A Fully Integrated Microfluidic Device with Immobilized Dyes for Simultaneous Detection of Cell-Free DNA and Histones from Plasma Using Dehydrated Agarose Gates

Sepsis, a life-threatening condition resulting from a failing host response to infection, causes millions of deaths annually, necessitating rapid and simple prognostic assessments. A variety of genomic and proteomic biomarkers have been developed for sepsis. For example, it has been shown that the level of plasma cell-free DNA (cfDNA) and circulating histones increases considerably during sepsis, and they are linked with sepsis severity and mortality. Developing a diagnostic tool that is capable of assessing such diverse biomarkers is challenging as the detection methodology is quite different for each. Here, a fully integrated microfluidic device capable of detecting a genomic biomarker (cfDNA) and a proteomic biomarker (total circulating histones) using a common detection platform has been demonstrated. The microfluidic device utilizes dehydrated agarose gates loaded with pH-specific agarose to electrophoretically trap cfDNA and histones at their respective isoelectric points. It also incorporates fluorescent dyes within the device, eliminating the need for off-chip sample preparation and allowing the direct testing of plasma samples without the need for labeling DNA and histones with fluorescent dyes beforehand. Xurography, which is a low-cost and rapid method for fabrication of microfluidics, is used in all the fabrication steps. Experimental results demonstrate the effective accumulation and separation of cfDNA and histones in the agarose gates in a total processing time of 20 min, employing 10 and 30 Volts for cfDNA and histone accumulation and detection, respectively. The device can potentially be used to distinguish between the survivors and non-survivors of sepsis. The integration of the detection of both biomarkers into a single device and dye immobilization enhances its clinical utility for rapid point-of-care assessment of sepsis prognosis.

Isoelectric trapping and discrimination of histones from plasma in a microfluidic device using dehydrated isoelectric gate

Histones are basic proteins with an isoelectric point around 11. It has been shown that the level of plasma circulating histones increases significantly during sepsis, and circulating free histones are associated with sepsis severity and mortality. It was found that the median plasma total free histone concentration of sepsis ICU non-survivors is higher compared to survivors. Therefore, histone concentration can serve as a prognostic indicator and there is a need for a simple, low-cost, and rapid method for measuring histone levels. In this work, we have developed a microfluidic device containing an isoelectric membrane made of dehydrated agarose gel of a specific pH embedded in a porous membrane for isoelectric trapping of histones rapidly. Although isoelectric gates have been used for trapping proteins before, they have to be introduced at the time of the experiment. Here, we show that isoelectric gates formed by gels loaded in a scaffold can be integrated directly into the fabrication process flow, dehydrated for storage, and rehydrated during the experiment and still function effectively to achieve isoelectric trapping. A low-cost and rapid microfabrication technique, xurography, was used for agarose integration and device fabrication. The integrated device was tested with samples containing buffered histone, histone in the presence of high-concentration bovine serum albumin (BSA), and histone spiked in blood plasma. The results show that the device can be used to distinguish between survivors and non-survivors of sepsis in less than 10 min, making it suitable as a point-of-care device for sepsis prognosis.

Identification and Quantification of Aqueous Disinfectants Using an Array of Carbon Nanotube-Based Chemiresistors

Disinfection of water is essential to prevent the growth of pathogens, but at high levels, it can cause harm to human health. Therefore, accurate monitoring of disinfectant concentrations in water is essential to ensure safe drinking water. The use of multiple disinfectants at different stages in water treatment plants makes it necessary to also identify the type and concentrations of all of the disinfectant species present. Here, we demonstrate an effective approach to identify and quantify multiple disinfectants (using the example of free chlorine and potassium permanganate) in water using single-walled carbon nanotube (SWCNT)-based reagent-free chemiresistive sensing arrays. Facile fabrication of chemiresistive devices makes them a popular choice for the implementation of sensor arrays. Our sensing array consists of functionalized and unfunctionalized (blank) SWCNT sensors to distinguish the disinfectants. The distinct responses from the different sensors at varying concentrations and pH can be fitted to the mathematical model of a Langmuir adsorption isotherm separately for each sensor. Blank and functionalized sensors respond through different mechanisms that result in varying responses that are concentration- and pH-dependent. Chemometric techniques such as principal component analysis (PCA) and partial least-squares-discriminant analysis (PLS-DA) were used to analyze the sensor data. PCA showed an excellent separation of the analytes over five different pHs (5.5, 6.5, 7.5, 8.5, and 9.5). PLS-DA provided excellent separability as well as good predictability with a Q2 of 94.26% and an R2 of 95.67% for the five pH regions of the two analytes. This proof-of-concept solid-state chemiresistive sensing array can be developed for specific disinfectants that are commonly used in water treatment plants and can be deployed in water distribution and monitoring facilities. We have demonstrated the applicability of chemiresistive devices in a sensor array format for the first time for aqueous disinfectant monitoring.

Impact of 3D collagen-based model and hydrostatic pressure on periodontal ligament fibroblast: A morpho-biochemical analysis

This study developed a customized hydrostatic pressure-based loading environment to investigate the effect of static hydrostatic pressure on the periodontal ligament fibroblasts (PDLf) in a three-dimensional (3D) collagen-based model. The cylindrical tissue constructs were comprised of PDL fibroblast cells seeded in type I collagen matrices and divided into three experimental groups: Control (no load), low-load (∼0.07 kPa), and high-load (∼60 kPa), all subjected to 24 h of experimental duration. Cells in the 3D construct were stained with fluorophore-conjugated antibodies for cytoskeletal protein F-actin and matricellular protein periostin. Cell culture supernatant was assessed for receptor activator of nuclear factor kappaB ligand (RANKL) and osteoprotegerin (OPG) expression. Transmission electron microscopy examined the contact between the cells and the collagen matrix. Ultrastructural changes in the 3D collagen matrix were also analyzed using scanning electron microscopy. Experiments were performed in triplicates, and data was analyzed using one-way ANOVA (p < 0.05). The 3D PDLf constructs from the low-load group demonstrated the highest levels of homogeneous cell distribution and higher expression of F-actin and periostin with enhanced interaction with the matrix. The collagen matrix in this group showed more closely packed fibers forming thicker bundles when compared to the control and the high-load 3D PDLf constructs. Nonuniform cell distribution with decreased expression of F-actin and periostin was observed in the control and high-load PDLf constructs. The high-load group showed the highest RANKL/OPG expression. This study demonstrated low-level hydrostatic pressure's role in regulating PDLf functions and extracellular matrix response, while excessive hydrostatic pressure may be detrimental to PDL fibroblast cell function.

Three-dimensional oxygen concentration monitoring in hydrogels using low-cost phosphorescence lifetime imaging for tissue engineering

Oxygen concentration measurement in 3D hydrogels is vital in 3D cell culture and tissue engineering. However, standard 3D imaging systems capable of measuring oxygen concentration with adequate precision are based on advanced microscopy platforms, which are not accessible in many laboratories due to the system's complexity and the high price. In this work, we present a fast and low-cost phosphorescence lifetime imaging design for measuring the lifetime of oxygen-quenched phosphorescence emission with 0.25 µs temporal precision and sub-millimeter spatial resolution in 3D. By combining light-sheet illumination and the frequency-domain lifetime measurement using a commercial rolling-shutter CMOS camera in the structure of a conventional optical microscope, this design is highly customizable to accommodate application-specific research needs while also being low-cost as compared to advanced instruments. As a demonstration, we made a fluidic device with a gas-permeable film to create an artificial oxygen gradient in the hydrogel sample. Dye-embedded beads were distributed in the hydrogel to conduct continuous emission lifetime monitoring when nitrogen was pumped through the fluidic channel and changed oxygen distribution in the sample. The dynamics of the changes in lifetime co-related with their location in the gel of size 0.5 mm×1.5 mm×700 µm demonstrate the ability of this design to measure the oxygen concentration stably and precisely in 3D samples.

