Microfluidic Chamber Research Articles

Real-time continuous monitoring of dynamic concentration profiles studied with biosensing by particle motion.

Real-time monitoring-and-control of biological systems requires lab-on-a-chip sensors that are able to accurately measure concentration-time profiles with a well-defined time delay and accuracy using only small amounts of sampled fluid. Here, we study real-time continuous monitoring of dynamic concentration profiles in a microfluidic measurement chamber. Step functions and sinusoidal oscillations of concentrations were generated using two pumps and a herringbone mixer. Concentrations in the bulk of the measurement chamber were quantified using a solution with a dye and light absorbance measurements. Concentrations near the surface were measured using a reversible cortisol sensor based on particle motion. The experiments show how the total time delay of the real-time sensor has contributions from advection, diffusion, reaction kinetics at the surface and signal processing. The total time delay of the studied real-time cortisol sensor was ∼90 seconds for measuring 63% of the concentration change. Monitoring of sinusoidal cortisol concentration-time profiles showed that the sensor has a low-pass frequency response with a cutoff frequency of ∼4 mHz and a lag time of ∼60 seconds. The described experimental methodology paves the way for the development of monitoring-and-control in lab-on-a-chip systems and for further engineering of the analytical characteristics of real-time continuous biosensors.

Acoustofluidic large-scale mixing for enhanced microfluidic immunostaining for tissue diagnostics.

The usage of microfluidics for automated and fast immunoassays has gained a lot of interest in the last decades. This integration comes with certain challenges, like the reconciliation of laminar flow patterns of micro-scale systems with diffusion-limited mass transport. Several methods have been investigated to enhance microfluidic mixing in microsystems, including acoustic-based fluidic streaming. Here, we report both by numerical simulation and experiments on the beneficiary effect of acoustic agitation on the uniformity of immunostaining in large-size and thin microfluidic chambers. Moreover, we investigate by numerical simulation the impact of reducing the incubation times and the concentrations of the biochemical detection reagents on the obtained immunoassay signal. Finally, acoustofluidic mixing was successfully used to reduce by 80% the incubation time of the Her2 (human epidermal growth factor receptor 2) and CK (cytokeratins) biomarkers for the spatial immunostaining of breast cancer cell pellets, or reducing their concentration by 66% and achieving a higher signal-to-background ratio than comparable spatially resolved immunostaining with static incubation.

Design and 3D printing of an electrochemical sensor for Listeria monocytogenes detection based on loop mediated isothermal amplification

The aim of this work is the design and 3D printing of a new electrochemical sensor for the detection of Listeria monocytogenes based on loop mediated isothermal amplification (LAMP). The food related diseases involve a serious health issue all over the world. Listeria monocytogenes is one of the major problems of contaminated food, this pathogen causes a disease called listeriosis with a high rate of hospitalization and mortality. Having a fast, sensitive and specific detection method for food quality control is a must in the food industry to avoid the presence of this pathogen in the food chain (raw materials, facilities and products). A point-of-care biosensor based in LAMP and electrochemical detection is one of the best options to detect the bacteria on site and in a very short period of time. With the numerical analysis of different geometries and flow rates during sample injection in order to avoid bubbles, an optimized design of the microfluidic biosensor chamber was selected for 3D-printing and experimental analysis.For the electrochemical detection, a novel custom gold concentric-3-electrode consisting in a working electrode, reference electrode and a counter electrode was designed and placed in the bottom of the chamber. The LAMP reaction was optimized specifically for a primers set with a limit of detection of 1.25 pg of genomic DNA per reaction and 100% specific for detecting all 12 Listeria monocytogenes serotypes and no other Listeria species or food-related bacteria. The methylene blue redox-active molecule was tested as the electrochemical transducer and shown to be compatible with the LAMP reaction and very clearly distinguished negative from positive food samples when the reaction is measured at the end-point inside the biosensor.

Data-Driven Intelligent Manipulation of Particles in Microfluidics.

