Use Of Microfluidic Systems Research Articles

Synergistic potential of stem cells and microfluidics in regenerative medicine.

Regenerative medicine has immense potential to revolutionize healthcare by using regenerative capabilities of stem cells. Microfluidics, a cutting-edge technology, offers precise control over cellular microenvironments. The integration of these two fields provides a deep understanding of stem cell behavior and enables the development of advanced therapeutic strategies. This critical review explores the use of microfluidic systems to culture and differentiate stem cells with precision. We examined the use of microfluidic platforms for controlled nutrient supply, mechanical stimuli, and real-time monitoring, providing an unprecedented level of detail in studying cellular responses. The convergence of stem cells and microfluidics holds immense promise for tissue repair, regeneration, and personalized medicine. It offers a unique opportunity to revolutionize the approach to regenerative medicine, facilitating the development of advanced therapeutic strategies and enhancing healthcare outcomes.

State‐of‐the‐Art CO2 Reduction in Electrochemical Microfluidic Systems: A Short Review and New Perspectives

AbstractThe need to mitigate carbon dioxide has motivated an influx of interest in innovative technologies, and microfluidic systems have emerged as a promising forefront in this endeavor. This short review analyzes CO2 reduction within microfluidic platforms, thoroughly investigating existing methodologies, challenges, and novel perspectives. This work commences with a detailed exposition of the fundamental principles governing microfluidic electrolyzers, elucidating the interaction of microchannels and electrodes. We show the electrochemical reactions supporting CO2 reduction, detailing the processes at the cathode. The use of microfluidic systems encompasses precise control over reaction conditions, efficient mass transport, reduced energy consumption, high throughput screening capabilities, integration with analytical tools, and portability. Catalyst selection for optimal CO2 reduction products, technical complexities, integration of renewable energy sources, and cost‐effectiveness are notable challenges on the horizon. A perspective on potential pathways to resolution is delineated, with each impediment succinctly but insightfully addressed. Moreover, this review extends beyond a looking‐back analysis, propounding innovative perspectives. It posits the concept of microfluidic fuel cells directly fueled by CO2. This work seeks to inspire new researchers and innovation in the field by comparing the present state‐of‐the‐art with prospective avenues of exploration.

Microfluidic technology for cell biology-related applications: a review.

Fluid flow at the microscale level exhibits a unique phenomenon that can be explored to fabricate microfluidic devices integrated with components that can perform various biological functions. In this manuscript, the importance of physics for microscale fluid dynamics using microfluidic devices has been reviewed. Microfluidic devices provide new opportunities with regard to spatial and temporal control over cell growth. Furthermore, the manuscript presents an overview of cellular stimuli observed by combining surfaces that mimic the complex biochemistries and different geometries of the extracellular matrix, with microfluidic channels regulating the transport of fluids, soluble factors, etc. We have also explained the concept of mechanotransduction, which defines the relation between mechanical force and biological response. Furthermore, the manipulation of cellular microenvironments by the use of microfluidic systems has been highlighted as a useful device for basic cell biology research activities. Finally, the article focuses on highly integrated microfluidic platforms that exhibit immense potential for biomedical and pharmaceutical research as robust and portable point-of-care diagnostic devices for the assessment of clinical samples.

Development of 5-fluorouracil-dichloroacetate mutual prodrugs as anticancer agents

5-Fluorouracil (5-FU) is one of the most widely applied chemotherapeutic agents with a broad spectrum of activity. However, despite this versatile activity, its use poses many limitations. Herein, novel derivatives of 5-FU and dichloroacetic acid have been designed and synthesized as a new type of codrugs, also known as mutual prodrugs, to overcome the drawbacks of 5-FU and enhance its therapeutic efficiency. The stability of the obtained compounds has been tested at various pH values using different analytical techniques, namely HPLC and potentiometry. The antiproliferative activity of the new 5-FU derivatives was assessed in vitro on SK-MEL-28 and WM793 human melanoma cell lines in 2D culture as well as on A549 human lung carcinoma, MDA-MB-231 breast adenocarcinoma, LL24 normal lung tissue, and HMF normal breast tissue as a multicellular 3D spheroid model cultured in standard (static) conditions and with the use of microfluidic systems, which to a great extent resembles the in vivo environment. In all cases, new mutual prodrugs showed a higher cytotoxic activity toward cancer models and lower to normal cell models than the parent 5-FU itself.