Advancing our understanding of bioreactors for industrial-sized cell culture: health care and cellular agriculture implications

Bioreactors are advanced biomanufacturing tools that have been widely used to develop various applications in the fields of health care and cellular agriculture. In recent years, there has been a growing interest in the use of bioreactors to enhance the efficiency and scalability of these technologies. In cell therapy, bioreactors have been used to expand and differentiate cells into specialized cell types that can be used for transplantation or tissue regeneration. In cultured meat production, bioreactors offer a controlled and efficient means of producing meat without the need for animal farming. Bioreactors can support the growth of muscle cells by providing the necessary conditions for cell proliferation, differentiation, and maturation, including the provision of oxygen and nutrients. This review article aims to provide an overview of the current state of bioreactor technology in both cell therapy and cultured meat production. It will examine the various bioreactor types and their applications in these fields, highlighting their advantages and limitations. In addition, it will explore the future prospects and challenges of bioreactor technology in these emerging fields. Overall, this review will provide valuable insights for researchers and practitioners interested in using bioreactor technology to develop innovative solutions in the biomanufacturing of therapeutic cells and cultured meat.

Solid-state, reagent-free and one-step laser-induced synthesis of graphene-supported metal nanocomposites from metal leaves and application to glucose sensing

The laser-induced method to prepare three-dimensional (3D) porous graphene has been widely used in many fields owing to its low-cost, easy operation, maskless patterning and ease of mass production. Metal nanoparticles are further introduced on the surface of 3D graphene to enhance its property. The existing methods, however, such as laser irradiation and electrodeposition of metal precursor solution, suffer from many shortcomings, including complicated procedure of metal precursor solution preparation, strict experimental control, and poor adhesion of metal nanoparticles. Herein, a solid-state, reagent-free, and one-step laser-induced strategy has been developed for the fabrication of metal nanoparticle modified-3D porous graphene nanocomposites. Commercial transfer metal leaves were covered on a polyimide film followed by direct laser irradiation to produce 3D graphene nanocomposites modified with metal nanoparticles. The proposed method is versatile and applicable to incorporate various metal nanoparticles including gold silver, platinum, palladium, and copper. Furthermore, the 3D graphene nanocomposites modified with AuAg alloy nanoparticles were successfully synthesized in both 21 Karat (K) and 18K gold leaves. Its electrochemical characterization demonstrated that the synthesized 3D graphene-AuAg alloy nanocomposites exhibited excellent electrocatalytic properties. Finally, we fabricated LIG-AuAg alloy nanocomposites as enzyme-free flexible sensors for glucose detection. The LIG-18K electrodes exhibited the superior glucose sensitivity of 1194 μA mM^-1 cm^-2 and low detection limits of 0.21 μM. The LIG-21K nanocomposite sensors showed two linear ranges from 1 μM to 1 mM and 2 mM-20 mM with good sensitivity. Furthermore, the flexible glucose sensor showed good stability, sensitivity, and ability to sense in blood plasma samples. The proposed one-step fabrication of reagent-free and metal alloy nanoparticles on LIG with excellent electrochemical performance opens up possibilities for diversifying potential applications of sensing, water treatment and electrocatalysis.

A reagent-free phosphate chemiresistive sensor using carbon nanotubes functionalized with crystal violet

Phosphate is important for plant and animal growth. Therefore, it is commonly added as a fertilizer in agricultural fields. Phosphorus is typically measured using colorimetric or electrochemical sensors. Colorimetric sensors suffer from a limited measuring range and toxic waste generation while electrochemical sensors suffer from long-term drifts due to reference electrodes. Here, we propose a solid-state, reagent-free and reference electrode-free chemiresistive sensor for measuring phosphate using single-walled carbon nanotubes functionalized with crystal violet. The functionalized sensor exhibited a measuring range from 0.1 mM to 10 mM at pH 8. No significant interference was observed for common interfering anions like nitrates, sulphates, and chlorides. This study showed a proof-of-concept chemiresistive sensor, which can potentially be used to measure phosphate levels in hydroponics and aquaponics systems. The dynamic measuring range further needs to be extended for surface water samples.

Efficient, Breathable, and Compostable Multilayer Air Filter Material Prepared from Plant-Derived Biopolymers

State-of-art face masks and respirators are fabricated as single-use devices using microfibrous polypropylene fabrics, which are challenging to be collected and recycled at a community scale. Compostable face masks and respirators can offer a viable alternative to reducing their environmental impact. In this work, we have developed a compostable air filter produced by electrospinning a plant-derived protein, zein, on a craft paper-based substrate. The electrospun material is tailored to be humidity tolerant and mechanically durable by crosslinking zein with citric acid. The electrospun material demonstrated a high particle filtration efficiency (PFE) of 91.15% and a high pressure drop (PD) of 191.2 Pa using an aerosol particle diameter of 75 ± 2 nm at a face velocity of 10 cm/s. We deployed a pleated structure to reduce the PD or improve the breathability of the electrospun material without compromising the PFE over short- and long-duration tests. Over a 1 h salt loading test, the PD of a single-layer pleated filter increased from 28.9 to 39.1 Pa, while that of the flat sample increased from 169.3 to 327 Pa. The stacking of pleated layers enhanced the PFE while retaining a low PD; a two-layer stack with a pleat width of 5 mm offers a PFE of 95.4 ± 0.34% and a low PD of 75.2 ± 6.1 Pa.

Red blood cell dynamics in extravascular biological tissues modelled as canonical disordered porous media

The dynamics of blood flow in the smallest vessels and passages of the human body, where the cellular character of blood becomes prominent, plays a dominant role in the transport and exchange of solutes. Recent studies have revealed that the microhaemodynamics of a vascular network is underpinned by its interconnected structure, and certain structural alterations such as capillary dilation and blockage can substantially change blood flow patterns. However, for extravascular media with disordered microstructure (e.g. the porous intervillous space in the placenta), it remains unclear how the medium’s structure affects the haemodynamics. Here, we simulate cellular blood flow in simple models of canonical porous media representative of extravascular biological tissue, with corroborative microfluidic experiments performed for validation purposes. For the media considered here, we observe three main effects: first, the relative apparent viscosity of blood increases with the structural disorder of the medium; second, the presence of red blood cells (RBCs) dynamically alters the flow distribution in the medium; third, symmetry breaking introduced by moderate structural disorder can promote more homogeneous distribution of RBCs. Our findings contribute to a better understanding of the cell-scale haemodynamics that mediates the relationship linking the function of certain biological tissues to their microstructure.

Integration of hydrogels into microfluidic devices with porous membranes as scaffolds enables their drying and reconstitution

Hydrogels are a critical component of many microfluidic devices. They have been used in cell culture applications, biosensors, gradient generators, separation microdevices, micro-actuators, and microvalves. Various techniques have been utilized to integrate hydrogels into microfluidic devices such as flow confinement and gel photopolymerization. However, in these methods, hydrogels are typically introduced in post processing steps which add complexity, cost, and extensive fabrication steps to the integration process and can be prone to user induced variations. Here, we introduce an inexpensive method to locally integrate hydrogels into microfluidic devices during the fabrication process without the need for post-processing. In this method, porous and fibrous membranes such as electrospun membranes are used as scaffolds to hold gels and they are patterned using xurography. Hydrogels in various shapes as small as 200 μm can be patterned using this method in a scalable manner. The electrospun scaffold facilitates drying and reconstitution of these gels without loss of shape or leakage that is beneficial in a number of applications. Such reconstitution is not feasible using other hydrogel integration techniques. Therefore, this method is suitable for long time storage of hydrogels in devices which is useful in point-of-care (POC) devices. This hydrogel integration method was used to demonstrate gel electrophoretic concentration and quantification of short DNA (150 bp) with different concentrations in rehydrated agarose embedded in electrospun polycaprolactone (PCL) membrane. This can be developed further to create a POC device to quantify cell-free DNA, which is a prognostic biomarker for severe sepsis patients.