Automated manipulation of small particles using external (e.g., magnetic, electric and acoustic) fields has been an emerging technique widely used in different areas. The manipulation typically necessitates a reduced-order physical model characterizing the field-driven motion of particles in a complex environment. Such models are available only for highly idealized settings but are absent for a general scenario of particle manipulation typically involving complex nonlinear processes, which has limited its application. In this work, the authorspresent a data-driven architecture for controlling particles in microfluidics based on hydrodynamic manipulation. The architecture replaces the difficult-to-derive model by a generally trainable artificial neural network to describe the kinematics of particles, and subsequently identifies the optimal operations to manipulate particles. The authorssuccessfully demonstrate a diverse set of particle manipulations in a numerically emulated microfluidic chamber, including targeted assembly of particles and subsequent navigation of the assembled cluster, simultaneous path planning for multiple particles, and steering one particle through obstacles. Theapproach achieves both spatial and temporal controllability of high precision for these settings. This achievement revolutionizes automated particle manipulation, showing the potential of data-driven approaches and machine learning in improving microfluidic technologies for enhanced flexibility andintelligence.

Evaluation of dry stored disposable sensor strip on rapid SARS-CoV-2 detection platform

This study investigated a SARS-CoV-2 virus detection mechanism using dry-stored disposable strips. The accuracy of this sensing platform is as good as polymerase chain reaction (PCR) with a detection time of fewer than 30 s. SARS-CoV-2 antibodies were biofunctionalized on disposable strips similar to glucose detection strips to detect the presence and concentrations of SARS-CoV-2 in saliva samples. Eight 1 ms electric pulses were sent through the sensor strip with a saliva sample in its microfluidic chamber. A circuit board embedded with MOSFET was also employed to amplify the detected signals and convert the signal to digital readings displayed on an LCD screen. The COV-antibody functionalized disposable strips were stored in a dry condition for at least one day before analyzing clinical human saliva samples with known cycling threshold (Ct) values confirmed with conventional PCR tests. Results demonstrate our system is capable of showing qualitative positive or negative results within 30 s and providing quantitative SARS-CoV-2 concentrations in terms of Ct values in 5 min.

An electrochemical aptasensor for Δ9-tetrahydrocannabinol detection in saliva on a microfluidic platform

We present a novel “on-off”, cost-effective, rapid electrochemical aptasensor combined with a microfluidics cartridge system for the detection of Δ9-THC (Δ9-tetrahydrocannabinol) in human saliva via differential pulse voltammetry. The assay relied on the competitive binding between the Δ9-THC and a soluble redox indicator methylene blue, using an aptamer selected via FRELEX. We found that the aptasensor can detected 1 nM of Δ9-THC in PBS in a three-electrode cell system, while the sensitivity and both the dissociation constant (Kd) and association constant (Kb) were dependent on the aptamer density. The aptamer also showed great affinity towards Δ9-THC when tested against cannabinol and cannabidiol. The same limit of detection of 1 nM in PBS was achieved in small volume samples (∼60 μL) using the aptamer-modified gold screen-printed electrodes combined with the microfluidic cartridge setup, however, the presence of 10% raw human saliva had a negative effect which manifested in a 10-fold increase in the LOD due to interfering elements. Filtering the saliva, improved the tested volume to 50% and the LOD to 5 nM of Δ9-THC which is lower than the concentrations associated with impairment (6.5–32 nM). The aptasensor showed a good storage capability up to 3 days, however, the reusability significantly dropped from 10 cycles (freshly prepared) to 5 cycles. The results clearly demonstrate the feasibility of the aptasensor platform with the microfluidics chamber towards a point-of-care testing application for the detection of Δ9-THC in saliva.

Dynamics of capillary blood flow responses to acute local changes in oxygen and carbon dioxide concentrations.

