Nanotopographical manipulation of focal adhesion formation for enhanced differentiation of human neural stem cells

Interface-Mediated Neurogenic Signaling: The Impact of Surface Geometry and Chemistry on Neural Cell Behavior for Regenerative and Brain-Machine Interfacing Applications

Nanomaterial advancements have driven progress in central and peripheral nervous system applications such as tissue regeneration and brain-machine interfacing. Ideally, neural interfaces with native tissue shall seamlessly integrate, a process that is often mediated by the interfacial material properties. Surface topography and material chemistry are significant extracellular stimuli that can influence neural cell behavior to facilitate tissue integration and augment therapeutic outcomes. This review characterizes topographical modifications, including micropillars, microchannels, surface roughness, and porosity, implemented on regenerative scaffolding and brain-machine interfaces. Their impact on neural cell response is summarized through neurogenic outcome and mechanistic analysis. The effects of surface chemistry on neural cell signaling with common interfacing compounds like carbon-based nanomaterials, conductive polymers, and biologically inspired matrices are also reviewed. Finally, the impact of these extracellular mediated neural cues on intracellular signaling cascades is discussed to provide perspective on the manipulation of neuron and neuroglia cell microenvironments to drive therapeutic outcomes.

Recent advances in enhances peripheral nerve orientation: the synergy of micro or nano patterns with therapeutic tactics

Several studies suggest that topographical patterns influence nerve cell fate. Efforts have been made to improve nerve cell functionality through this approach, focusing on therapeutic strategies that enhance nerve cell function and support structures. However, inadequate nerve cell orientation can impede long-term efficiency, affecting nerve tissue repair. Therefore, enhancing neurites/axons directional growth and cell orientation is crucial for better therapeutic outcomes, reducing nerve coiling, and ensuring accurate nerve fiber connections. Conflicting results exist regarding the effects of micro- or nano-patterns on nerve cell migration, directional growth, immunogenic response, and angiogenesis, complicating their clinical use. Nevertheless, advances in lithography, electrospinning, casting, and molding techniques to intentionally control the fate and neuronal cells orientation are being explored to rapidly and sustainably improve nerve tissue efficiency. It appears that this can be accomplished by combining micro- and nano-patterns with nanomaterials, biological gradients, and electrical stimulation. Despite promising outcomes, the unclear mechanism of action, the presence of growth cones in various directions, and the restriction of outcomes to morphological and functional nerve cell markers have presented challenges in utilizing this method. This review seeks to clarify how micro- or nano-patterns affect nerve cell morphology and function, highlighting the potential benefits of cell orientation, especially in combined approaches.

Manipulating Stem Cell Fate with Disordered Bioactive Cues on Surfaces: The Role of Bioactive Ligand Selection

The development of 2D or 3D bioactive platforms for rapidly isolating pure populations of cells from adult stem cells holds promise for advancing the understanding of cellular mechanisms, drug testing, and tissue engineering. Over the years, methods have emerged to synthesize bioactive micro- and nanostructured 2D materials capable of directing stem cell fate. We introduce a novel method for randomly micro- or nanopatterning any protein/peptide onto both 2D and 3D scaffolds via spray technology. Our goal is to investigate the impact of arranging bioactive micropatterns (ordered vs disordered) on surfaces to guide human mesenchymal stem cell (hMSC) differentiation. The spray technology efficiently coats materials with controlled, cost-effective bioactive micropatterns in various sizes and shapes. BMP-2 mimetic peptides were covalently grafted, individually or in combination with RGD peptides, onto activated polyethylene terephthalate (PET) surfaces through a spraying process, incorporating nano/microscale parameters like size, shape, and composition. The study explores different peptide distributions on surfaces and various peptide combinations. Four surfaces were homogeneously functionalized with these peptides (M1 to M4 with various densities of peptides), and six surfaces with disordered micro- and nanopatterns of peptides (S0 to S5 with different sizes of peptide patterns) were synthesized. Fluorescence microscopy assessed peptide distribution, followed by hMSC culture for 2 weeks, and evaluated osteogenic differentiation via immunocytochemistry and RT-qPCR for osteoblast and osteocyte markers. Cells on uniformly peptide-functionalized surfaces exhibited cuboidal forms, while those on surfaces with disordered patterns tended toward columnar or cuboidal shapes. Surfaces S4 and S5 showed dendrite-like formations resembling an osteocyte morphology. S5 showed significant overexpression of osteoblast (OPN) and osteocyte markers (E11, DMP1, and SOST) compared to control surfaces and other micropatterned surfaces. Notably, despite sharing an equivalent quantity of peptides with a homogeneous functionalized surface, S5 displayed a distinct distribution of peptides, resulting in enhanced osteogenic differentiation of hMSCs.

Nanoscale surface coatings and topographies for neural interfaces

With the lack of minimally invasive tools for probing neuronal systems across spatiotemporal scales, understanding the working mechanism of the nervous system and limited assessments available are imperative to prevent or treat neurological disorders. In particular, nanoengineered neural interfaces can provide a solution to this technological barrier. This review covers recent surface engineering approaches, including nanoscale surface coatings, and a range of topographies from the microscale to the nanoscale, primarily focusing on neural-interfaced biosystems. Specifically, the immobilization of bioactive molecules to fertilize the neural cell lineage, topographical engineering to induce mechanotransduction in neural cells, and enhanced cell-chip coupling using three-dimensional structured surfaces are highlighted. Advances in neural interface design will help us understand the nervous system, thereby achieving the effective treatments for neurological disorders. STATEMENT OF SIGNIFICANCE: • This review focuses on designing bioactive neural interface with a nanoscale chemical modification and topographical engineering at multiscale perspective. • Versatile nanoscale surface coatings and topographies for neural interface are summarized. • Recent advances in bioactive materials applicable for neural cell culture, electrophysiological sensing, and neural implants are reviewed.

State of the Art and Current Challenges on Electroactive Biomaterials and Strategies for Neural Tissue Regeneration

The loss or failure of an organ/tissue stands as one of the healthcare system's most prevalent, devastating, and costly challenges. Strategies for neural tissue repair and regeneration have received significant attention due to their particularly strong impact on patients' well-being. Many research efforts are dedicated not only to control the disease symptoms but also to find solutions to repair the damaged tissues. Neural tissue engineering (TE) plays a key role in addressing this problem and significant efforts are being carried out to develop strategies for neural repair treatment. In the last years, active materials allowing to tune cell-materials interaction are being increasingly used, representing a recent paradigm in TE applications. Among the most important stimuli influencing cell behavior are the electrical and mechanical ones. In this way, materials with the ability to provide this kind of stimuli to the neural cells seem to be appropriate to support neural TE. In this scope, this review summarizes the different biomaterials types used for neural TE, highlighting the relevance of using active biomaterials and electrical stimulation. Furthermore, this review provides not only a compilation of the most relevant studies and results but also strategies for novel and more biomimetic approaches for neural TE.