Potential role of blood biomarkers in patients with fibromyalgia: a systematic review with meta-analysis

ABSTRACT

Fibromyalgia (FM) is a complex chronic pain condition. Its symptoms are nonspecific, and to date, no objective test exists to confirm FM diagnosis. Potential objective measures include the circulating levels of blood biomarkers. This systematic review and meta-analysis aim to review studies assessing blood biomarkers' levels in patients with FM compared with healthy controls. We systematically searched the PubMed, MEDLINE, EMBASE, and PsycINFO databases. Fifty-four studies reporting the levels of biomarkers in blood in patients with FM were included. Data were extracted, and the methodological quality was assessed independently by 2 authors. The methodological quality of 9 studies (17%) was low. The results of most studies were not directly comparable given differences in methods and investigated target immune mediators. Thus, data from 40 studies only were meta-analyzed using a random-effects model. The meta-analysis showed that patients with FM had significantly lower levels of interleukin-1 β and higher levels of IL-6, IL-8, tumor necrosis factor-alpha, interferon gamma, C-reactive protein, and brain-derived neurotrophic factor compared with healthy controls. Nevertheless, this systematic literature review and meta-analysis could not support the notion that these blood biomarkers are specific biomarkers of FM. Our literature review, however, revealed that these same individual biomarkers may have the potential role of identifying underlying pathologies or other conditions that often coexist with FM. Future research is needed to evaluate the potential clinical value for these biomarkers while controlling for the various confounding variables.

Microfluidic device for single step measurement of protein C in plasma samples for sepsis prognosis

Protein C is a vitamin K dependant protein in plasma that plays an essential role in regulating the coagulation cascade and inflammatory response. As a result of its importance in these roles, it has been suggested as a biomarker for prognosis of patients affected by sepsis. Sepsis is a dysregulated host response to an infection that is the leading cause of mortality in U.S. hospitals and results in the highest cost of hospitalization. It was found that protein C concentration in non-surviving sepsis patients is significantly lower (1.8 μg mL^-1) than in survivors and healthy patients who have a protein C concentration of 3.9-5.9 μg mL^-1. Current methods for diagnosing sepsis rely on expensive immunoassays or functional assays that require multiple steps for isolation and activation of protein C. We demonstrate in this paper a low cost, single step assay for detection of protein C in blood plasma. This was done by combining isoelectric gates with barium-immobilized metal affinity trapping. The electric field was optimized for use with immobilized metal affinity using COMSOL simulation. The integrated device was tested with samples containing buffered protein C, protein C in the presence of high concentration bovine serum albumin and alpha 1-proteinase inhibitor, and in blood plasma with spiked protein C. The stability of the measured values was tested by monitoring the intensity of a mixture of protein C with BSA and A1PI every minute to determine that measurement after 40 minutes was optimal. The results showed that the device could be used to distinguish a reduction in protein C from 4.46 μg mL^-1 to 1.96 μg mL^-1 with greater than 98% confidence in plasma making it suitable for sepsis prognosis.

Defect Density-Dependent pH Response of Graphene Derivatives: Towards the Development of pH-Sensitive Graphene Oxide Devices

In this study, we demonstrate that a highly pH-sensitive substrate could be fabricated by controlling the type and defect density of graphene derivatives. Nanomaterials from single-layer graphene resembling a defect-free structure to few-layer graphene and graphene oxide with high defect density were used to demonstrate the pH-sensing mechanisms of graphene. We show the presence of three competing mechanisms of pH sensitivity, including the availability of functional groups, the electrochemical double layer, and the ion trapping that determines the overall pH response. The graphene surface was selectively functionalized with hydroxyl, amine, and carboxyl groups to understand the role and density of the graphene pH-sensitive functional groups. Later, we establish the development of highly pH-sensitive graphene oxide by controlling its defect density. This research opens a new avenue for integrating micro–nano-sized pH sensors based on graphene derivatives into next-generation sensing platforms.

Deciphering Stem Cell from Apical Papilla - Macrophage Choreography using a Novel 3D Organoid System

INTRODUCTION

Immune cell - mesenchymal stem cell crosstalk modulates the process of repair and regeneration. In this study, a novel heterogenous cell containing matrix based three-dimensional (3D) tissue-construct was employed to study the interactions between stem cells from apical papilla (SCAP) and macrophage for a comprehensive understanding on the cellular signalling mechanisms guiding inflammation and repair.

METHODS

SCAP and macrophages were seeded with collagen in 3D printed molds to generate self-assembled tissue-constructs, which were exposed to three conditions: no stimulation, lipopolysaccharide (LPS), and interleukin-4 (IL-4) from 0 to 14 days. Specimens from each group were evaluated for cellular interactions, inflammatory mediators (IL-1β, TNF-α, MDC, MIP-1β, MCP-1, IL-6, IL-8, TGF-β1, IL-1RA, IL-10), expression of surface markers (CD80, 206), transcription factors (pSTAT1, pSTAT6) and SCAP differentiation markers (DSPP, DMP-1, and alizarin red) using confocal laser scanning microscopy and multiplex cytokine profiling from 2 to 14 days.

RESULTS

SCAP and macrophages displayed a cytokine-mediated interaction and differentiation characteristics. The increased pro-inflammatory cytokines/chemokines: IL-1β, TNF-α, MDC and MIP-1β in the earlier phase followed by the higher ratio of pSTAT6/pSTAT1 and decreased CD206 (p<0.05), indicated a distinct polarization behavior in macrophages during repair in LPS group. Conversely, the equal ratio of pSTAT6/pSTAT1, late increase in CD206 and amplified secretion of IL-1RA, IL-10 and TGF-β1 (p<0.05) in the anti-inflammatory environment, directed alternative macrophage polarization, promoting SCAP differentiation and tissue modeling in IL-4 group.

CONCLUSIONS

The novel 3D organoid system developed in this study allowed a comprehensive analysis of the SCAP-macrophage interactions during inflammation and healing, providing a deeper insight on the periapical dynamics of immature tooth.

Single-step measurement of cell-free DNA for sepsis prognosis using a thread-based microfluidic device

Cell-free DNA (cfDNA) content in plasma has been studied as a biomarker for sepsis. Recent publications show that the cfDNA content in sepsis patients entering intensive care unit who were likely to survive had a total cfDNA concentration of 1.16 ± 0.13 μg/mL compared to 4.65 ± 0.48 μg/mL of non-survivors. Current methods for measuring cfDNA content in plasma were designed to amplify and measure low concentrations of specific DNA, making them unsuitable for low-cost measurement of total cfDNA content in plasma. Here, we have developed a point of care (POC) device that uses a thread silicone device as a medium to store a fluorescent dye which eliminates the need for preparatory steps, external aliquoting and dispensing of reagents, preconcentration, and external mixing while reducing the detection cost. The device was paired with a portable imaging system with an excitation filter at 472 ± 10 nm and an emission filter of 520 ± 10 nm that can be operated with just 100 mA current supply. The device was demonstrated for use in the quantification of buffered cfDNA samples in a range 1-6 μg/mL with a sensitivity of 5.72 AU/μg/mL and with cfDNA spiked in plasma with a range of 1-3 μg/mL and a sensitivity of 5.43 AU/μg/mL. The results showed that the device could be used as a low-cost, rapid, and portable POC device for differentiating between survivors and non-survivors of sepsis within 20 min.

Engineering a novel stem cells from apical papilla - macrophages organoid for regenerative endodontics

INTRODUCTION

Three-dimension (3D) tissue-construct with a heterogeneous cell population is critical to understand the interactions between immune cells and stem cells from apical papilla (SCAP) in the periapical region for developing treatment strategies in regenerative endodontics. This study aims to develop and characterize a 3D tissue-construct with binary cell system for studying the interactions between SCAP and macrophages in presence of lipopolysaccharide (LPS - pro-inflammatory) and interleukin-4 (IL-4 - anti-inflammatory) environments.

METHODS

SCAP and macrophages were seeded in the 3D printed dumbbell-shaped molds to generate tissue-constructs with binary cell population. Two experimental (LPS and IL-4) and control (non-stimulation) conditions were applied to the tissue-constructs to determine the characteristics of the tissue-construct, volume of viable cells and their morphology using a confocal laser scanning microscopy from 0 to 7 days period. Experiments were conducted in triplicates and data were analyzed with trend analysis and two-way analysis of variance at the significance of p < 0.05.