Objectives: We aimed to quantify the magnitude and time transients of capillary blood flow responses to acute changes in local oxygen concentration ([O2]), and carbon dioxide concentration ([CO2]) in skeletal muscle. Additionally, we sought to quantify the combined response to both low [O2] and high [CO2] to mimic muscle microenvironment changes at the onset of exercise. Methods: 13 Sprague Dawley rats were anaesthetized, mechanically ventilated, and instrumented with indwelling catheters for systemic monitoring. The extensor digitorum longus muscle was blunt dissected, and reflected over a microfluidic gas exchange chamber in the stage of an inverted microscope. Four O2 challenges, four CO2 challenges, and a combined low O2 (7-2%) and high CO2 (5-10%) challenges were delivered to the surface with simultaneous visualization of capillary blood flow responses. Recordings were made for each challenge over a 1-min baseline period followed by a 2-min step change. The combined challenge employed a 1-min [O2] challenge followed by a 2-min change in [CO2]. Mean data for each sequence were fit using least-squared non-linear exponential models to determine the dynamics of each response. Results: 7-2% [O2] challenges decreased capillary RBC saturation within 2s following the step change (46.53 ± 19.56% vs. 48.51 ± 19.02%, p < 0.0001, τ = 1.44s), increased RBC velocity within 3s (228.53 ± 190.39μm/s vs. 235.74 ± 193.52μm/s, p < 0.0003, τ = 35.54s) with a 52% peak increase by the end of the challenge, hematocrit and supply rate show similar dynamics. 5-10% [CO2] challenges increased RBC velocity within 2s following the step change (273.40 ± 218.06μm/s vs. 276.75 ± 215.94μm/s, p = 0.007, τ = 79.34s), with a 58% peak increase by the end of the challenge, supply rate and hematocrit show similar dynamics. Combined [O2] and [CO2] challenges resulted in additive responses to all microvascular hemodynamic measures with a 103% peak velocity increase by the end of the collection period. Data for mean responses and exponential fitting parameters are reported for all challenges. Conclusion: Microvascular level changes in muscle [O2] and [CO2] provoked capillary hemodynamic responses with differing time transients. Simulating exercise via combined [O2] and [CO2] challenges demonstrated the independent and additive nature of local blood flow responses to these agents.

Towards spatially-organized organs-on-chip: Photopatterning cell-laden thiol-ene and methacryloyl hydrogels in a microfluidic device.

Micropatterning techniques for 3D cell cultures enable the recreation of tissue-level structures, but the combination of patterned hydrogels with organs-on-chip to generate organized 3D cultures under microfluidic perfusion remains challenging. To address this technological gap, we developed a user-friendly in-situ micropatterning protocol that integrates photolithography of crosslinkable, cell-laden hydrogels with a simple microfluidic housing, and tested the impact of crosslinking chemistry on stability and spatial resolution. Working with gelatin functionalized with photo-crosslinkable moieties, we found that inclusion of cells at high densities (≥ 107/mL) did not impede thiol-norbornene gelation, but decreased the storage moduli of methacryloyl hydrogels. Hydrogel composition and light dose were selected to match the storage moduli of soft tissues. To generate the desired pattern on-chip, the cell-laden precursor solution was flowed into a microfluidic chamber and exposed to 405 nm light through a photomask. The on-chip 3D cultures were self-standing and the designs were interchangeable by simply swapping out the photomask. Thiol-ene hydrogels yielded highly accurate feature sizes from 100 - 900 μm in diameter, whereas methacryloyl hydrogels yielded slightly enlarged features. Furthermore, only thiol-ene hydrogels were mechanically stable under perfusion overnight. Repeated patterning readily generated multi-region cultures, either separately or adjacent, including non-linear boundaries that are challenging to obtain on-chip. As a proof-of-principle, primary human T cells were patterned on-chip with high regional specificity. Viability remained high (> 85%) after 12-hr culture with constant perfusion. We envision that this technology will enable researchers to pattern 3D co-cultures to mimic organ-like structures that were previously difficult to obtain.