Regulation of Tendon Stem Cell Behavior by Designed Nanoporous Topography of Microfibers

Nano scale topography scaffold is more bioactive and biomimetic than smooth fiber topographies. Tendon stem cells (TSCs) play important roles in the tendinogenesis of tendon tissue engineering, but the effects and mechanisms of nano topography on TSC behavior are still unclear. This study determined whether the morphology, proliferation, cytoskeleton, and differentiation of TSCs are affected by topography of scaffold in vitro. The porous PA56 scaffolds were prepared with different concentration ratios of glycerol as the molecular template by electrospinning. Its topological characteristics, hydrophilicity, and degradation properties varied with glycerol proportion and movement rate of the receiving plate. Porous fibers promoted the proliferation of TSCs and the number of TSCs varied with topography. Although there was no significant difference due to the small sample size, the number of pseudopodia and cell polarizability still showed differences among different topographies. The morphology of actin cytoskeleton of TSCs showed difference among cultured on porous fibers, smooth fibers, and in culture media with no fiber, suggesting the orientation growth of cells on porous fiber. Moreover, porous fibers promoted teno-lineage differentiation of TSCs by upregulating tendon-specific gene expression. These findings provide evidence that nano porous topography scaffold promotes TSC proliferation, cytoskeleton orientation, and tenogenic differentiation.

Customizing 3D Structures of Vertically Aligned Carbon Nanotubes to Direct Neural Stem Cell Differentiation

Neural tissue-related illnesses have a high incidence and prevalence in society. Despite intensive research efforts to enhance the regeneration of neural cells into functional tissue, effective treatments are still unavailable. Here, a novel therapeutic approach based on vertically aligned carbon nanotube forests (VA-CNT forests) and periodic VA-CNT micropillars produced by thermal chemical vapor deposition is explored. In addition, honeycomb-like and flower-like morphologies are created. Initial viability testing reveals that NE-4C neural stem cells seeded on all morphologies survive and proliferate. In addition, free-standing VA-CNT forests and capillary-driven VA-CNT forests are created, with the latter demonstrating enhanced capacity to stimulate neuritogenesis and network formation under minimal differentiation medium conditions. This is attributed to the interaction between surface roughness and 3D-like morphology that mimics the native extracellular matrix, thus enhancing cellular attachment and communication. These findings provide a new avenue for the construction of electroresponsive scaffolds based on CNTs for neural tissue engineering.

Trends in mechanobiology guided tissue engineering and tools to study cell-substrate interactions: a brief review

Sensing the mechanical properties of the substrates or the matrix by the cells and the tissues, the subsequent downstream responses at the cellular, nuclear and epigenetic levels and the outcomes are beginning to get unraveled more recently. There have been various instances where researchers have established the underlying connection between the cellular mechanosignalling pathways and cellular physiology, cellular differentiation, and also tissue pathology. It has been now accepted that mechanosignalling, alone or in combination with classical pathways, could play a significant role in fate determination, development, and organization of cells and tissues. Furthermore, as mechanobiology is gaining traction, so do the various techniques to ponder and gain insights into the still unraveled pathways. This review would briefly discuss some of the interesting works wherein it has been shown that specific alteration of the mechanical properties of the substrates would lead to fate determination of stem cells into various differentiated cells such as osteoblasts, adipocytes, tenocytes, cardiomyocytes, and neurons, and how these properties are being utilized for the development of organoids. This review would also cover various techniques that have been developed and employed to explore the effects of mechanosignalling, including imaging of mechanosensing proteins, atomic force microscopy (AFM), quartz crystal microbalance with dissipation measurements (QCMD), traction force microscopy (TFM), microdevice arrays, Spatio-temporal image analysis, optical tweezer force measurements, mechanoscanning ion conductance microscopy (mSICM), acoustofluidic interferometric device (AID) and so forth. This review would provide insights to the researchers who work on exploiting various mechanical properties of substrates to control the cellular and tissue functions for tissue engineering and regenerative applications, and also will shed light on the advancements of various techniques that could be utilized to unravel the unknown in the field of cellular mechanobiology.

Insights into the Molecular Mechanisms Regulating Cell Behavior in Response to Magnetic Materials and Magnetic Stimulation in Stem Cell (Neurogenic) Differentiation

Magnetic materials and magnetic stimulation have gained increasing attention in tissue engineering (TE), particularly for bone and nervous tissue reconstruction. Magnetism is utilized to modulate the cell response to environmental factors and lineage specifications, which involve complex mechanisms of action. Magnetic fields and nanoparticles (MNPs) may trigger focal adhesion changes, which are further translated into the reorganization of the cytoskeleton architecture and have an impact on nuclear morphology and positioning through the activation of mechanotransduction pathways. Mechanical stress induced by magnetic stimuli translates into an elongation of cytoskeleton fibers, the activation of linker in the nucleoskeleton and cytoskeleton (LINC) complex, and nuclear envelope deformation, and finally leads to the mechanical regulation of chromatin conformational changes. As such, the internalization of MNPs with further magnetic stimulation promotes the evolution of stem cells and neurogenic differentiation, triggering significant changes in global gene expression that are mediated by histone deacetylases (e.g., HDAC 5/11), and the upregulation of noncoding RNAs (e.g., miR-106b~25). Additionally, exposure to a magnetic environment had a positive influence on neurodifferentiation through the modulation of calcium channels' activity and cyclic AMP response element-binding protein (CREB) phosphorylation. This review presents an updated and integrated perspective on the molecular mechanisms that govern the cellular response to magnetic cues, with a special focus on neurogenic differentiation and the possible utility of nervous TE, as well as the limitations of using magnetism for these applications.

Bioinspired micro- and nano-structured neural interfaces

The development of a functional nervous system requires neurons to interact with and promptly respond to a wealth of biochemical, mechanical and topographical cues found in the neural extracellular matrix (ECM). Among these, ECM topographical cues have been found to strongly influence neuronal function and behavior. Here, we discuss how the blueprint of the architectural organization of the brain ECM has been tremendously useful as a source of inspiration to design biomimetic substrates to enhance neural interfaces and dictate neuronal behavior at the cell-material interface. In particular, we focus on different strategies to recapitulate cell-ECM and cell-cell interactions. In order to mimic cell-ECM interactions, we introduce roughness as a first approach to provide informative topographical biomimetic cues to neurons. We then examine 3D scaffolds and hydrogels, as softer 3D platforms for neural interfaces. Moreover, we will discuss how anisotropic features such as grooves and fibers, recapitulating both ECM fibrils and axonal tracts, may provide recognizable paths and tracks that neuron can follow as they develop and establish functional connections. Finally, we show how isotropic topographical cues, recapitulating shapes, and geometries of filopodia- and mushroom-like dendritic spines, have been instrumental to better reproduce neuron-neuron interactions for applications in bioelectronics and neural repair strategies. The high complexity of the brain architecture makes the quest for the fabrication of create more biologically relevant biomimetic architectures in continuous and fast development. Here, we discuss how recent advancements in two-photon polymerization and remotely reconfigurable dynamic interfaces are paving the way towards to a new class of smart biointerfaces forin vitroapplications spanning from neural tissue engineering as well as neural repair strategies.

High-Content Screening and Analysis of Stem Cell-Derived Neural Interfaces Using a Combinatorial Nanotechnology and Machine Learning Approach

A systematic investigation of stem cell-derived neural interfaces can facilitate the discovery of the molecular mechanisms behind cell behavior in neurological disorders and accelerate the development of stem cell-based therapies. Nevertheless, high-throughput investigation of the cell-type-specific biophysical cues associated with stem cell-derived neural interfaces continues to be a significant obstacle to overcome. To this end, we developed a combinatorial nanoarray-based method for high-throughput investigation of neural interface micro-/nanostructures (physical cues comprising geometrical, topographical, and mechanical aspects) and the effects of these complex physical cues on stem cell fate decisions. Furthermore, by applying a machine learning (ML)-based analytical approach to a large number of stem cell-derived neural interfaces, we comprehensively mapped stem cell adhesion, differentiation, and proliferation, which allowed for the cell-type-specific design of biomaterials for neural interfacing, including both adult and human-induced pluripotent stem cells (hiPSCs) with varying genetic backgrounds. In short, we successfully demonstrated how an innovative combinatorial nanoarray and ML-based platform technology can aid with the rational design of stem cell-derived neural interfaces, potentially facilitating precision, and personalized tissue engineering applications.