RESULTS

The tissue-constructs revealed distinct SCAP-macrophage interaction in pro-/anti-inflammatory environments. SCAP displayed characteristic self-organization as a cap-shaped structure in the tissue-construct. The growth of cells and cell-to-cell as well as cell-to-matrix interactions resulted in 70% and 30% decreased dimension of the tissue graft on the SCAP side and macrophage side respectively at day 7 (p < 0.0001). The tissue environments influenced macrophages-SCAP interactions, resulting in altered viable cell volume (p < 0.05), morphology and structural organization.

CONCLUSIONS

This study developed and characterized an apical papilla organoid in a 3D collagen based tissue-construct for studying SCAP-macrophage crosstalk in tissue regeneration as well as repair.

High-resolution fabrication of nanopatterns by multistep iterative miniaturization of hot-embossed prestressed polymer films and constrained shrinking

The fabrication of nanostructures and nanopatterns is of crucial importance in microelectronics, nanofluidics, and the manufacture of biomedical devices and biosensors. However, the creation of nanopatterns by means of conventional nanofabrication techniques such as electron beam lithography is expensive and time-consuming. Here, we develop a multistep miniaturization approach using prestressed polymer films to generate nanopatterns from microscale patterns without the need of complex nanolithography methods. Prestressed polymer films have been used as a miniaturization technique to fabricate features with a smaller size than the initial imprinted features. However, the height of the imprinted features is significantly reduced after the thermal shrinking of the prestressed films due to the shape memory effect of the polymer, and as a result, the topographical features tend to disappear after shrinking. We have developed a miniaturization approach that controls the material flow and maintains the shrunken patterns by applying mechanical constraints during the shrinking process. The combination of hot embossing and constrained shrinking makes it possible to reduce the size of the initial imprinted features even to the nanoscale. The developed multistep miniaturization approach allows using the shrunken pattern as a master for a subsequent miniaturization cycle. Well-defined patterns as small as 100 nm are fabricated, showing a 10-fold reduction in size from the original master. The developed approach also allows the transfer of the shrunken polymeric patterns to a silicon substrate, which can be used as a functional substrate for many applications or directly as a master for nanoimprint lithography.

Adhesive-Based Fabrication Technique for Culture of Lung Airway Epithelial Cells with Applications in Cell Patterning and Microfluidics

This work describes a versatile and cost-effective cell culture method for micropatterning and growing adherent cells on porous membranes using pressure-sensitive double-sided adhesives. This technique also allows cell culture using conventional methods and their easy integration into microfluidic chip devices. Adhesives can be used to form different patterns of cultured cells, which can be used for cell proliferation and wound-healing models. To demonstrate the viability of our system, we evaluate the toxicity effect of five different adhesives on two distinct airway epithelial cell lines and show functional applications for cell patterning and microfluidic cell culture chip fabrication. We developed a sandwiched microfluidic device that enabled us to culture cells in a submerged condition and transformed it into a dynamic platform when required. The viability of cells and their inflammatory responses to IL-1β stimulation were investigated. Our technique is applicable for conventional culturing of cells, widely available in biomedical research labs, while enabling the introduction of perfusion for an advanced dynamic cell culture model when needed.

Defect Engineering of Graphene to Modulate pH Response of Graphene Devices

Graphene-based pH sensors are a robust, durable, sensitive, and scalable approach for the sensitive detection of pH in various environments. However, the mechanisms through which graphene responds to pH variations are not well-understood yet. This study provides a new look into the surface science of graphene-based pH sensors to address the existing gaps and inconsistencies among the literature concerning sensing response, the role of defects, and surface/solution interactions. Herein, we demonstrate the dependence of the sensing response on the defect density level of graphene, measured by Raman spectroscopy. At the crossover point (I_D/I_G = 0.35), two countervailing mechanisms balance each other out, separating two regions where either a surface defect induced (negative slope) or a double layer induced (positive slope) response dominates. For ratios above 0.35, the pH-dependent induction of charges at surface functional groups (both pH-sensitive and nonsensitive groups) dominates the device response. Below a ratio of 0.35, the response is dominated by the modulation of charge carriers in the graphene due to the electric double layer formed from the interaction between the graphene surface and the electrolyte solution. Selective functionalization of the surface was utilized to uncover the dominant acid-base interactions of carboxyl and amine groups at low pH while hydroxyl groups control the high pH range sensitivity. The overall pH-sensing characteristics of the graphene will be determined by the balance of these two mechanisms.

Constrained shrinking of nanoimprinted pre-stressed polymer films to achieve programmable, high-resolution, miniaturized nanopatterns

Nanoimprint lithography is an emerging technology to form patterns and features in the nanoscale. Production of nanoscale patterns is challenging particularly in the sub-50 nm range. Pre-stressed polymer films with embedded microscale pattern can be miniaturized by shrinking induced due to thermal stress release. However, when pre-stressed films are thermally nanoimprinted with sub-micron features and shruken, they lose all the topographical features due to material recovery. Here we report a new approach that prevents recovery and allows retention of shrunken patterns even at the scale of <50 nm. We have discovered that when the shrinking process is mechanically constrained in one direction, the thermal treatment only relieves the stress in the orthogonal direction leading to a uniaxial shrinkage in that direction while preserving the topographical features. A second step, with the constraint in the orthogonal direction leads to biaxial shrinkage and preservation of all of the topographical features. This new technique can produce well defined and high resolution nanostructures at dimensions below 50 nm. The process is programmable and the thermal treatment can be tuned to shrink features to various dimension below the original imprint which we use to produce tunable and gradient plasmonic structures.

C. elegans electrotaxis behavior is modulated by heat shock response and unfolded protein response signaling pathways

The nematode C. elegans is a leading model to investigate the mechanisms of stress-induced behavioral changes coupled with biochemical mechanisms. Our group has previously characterized C. elegans behavior using a microfluidic-based electrotaxis device, and showed that worms display directional motion in the presence of a mild electric field. In this study, we describe the effects of various forms of genetic and environmental stress on the electrotactic movement of animals. Using exposure to chemicals, such as paraquat and tunicamycin, as well as mitochondrial and endoplasmic reticulum (ER) unfolded protein response (UPR) mutants, we demonstrate that chronic stress causes abnormal movement. Additionally, we report that pqe-1 (human RNA exonuclease 1 homolog) is necessary for the maintenance of multiple stress response signaling and electrotaxis behavior of animals. Further, exposure of C. elegans to several environmental stress-inducing conditions revealed that while chronic heat and dietary restriction caused electrotaxis speed deficits due to prolonged stress, daily exercise had a beneficial effect on the animals, likely due to improved muscle health and transient activation of UPR. Overall, these data demonstrate that the electrotaxis behavior of worms is susceptible to cytosolic, mitochondrial, and ER stress, and that multiple stress response pathways contribute to its preservation in the face of stressful stimuli.

Engineering Murine Adipocytes and Skeletal Muscle Cells in Meat-like Constructs Using Self-Assembled Layer-by-Layer Biofabrication: A Platform for Development of Cultivated Meat

Global meat consumption has been growing on a per capita basis over the past 20 years resulting in ever-increasing devotion of resources in the form of arable land and potable water to animal husbandry which is unsustainable and inefficient. One approach to meet this insatiable demand is to use biofabrication methods used in tissue engineering in order to make skeletal muscle tissue-like constructs known as cultivated meat to be used as a food source. Here, we demonstrate the use of a scaffold-free biofabrication method that forms cell sheets composed of murine adipocytes and skeletal muscle cells and assembles these sheets in parallel to create a 3D meat-like construct without the use of any exogenous materials. This layer-by-layer self-assembly and stacking process is fast (4 days of culture to form sheets and few hours for assembly) and scalable (stable sheets with diameters >3 cm are formed). Tissues formed with only muscle cells were equivalent to lean meat with comparable protein and fat contents (lean beef had 1.5 and 0.9 times protein and fat, respectively, as our constructs) and incorporating adipocyte cells in different ratios to myoblasts and/or treatment with different media cocktails resulted in a 5% (low fat meat) to 35% (high fat meat) increase in the fat content. Not only such constructs can be used as cultivated meat, they can also be used as skeletal muscle models.