Analysis of Extracellular Vesicles Lysing using Surface Acoustic Wave Resonator

The integration of a Y-channel microfluidic system with an annular SAW device developed using MEMS technology has built an efficient platform for mixing and lysing of extracellular vesicles. The travelling SAW used in this study operating at a frequency of 50 MHz is capable of generating surface acoustic waves stream on a liquid sample inside a Y-chamber. At a height of 80µm the PDMS chamber and a liquid sample flow rate of 10µl/min can produce a mixing method that is able to generate gas bubbles that cause the occurrence of microcavities which are the agents of the extracellular vesicle lysing mechanism. This method of rupturing extracellular vesicles through cavitation techniques results in cell rupture through a combination of shear force and pressure changes without destroying proteins and nucleic acids. The Bradford assay is used to observe the increased presence of proteins resulting from the rupture of extracellular vesicles after exposure to acoustic waves. Based on the results, it can be concluded that the most optimal SAW exposure time and power is at 20dBM and 60 seconds. Through this test it can also be observed that a longer exposure period will generate heat which results in the degradation of the proteins that come out of the extracellular vesicles. It can be concluded that the results of this study prove that mechanical method of integrating an annular -SAW device and a Y-channel PDMS microfluidic chamber for micro-mixing, the analysis of biological cells and lysing mechanism can be achieved more effectively compared to conventional methods.

An autonomous microchip for real-time, label-free immune cell analysis

Characterization of cell populations and identification of distinct subtypes based on surface markers are needed in a variety of applications from basic research and clinical assays to cell manufacturing. Conventional immunophenotyping techniques such as flow cytometry or fluorescence microscopy require immunolabeling of cells, expensive and complex instrumentation, skilled operators, and are therefore incompatible with field deployment and automated cell manufacturing systems. In this work, we introduce an autonomous microchip that can electronically quantify the immunophenotypical composition of a cell suspension. Our microchip identifies different cell subtypes by capturing each in different microfluidic chambers functionalized against the markers of the target populations. All on-chip activity is electronically monitored by an integrated sensor network, which informs an algorithm determining subpopulation fractions from chip-wide immunocapture statistics in real time. Moreover, optimal operational conditions within the chip are enforced through a closed-loop feedback control on the sensor data and the cell flow speed, and hence, the antibody-antigen interaction time is maintained within its optimal range for selective immunocapture. We apply our microchip to analyze a mixture of unlabeled CD4+ and CD8+ T cell sub-populations and then validated the results against flow cytometry measurements. The demonstrated capability to quantitatively analyze immune cells with no labels has the potential to enable not only autonomous biochip-based immunoassays for remote testing but also cell manufacturing bioreactors with built-in, adaptive quality control.

The improvement of temperature sensitivity by controlling the thermal expansion coefficient of no-core fiber

In this paper, a liquid sealed temperature sensor is assembled based on single-mode-no-core-single-mode (SNCS) optical fiber structure. Theoretical calculations and experiments verify the sensing characteristics of this structure. The structure improves the temperature sensitivity to −355 pm/°C by encapsulating an organic solvent with large thermal optical coefficient and using packaging material with large thermal expansion coefficient. The theoretical results are in good agreement with the experimental results. Theoretical simulations are completed on MATLAB using far from the cut-off condition. The SNCS structure is encapsulated in a microfluidic chamber by applying microfluidic processing technology. The axial thermal expansion coefficient of the no-core fiber (NCF) is increased and radial thermal expansion coefficient is suppressed by the polydimethylsiloxane (PDMS) mold stretching NCF to improve the temperature sensitivity. The enhancement effect of PDMS stretching NCF on temperature sensitivity is verified by contrast experiment. Due to the wrapping of PDMS, the sensor has strong resistance to mechanical damage and external interference.

Use of Dual Optical Tweezers and Microfluidics for Single-Molecule Studies.