Two-Photon Polymerization of 2.5D and 3D Microstructures Fostering a Ramified Resting Phenotype in Primary Microglia

Microglia are the resident macrophages of the central nervous system and contribute to maintaining brain’s homeostasis. Current 2D “petri-dish” in vitro cell culturing platforms employed for microglia, are unrepresentative of the softness or topography of native brain tissue. This often contributes to changes in microglial morphology, exhibiting an amoeboid phenotype that considerably differs from the homeostatic ramified phenotype in healthy brain tissue. To overcome this problem, multi-scale engineered polymeric microenvironments are developed and tested for the first time with primary microglia derived from adult rhesus macaques. In particular, biomimetic 2.5D micro- and nano-pillar arrays (diameters = 0.29–1.06 µm), featuring low effective shear moduli (0.25–14.63 MPa), and 3D micro-cages (volume = 24 × 24 × 24 to 49 × 49 × 49 μm³) with and without micro- and nano-pillar decorations (pillar diameters = 0.24–1 µm) were fabricated using two-photon polymerization (2PP). Compared to microglia cultured on flat substrates, cells growing on the pillar arrays exhibit an increased expression of the ramified phenotype and a higher number of primary branches per ramified cell. The interaction between the cells and the micro-pillar-decorated cages enables a more homogenous 3D cell colonization compared to the undecorated ones. The results pave the way for the development of improved primary microglia in vitro models to study these cells in both healthy and diseased conditions.

Biophysical Regulations of Epigenetic State and Notch Signaling in Neural Development Using Microgroove Substrates

A number of studies have recently shown how surface topography can alter the behavior and differentiation patterns of different types of stem cells. Although the exact mechanisms and molecular pathways involved remain unclear, a consistent portion of the literature points to epigenetic changes induced by nuclear remodeling. In this study, we investigate the behavior of clinically relevant neural populations derived from human pluripotent stem cells when cultured on polydimethylsiloxane microgrooves (3 and 10 μm depth grooves) to investigate what mechanisms are responsible for their differentiation capacity and functional behavior. Our results show that microgrooves enhance cell alignment, modify nuclear geometry, and significantly increase cellular stiffness, which we were able to measure at high resolution with a combination of light and electron microscopy, scanning ion conductance microscopy (SICM), and atomic force microscopy (AFM) coupled with quantitative image analysis. The microgrooves promoted significant changes in the epigenetic landscape, as revealed by the expression of key histone modification markers. The main behavioral change of neural stem cells on microgrooves was an increase of neuronal differentiation under basal conditions on the microgrooves. Through measurements of cleaved Notch1 levels, we found that microgrooves downregulate Notch signaling. We in fact propose that microgroove topography affects the differentiation potential of neural stem cells by indirectly altering Notch signaling through geometric segregation and that this mechanism in parallel with topography-dependent epigenetic modulations acts in concert to enhance stem cell neuronal differentiation.

Nano-bio interactions of 2D molybdenum disulfide

Two-dimensional (2D) molybdenum disulfide (MoS₂) is an ultrathin nanomaterial with a high degree of anisotropy, surface-to-volume ratio, chemical functionality and mechanical strength. These properties together enable MoS₂ to emerge as a potent nanomaterial for diverse biomedical applications including drug delivery, regenerative medicine, biosensing and bioelectronics. Thus, understanding the interactions of MoS₂ with its biological interface becomes indispensable. These interactions, referred to as "nano-bio" interactions, play a key role in determining the biocompatibility and the pathways through which the nanomaterial influences molecular, cellular and biological function. Herein, we provide a critical overview of the nano-bio interactions of MoS₂ and emphasize on how these interactions dictate its biomedical applications including intracellular trafficking, biodistribution and biodegradation. Also, a critical evaluation of the interactions of MoS₂ with proteins and specific cell types such as immune cells and progenitor/stem cells is illustrated which governs the short-term and long-term compatibility of MoS₂-based biomedical devices.

Bioengineered Hierarchical Bonelike Compartmentalized Microconstructs Using Nanogrooved Microdiscs

Fabrication of vascularized large-scale constructs for regenerative medicine remains elusive since most strategies rely solely on cell self-organization or overly control cell positioning, failing to address nutrient diffusion limitations. We propose a modular and hierarchical tissue-engineering strategy to produce bonelike tissues carrying signals to promote prevascularization. In these 3D systems, disc-shaped microcarriers featuring nanogrooved topographical cues guide cell behavior by harnessing mechanotransduction mechanisms. A sequential seeding strategy of adipose-derived stromal cells and endothelial cells is implemented within compartmentalized, liquefied-core macrocapsules in a self-organizing and dynamic system. Importantly, our system autonomously promotes osteogenesis and construct's mineralization while promoting a favorable environment for prevascular-like endothelial organization. Given its modular and self-organizing nature, our strategy may be applied for the fabrication of larger constructs with a highly controlled starting point to be used for local regeneration upon implantation or as drug-screening platforms.

Hipster microcarriers: exploring geometrical and topographical cues of non-spherical microcarriers in biomedical applications

Structure and organisation are key aspects of the native tissue environment, which ultimately condition cell fate via a myriad of processes, including the activation of mechanotransduction pathways. By modulating the formation of integrin-mediated adhesions and consequently impacting cell contractility, engineered geometrical and topographical cues may be introduced to activate downstream signalling and ultimately control cell morphology, proliferation, and differentiation. Microcarriers appear as attractive vehicles for cell-based tissue engineering strategies aiming to modulate this 3D environment, but also as vehicles for cell-free applications, given the ease in tuning their chemical and physical properties. In this review, geometry and topography are highlighted as two preponderant features in actively regulating interactions between cells and the extracellular matrix. While most studies focus on the 2D environment, we focus on how the incorporation of these strategies in 3D systems could be beneficial. The techniques applied to design 3D microcarriers with unique geometries and surface topographical cues are covered, as well as specific tissue engineering approaches employing these microcarriers. In fact, successfully achieving a functional histoarchitecture may depend on a combination of fine-tuned geometrically shaped microcarriers presenting intricately tailored topographical cues. Lastly, we pinpoint microcarrier geometry as a key player in cell-free biomaterial-based strategies, and its impact on drug release kinetics, the production of steerable microcarriers to target tumour cells, and as protein or antibody biosensors.