Multi-step proportional miniaturization to sub-micron dimensions using pre-stressed polymer films

The ability to define patterns and fabricate structures at the nanoscale in a scalable manner is crucial not only in integrated circuit fabrication but also in fabrication of nanofluidic devices as well as in nano and micromechanical systems. Top down fabrication at the nanoscale often involves fabrication of a master using a direct write method and then its replication using a variety of methods such as by hot embossing, nanoimprint lithography, or soft lithography. Nevertheless, fabrication of the master is a time consuming and expensive process. One interesting approach is to define patterns at larger dimensions on pre-stressed films using methods such as xurography or lithography which are scalable and heat them to de-stress and shrink which can reduce the size proportionally. Although attractive, suitable fabrication processes that can perform iterative shrinking of patterns over several cycles and into the nanoscale have not been demonstrated. Here, we demonstrate a fabrication process that is capable of accurately producing patterns and features over several cycles of miniaturization and shrinking to achieve resolution in the order of 100 s of nanometers. In this approach, a pattern transfer method is developed by combining soft imprint lithography followed by reactive ion etching, both of which are scalable processes, to transfer the original patterns into a shrinkable polymer film. The patterned shrinkable film is heated to allow thermal shrinking. As a result, the pattern size was decreased by 60% of the original size in a single cycle. This reduced pattern was used as the master for the next cycle and three cycles of miniaturization was demonstrated. Sub-micron patterns of 750 nm were generated by the multi-step miniaturization method, showing approximately 20× reduction in size of the original patterns. Finally, these patterns are transferred into features on a silicon substrate to demonstrate its application in semiconductor microfabrication or its use as a master template for microsystems applications.

A Pumpless Microfluidic Neonatal Lung Assist Device for Support of Preterm Neonates in Respiratory Distress

Premature neonates suffer from respiratory morbidity as their lungs are immature, and current supportive treatment such as mechanical ventilation or extracorporeal membrane oxygenation causes iatrogenic injuries. A non-invasive and biomimetic concept known as the "artificial placenta" (AP) would be beneficial to overcome complications associated with the current respiratory support of preterm infants. Here, a pumpless oxygenator connected to the systemic circulation supports the lung function to relieve respiratory distress. In this paper, the first successful operation of a microfluidic, artificial placenta type neonatal lung assist device (LAD) on a newborn piglet model, which is the closest representation of preterm human infants, is demonstrated. This LAD has high oxygenation capability in both pure oxygen and room air as the sweep gas. The respiratory distress that the newborn piglet is put under during experimentation, repeatedly and over a significant duration of time, is able to be relieved. These findings indicate that this LAD has a potential application as a biomimetic artificial placenta to support the respiratory needs of preterm neonates.

π-SACS: pH Induced Self-Assembled Cell Sheets Without the Need for Modified Surfaces

The ability to form tissue-like constructs that have high cell density with proper cell-cell and cell-ECM interactions is critical for many applications including tissue models for drug discovery and tissue regeneration. Newly emerging bioprinting methods sometimes lack the high cellular density needed to provide biophysical cues to orchestrate cellular behavior to recreate tissue architecture and function. Alternate methods using self-assembly can be used to create tissue-like constructs with high cellular density and well-defined microstructure in the form of spheroids, organoids, or cell sheets. Cell sheets have a particularly interesting architecture in the context of tissue regeneration and repair as they can be applied as patches to integrate with surrounding tissues. Until now, the preparation of these sheets has involved culturing on specialized substrates that can be triggered by temperature or phase change (hydrophobic to hydrophilic) to release cells growing on them and form sheets. Here a new technique is proposed that allows delamination of cells and secreted ECM and rapid self-assembly into a cell sheet using a simple pH trigger and without the need to use responsive surfaces or applying external stimuli such as electrical and magnetic fields, only with routine tissue culture plates. This technique can be used with cells that are capable of syncytialization and fusion such as skeletal muscle cells and placenta cells. Using C2C12 myoblast cells we show that the pH trigger induces a rapid delamination of the cells as a continuous layer that self-assembles into a thick dense sheet. The delamination process has little effect on cell viability and maturation and preserves the ECM components that allow sheets to adhere to each other within a short incubation time enabling formation of thicker constructs when multiple sheets are stacked (double- and quadruple-layer constructs are formed here). These thick grafts can be used for regeneration purposes or as in vitro models.

Tissue-in-a-Tube: three-dimensional in vitro tissue constructs with integrated multimodal environmental stimulation

Three-dimensional (3D) in vitro tissue models are superior to two-dimensional (2D) cell cultures in replicating natural physiological/pathological conditions by recreating the cellular and cell-matrix interactions more faithfully. Nevertheless, current 3D models lack either the rich multicellular environment or fail to provide appropriate biophysical stimuli both of which are required to properly recapitulate the dynamic in vivo microenvironment of tissues and organs. Here, we describe the rapid construction of multicellular, tubular tissue constructs termed Tissue-in-a-Tube using self-assembly process in tubular molds with the ability to incorporate a variety of biophysical stimuli such as electrical field, mechanical deformation, and shear force of the fluid flow. Unlike other approaches, this method is simple, requires only oxygen permeable silicone tubing that molds the tissue construct and thin stainless-steel pins inserted in it to anchor the construct and could be used to provide electrical and mechanical stimuli, simultaneously. The annular region between the tissue construct and the tubing is used for perfusion. Highly stable, macroscale, and robust constructs anchored to the pins form as a result of self-assembly of the extracellular matrix (ECM) and cells in the bioink that is filled into the tubing. We demonstrate patterning of grafts containing cell types in the constructs in axial and radial modes with clear interface and continuity between the layers. Different environmental factors affecting cell behavior such as compactness of the structure and size of the constructs can be controlled through parameters such as initial cell density, ECM content, tubing size, as well as the distance between anchor pins. Using connectors, network of tubing can be assembled to create complex macrostructured tissues (centimeters length) such as fibers that are bifurcated or columns with different axial thicknesses which can then be used as building blocks for biomimetic constructs or tissue regeneration. The method is versatile and compatible with various cell types including endothelial, epithelial, skeletal muscle cells, osteoblast cells, and neuronal cells. As an example, long mature skeletal muscle and neuronal fibers as well as bone constructs were fabricated with cellular alignment dictated by the applied electrical field. The versatility, speed, and low cost of this method is suited for widespread application in tissue engineering and regenerative medicine.

Electrokinetic transport and distribution of antibacterial nanoparticles for endodontic disinfection

AIM

To assess a novel, noninvasive intervention capable of mobilizing charged antibacterial nanoparticles to the apical portions of the root canal system, utilizing the principles of electrokinetics.

METHODS

Experiments were conducted in three stages. Stage-1: A computer model was generated to predict and visualize the electric field and current density distribution generated by the proposed intervention. Stage-2: Transport of chitosan nanoparticles (CSnp) was evaluated qualitatively using a transparent microfluidic model with fluorescent-labelled CSnp. Stage-3: An ex vivo model was utilized to study the antimicrobial efficacy of the proposed treatment against 3-week-old monospecies E. faecalis biofilms. Scanning electron microscopy (SEM) was also utilized in this stage to confirm the deposition of CSnp.

RESULTS

The results of the computer simulations predicted an electric field and current density that reach their maxima at the apical constriction of the root canal. Correspondingly, the microfluidic experiments demonstrated rapid, controlled CSnp transport throughout the simulated root canal anatomy with subsequent distribution and deposition in the apical constriction as well as periapical regions. Infected root canals when subjected to the novel treatment method resulted in a mean bacterial reduction of 2.1 log CFU. SEM analysis revealed electrophoretic deposition of chitosan nanoparticles onto the root canal dentine walls in the apical region.