Numerical study of the influence of geometry and flow on the mixing process of non-Newtonian fluids in micromixers

This article is designed for the study of the mixing of non-Newtonian fluids using a kenics micromixer. The governing equations are solved numerically using a CFD code. The species transport model was chosen to characterize the mixing. The flow regime is laminar. The generalized Reynolds number ranges from 0.1 to 120. The CMC solutions supplied to the power law model are used in the simulations as a non-Newtonian fluid. The mixing efficiency was assessed by calculating the mixing index MI. Two geometric configurations of T-type and Y-type micromixers are investigated, and their hydrodynamic mixing performance is compared. The results of the numerical simulations show that the proposed micro kenics have the best mixing index which exceeds 0.98 for all values of (n) and Reg less than or equal to 25 considered in this study. This micromixer had real potential to improve mixing performance because the kinematic properties are totally chaotic. Finally, this micromixer is suitable for use in microfluidic systems that demand rapid mixing while maintaining low Reynolds numbers.

Microfluidic technology for macro systems: Removal of textile dyes from wastewater in a microreactor

Wastewater from textile industry contains considerable amount of dissolved dye that can trigger environmental issues if is not treated properly. Numerous methods have been developed to degrade recalcitrant pollutants safely and utterly. Among them, enzymatic treatment of wastewater is gaining attention due to the enzyme’s specificity, easier manipulation, and generation of less toxic by-products. Still, the cost of enzymatic systems is the main limitation keeping the biocatalysts at lab-scale. Alternative solution for reducing the cost of enzymatic reaction systems is the use of microfluidic systems, which contribute to better mixing, process intensification and cleaner production. In this study, implementation of horseradish peroxidase for removal of the textile dye Acid Violet 109 is performed in a microfluidic reactor. The microreactor consists of three plunger pump units, two mixers and PTFE tube. The process parameters: residence time, dye, hydrogen peroxide, enzyme activity, the reactors’ diameter and length were optimized. Under the optimal process conditions: 30 mg/L dye concentration, 0.8 U/mL horseradish peroxidase activity, 0.1 mM hydrogen peroxide, 0.25 mm reactor’s diameter, 97,3 % removal was achieved at residence time of 6 min. The results from this study show that enzymatic microfluidic reactors are a convenient technology for dye removal.

Direct 3D printed biocompatible microfluidics: assessment of human mesenchymal stem cell differentiation and cytotoxic drug screening in a dynamic culture system

BackgroundIn vivo-mimicking conditions are critical in in vitro cell analysis to obtain clinically relevant results. The required conditions, comparable to those prevalent in nature, can be provided by microfluidic dynamic cell cultures. Microfluidics can be used to fabricate and test the functionality and biocompatibility of newly developed nanosystems or to apply micro- and nanoelectromechanical systems embedded in a microfluidic system. However, the use of microfluidic systems is often hampered by their accessibility, acquisition cost, or customization, especially for scientists whose primary research focus is not microfluidics.ResultsHere we present a method for 3D printing that can be applied without special prior knowledge and sophisticated equipment to produce various ready-to-use microfluidic components with a size of 100 µm. Compared to other available methods, 3D printing using fused deposition modeling (FDM) offers several advantages, such as time-reduction and avoidance of sophisticated equipment (e.g., photolithography), as well as excellent biocompatibility and avoidance of toxic, leaching chemicals or post-processing (e.g., stereolithography). We further demonstrate the ease of use of the method for two relevant applications: a cytotoxicity screening system and an osteoblastic differentiation assay. To our knowledge, this is the first time an application including treatment, long-term cell culture and analysis on one chip has been demonstrated in a directly 3D-printed microfluidic chip.ConclusionThe direct 3D printing method is tested and validated for various microfluidic components that can be combined on a chip depending on the specific requirements of the experiment. The ease of use and production opens up the potential of microfluidics to a wide range of users, especially in biomedical research. Our demonstration of its use as a cytotoxicity screening system and as an assay for osteoblastic differentiation shows the methods potential in the development of novel biomedical applications. With the presented method, we aim to disseminate microfluidics as a standard method in biomedical research, thus improving the reproducibility and transferability of results to clinical applications.Graphical

Two-Phase Biocatalysis in Microfluidic Droplets.

This Perspective discusses the literature related to two-phase biocatalysis in microfluidic droplets. Enzymes used as catalysts in biocatalysis are generally less stable in organic media than in their native aqueous environments; however, chemical and pharmaceutical compounds are often insoluble in water. The use of aqueous/organic two-phase media provides a solution to this problem and has therefore become standard practice for multiple biotransformations. In batch, two-phase biocatalysis is limited by mass transport, a limitation that can be overcome with the use of microfluidic systems. Although, two-phase biocatalysis in laminar flow systems has been extensively studied, microfluidic droplets have been primarily used for enzyme screening. In this Perspective, we summarize the limited published work on two-phase biocatalysis in microfluidic droplets and discuss the limitations, challenges, and future perspectives of this technology.

