilitate osteogenic differentiation potential of human mesenchymal stem cells (hMSCs). More importantly, the aligned PCL-tHA/pep composite nanofibers showed more osteogenic activity than did randomly oriented counterparts, even under nonosteoinductive conditions, indicating excellent performance of biomimetic design in cell fate decision. After in vivo implantation, the PCL-tHA/pep composite nanofibers with highly ordered structure could significantly promote the regeneration of lamellar-like bones in a rat calvarial critical-sized defect. Accordingly, the presented strategy in our work could be applied for a wide range of potential applications in not only bone regeneration application but also pharmaceutical science.