Visual biochemistry is a powerful technique for observing the stochastic properties of single enzymes or enzyme complexes that are obscured in the averaging that takes place in bulk-phase studies. To achieve visualization, dual optical tweezers, where one trap is fixed and the other is mobile, are focused into one channel of a multi-stream microfluidic chamber positioned on the stage of an inverted fluorescence microscope. The optical tweezers trap single molecules of fluorescently labeled DNA and fluid flow through the chamber and past the trapped beads, stretches the DNA to B-form (under minimal force, i.e., 0 pN) with the nucleic acid being observed as a white string against a black background. DNA molecules are moved from one stream to the next, by translating the stage perpendicular to the flow to enable the initiation of reactions in a controlled manner. To achieve success, microfluidic devices with optically clear channels are mated to glass syringes held in place in a syringe pump. Optimal results use connectors permanently bonded to the flow cell, tubing that is mechanically rigid and chemically resistant, and which is connected to switching valves that eliminate bubbles that prohibit laminar flow.

Hemostatic Ability of Thrombosomes® in Blood from Thrombocytopenic Patients Using the Total Thrombus Formation Analysis System (T-TAS) and Confocal Microscopy in Microfluidic Chambers

Hemostatic Ability of Thrombosomes® in Blood from Thrombocytopenic Patients Using the Total Thrombus Formation Analysis System (T-TAS) and Confocal Microscopy in Microfluidic Chambers

Dynamic Sickling Assay: Using Enzymatically Induced Hypoxia to Assess Real-Time Sickling Scalable from Large Erythrocyte Populations to Individual Cells

Background: There is a pressing need for assays to assess both patient condition and to monitor the progress of Sickle Cell Disease (SCD) therapies. It would be beneficial for an assay to allow assessment of oxygen dissociation, hemoglobin polymerization and Red Blood Cell (RBc) sickling under both equilibrium (mimicking longer-term effects) and non-equilibrium (simulating in-vivo process) conditions. Also desirable is the CLIA-waived system suitable for use in clinical trials and ultimately for clinical management of patients on SCD therapies including those those targeting Hb oxygen affinity. Our proposed work introduces an RBC hypoxia-induced sickling assay as a clinical tool to assess SCD patient condition and to assist in development, monitoring, and optimization of SCD therapies. Methods: The system uses an enzymatic oxygen scrubbing system allowing for a wide range of deoxygenation rates and final hypoxia severity. Diluted blood samples were supplemented with Protocatechuic acid (PCA) and then with Protocatechuate 3,4-Dioxygenase (PCD) enzyme inducing hypoxia at a predetermined rate. The sample was injected into an anaerobic microfluidic chamber with the resulting Red Blood Cell (RBC) morphological changes observed through time-lapsed photography. Image analysis allows for identification and quantification of sickled RBC linked to different polymerization scenarios/mechanisms. An oxygen probe was used to track the rate of medium deoxygenation. Sickling profiles were constructed to represent a percent of sickled RBC in a total cell population measured every two seconds after the enzymatic reaction is initiated. Profiles were assessed though i) percent sickling at normoxia, ii) morphological Point of Sickling (mPoS) and iii) time delay of sickling both measured at 5% increase in sickling over the normoxia sickling baseline, iv rate of sickling, v) size of the sickling fraction and vi) Area under the Curve (AUC). The last four parameters are measured for each sickling fraction if more than one such is present. Results: In control experiments PCA/PCD system was shown to allow reliable and reproducible sample deoxygenation currently enabled in a range from seconds to hours. Comprehensive multidimensional profiles were constructed presenting fraction of sickled RBC as a function of a) time from enzymatic reaction initiation, and b) one or more of rate of oxygen consumption, end of reaction hypoxia level, or oxygen tension in the medium. Such profiling allows for fast optimization of assay parameters to target assay conditions most suitable for detection of desired effects.Significant changes in sickling profiles, with marked delay in sickling, were observed upon treatment of RBC with hemoglobin-modifying drugs like voxelotor.Sickling profiles of Sickle Trait (SCT) patients showed significant delay in sickling compared to SS-type SCD patients. The method shows the potential to differentiate SCT patients based on the risk of adverse conditions to occur due to the patient's trait status.By stopping the flow, the system allows tracking of morphological status of individual cells over the full course of medium deoxygenation. Individual cells show pronounced differences in their propensity to sickle, potentially correlated to individual cell Hb F content. Change in morphology of sickling cells from biconcave disk to crescent and then to holly leaf and granular forms had been observed upon progressively decreasing medium oxygen tension.RBC microparticle formation can be observed and tracked over time as an additional metric of erythrocyte response to developing hypoxia Conclusions: By using enzymatically induced hypoxia in a microfluidic environment, presented system allows comprehensive analysis of RBC sickling dynamics in a wide range of deoxygenation rates and conditions. It would find utility in SCD therapy development by offering a robust and high throughput method for assessing critical RBC response to therapies. With no need for cumbersome gas cylinders and low training requirements, a stand-alone system with single use disposable cartridges would also have utility in clinical trials both in the US and abroad, due to simplicity of use suitable for developing countries with limited infrastructure. When validated, the system can be adapted for Point of Care use either as complementary to other blood tests or in an independent monitoring mode.