An In Vitro Study of the Effects of Mechanical and Enzymatic Isolation of Stromal Vascular Fraction on Wound Healing

ABSTRACT

The adipose-derived stromal vascular fraction (SVF) is considered to be an attractive source of stem cells in cell therapy. Besides stem cells, it also contains functional cells, such as macrophages, precursor cells, somatic stem cells, and pericytes. Collagenase digestion is the most frequently used method to isolate SVF, but it is time-consuming and costly and has some problems, such as infectious agents and immune reactions. In this research, we compared the yield, cell population ratios, and cell viability when isolating SVF by the ultrasonic physics (U-SVF) method and traditional enzymatic method (E-SVF). Then, we isolated exosomes from U-SVF and E-SVF, respectively, and cocultured them with fibroblasts to investigate the potential of applying this cell secretion in wound repair. The results showed that there was no significant difference between the ultrasonic method and enzymatic method in terms of cell viability, cell numbers, or the expression of CD markers of stem cells. However, exosome analysis identified a greater number and smaller size of exosome particles obtained by U-SVF. In terms of cell proliferation efficiency, although the proliferation efficiency of U-SVF was lower than that of E-SVF. Trilineage differentiation experiments revealed that both E-SVF and U-SVF had good differentiation ability, owing to high stem cell content. Finally, E-SVF and U-SVF exosomes were cocultured with fibroblasts. The efficiency of fibroblast migration increased in the SVF exosome treated groups, and the expression of related genes (integrin α5β1) was slightly upregulated; however, the expression of FAK, AKT, ERK, and RhoA was significantly upregulated at 24 hours. From the abovementioned experiments, we found that there was no significant difference in stem cell-related characteristics between SVF isolated by ultrasonic cavitation and SVF isolated by the enzymatic method. In addition, exosomes secreted by SVF may have excellent therapeutic effect on skin injuries, which provides a new viewpoint and therapeutic strategy for soft tissue repair.

A practical guide to promote informatics-driven efficient biotopographic material development

Micro/nano topographic structures have shown great utility in many biomedical areas including cell therapies, tissue engineering, and implantable devices. Computer-assisted informatics methods hold great promise for the design of topographic structures with targeted properties for a specific medical application. To benefit from these methods, researchers and engineers require a highly reusable "one structural parameter - one set of cell responses" database. However, existing confounding factors in topographic cell culture devices seriously impede the acquisition of this kind of data. Through carefully dissecting the confounding factors and their possible reasons for emergence, we developed corresponding guideline requirements for topographic cell culture device development to remove or control the influence of such factors. Based on these requirements, we then suggested potential strategies to meet them. In this work, we also experimentally demonstrated a topographic cell culture device with controlled confounding factors based on these guideline requirements and corresponding strategies. A "guideline for the development of topographic cell culture devices" was summarized to instruct researchers to develop topographic cell culture devices with the confounding factors removed or well controlled. This guideline aims to promote the establishment of a highly reusable "one structural parameter - one set of cell responses" database that could facilitate the application of informatics methods, such as artificial intelligence, in the rational design of future biotopographic structures with high efficacy.

Application of New Materials in Auditory Disease Treatment

Auditory diseases are disabling public health problems that afflict a significant number of people worldwide, and they remain largely incurable until now. Driven by continuous innovation in the fields of chemistry, physics, and materials science, novel materials that can be applied to hearing diseases are constantly emerging. In contrast to conventional materials, new materials are easily accessible, inexpensive, non-invasive, with better acoustic therapy effects and weaker immune rejection after implantation. When new materials are used to treat auditory diseases, the wound healing, infection prevention, disease recurrence, hair cell regeneration, functional recovery, and other aspects have been significantly improved. Despite these advances, clinical success has been limited, largely due to issues regarding a lack of effectiveness and safety. With ever-developing scientific research, more novel materials will be facilitated into clinical use in the future.

Exploring Cell Surface-Nanopillar Interactions with 3D Super-Resolution Microscopy

Plasma membrane topography has been shown to strongly influence the behavior of many cellular processes such as clathrin-mediated endocytosis, actin rearrangements, and others. Recent studies have used three-dimensional (3D) nanostructures such as nanopillars to imprint well-defined membrane curvatures (the "nano-bio interface"). In these studies, proteins and their interactions were probed by two-dimensional fluorescence microscopy. However, the low resolution and limited axial detail of such methods are not optimal to determine the relative spatial position and distribution of proteins along a 100 nm-diameter object, which is below the optical diffraction limit. Here, we introduce a general method to explore the nanoscale distribution of proteins at the nano-bio interface with 10-20 nm precision using 3D single-molecule super-resolution (SR) localization microscopy. This is achieved by combining a silicone-oil immersion objective and 3D double-helix point spread function microscopy. We carefully adjust the objective to minimize spherical aberrations between quartz nanopillars and the cell. To validate the 3D SR method, we imaged the 3D shape of surface-labeled nanopillars and compared the results with electron microscopy measurements. Turning to transmembrane-anchored labels in cells, the high quality 3D SR reconstructions reveal the membrane tightly wrapping around the nanopillars. Interestingly, the cytoplasmic protein AP-2 involved in clathrin-mediated endocytosis accumulates along the nanopillar above a specific threshold of 1/R (the reciprocal of the radius) membrane curvature. Finally, we observe that AP-2 and actin preferentially accumulate at positive Gaussian curvature near the pillar caps. Our results establish a general method to investigate the nanoscale distribution of proteins at the nano-bio interface using 3D SR microscopy.

Cellular properties of human gingival fibroblasts on novel and conventional implant-abutment materials

OBJECTIVES

To characterize human-gingival-fibroblast-(HGFs) viability, proliferation and adhesion on polymer-infiltrated-ceramic-network-(PICN), polyetheretherketone-(PEEK), hydroxyapatite-reinforced-polyetheretherketone-(HA-PEEK), polyetherketoneketone-(PEKK), as well as conventional titanium-(Ti) and zirconia ceramic-(Zr) implant materials in-vitro.

METHODS

Six materials (n = 40/group, 240 specimens) were standardized for surface roughness, assessed employing water contact angle measurements (WCA) and loaded with HGFs. HGF viability and proliferation were assessed at 24 and 72 h. Cell adhesion strength was evaluated after 24 h exposure to lateral shear forces using a shaking-device at 320 and 560-rpm.and qualitatively tested by scanning-electron-microscopy-(SEM) at 3, 24 and 72 h.

RESULTS

PICN demonstrated the lowest mean WCA (48.2 ± 6.3º), followed by Zr (73.8 ± 5.1º), while HA-PEEK showed the highest WCA (87.2 ± 1.5º; p ≤ 0.05). After 24 h, Zr showed the highest mean HGFs-viability rate (88 ± 14%), while PEKK showed the lowest one (78 ± 7%). At 72 h, Zr continued to show the highest HGF-viability (80 ± 6%) compared to PEKK (67.5 ± 6%) and PEEK (67%±5). SEM did not reveal differences between different materials with respect to cell attachment at 3, 24 or 72 h. At 320 rpm shaking, HGFs showed to be best attached to PICN (mean%-of-detached-cells ± SD; 26 ± 11%) and worst to PEEK (54 ± 18%). At 560 rpm shaking, Zr showed the least detached cells (32 ± 4%), while HA-PEEK revealed the highest number of detached cells (58 ± 3%; ANOVA/Tukey-post-hoc-test, differences not statistically significant).

SIGNIFICANCE

Dental implant abutment materials and their wettability strongly affect HGF proliferation and adhesion properties. Although, PICN showed the best wettability properties, Zr exhibited the strongest adhesion strength at high shaking. Within the current study's limitations, Zr remains the most biocompatible abutment material.

