Characterizing On-Chip Angiogenesis Induction in a Microphysiological System as a Functional Measure of Mesenchymal Stromal Cell Bioactivity.

Mesenchymal stromal cells (MSCs) continue to be proposed for clinical investigation to treat myriad diseases given their purported potential to stimulate endogenous regenerative processes, such as angiogenesis. However, MSC functional heterogeneity has hindered clinical success and still poses a substantial manufacturing challenge from a product quality control perspective. Here, a quantitative bioassay based on an enhanced-throughput is described, microphysiological system (MPS) to measure the specific bioactivity of MSCs to stimulate angiogenesis as a potential measure of MSC potency. Using this novel bioassay, MSCs derived from multiple donors at different passages are co-cultured with human umbilical vein endothelial cells and exhibit significant heterogeneity in angiogenic potency between donors and cell passage. Depending on donor source and cellular passage number, MSCs varied in their ability to stimulate tip cell dominant or stalk cell dominant phenotypes in angiogenic sprout morphology which correlated with expression levels of hepatocyte growth factor (HGF). These findings suggest that MSC angiogenic bioactivity may be considered as a possible potency attribute in MSC quality control strategies. Development of a reliable and functionally relevant potency assay for measuring clinically relevant potency attributes of MSCs will help to improve consistency in quality and thereby, accelerate clinical development of these cell-based products.

U-IMPACT: a universal 3D microfluidic cell culture platform.

The development of organs-on-a-chip has resulted in advances in the reconstruction of 3D cellular microenvironments. However, there remain limitations regarding applicability and manufacturability. Here, we present an injection-molded plastic array 3D universal culture platform (U-IMPACT) for various biological applications in a single platform, such as cocultures of various cell types, and spheroids (e.g., tumor spheroids, neurospheres) and tissues (e.g., microvessels). The U-IMPACT consists of three channels and a spheroid zone with a 96-well plate form factor. Specifically, organoids or spheroids (~500 µm) can be located in designated areas, while cell suspensions or cell-laden hydrogels can be selectively placed in three channels. For stable multichannel patterning, we developed a new patterning method based on capillary action, utilizing capillary channels and the native contact angle of the materials without any modification. We derived the optimal material hydrophilicity (contact angle of the body, 45-90°; substrate, <30°) for robust patterning through experiments and theoretical calculations. We demonstrated that the U-IMPACT can implement 3D tumor microenvironments for angiogenesis, vascularization, and tumor cell migration. Furthermore, we cultured neurospheres from induced neural stem cells. The U-IMPACT can serve as a multifunctional organ-on-a-chip platform for high-content and high-throughput screening.

A microphysiological system-based potency bioassay for the functional quality assessment of mesenchymal stromal cells targeting vasculogenesis.

Mesenchymal stromal cells (MSCs) continue to be proposed for use in clinical trials to treat various diseases due to their therapeutic potential to pleiotropically influence endogenous regenerative processes, such as vasculogenesis. However, the functional heterogeneity of MSCs has hampered their clinical success and poses a significant manufacturing challenge with respect to MSC quality control. Here, we evaluated and qualified a quantitative bioassay based on an enhanced-throughput, microphysiological system to measure the specific paracrine bioactivity of MSCs to stimulate vasculogenesis as a measure of MSC potency. Using this novel bioassay, MSCs derived from multiple donors at different passages were co-cultured with human umbilical vein endothelial cells (HUVECs) and exhibited significant heterogeneity in vasculogenic potency between donors and cell passage. Using our microphysiological system (MPS)-based platform, we demonstrated that variations in MSC vasculogenic bioactivity were maintained when assayed across laboratories and operators. The differences in MSC vasculogenic bioactivity were also correlated with the baseline expression of several genes involved in vasculogenesis (hepatocyte growth factor (HGF), angiopoietin-1 (ANGPT)) or the production of matricellular proteins (fibronectin (FN), insulin-like growth factor-binding protein 7 (IGFBP7)). These findings emphasize the significant functional heterogeneity of MSCs in vasculogenic bioactivity and suggest that changes in baseline gene expression of vasculogenic or matricellular protein genes during manufacturing may affect this bioactivity. The development of a reliable and functionally relevant potency assay for measuring the specific vasculogenic bioactivity of manufactured MSCs will help to reliably assure their quality when used in appropriate clinical trials.

Near-field thermophotovoltaics for efficient heat to electricity conversion at high power density.

Thermophotovoltaic approaches that take advantage of near-field evanescent modes are being actively explored due to their potential for high-power density and high-efficiency energy conversion. However, progress towards functional near-field thermophotovoltaic devices has been limited by challenges in creating thermally robust planar emitters and photovoltaic cells designed for near-field thermal radiation. Here, we demonstrate record power densities of ~5 kW/m2 at an efficiency of 6.8%, where the efficiency of the system is defined as the ratio of the electrical power output of the PV cell to the radiative heat transfer from the emitter to the PV cell. This was accomplished by developing novel emitter devices that can sustain temperatures as high as 1270 K and positioning them into the near-field (<100 nm) of custom-fabricated InGaAs-based thin film photovoltaic cells. In addition to demonstrating efficient heat-to-electricity conversion at high power density, we report the performance of thermophotovoltaic devices across a range of emitter temperatures (~800 K-1270 K) and gap sizes (70 nm-7 µm). The methods and insights achieved in this work represent a critical step towards understanding the fundamental principles of harvesting thermal energy in the near-field.