Microfluidic Chamber Technology to Study Missorting and Spreading of Tau Protein in Alzheimer's Disease.

Tau is a microtubule-associated protein found mainly in the axons of neurons in the brain. Abnormal changes in Tau (e.g., aggregation, hyperphosphorylation) are hallmarks of Alzheimer's disease. Two processes of relocalization of Tau may be related to early states of the pathology and have received much attention: (1) the redistribution of Tau within cells (termed "somatodendritic missorting") and (2) the release and reuptake of Tau from donor to acceptor cells (termed "spreading"). Because of the tripartite nature of neurons (cell body, dendrites, axons), these changes can be studied by microfluidic chambers (MFCs) which allow separation and observation of Tau in neuronal compartments. In this chapter, we present some methods and research results obtained by using microfluidic devices.

A lab-on-chip platform for simultaneous culture and electrochemical detection of bacteria

A simple, cost-effective and miniaturized lab-on-a-chip platform has been developed amenable to perform simultaneous cultivation and detection of bacteria. A microfluidic chamber was integrated to screen-printed electrodes for electrochemical detection of bacteria. The temperature required for the bacterial culture was provided through the optimized laser-induced graphene heaters. The concentration of bacteria was quantified accurately with the three-electrode system in the range of 2×104 to 1.1×109 CFU/mL without any need of biological modifications to the electrodes. The viability of cultured bacteria in the microfluidic device was also confirmed through fluorescent imaging. Furthermore, the metabolic activity of the cultured bacteria was validated through a miniaturized microbial fuel cell. Furthermore, the specificity of electrodes was also performed through electrochemical technique. Finally, a handheld and portable lab-on-a-chip platform was realized by 3D packaging, integrated with a portable potentiostat for real-time and on-field applications.

Nexinhib20 Inhibits Neutrophil Adhesion and β2 Integrin Activation by Antagonizing Rac-1-Guanosine 5'-Triphosphate Interaction.

Neutrophils are critical for mediating inflammatory responses. Inhibiting neutrophil recruitment is an attractive approach for preventing inflammatory injuries, including myocardial ischemia-reperfusion (I/R) injury, which exacerbates cardiomyocyte death after primary percutaneous coronary intervention in acute myocardial infarction. In this study, we found out that a neutrophil exocytosis inhibitor Nexinhib20 inhibits not only exocytosis but also neutrophil adhesion by limiting β2 integrin activation. Using a microfluidic chamber, we found that Nexinhib20 inhibited IL-8-induced β2 integrin-dependent human neutrophil adhesion under flow. Using a dynamic flow cytometry assay, we discovered that Nexinhib20 suppresses intracellular calcium flux and β2 integrin activation after IL-8 stimulation. Western blots of Ras-related C3 botulinum toxin substrate 1 (Rac-1)-GTP pull-down assays confirmed that Nexinhib20 inhibited Rac-1 activation in leukocytes. An in vitro competition assay showed that Nexinhib20 antagonized the binding of Rac-1 and GTP. Using a mouse model of myocardial I/R injury, Nexinhib20 administration after ischemia and before reperfusion significantly decreased neutrophil recruitment and infarct size. Our results highlight the translational potential of Nexinhib20 as a dual-functional neutrophil inhibitory drug to prevent myocardial I/R injury.