Stem Cell-Based Therapies in Hearing Loss

In recent years, neural stem cell transplantation has received widespread attention as a new treatment method for supplementing specific cells damaged by disease, such as neurodegenerative diseases. A number of studies have proved that the transplantation of neural stem cells in multiple organs has an important therapeutic effect on activation and regeneration of cells, and restore damaged neurons. This article describes the methods for inducing the differentiation of endogenous and exogenous stem cells, the implantation operation and regulation of exogenous stem cells after implanted into the inner ear, and it elaborates the relevant signal pathways of stem cells in the inner ear, as well as the clinical application of various new materials. At present, stem cell therapy still has limitations, but the role of this technology in the treatment of hearing diseases has been widely recognized. With the development of related research, stem cell therapy will play a greater role in the treatment of diseases related to the inner ear.

Biomaterials patterning regulates neural stem cells fate and behavior: The interface of biology and material science

The combination of nanotechnology and stem cell biology is one of the most promising advances in the field of regenerative medicine. This novel combination has widely been utilized in vitro settings in an attempt to develop efficient therapeutic strategies to overcome the limited capacity of the central nervous system (CNS) in replacing degenerating neural cells with functionally normal cells after the onset of acute and chronic neurological disorders. Importantly, biomaterials, not only, enhance the endogenous CNS neurogenesis and plasticity, but also, could provide a desirable supportive microenvironment to harness the full potential of the in vitro expanded neural stem cells (NSCs) for regenerative purposes. Here, first, we discuss how the physical and biochemical properties of biomaterials, such as their stiffness and elasticity, could influence the behavior of NSCs. Then, since the NSCs niche or microenvironment is of fundamental importance in controlling the dynamic destiny of NSCs such as their quiescent and proliferative states, topographical effects of surface diversity in biomaterials, that is, the micro-and nano-patterned surfaces will be discussed in detail. Finally, the influence of biomaterials as artificial microenvironments on the behavior of NSCs through the specific mechanotransduction signaling pathway mediated by focal adhesion formation will be reviewed.

Neuromechanobiology: An Expanding Field Driven by the Force of Greater Focus

The brain processes information by transmitting signals through highly connected and dynamic networks of neurons. Neurons use specific cellular structures, including axons, dendrites and synapses, and specific molecules, including cell adhesion molecules, ion channels and chemical receptors to form, maintain and communicate among cells in the networks. These cellular and molecular processes take place in environments rich of mechanical cues, thus offering ample opportunities for mechanical regulation of neural development and function. Recent studies have suggested the importance of mechanical cues and their potential regulatory roles in the development and maintenance of these neuronal structures. Also suggested are the importance of mechanical cues and their potential regulatory roles in the interaction and function of molecules mediating the interneuronal communications. In this review, the current understanding is integrated and promising future directions of neuromechanobiology are suggested at the cellular and molecular levels. Several neuronal processes where mechanics likely plays a role are examined and how forces affect ligand binding, conformational change, and signal induction of molecules key to these neuronal processes are indicated, especially at the synapse. The disease relevance of neuromechanobiology as well as therapies and engineering solutions to neurological disorders stemmed from this emergent field of study are also discussed.

Facile fabrication of ordered discontinuous nanotopography on photosensitive substrates for enhanced neuronal differentiation

Controlling the development and morphology of neurons is important for basic neuroscience research as well as for applications in nerve regeneration and neural interfaces. Various studies have shown that nanoscale topographies can promote the development of neuronal cells and the differentiation of neural stem cells; however, the fabrication of these nanotopographical features often involves expensive and sophisticated techniques. Here, we employ nanosphere lens lithography combined with UV-LED technology to create nanopatterns on an SU-8 photoresist. We develop a facile method to create a reusable polystyrene nanosphere (PS-NS) lens array by the spontaneous formation of a hexagonal close-packed array of PS-NSs at a water-air interface and its subsequent transfer to a polydimethylsiloxane carrier film without using any special equipment. We show that this simple technique can create ordered arrays of nanodots on an SU-8 film, the dimensions of which can be controlled by the size of the PS-NSs. When used as a substrate for the neuronal differentiation of pheochromocytoma (PC12) cells, the nanopatterned SU-8 films exhibit enhanced differentiation parameters with respect to conventional tissue culture plastic as compared with their flat counterparts. The method proposed here can greatly facilitate the nanopatterning of various photosensitive substrates for the development of implants for nerve regeneration and neural interfacing.

Enhanced efficiency of nonviral direct neuronal reprogramming on topographical patterns

Nonviral direct neuronal reprogramming holds significant potential in the fields of tissue engineering and regenerative medicine. However, the issue of low reprogramming efficiency poses a major barrier to its application. We propose that topographical cues, which have been applied successfully to enhance lineage-directed differentiation and multipotent stem cell transdifferentiation, could improve nonviral direct neuronal reprogramming efficiency. To investigate, we used a polymer-BAM (Brn2, Ascl1, Myt1l) factor transfection polypex to reprogram primary mouse embryonic fibroblasts. Using a multiarchitecture chip, we screened for patterns that may improve transfection and/or subsequent induced neuron reprogramming efficiency. Selected patterns were then investigated further by analyzing β-tubulin III (TUJ1) and microtubule-associated protein 2 (MAP2) protein expression, cell morphology and electrophysiological function of induced neurons. Certain hierarchical topographies, with nanopatterns imprinted on micropatterns, significantly improved the percentage of TUJ1+ and MAP2+ cells. It is postulated that the microscale base pattern enhances initial BAM expression while the nanoscale sub-pattern promotes subsequent maturation. This is because the base pattern alone increased expression of TUJ1 and MAP2, while the nanoscale pattern was the only pattern yielding induced neurons capable of firing multiple action potentials. Nanoscale patterns also produced the highest fraction of cells showing spontaneous synaptic activity. Overall, reprogramming efficiency with one dose of polyplex on hierarchical patterns was comparable to that of five doses without topography. Thus, topography can enhance nonviral direct reprogramming of fibroblasts into induced neurons.

Engineering in vitro human neural tissue analogs by 3D bioprinting and electrostimulation

There is a fundamental need for clinically relevant, reproducible, and standardized in vitro human neural tissue models, not least of all to study heterogenic and complex human-specific neurological (such as neuropsychiatric) disorders. Construction of three-dimensional (3D) bioprinted neural tissues from native human-derived stem cells (e.g., neural stem cells) and human pluripotent stem cells (e.g., induced pluripotent) in particular is appreciably impacting research and conceivably clinical translation. Given the ability to artificially and favorably regulate a cell's survival and behavior by manipulating its biophysical environment, careful consideration of the printing technique, supporting biomaterial and specific exogenously delivered stimuli, is both required and advantageous. By doing so, there exists an opportunity, more than ever before, to engineer advanced and precise tissue analogs that closely recapitulate the morphological and functional elements of natural tissues (healthy or diseased). Importantly, the application of electrical stimulation as a method of enhancing printed tissue development in vitro, including neuritogenesis, synaptogenesis, and cellular maturation, has the added advantage of modeling both traditional and new stimulation platforms, toward improved understanding of efficacy and innovative electroceutical development and application.