Microfluidic synthesis of retinoic acid-loaded nanoparticles for neural differentiation of trabecular meshwork mesenchymal stem cell.

This study aimed to fabricate the PCL-nanoparticles (NPs) loaded retinoic acid (RA) using the microfluidic system for successful cellular uptake and induction of neuronal differentiation of trabecular meshwork mesenchymal stem cells (TMMSCs). A microfluidic system used to synthesize RA-loaded NPs, DLS, FTIR, TEM, and UV-spectroscopywas recruited to characterize and study the release of RA. Also, the toxicity, cellular uptake, and neuronal differential of TMMSCs have been assessed. According to the obtained results, thespherical NPs (117.6±0.35 nm, ‒19.4±5.3) and RA-loaded NPs (121.6±0.75 nm, ‒23.6±1.3) were synthesized successfully by microfluidic system. 7.8±2.04 % of RA was loaded in NPs, and 25 % was released in the first four hours. Thus, the NPs have been successfully internalized into the stem cells, leading to a significant increase in neural genes and protein (β Tubulin III and Map-2) expression. Our study's harvested results have represented valid data for practical use of microfluidic systems in the term of NPs loaded RA synthesis and its successful function to cellular internalization and euronal differentiation of TMMSCs (Tab. 2, Fig. 10, Ref. 46).

Isolation of Plant Root Nuclei for Single Cell RNA Sequencing.

The characterization of the transcriptional similarities and differences existing between plant cells and cell types is important to better understand the biology of each cell composing the plant, to reveal new molecular mechanisms controlling gene activity, and to ultimately implement meaningful strategies to enhance plant cell biology. To gain a deeper understanding of the regulation of plant gene activity, the individual transcriptome of each plant cell needs to be established. Until recently, single cell approaches were mostly limited to bulk transcriptomic studies on selected cell types. Accessing specific cell types required the development of labor-intensive strategies. Recently, single cell sequencing strategies were successfully applied on isolated Arabidopsis thaliana root protoplasts. However, this strategy relies on the successful isolation of viable protoplasts upon the optimization of the enzymatic cocktails required to digest the cell wall and on the compatibility of fragile plant protoplasts with the use of microfluidic systems to generate single cell transcriptomic libraries. To overcome these difficulties, we present a simple and fast alternative strategy: the isolation and use of plant nuclei to access meaningful transcriptomic information from plant cells. This protocol was specifically developed to enable the use of the plant nuclei with 10× Genomics' Chromium technology partitions technology. Briefly, the plant nuclei are released from the root by chopping into a nuclei isolation buffer before purification by filtration then nuclei sorting. Upon sorting, the nuclei are resuspended in a low divalent ion buffer compatible with the Chromium technology in order to create single nuclei ribonucleic acid-sequencing libraries (sNucRNA-seq). © 2020 Wiley Periodicals LLC. Basic Protocol 1: Arabidopsis seed sterilization and planting Basic Protocol 2: Nuclei isolation from Arabidopsis roots Basic Protocol 3: Fluorescent-activated nuclei sorting (FANS) purification Support Protocol: Estimation of nuclei density using Countess II automated cell counter Alternate Protocol 1: Proper growth conditions for Medicago truncatula and Sorghum bicolor Alternate Protocol 2: Estimation of nuclei density using sNucRNA-seq technology.

In Pursuit of Designing Multicellular Engineered Living Systems: A Fluid Mechanical Perspective

From intracellular protein signaling to embryonic symmetry-breaking, fluid transport ubiquitously drives biological events in living systems. We provide an overview of the fundamental fluid mechanics and transport phenomena across a range of length scales in cellular systems, with emphasis on how cellular functions are influenced by fluid transport. We also highlight how understanding the physical basis of these fluid dynamic phenomena can be implemented to engineer increasingly complex multicellular systems that recapitulate tissue-level functions. Examples discussed include the manipulation of intracellular fluid volume to achieve cell differentiation/dedifferentiation and the use of microfluidic systems to control the spatial and temporal distribution of morphogens and fluid forces to generate vascularized organoids.

Disordered protein-graphene oxide co-assembly and supramolecular biofabrication of functional fluidic devices

Supramolecular chemistry offers an exciting opportunity to assemble materials with molecular precision. However, there remains an unmet need to turn molecular self-assembly into functional materials and devices. Harnessing the inherent properties of both disordered proteins and graphene oxide (GO), we report a disordered protein-GO co-assembling system that through a diffusion-reaction process and disorder-to-order transitions generates hierarchically organized materials that exhibit high stability and access to non-equilibrium on demand. We use experimental approaches and molecular dynamics simulations to describe the underlying molecular mechanism of formation and establish key rules for its design and regulation. Through rapid prototyping techniques, we demonstrate the system’s capacity to be controlled with spatio-temporal precision into well-defined capillary-like fluidic microstructures with a high level of biocompatibility and, importantly, the capacity to withstand flow. Our study presents an innovative approach to transform rational supramolecular design into functional engineering with potential widespread use in microfluidic systems and organ-on-a-chip platforms.