CONCLUSION

The findings from this study demonstrate that the combination of cationic antibacterial nanoparticles with a low-intensity electric field results in particle transportation (electrophoresis) and deposition within the root canal. This results in a synergistic antibiofilm efficacy and has the potential to enhance root canal disinfection.

Influence of wastewater microbial community on the performance of miniaturized microbial fuel cell biosensor

Microbial fuel cells (MFCs) based sensors had been studied in measuring biochemical oxygen demand (BOD) or the equivalent chemical oxygen demand (COD) recently. Limited attention has been paid to the effect of the microbial communities in wastewater on the responses of these sensors. This study systematically evaluated, for the first time, the effect of wastewater samples from a variety of sources on the electrical response of a micro-fabricated double-chamber MFC device. It was found that the response of the MFC is positively correlated with the bacterial composition, in particular electroactive bacteria. The presence of aerobic bacteria in the sample reduces the current generation. These findings indicated that the bacterial content of the water sample could be a significant interference source and must be considered in the use of µMFC-based sensors. Filtering samples may be effective in improving the reliability of these microsensors.

Microfluidic Device for Microinjection of Caenorhabditis elegans

Microinjection is an established and reliable method to deliver transgenic constructs and other reagents to specific locations in C. elegans worms. Specifically, microinjection of a desired DNA construct into the distal gonad is the most widely used method to generate germ-line transformation of C. elegans. Although, current C. elegans microinjection method is effective to produce transgenic worms, it requires expensive multi degree of freedom (DOF) micromanipulator, careful injection alignment procedure and skilled operator, all of which make it slow and not suitable for scaling to high throughput. A few microfabricated microinjectors have been developed recently to address these issues. However, none of them are capable of immobilizing a freely mobile animal such as C. elegans worm using a passive immobilization mechanism. Here, a microfluidic microinjector was developed to passively immobilize a freely mobile animal such as C. elegans and simultaneously perform microinjection by using a simple and fast mechanism for needle actuation. The entire process of the microinjection takes ~30 s which includes 10 s for worm loading and aligning, 5 s needle penetration, 5 s reagent injection and 5 s worm unloading. The device is suitable for high-throughput and can be potentially used for creating transgenic C. elegans.

Electroplating of Multiple Materials in Parallel Using Patterned Gels with Applications in Electrochemical Sensing

Electrodeposition is a versatile technique for the fabrication of electrodes in micro-electroanalytical devices. Conductive but low-cost materials, such as copper, can be coated with functional yet higher-cost materials such as gold or silver using electrodeposition to lower the overall cost while maintaining functionality. When the electrodeposition of multiple materials is required, current methods use a multistep process that deposits one material at a time, which requires a significant amount of time and a significant number of steps. Additionally, they use a large volume of electrolytes suitable for coating large objects, which is wasteful and unnecessary for the prototyping or coating of microelectrodes with a small area. In this paper, a new method of electroplating is introduced in which we used gels to immobilize and pattern electroplating electrolytes on a substrate surface. Agarose, as an immobilizing medium, enables the immersion of the substrate in a common working electrolyte without cross-mixing different electrolytes. We demonstrate the printing of jelly electrolytes by using spot-dispensing or microfluidic flow. Xurographically patterned films laminated on the substrate function as a mask and confine the printed gels to desired locations. After printing, the substrate is placed in a common working electrolyte container, and multimaterial patterns are produced through the application of an electrical current in a single step.

Chloroform and desflurane immobilization with recovery of viable Drosophila larvae for confocal imaging

Imaging of living, intact Drosophila larvae is challenged if normal bodily function must be observed or when healthy larvae must be recovered for subsequent studies. Here, we describe a simple and short protocol that employs transient airborne chloroform or desflurane (1,2,2,2-tetrafluoroethyl difluoromethyl ether) to efficiently immobilize larvae without the use of manipulation devices, vaporizers or imaging chambers. This non-lethal method allows the use of anesthetics while allowing tracking of individual Drosophila into adulthood for follow-up experiments. At dosages sufficient to immobilize larvae, Desflurane, but not chloroform reduced the central nervous system response to auditory stimulus. Desflurane doses were sufficient to arrest the heart, however significant rapid recovery was observed. With our method, chloroform provided more rapid anesthesia but slower recovery than Desflurane. Without specialized hardware, this technique allows for repeated imaging of living Drosophila larvae.

A rapid biofabrication technique for self-assembled collagen-based multicellular and heterogeneous 3D tissue constructs

Although monolayer cell culture models are considered as gold standard for in vitro modeling of pathophysiological events, they cannot reconstruct in vivo like gradient of gases and nutrients and lack proper cell-cell and cell-matrix interactions. Spherical cellular aggregates, otherwise known as multicellular spheroids, are widely used as three-dimensional in vitro models to mimic natural in vivo cellular microenvironment for applications such as drug screening. Although very useful, the previously established techniques are limited to low cell numbers, their processes are usually slow, and sometimes show limitations in terms of the cell type that can be used. Here, a versatile technique based on rapid self-assembly of cells and extracellular matrix material in different shapes using microfabricated molds is introduced to form multicellular tissue constructs. The self-assembly process takes less than 6 h and produces a mechanically robust tissue construct that could be handled easily. We demonstrate that a variety of shapes including spherical, cuboidal, dumbbell- and cross-like shapes could be fabricated using this approach. Interestingly, the structures formed with non-spherical shapes were able to retain that shape even after removal from the molds and during long term cell culture. This versatile approach is applicable to a variety of cell types (breast cancer cell lines MCF-7, MDA-MB-321, Hs-578T; osteosarcoma cell line SaOS-2; endothelial cell line HUVEC) as well as a range of cell numbers (10⁴-10⁶). Furthermore, we also show that the constructs could be spatially patterned to position various cell types in a precisely controlled way. Such heterogeneous constructs that are formed provide physiologically relevant cell densities, 3D structure as well as close positioning of multiple types of cells that are not possible using other fabrication approaches. This fabrication approach will find significant applications in developing 3D cell culture models for drug discovery as well as tissue grafts for implantation. STATEMENT OF SIGNIFICANCE: In this manuscript we describe a method for rapid formation of tissue constructs (6 h as opposed to several days for current state of art methods). We also identify the essential factors needed for such a rapid consolidation into a construct. We demonstrate the ability to form non-spherical constructs of various shapes that retain their shape over long term as opposed to those formed with current state of art that lose their shape during long time cell culture. We also show the ability to form precise heterogeneous constructs consisting of multiple cell types and with well-defined interfaces that are not possible with current state of art methods. This method could be used with a wide variety of cell types and are mechanically robust within 6 h to be handled with tweezers. We believe that such multicellular, heterogeneous constructs would be of significant use to biologists and drug discovery researchers investigating mechanisms involved in diseases processes or the effect of drug on them.

An ultra-thin, all PDMS-based microfluidic lung assist device with high oxygenation capacity

Preterm neonates with immature lungs require a lung assist device (LAD) to maintain oxygen saturation at normal levels. Over the last decade, microfluidic blood oxygenators have attracted considerable interest due to their ability to incorporate unique biomimetic design and to oxygenate in a physiologically relevant manner. Polydimethylsiloxane (PDMS) has become the main material choice for these kinds of devices due to its high gas permeability. However, fabrication of large area ultrathin microfluidic devices that can oxygenate sufficient blood volumes at clinically relevant flow rates, entirely made of PDMS, have been difficult to achieve primarily due to failure associated with stiction of thin PDMS membranes to each other at undesired locations during assembly. Here, we demonstrate the use of a modified fabrication process to produce large area ultrathin oxygenators entirely made of PDMS and robust enough to withstand the hydraulic conditions that are encountered physiologically. We also demonstrate that a LAD assembled from these ultrathin double-sided microfluidic blood oxygenators can increase the oxygen saturation level by 30% at a flow rate of 30 ml/min and a pressure drop of 21 mm Hg in room air which is adequate for 1 kg preterm neonates. In addition, we demonstrated that our LAD could withstand high blood flow rate of 150 ml/min and increase oxygen saturation by 26.7% in enriched oxygen environment which is the highest gas exchange reported so far by any microfluidic-based blood oxygenators. Such performance makes this LAD suitable to provide support to 1 kg neonate suffering from respiratory distress syndrome.