On the Use of Black Ti as a Bone Substituting Biomaterial: Behind the Scenes of Dual-Functionality

Despite the potential of small-scale pillars of black titanium (bTi) for killing the bacteria and directing the fate of stem cells, not much is known about the effects of the pillars' design parameters on their biological properties. Here, three distinct bTi surfaces are designed and fabricated through dry etching of the titanium, each featuring different pillar designs. The interactions of the surfaces with MC3T3-E1 preosteoblast cells and Staphylococcus aureus bacteria are then investigated. Pillars with different heights and spatial organizations differently influence the morphological characteristics of the cells, including their spreading area, aspect ratio, nucleus area, and cytoskeletal organization. The preferential formation of focal adhesions (FAs) and their size variations also depend on the type of topography. When the pillars are neither fully separated nor extremely tall, the colocalization of actin fibers and FAs as well as an enhanced matrix mineralization are observed. However, the killing efficiency of these pillars against the bacteria is not as high as that of fully separated and tall pillars. This study provides a new perspective on the dual-functionality of bTi surfaces and elucidates how the surface design and fabrication parameters can be used to achieve a surface topography with balanced bactericidal and osteogenic properties.

Neural priming of adipose-derived stem cells by cell-imprinted substrates

Cell-imprinting technology is a novel method for directing stem cell fate using substrates molded from target cells. Here, we fabricated and studied cell-imprinted substrates for neural priming in human adipose-derived stem cells in the absence of chemical cues. We molded polydimethylsiloxane silicone substrates on fixed differentiated neural progenitor cells (ReNcell^TMVM). The ReNcell^TMcell line consists of immortalized human neural progenitor cells that are capable to differentiate into neural cells. The fabricated cell-imprinted silicone substrates represent the geometrical micro- and nanotopology of the target cell morphology. During the molding procedure, no transfer of cellular proteins was detectable. In the first test with undifferentiated ReNcell^TMVM cells, the cell-imprinted substrates could accelerate neural differentiation. With adipose-derived stem cells cultivated on the imprinted substrates, we observed modifications of cell morphology, shifting from spread to elongated shape. Both immunofluorescence and quantitative gene expression analysis showed upregulation of neural stem cell and early neuronal markers. Our study, for the first time, demonstrated the effectiveness of cell-imprinted substrates for neural priming of adipose-derived stem cells for regenerative medicine applications.

Graphene-Based Scaffolds for Regenerative Medicine

Leading-edge regenerative medicine can take advantage of improved knowledge of key roles played, both in stem cell fate determination and in cell growth/differentiation, by mechano-transduction and other physicochemical stimuli from the tissue environment. This prompted advanced nanomaterials research to provide tissue engineers with next-generation scaffolds consisting of smart nanocomposites and/or hydrogels with nanofillers, where balanced combinations of specific matrices and nanomaterials can mediate and finely tune such stimuli and cues. In this review, we focus on graphene-based nanomaterials as, in addition to modulating nanotopography, elastic modulus and viscoelastic features of the scaffold, they can also regulate its conductivity. This feature is crucial to the determination and differentiation of some cell lineages and is of special interest to neural regenerative medicine. Hereafter we depict relevant properties of such nanofillers, illustrate how problems related to their eventual cytotoxicity are solved via enhanced synthesis, purification and derivatization protocols, and finally provide examples of successful applications in regenerative medicine on a number of tissues.

Patterned Piezoelectric Scaffolds for Osteogenic Differentiation

The morphological clues of scaffolds can determine cell behavior and, therefore, the patterning of electroactive polymers can be a suitable strategy for bone tissue engineering. In this way, this work reports on the influence of poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) electroactive micropatterned scaffolds on the proliferation and differentiation of bone cells. For that, micropatterned P(VDF-TrFE) scaffolds were produced by lithography in the form of arrays of lines and hexagons and then tested for cell proliferation and differentiation of pre-osteoblast cell line. Results show that more anisotropic surface microstructures promote bone differentiation without the need of further biochemical stimulation. Thus, the combination of specific patterns with the inherent electroactivity of materials provides a promising platform for bone regeneration.

Fabrication and Characterization of Neurocompatible Ulvan-Based Layer-by-Layer Films

Construction of extracellular matrix-mimetic nanofilms has considerable potential in biomedical and nanomedicinal fields. In this work, we fabricated neurocompatible layer-by-layer (LbL) films based on ulvan (ULV), a highly sulfated polysaccharide having compositional similarity to glycosaminoglycans that play important functional roles in the brain. ULV was durably assembled as a film with chitosan, another marine-derived polysaccharide, and the film enabled the stable adhesion of primary hippocampal neurons with high viability, comparable to the conventional poly-d-lysine surface. Notably, the ULV-based LbL films accelerated neurite outgrowth and selectively suppressed the adhesion of astrocytes, highlighting its potential as an advanced platform for neural implants and devices.

Multifunctional Coating with Both Thermal Insulation and Antibacterial Properties Applied to Nickel-Titanium Alloy

BACKGROUND

With excellent shape memory and superelastic properties, shape memory alloy (SMA) is an ideal actuator, and it can form smart structure for different applications in medical field. However, SMA devices cause apparent thermal damage to the surrounding tissues when it works in vivo, making the application of smart structure that is composed of SMA actuator in vivo is greatly limited.

METHODS

In this paper, coating (APA) with PLA as the main body to limit the heat conduction, a multifunctional Ag nanoparticles (AgNPs)/polylactic acid (PLA)/Al2O3 was synthesized. The Al2O3 layer was formed by micro-arc oxidation (MAO) and AgNPs were synthesized by silver nitrate and ethylene glycol. Scanning electron microscopy, transmission electron microscope, and Fourier transform infrared spectra were applied to analyze the morphology and characterization of APA coating. The antimicrobial activity, thermal insulation activity, and biocompatibility of APA coating were furtherly explored and verified through animal experiments and immunohistochemistry.

RESULTS

With different particle sizes and concentrations of AgNPs, APA multi-functional films were successfully prepared. The Al2O3 layer was closely combined with SMA and formed a porous surface, so the PLA and AgNPs layers can firmly adhere to SMA, thus reducing the release of nickel ions in SMA. AgNPs gave APA coating excellent antibacterial activity and effectively inhibited the growth of Staphylococcus aureus. In addition, coupled with the low thermal conductivity of PLA and Al2O3, AgNPs were tightly anchored on the surface of PLA, which has high infrared reflectivity, making the APA coating obtain good thermal insulation performance.

CONCLUSION

We have successfully prepared the APA coating and obtained the optimum amount of AgNPs, which makes it have good thermal insulation performance, good antibacterial activity and good biocompatibility, which provides a new prospect for the application of SMA.

Engraving the Surface of Electrospun Microfibers with Nanoscale Grooves Promotes the Outgrowth of Neurites and the Migration of Schwann Cells

We report a simple method based upon coaxial electrospinning for the fabrication of aligned microfibers engraved with nanoscale grooves to promote neurite outgrowth and cell migration. The success of this method relies on the immiscibility between poly(ϵ-caprolactone) (PCL) and poly(vinyl pyrrolidone) (PVP) in 2,2,2-trifluoroethanol (TFE) for the generation of PVP/TFE pockets on the surface of a PCL jet. The pockets are stretched and elongated along with the jet, eventually resulting in the formation of nanoscale grooves upon the removal of PVP. The presence of nanoscale grooves greatly enhances the outgrowth of neurites from both PC12 cells and chick embryonic dorsal root ganglia (DRG) bodies, as well as the migration of Schwann cells. The enhancements can be maximized by optimizing the dimensions of the grooves for potential use in applications involving neurite extension and wound closure.