Rotational acoustofluidic fields induced by cross structures with asymmetric radiation surface arrangements

In this study, a novel strategy to generate sophisticated acoustic streaming vortices, which would be available for rotational manipulation of micro-/nano-scale objects, is proposed and simulated. All structural units in the microfluidic chamber are symmetric in design, and all radiation surfaces have the same settings of input frequency, oscillation amplitude, and initial phase. Different kinds of asymmetric acoustofluidic patterns can be generated in the originally static microfluidic chamber only because of the asymmetric arrangement of multiple radiation surfaces in space. The calculation results of kaleidoscopic acoustofluidic fields together with particle movement trajectories induced by cross structures with different radiation surface distributions further demonstrate the versatile particle manipulation capabilities of these functional microfluidic devices. In comparison to the existing oscillation modulation method, which requires multiple radiation surfaces with different initial phases, acoustofluidic devices with a same initial phase of all radiation surfaces can significantly reduce the required number of auxiliary signal generators and power amplifiers. The proposed generation method of acoustofluidic patterns is promising for microfluidic mixing without rotating machinery, driving operation of microrobots, and rotational manipulation of biological samples.

A fibrin enhanced thrombosis model for medical devices operating at low shear regimes or large surface areas.

Over the past decade, much of the development of computational models of device-related thrombosis has focused on platelet activity. While those models have been successful in predicting thrombus formation in medical devices operating at high shear rates (> 5000 s-1), they cannot be directly applied to low-shear devices, such as blood oxygenators and catheters, where emerging information suggest that fibrin formation is the predominant mechanism of clotting and platelet activity plays a secondary role. In the current work, we augment an existing platelet-based model of thrombosis with a partial model of the coagulation cascade that includes contact activation of factor XII and fibrin production. To calibrate the model, we simulate a backward-facing-step flow channel that has been extensively characterized in-vitro. Next, we perform blood perfusion experiments through a microfluidic chamber mimicking a hollow fiber membrane oxygenator and validate the model against these observations. The simulation results closely match the time evolution of the thrombus height and length in the backward-facing-step experiment. Application of the model to the microfluidic hollow fiber bundle chamber capture both gross features such as the increasing clotting trend towards the outlet of the chamber, as well as finer local features such as the structure of fibrin around individual hollow fibers. Our results are in line with recent findings that suggest fibrin production, through contact activation of factor XII, drives the thrombus formation in medical devices operating at low shear rates with large surface area to volume ratios.

Microfluidic devices as model platforms of CNS injury-ischemia to study axonal regeneration by regulating mitochondrial transport and bioenergetic metabolism

Central nervous system (CNS) neurons typically fail to regenerate their axons after injury leading to neurological impairment. Axonal regeneration is a highly energy-demanding cellular program that requires local mitochondria to supply most energy within injured axons. Recent emerging lines of evidence have started to reveal that injury-triggered acute mitochondrial damage and local energy crisis contribute to the intrinsic energetic restriction that accounts for axon regeneration failure in the CNS. Characterizing and reprogramming bioenergetic signaling and mitochondrial maintenance after axon injury-ischemia is fundamental for developing therapeutic strategies that can restore local energy metabolism and thus facilitate axon regeneration. Therefore, establishing reliable and reproducible neuronal model platforms is critical for assessing axonal energetic metabolism and regeneration capacity after injury-ischemia. In this focused methodology article, we discuss recent advances in applying cutting-edge microfluidic chamber devices in combination with state-of-the-art live-neuron imaging tools to monitor axonal regeneration, mitochondrial transport, bioenergetic metabolism, and local protein synthesis in response to injury-ischemic stress in mature CNS neurons.