3D bioprinting of heterogeneous bi- and tri-layered hollow channels within gel scaffolds using scalable multi-axial microfluidic extrusion nozzle

One of the primary focuses in recent years in tissue engineering has been the fabrication and integration of vascular structures into artificial tissue constructs. However, most available methodologies lack the ability to create multi-layered concentric conduits inside natural extracellular matrices (ECMs) and gels that replicate more accurately the hierarchical architecture of biological blood vessels. In this work, we present a new microfluidic nozzle design capable of multi-axial extrusion in order to 3D print and pattern bi- and tri-layered hollow channel structures. This nozzle allows, for the first time, for these structures to be embedded within layers of gels and ECMs in a fast, simple and low-cost manner. By varying flow rates (1-6 ml min^-1), printspeeds (1-16 m min^-1), and material concentration (25-175 mM and 1.5%-2.5% for calcium chloride and alginate, respectively) we are able to accurately determine the operational printing range as well as achieve a wide range of conduit dimensions (0.69-2.31 mm) that can be printed within a few seconds. Our scalable design allows for multi-axial extrusion and versatility in material incorporation in order to create heterogeneous structures. We demonstrate the ability to print distinct concentric layers of different cell types, namely endothelial cells and fibroblasts. By incorporating various layers of different cell-friendly materials (such as collagen and fibrin) alongside materials with high mechanical strength (i.e. alginate), we were able to increase long-term cell viability and growth without compromising the structural integrity. In this way, we can improve cellular adhesion in our biocompatible constructs as well as allow them to remain structurally sound. We are able to realize complex heterogeneous, hierarchical architectures that have strong potential for use not only in vascular tissue applications, but also in other artificially fabricated tubular or fiber-like structures such as skeletal muscle or nerve conduits.

An ultra-thin highly flexible microfluidic device for blood oxygenation

Many neonates who are born premature suffer from respiratory distress syndrome (RDS) for which mechanical ventilation and an extracorporeal membrane oxygenation (ECMO) device are used in treatment. However, the use of these invasive techniques results in higher risk of complications like bronchopulmonary dysplasia or requires surgery to gain vascular access. An alternative biomimetic approach is to use the umbilical cord as a vascular access and to connect a passive device to the baby that functions like a placenta. This concept, known as the artificial placenta, provides enough oxygenation and causes minimal distress or complications. Herein, we have developed a new artificial placenta-type microfluidic blood oxygenator (APMBO) with high gas exchange, low priming volume and low hydraulic resistance such that it can be operated only by pressure differential provided by the baby's heart. Mimicking the placenta, we have made our new device ultra-thin and flexible so that it can be folded into a desired shape without losing its capability for gas exchange and achieve a compact form factor. The ability to fold allowed optimization of connectors and reduced the overall priming volume to the sub-milliliter range while achieving a high oxygen uptake which would be sufficient for preterm neonates with a birth-weight of around 0.5 kg.

C. elegans MANF Homolog Is Necessary for the Protection of Dopaminergic Neurons and ER Unfolded Protein Response

Neurotrophic factors (NTFs) are important for the development, function, and survival of neurons in the mammalian system. Mesencephalic astrocyte-derived neurotrophic factor (MANF) and cerebral dopamine neurotrophic factor (CDNF) are two recently identified members of a novel family of NTFs in vertebrates that function to protect dopaminergic neurons. Although these genes are conserved across eukaryotes, their mechanism of neuroprotection is not fully understood. Sequence searches for MANF/CDNF homologs in invertebrates have identified a single ortholog that is most related to MANF. Here we report the in vivo characterization of the MANF gene, manf-1, in the nematode Caenorhabditis elegans. We found that manf-1 mutants have an accelerated, age-dependent decline in the survival of dopaminergic neurons. The animals also show increased endoplasmic reticulum (ER) stress, as revealed by reporter gene expression analysis of hsp-4, an ER chaperone BiP/GRP78 homolog, suggesting that a failure to regulate the ER unfolded protein response (ER-UPR) may be a contributing factor to dopaminergic neurodegeneration. Expression studies of manf-1 revealed that the gene is broadly expressed in a pattern that matches closely with hsp-4. Consistent with the requirements of manf-1 in the ER-UPR, we found that aggregates of α-Synuclein, a major constituent of Lewy bodies, were significantly increased in body wall muscles of manf-1 mutant animals. Overall, our work demonstrates the important role of manf-1 in dopaminergic neuronal survival and the maintenance of ER homeostasis in C. elegans.

An artificial placenta type microfluidic blood oxygenator with double-sided gas transfer microchannels and its integration as a neonatal lung assist device

Preterm neonates suffering from respiratory distress syndrome require assistive support in the form of mechanical ventilation or extracorporeal membrane oxygenation, which may lead to long-term complications or even death. Here, we describe a high performance artificial placenta type microfluidic oxygenator, termed as a double-sided single oxygenator unit (dsSOU), which combines microwire stainless-steel mesh reinforced gas permeable membranes on both sides of a microchannel network, thereby significantly reducing the diffusional resistance to oxygen uptake as compared to the previous single-sided oxygenator designs. The new oxygenator is designed to be operated in a pumpless manner, perfused solely due to the arterio-venous pressure difference in a neonate and oxygenate blood through exposure directly to ambient atmosphere without any air or oxygen pumping. The best performing dsSOUs showed up to ∼343% improvement in oxygen transfer compared to a single-sided SOU (ssSOU) with the same height. Later, the dsSOUs were optimized and integrated to build a lung assist device (LAD) that could support the oxygenation needs for a 1-2 kg neonate under clinically relevant conditions for the artificial placenta, namely, flow rates ranging from 10 to 60 ml/min and a pressure drop of 10-60 mmHg. The LAD provided an oxygen uptake of 0.78-2.86 ml/min, which corresponded to the increase in oxygen saturation from 57 ± 1% to 93%-100%, under pure oxygen environment. This microfluidic lung assist device combines elegant design with new microfabrication methods to develop a pumpless, microfluidic blood oxygenator that is capable of supporting 30% of the oxygen needs of a pre-term neonate.

Extracellular matrix surface regulates self-assembly of three-dimensional placental trophoblast spheroids

The incorporation of the extracellular matrix (ECM) is essential for generating in vitro models that truly represent the microarchitecture found in human tissues. However, the cell-cell and cell-ECM interactions in vitro remains poorly understood in placental trophoblast biology. We investigated the effects of varying the surface properties (surface thickness and stiffness) of two ECMs, collagen I and Matrigel, on placental trophoblast cell morphology, viability, proliferation, and expression of markers involved in differentiation/syncytial fusion. Most notably, thicker Matrigel surfaces were found to induce the self-assembly of trophoblast cells into 3D spheroids that exhibited thickness-dependent changes in viability, proliferation, syncytial fusion, and gene expression profiles compared to two-dimensional cultures. Changes in F-actin organization, cell spread morphologies, and integrin and matrix metalloproteinase gene expression profiles, further reveal that the response to surface thickness may be mediated in part through cellular stiffness-sensing mechanisms. Our derivation of self-assembling trophoblast spheroid cultures through regulation of ECM surface alone contributes to a deeper understanding of cell-ECM interactions, and may be important for the advancement of in vitro platforms for research or diagnostics.