Polycaprolactone fumarate acts as an artificial neural network to promote the biological behavior of neural stem cells

Herein, we investigated the effect of electrospun polycaprolactone fumarate (PCLF) nanofibers on neural stem cell (NSC) behavior in the in vitro setting. Murine NSCs were isolated from adult mice subventricular zone and immunophenotyped by flow cytometry assay and immunofluorescence staining. Cells were cultured on the plastic surface, laminin-coated surface, and electrospun PCLF nanofibers. Cell morphology, attachment, and spreading were evaluated by scanning electron microscopy analysis. Cell viability and proliferation rates were evaluated by MTT assay. The proliferation of plated cells was investigated by monitoring Ki-67-positive cells using flow cytometry analysis. The protein levels of Map-2 and GFAP were detected by using immunofluorescence staining to show neural and astrocyte differentiation capacity. Scanning electron microscopy images revealed an extensive distribution, morphological adaptation, and cell-to-cell connectivity in NSCs upon culture on the PCLF surface. MTT analysis showed that the NSCs had more survival rates on the PCLF surface compared to the laminin and control groups over time (p < 0.05). In contrast to the laminin group, Ki-67 analysis showed a decrease of proliferating cells in the PCLF group. Immunofluorescence staining revealed the prominent increase of Map-2 and GFAP reduction in NSCs from the PCLF group compared to the laminin and control groups, showing the stimulatory effect of PCLF on targeted maturation of NSCs (p < 0.05). In brief, PCLF based construct promotes NSCs morphological adaptation and neuronal differentiation, suggesting PCLF as an appropriate and applicable substrate in neural tissue engineering.

Adhesion force spectroscopy with nanostructured colloidal probes reveals nanotopography-dependent early mechanotransductive interactions at the cell membrane level

Mechanosensing, the ability of cells to perceive and interpret the microenvironmental biophysical cues (such as the nanotopography), impacts strongly cellular behaviour through mechanotransductive processes and signalling. These events are predominantly mediated by integrins, the principal cellular adhesion receptors located at the cell/extracellular matrix (ECM) interface. Because of the typical piconewton force range and nanometre length scale of mechanotransductive interactions, achieving a detailed understanding of the spatiotemporal dynamics occurring at the cell/microenvironment interface is challenging; sophisticated interdisciplinary methodologies are required. Moreover, an accurate control over the nanotopographical features of the microenvironment is essential, in order to systematically investigate and precisely assess the influence of the different nanotopographical motifs on the mechanotransductive process. In this framework, we were able to study and quantify the impact of microenvironmental nanotopography on early cellular adhesion events by means of adhesion force spectroscopy based on innovative colloidal probes mimicking the nanotopography of natural ECMs. These probes provided the opportunity to detect nanotopography-specific modulations of the molecular clutch force loading dynamics and integrin clustering at the level of single binding events, in the critical time window of nascent adhesion formation. Following this approach, we found that the nanotopographical features are responsible for an excessive force loading in single adhesion sites after 20-60 s of interaction, causing a drop in the number of adhesion sites. However, by manganese treatment we demonstrated that the availability of activated integrins is a critical regulatory factor for these nanotopography-dependent dynamics.

Tenocyte-imprinted substrate: a topography-based inducer for tenogenic differentiation in adipose tissue-derived mesenchymal stem cells

Tendon tissue engineering based on stem cell differentiation has attracted a great deal of attention in recent years. Previous studies have examined the effect of cell-imprinted polydimethylsiloxane (PDMS) substrate on induction differentiation in stem cells. In this study, we used tenocyte morphology as a positive mold to create a tenocyte-imprinted substrate on PDMS. The morphology and topography of this tenocyte replica on PDMS was evaluated with scanning electron microscopy (SEM) and atomic force microscopy. The tenogenic differentiation induction capacity of the tenocyte replica in adipose tissue-derived mesenchymal stem cells (ADSCs) was then investigated and compared with other groups, including tissue replica (which was produced similarly to the tenocyte replica and was evaluated by SEM), decellularized tendon, and bone morphogenic protein (BMP)-12, as other potential inducers. This comparison gives us an estimate of the ability of tenocyte-imprinted PDMS (called cell replica in the present study) to induce differentiation compared to other inducers. For this reason, ADSCs were divided into five groups, including control, cell replica, tissue replica, decellularized tendon and BMP-12. ADSCs were seeded on each group separately and investigated by the real-time reverse transcription polymerase chain reaction (RT-PCR) technique after seven and 14 days. Our results showed that in spite of the higher effect of the growth factor on tenogenic differentiation, the cell replica can also induce tenocyte marker expression (scleraxis and tenomodulin) in ADSCs. Moreover, the tenogenic differentiation induction capacity of the cell replica was greater than tissue replica. Immunocytochemistry analysis revealed that ADSCs seeding on the cell replica for 14 days led to scleraxis and tenomodulin expression at the protein level. In addition, immunohistochemistry indicated that contrary to the promising results in vitro, there was little difference between ADSCs cultured on tenocyte-imprinted PDMS and untreated ADSCs. The results of such studies could lead to the production of inexpensive cell culture plates or biomaterials that can induce differentiation in stem cells without growth factors or other supplements.

Coating Materials for Neural Stem/Progenitor Cell Culture and Differentiation

Neural stem/progenitor cells (NSPCs) have a potential to treat various neurological diseases, such as Parkinson's Disease, Alzheimer's Disease, and Spinal Cord Injury. However, the limitation of NSPC sources and the difficulty to maintain their stemness or to differentiate them into specific therapeutic cells are the main hurdles for clinical research and application. Thus, for obtaining a therapeutically relevant number of NSPCs in vitro, it is important to understand factors regulating their behaviors and to establish a protocol for stable NSPC proliferation and differentiation. Coating materials for cell culture, such as Matrigel, laminin, collagen, and other coating materials, can significantly affect NSPC characteristics. This article provides a review of coating materials for NSPC culturing in both two dimensions and three dimensions, and their functions in NSPC proliferation and differentiation, and presents a useful guide to select coating materials for researchers.

Introduction of Specific 3D Micromorphologies in Collagen Scaffolds Using Odd and Even Dicarboxylic Acids

The construction of scaffolds and subsequent incorporation of cells and biologics have been widely investigated to regenerate damaged tissues. Scaffolds act as a template to guide tissue formation, and their characteristics have a considerable impact on the regenerative process. Whereas many technologies exist to induce specific two-dimensional (2D) morphologies into biomaterials, the introduction of three-dimensional (3D) micromorphologies into individual pore walls of scaffolds produced from biological molecules such as collagen poses a challenge. We here report the use of dicarboxylic acids to induce specific micromorphologies in collagen scaffolds and evaluate their effect on cellular migration and differentiation. Insoluble type I collagen fibrils were suspended in monocarboxylic and dicarboxylic acids of different concentrations, and unidirectional and random pore scaffolds were constructed by freezing and lyophilization. The application of various acids and concentrations resulted in variations in 3D micromorphologies, including wall structure, wall thickness, and pore size. The use of dicarboxylic acids resulted in acid-specific micromorphologies, whereas monocarboxylic acids did not. Dicarboxylic acids with an odd or even number of C-atoms resulted in frayed/fibrillar or smooth wall structures, respectively, with varying appearances. The formation of micromorphologies was concentration-dependent. In vitro analysis indicated the cytocompatibility of scaffolds, and micromorphology-related cell behavior was indicated by enhanced myosin staining and myosin heavy chain gene expression for C2C12 myoblasts cultured on scaffolds with frayedlike micromorphologies compared to those with smooth micromorphologies. In conclusion, porous collagen scaffolds with various intrawall 3D micromorphologies can be constructed by application of dicarboxylic acids, superimposing the second level of morphology to the overall scaffold structure. Acid crystal formation is key to the specific micromorphologies observed and can be explained by the odd/even theory for dicarboxylic acids. Scaffolds with a 3D micrometer-defined topography may be used as a screening platform to select optimal substrates for the regeneration of specific tissues.