Near-perfect photon utilization in an air-bridge thermophotovoltaic cell.

Thermophotovoltaic cells are similar to solar cells, but instead of converting solar radiation to electricity, they are designed to utilize locally radiated heat. Development of high-efficiency thermophotovoltaic cells has the potential to enable widespread applications in grid-scale thermal energy storage1,2, direct solar energy conversion3-8, distributed co-generation9-11 and waste heat scavenging12. To reach high efficiencies, thermophotovoltaic cells must utilize the broad spectrum of a radiative thermal source. However, most thermal radiation is in a low-energy wavelength range that cannot be used to excite electronic transitions and generate electricity. One promising way to overcome this challenge is to have low-energy photons reflected and re-absorbed by the thermal emitter, where their energy can have another chance at contributing towards photogeneration in the cell. However, current methods for photon recuperation are limited by insufficient bandwidth or parasitic absorption, resulting in large efficiency losses relative to theoretical limits. Here we demonstrate near-perfect reflection of low-energy photons by embedding a layer of air (an air bridge) within a thin-film In0.53Ga0.47As cell. This result represents a fourfold reduction in parasitic absorption relative to existing thermophotovoltaic cells. The resulting gain in absolute efficiency exceeds 6 per cent, leading to a very high power conversion efficiency of more than 30 per cent, as measured with an approximately 1,455-kelvin silicon carbide emitter. As the out-of-band reflectance approaches unity, the thermophotovoltaic efficiency becomes nearly insensitive to increasing cell bandgap or decreasing emitter temperature. Accessing this regime may unlock a range of possible materials and heat sources that were previously inaccessible to thermophotovoltaic energy conversion.

Hybrid Nanofiber Scaffold-Based Direct Conversion of Neural Precursor Cells/Dopamine Neurons.

The concept of cellular reprogramming was developed to generate induced neural precursor cells (iNPCs)/dopaminergic (iDA) neurons using diverse approaches. Here, we investigated the effects of various nanoscale scaffolds (fiber, dot, and line) on iNPC/iDA differentiation by direct reprogramming. The generation and maturation of iDA neurons (microtubule-associated protein 2-positive and tyrosine hydroxylase-positive) and iNPCs (NESTIN-positive and SOX2-positive) increased on fiber and dot scaffolds as compared to that of the flat (control) scaffold. This study demonstrates that nanotopographical environments are suitable for direct differentiation methods and may improve the differentiation efficiency.

From 2D to 3D: Strain- and elongation-free topological transformations of optoelectronic circuits.

Optoelectronic circuits in 3D shapes with large deformations can offer additional functionalities inaccessible to conventional planar electronics based on 2D geometries constrained by conventional photolithographic patterning processes. A light-sensing focal plane array (FPA) used in imagers is one example of a system that can benefit from fabrication on curved surfaces. By mimicking the hemispherical shape of the retina in the human eye, a hemispherical FPA provides a low-aberration image with a wide field of view. Due to the inherently high value of such applications, intensive efforts have been devoted to solving the problem of transforming a circuit fabricated on a flat wafer surface to an arbitrary shape without loss of performance or distorting the linear layouts that are the natural product of this fabrication paradigm. Here we report a general approach for fabricating electronic circuits and optoelectronic devices on nondevelopable surfaces by introducing shear slip of thin-film circuit components relative to the distorting substrate. In particular, we demonstrate retina-like imagers that allow for a topological transformation from a plane to a hemisphere without changing the relative positions of the pixels from that initially laid out on a planar surface. As a result, the resolution of the imager, particularly in the foveal region, is not compromised by stretching or creasing that inevitably results in transforming a 2D plane into a 3D geometry. The demonstration provides a general strategy for realizing high-density integrated circuits on randomly shaped, nondevelopable surfaces.

Development of a functional airway-on-a-chip by 3D cell printing.

We used 3D cell printing to emulate an airway coupled with a naturally-derived blood vessel network in vitro. Decellularized extracellular matrix bioink derived from porcine tracheal mucosa (tmdECM) was used to encapsulate and print endothelial cells and fibroblasts within a designated polycarprolactone (PCL) frame. Providing a niche that emulates conditions in vivo, tmdECM gradually drives endothelial re-orientation, which leads to the formation of a lumen and blood vessel network. A fully-differentiated in vitro airway model was assembled with the printed vascular platform, and collectively reproduced a functional interface between the airway epithelium and the vascular network. The model presented respiratory symptoms including asthmatic airway inflammation and allergen-induced asthma exacerbation in physiological context. Because of the adaptable and automated nature of direct 3D cell printing, we expect that this will have relevance in vivo and high reproducibility for production of high-content platforms for preclinical trials in biomedical research.

3D tissue formation by stacking detachable cell sheets formed on nanofiber mesh.