Steel reinforced composite silicone membranes and its integration to microfluidic oxygenators for high performance gas exchange

Respiratory distress syndrome (RDS) is one of the main causes of fatality in newborn infants, particularly in neonates with low birth-weight. Commercial extracorporeal oxygenators have been used for low-birth-weight neonates in neonatal intensive care units. However, these oxygenators require high blood volumes to prime. In the last decade, microfluidics oxygenators using enriched oxygen have been developed for this purpose. Some of these oxygenators use thin polydimethylsiloxane (PDMS) membranes to facilitate gas exchange between the blood flowing in the microchannels and the ambient air outside. However, PDMS is elastic and the thin membranes exhibit significant deformation and delamination under pressure which alters the architecture of the devices causing poor oxygenation or device failure. Therefore, an alternate membrane with high stability, low deformation under pressure, and high gas exchange was desired. In this paper, we present a novel composite membrane consisting of an ultra-thin stainless-steel mesh embedded in PDMS, designed specifically for a microfluidic single oxygenator unit (SOU). In comparison to homogeneous PDMS membranes, this composite membrane demonstrated high stability, low deformation under pressure, and high gas exchange. In addition, a new design for oxygenator with sloping profile and tapered inlet configuration has been introduced to achieve the same gas exchange at lower pressure drops. SOUs were tested by bovine blood to evaluate gas exchange properties. Among all tested SOUs, the flat design SOU with composite membrane has the highest oxygen exchange of 40.32 ml/min m². The superior performance of the new device with composite membrane was demonstrated by constructing a lung assist device (LAD) with a low priming volume of 10 ml. The LAD was achieved by the oxygen uptake of 0.48-0.90 ml/min and the CO₂ release of 1.05-2.27 ml/min at blood flow rates ranging between 8 and 48 ml/min. This LAD was shown to increase the oxygen saturation level by 25% at the low pressure drop of 29 mm Hg. Finally, a piglet was used to test the gas exchange capacity of the LAD in vivo. The animal experiment results were in accordance with in-vitro results, which shows that the LAD is capable of providing sufficient gas exchange at a blood flow rate of ∼24 ml/min.

Reagent-Free Quantification of Aqueous Free Chlorine via Electrical Readout of Colorimetrically Functionalized Pencil Lines

Colorimetric methods are commonly used to quantify free chlorine in drinking water. However, these methods are not suitable for reagent-free, continuous, and autonomous applications. Here, we demonstrate how functionalization of a pencil-drawn film with phenyl-capped aniline tetramer (PCAT) can be used for quantitative electric readout of free chlorine concentrations. The functionalized film can be implemented in a simple fluidic device for continuous sensing of aqueous free chlorine concentrations. The sensor is selective to free chlorine and can undergo a reagent-free reset for further measurements. Our sensor is superior to electrochemical methods in that it does not require a reference electrode. It is capable of quantification of free chlorine in the range of 0.1-12 ppm with higher precision than colorimetric (absorptivity) methods. The interactions of PCAT with the pencil-drawn film upon exposure to hypochlorite were characterized spectroscopically. A previously reported detection mechanism relied on the measurement of a baseline shift to quantify free chlorine concentrations. The new method demonstrated here measures initial spike size upon exposure to free chlorine. It relies on a fast charge built up on the sensor film due to intermittent PCAT salt formation. It has the advantage of being significantly faster than the measurement of baseline shift, but it cannot be used to detect gradual changes in free chlorine concentration without the use of frequent reset pulses. The stability of PCAT was examined in the presence of free chlorine as a function of pH. While most ions commonly present in drinking water do not interfere with the free chlorine detection, other oxidants may contribute to the signal. Our sensor is easy to fabricate and robust, operates reagent-free, and has very low power requirements and is thus suitable for remote deployment.

A microfluidic device for rapid quantification of cell-free DNA in patients with severe sepsis

A rapid and accurate method to identify severe sepsis patients at high risk of death is critically needed for clinical practice. In a recent study, the concentration of cell-free DNA (cfDNA) in blood was found to be a prognostic indicator for ICU mortality in patients with severe sepsis. However, current DNA quantification techniques are time-consuming and involve extensive sample preparation. In this paper, we demonstrate a low-cost microfluidic device capable of rapid quantification of cfDNA in a small droplet (<10 μl) of blood plasma and whole blood in 5 min using only electrical power. The cfDNA in samples is selectively labeled by PicoGreen and is extracted and concentrated by electrophoresis into a gel by application of a DC potential of 9 V. This device has potential as a prognostic tool for early and rapid assessment of septic patients.

Low-temperature solution processing of palladium/palladium oxide films and their pH sensing performance

Highly sensitive, easy-to-fabricate, and low-cost pH sensors with small dimensions are required to monitor human bodily fluids, drinking water quality and chemical/biological processes. In this study, a low-temperature, solution-based process is developed to prepare palladium/palladium oxide (Pd/PdO) thin films for pH sensing. A precursor solution for Pd is spin coated onto pre-cleaned glass substrates and annealed at low temperature to generate Pd and PdO. The percentages of PdO at the surface and in the bulk of the electrodes are correlated to their sensing performance, which was studied by using the X-ray photoelectron spectroscope. Large amounts of PdO introduced by prolonged annealing improve the electrode's sensitivity and long-term stability. Atomic force microscopy study showed that the low-temperature annealing results in a smooth electrode surface, which contributes to a fast response. Nano-voids at the electrode surfaces were observed by scanning electron microscope, indicating a reason for the long-term degradation of the pH sensitivity. Using the optimized annealing parameters of 200°C for 48 h, a linear pH response with sensitivity of 64.71±0.56 mV/pH is obtained for pH between 2 and 12. These electrodes show a response time shorter than 18 s, hysteresis less than 8 mV and stability over 60 days. High reproducibility in the sensing performance is achieved. This low-temperature solution-processed sensing electrode shows the potential for the development of pH sensing systems on flexible substrates over a large area at low cost without using vacuum equipment.

A Novel Intranasal Spray Device for the Administration of Nanoparticles to Rodents

Experimental intranasal (IN) delivery of nanoparticle (NP) drug carriers is typically performed using a pipette with or without anesthesia, a technique that may be a poor simulation of practical IN administration of drug-loaded NPs in humans. Existing IN spray devices suffer from drawbacks in terms of variability in dose-control and spray duration as well as the application of nonuniform pressure fields when a NP-formulated drug is aerosolized. Furthermore, existing spray devices require large volumes that may not be available or may be prohibitively expensive to prepare. In response, we have developed a novel pneumatically driven IN spray device for the administration of NPs, which is capable of administering extremely small quantities (50–100 μl) of NP suspension in a fine spray that disperses the NPs uniformly onto the tissue. This device was validated using haloperidol-loaded Solanum tuberosum lectin (STL)-functionalized, poly(ethylene glycol)–block-poly(d,l-lactic-co-glycolic acid) (PEG–PLGA) NPs targeted for delivery to the brain for schizophrenia treatment. A pneumatic pressure of 100 kPa was found to be optimal to produce a spray that effectively aerosolizes NP suspensions and delivers them evenly to the olfactory epithelium. IN administration of STL-functionalized NPs using the IN spray device increased brain tissue haloperidol concentrations by a factor of 1.2–1.5× compared to STL-functionalized NPs administered IN with a pipette. Such improved delivery enables the use of lower drug doses and thus offers both fewer local side-effects and lower costs without compromising therapeutic efficacy.

Surface modification of poly(dimethylsiloxane) with a covalent antithrombin-heparin complex for the prevention of thrombosis: use of polydopamine as bonding agent

A modified poly(dimethyl siloxane) (PDMS) material is under development for use in an extracorporeal microfluidic blood oxygenator designed as an artificial placenta to treat newborn infants suffering from severe respiratory insufficiency. To prevent thrombosis triggered by blood-material contact, an antithrombin-heparin (ATH) covalent complex was coated on PDMS surface using polydopamine (PDA) as a "bioglue". Experiments using radiolabelled ATH showed that the ATH coating on PDA-modified PDMS remained substantially intact after incubation in plasma, 2% SDS solution, or whole blood over a three day period. The anticoagulant activity of the ATH-modified surfaces was also demonstrated: in contact with plasma the ATH-coated PDMS was shown to bind antithrombin (AT) selectively from plasma and to inhibit clotting factor Xa. It is concluded that modification of PDMS with polydopamine and ATH shows promise as a means of improving the blood compatibility of PDMS and hence of the oxygenator device.