Laser-Induced Periodic Surface Structure Enhances Neuroelectrode Charge Transfer Capabilities and Modulates Astrocyte Function

The brain machine interface (BMI) describes a group of technologies capable of communicating with excitable nervous tissue within the central nervous system (CNS). BMIs have seen major advances in recent years, but these advances have been impeded because of a temporal deterioration in the signal to noise ratio of recording electrodes following insertion into the CNS. This deterioration has been attributed to an intrinsic host tissue response, namely, reactive gliosis, which involves a complex series of immune mediators, resulting in implant encapsulation via the synthesis of pro-inflammatory signaling molecules and the recruitment of glial cells. There is a clinical need to reduce tissue encapsulation in situ and improve long-term neuroelectrode functionality. Physical modification of the electrode surface at the nanoscale could satisfy these requirements by integrating electrochemical and topographical signals to modulate neural cell behavior. In this study, commercially available platinum iridium (Pt/Ir) microelectrode probes were nanotopographically functionalized using femto/picosecond laser processing to generate laser-induced periodic surface structures (LIPSS). Three different topographies and their physical properties were assessed by scanning electron microscopy and atomic force microscopy. The electrochemical properties of these interfaces were investigated using electrochemical impedance spectroscopy and cyclic voltammetry. The in vitro response of mixed cortical cultures (embryonic rat E14/E17) was subsequently assessed by confocal microscopy, ELISA, and multiplex protein array analysis. Overall LIPSS features improved the electrochemical properties of the electrodes, promoted cell alignment, and modulated the expression of multiple ion channels involved in key neuronal functions.

Extracellular matrix and biomimetic engineering microenvironment for neuronal differentiation

Extracellular matrix (ECM) influences cell differentiation through its structural and biochemical properties. In nervous system, neuronal behavior is influenced by these ECMs structures which are present in a meshwork, fibrous, or tubular forms encompassing specific molecular compositions. In addition to contact guidance, ECM composition and structures also exert its effect on neuronal differentiation. This short report reviewed the native ECM structure and composition in central nervous system and peripheral nervous system, and their impact on neural regeneration and neuronal differentiation. Using topographies, stem cells have been differentiated to neurons. Further, focussing on engineered biomimicking topographies, we highlighted the role of anisotropic topographies in stem cell differentiation to neurons and its recent temporal application for efficient neuronal differentiation.

Supramolecular Nanofibers for Encapsulation and In Situ Differentiation of Neural Stem Cells

Design and fabrication of fibrous materials by natural biological macromolecules in light of biomimetics to achieve spatially cellular arrangements are highly desirable in tissue engineering. Herein, chromatin-inspired supramolecular fibers formed through the interfacial polyelectrolyte complexation (IPC) process by DNA and histone proteins for encapsulation and in situ differentiation of murine brain-derived neural stem cells (NSCs) are reported. High cell viability of encapsulated NSCs demonstrates the excellent biocompatibility of fibers as 3D scaffolds. Moreover, a cell-adhesive peptide (K₆ -PEG-RGD) is introduced into fibers by electrostatic interaction to improve NSCs encapsulation efficiency and prevent them from migrating out of fibers for enhanced spatially cellular arrangement. In situ differentiation of NSCs into oligodendrocytes within fibers is revealed by immunocytochemical staining assay. Due to the robust abilities to encapsulate and in situ differentiate NSCs, these chromatin-inspired supramolecular fibers show great potential in neural system-related tissue.

Regulation and Directing Stem Cell Fate by Tissue Engineering Functional Microenvironments: Scaffold Physical and Chemical Cues

It is well known that stem cells reside within tissue engineering functional microenvironments that physically localize them and direct their stem cell fate. Recent efforts in the development of more complex and engineered scaffold technologies, together with new understanding of stem cell behavior in vitro, have provided a new impetus to study regulation and directing stem cell fate. A variety of tissue engineering technologies have been developed to regulate the fate of stem cells. Traditional methods to change the fate of stem cells are adding growth factors or some signaling pathways. In recent years, many studies have revealed that the geometrical microenvironment played an essential role in regulating the fate of stem cells, and the physical factors of scaffolds including mechanical properties, pore sizes, porosity, surface stiffness, three-dimensional structures, and mechanical stimulation may affect the fate of stem cells. Chemical factors such as cell-adhesive ligands and exogenous growth factors would also regulate the fate of stem cells. Understanding how these physical and chemical cues affect the fate of stem cells is essential for building more complex and controlled scaffolds for directing stem cell fate.

Enhancing Neurogenesis of Neural Stem Cells Using Homogeneous Nanohole Pattern-Modified Conductive Platform

Biocompatible platforms, wherein cells attach and grow, are important for controlling cytoskeletal dynamics and steering stem cell functions, including differentiation. Among various components, membrane integrins play a key role in focal adhesion of cells (18-20 nm in size) and are, thus, highly sensitive to the nanotopographical features of underlying substrates. Hence, it is necessary to develop a platform/technique that can provide high flexibility in controlling nanostructure sizes. We report a platform modified with homogeneous nanohole patterns, effective in guiding neurogenesis of mouse neural stem cells (mNSCs). Sizes of nanoholes were easily generated and varied using laser interference lithography (LIL), by changing the incident angles of light interference on substrates. Among three different nanohole patterns fabricated on conductive transparent electrodes, 500 nm-sized nanoholes showed the best performance for cell adhesion and spreading, based on F-actin and lamellipodia/filopodia expression. Enhanced biocompatibility and cell adhesion of these nanohole patterns ultimately resulted in the enhanced neurogenesis of mNSCs, based on the mRNAs expression level of the mNSCs marker and several neuronal markers. Therefore, platforms modified with homogeneous nanohole patterns fabricated by LIL are promising for the precise tuning of nanostructures in tissue culture platforms and useful for controlling various differentiation lineages of stem cells.

Extracellular Nanomatrix-Induced Self-Organization of Neural Stem Cells into Miniature Substantia Nigra-Like Structures with Therapeutic Effects on Parkinsonian Rats

Substantia nigra (SN) is a complex and critical region of the brain wherein Parkinson's disease (PD) arises from the degeneration of dopaminergic neurons. Miniature SN-like structures (mini-SNLSs) constructed from novel combination of nanomaterials and cell technologies exhibit promise as potentially curative cell therapies for PD. In this work, a rapid self-organization of mini-SNLS, with an organizational structure and neuronal identities similar to those of the SN in vivo, is achieved by differentiating neural stem cells in vitro on biocompatible silica nanozigzags (NZs) sculptured by glancing angle deposition, without traditional chemical growth factors. The differentiated neurons exhibit electrophysiological activity in vitro. Diverse physical cues and signaling pathways that are determined by the nanomatrices and lead to the self-organization of the mini-SNLSs are clarified and elucidated. In vivo, transplantation of the neurons from a mini-SNLS results in an early and progressive amelioration of PD in rats. The sculptured medical device reported here enables the rapid and specific self-organization of region-specific and functional brain-like structures without an undesirable prognosis. This development provides promising and significant insights into the screening of potentially curative drugs and cell therapies for PD.