We present a novel approach for assembling 3D tissue by layer-by-layer stacking of cell sheets formed on aligned nanofiber mesh. A rigid frame was used to repeatedly collect aligned electrospun PCL (polycaprolactone) nanofiber to form a mesh structure with average distance between fibers 6.4 µm. When human umbilical vein endothelial cells (HUVECs), human foreskin dermal fibroblasts, and skeletal muscle cells (C2C12) were cultured on the nanofiber mesh, they formed confluent monolayers and could be handled as continuous cell sheets with areas 3 × 3 cm2 or larger. Thicker 3D tissues have been formed by stacking multiple cell sheets collected on frames that can be nested (i.e. Matryoshka dolls) without any special tools. When cultured on the nanofiber mesh, skeletal muscle, C2C12 cells oriented along the direction of the nanofibers and differentiated into uniaxially aligned multinucleated myotube. Myotube cell sheets were stacked (upto 3 layers) in alternating or aligned directions to form thicker tissue with ∼50 µm thickness. Sandwiching HUVEC cell sheets with two dermal fibroblast cell sheets resulted in vascularized 3D tissue. HUVECs formed extensive networks and expressed CD31, a marker of endothelial cells. Cell sheets formed on nanofiber mesh have a number of advantages, including manipulation and stacking of multiple cell sheets for constructing 3D tissue and may find applications in a variety of tissue engineering applications.

Preparation of Nano-Porous Activated Carbon Aerogel Using a Single-Step Activation Method for Use as High-Power EDLC Electrode in Organic Electrolyte.

Carbon aerogel was chemically activated with KOH using two different activation methods (conventional activation method and single-step activation method) to yield the nano-porous activated carbon aerogel. Both nano-porous activated carbon aerogels exhibited a better capacitive behavior than carbon aerogel in organic electrolyte. However, a drastic decrease in the specific capacitance with increasing current density was observed in the ACA_C (activated carbon aerogel prepared by a conventional activation method), which is a general tendency of carbon electrode for EDLC in organic electrolyte. Interestingly, the specific capacitance of ACA_S electrode (activated carbon aerogel prepared by a single-step activation method) decreased slowly with increasing current density and its CV curve maintained a rectangular shape well even at a high scan rate of 500 mV/s. The enhanced electrochemical performance of ACA_S at a high current density was attributed to its low ionic resistance caused by the well-developed pore structure with appropriate pore size for easy moving of organic electrolyte ion. Therefore, it can be concluded that single-step activation method could be one of the efficient methods for preparation of nano-porous activated carbon aerogel electrode for high-power EDLC in organic electrolyte.

Creation of a Hybrid Scaffold with Dual Configuration of Aligned and Random Electrospun Fibers.

A novel hybrid construct was developed by combining aligned fibers (AFs) and random fibers (RFs) to form a scaffolding system. Homogeneous fiber-based structures were fabricated by electrospinning, which produced both random and aligned fiber mats depending on the collection method. The upper part of the scaffold contained an AF layer, which possessed a well-organized configuration that provided uniaxial topographic guidance. For mechanical stability and support, the lower part of the scaffold was composed of an RF layer. Despite the presence of randomly distributed RFs, desirable alignment and differentiation could be achieved in cultured C2C12 myoblasts by controlling the density of AF layer. The fibrous structure of the hybrid scaffold also exhibited high porosity and therefore reasonable permeability. Owing to the structural stability provided by the underlying RFs, the cell-laden fibrous scaffolds were amenable to physical manipulation, such as multilayering. Collectively, the morphological features and manipulable architecture of the developed scaffolds suggest that they would perform well in practical applications.

Stimuli-responsive hydrogel patterns for smart microfluidics and microarrays.

In this review, we highlight the properties, functions and applications of stimuli-responsive hydrogel patterns in bioanalytical applications. Stimuli-responsive hydrogel patterns can be realized by well-established micro- and nanofabrication technologies such as photolithography and micromolding, and are currently adopted as active components for manipulation of flow and biosamples in microchannel and microarray systems. We overview the properties of stimuli-responsive hydrogel materials and their fabrication methods along with some representative examples in microfluidics and microarrays.

The effect of Gunn's intramuscular stimulation for postherpetic neuralgia -A report of 4 cases-.

Herpes zoster is the consequence of reactivation of latent varicella zoster virus from dorsal root ganglia. Postherpetic neuralgia (PHN) may be diagnosed when pain persists in a dermatomal pattern long after the vesicular erruption has healed. PHN is a kind of neuropathic pain. The pathophysiology of PHN is uncertain, but neuropathic pain due to denervation supersensitivity may be important to understand the pathophysiology of PHN. Numerous treatment have been introduced for the management of PHN, but no methods that results in complete remission. Gunn's intramuscular stimulation (IMS) is one of the best treatment of chronic pain, especially neuropathic pain. We tried Gunn's IMS for treatment of PHN patients affecting thoracic dermatomes. As a result, the visual analogue scale (VAS) was decreased from 7-8 to 2-3 and the result were satisfactory. The purpose of this case report is to introduce the Gunn's IMS and review our experience for the treatment of PHN.