Field generated nematic microflows via backflow mechanism

Generation of flow is an important aspect in microfluidic applications and generally relies on external pumps or embedded moving mechanical parts which pose distinct limitations and protocols on the use of microfluidic systems. A possible approach to avoid moving mechanical parts is to generate flow by changing some selected property or structure of the fluid. In fluids with internal orientational order such as nematic liquid crystals, this process of flow generation is known as the backflow effect. In this article, we demonstrate the contact-free generation of microfluidic material flows in nematic fluids -including directed contact-free pumping- by external electric and optical fields based on the dynamic backflow coupling between nematic order and material flow. Using numerical modelling, we design efficient shaping and driving of the backflow-generated material flow using spatial profiles and time modulations of electric fields with oscillating amplitude, rotating electric fields and optical fields. Particularly, we demonstrate how such periodic external fields generate efficient net average nematic flows through a microfluidic channel, that avoid usual invariance under time-reversal limitations. We show that a laser beam with rotating linear polarization can create a vortex-like flow structure and can act as a local flow pump without moving mechanical parts. The work could be used for advanced microfluidic applications, possibly by creating custom microfluidic pathways without predefined channels based on the adaptivity of an optical set-up, with a far reaching unconventional idea to realize channel-less microfluidics.

Design and implementation of a passive micro flow sensor based on diamagnetic levitation

This study presents a prototype of a micro-flow sensor based on magnetic levitation for the use in microfluidic systems. Accurate assessment of flow rates is crucial in the microfluidic system design. Micro-sensors utilizing levitation constitute an important topic in this regard. Diamagnetic levitation is an efficient technique, which is useful in applications with low power consumption and eliminates friction. With the proposed approach, zero mechanical contact in a microfluidic channel can be achieved. A sensor capable of accurately measuring flow rates was designed in this study. The corresponding flow rate range was between 1000 μL/min and 7000 μL/min. Levitation was accomplished with pyrolytic graphite and a ring magnet (NdFeB) acting as a lifter. The displacement of the micro-magnet in the micro channel in longitudinal direction was monitored via a microscope-camera system and was measured via a laser sensor above the lifter-magnet. A commercial analysis software (COMSOL Multiphysics Version 5.3 CPU License No: 17076072) was used for dynamic analysis and validation of experimental results. The flow rates were obtained using the data from the laser sensor via an exclusively coded C# program. The developed sensor prototype, which has the advantages of simple structure, small size and low cost, is a substantial candidate for the use in microfluidic devices requiring high accuracy.

In vitro models of molecular and nano-particle transport across the blood-brain barrier.

The blood-brain barrier (BBB) is the tightest endothelial barrier in humans. Characterized by the presence of tight endothelial junctions and adherens junctions, the primary function of the BBB is to maintain brain homeostasis through the control of solute transit across the barrier. The specific features of this barrier make for unique modes of transport of solutes, nanoparticles, and cells across the BBB. Understanding the different routes of traffic adopted by each of these is therefore critical in the development of targeted therapies. In an attempt to move towards controlled experimental assays, multiple groups are now opting for the use of microfluidic systems. A comprehensive understanding of bio-transport processes across the BBB in microfluidic devices is therefore necessary to develop targeted and efficient therapies for a host of diseases ranging from neurological disorders to the spread of metastases in the brain.

Role of Microenvironment in Glioma Invasion: What We Learned from In Vitro Models.

The invasion properties of glioblastoma hamper a radical surgery and are responsible for its recurrence. Understanding the invasion mechanisms is thus critical to devise new therapeutic strategies. Therefore, the creation of in vitro models that enable these mechanisms to be studied represents a crucial step. Since in vitro models represent an over-simplification of the in vivo system, in these years it has been attempted to increase the level of complexity of in vitro assays to create models that could better mimic the behaviour of the cells in vivo. These levels of complexity involved: 1. The dimension of the system, moving from two-dimensional to three-dimensional models; 2. The use of microfluidic systems; 3. The use of mixed cultures of tumour cells and cells of the tumour micro-environment in order to mimic the complex cross-talk between tumour cells and their micro-environment; 4. And the source of cells used in an attempt to move from commercial lines to patient-based models. In this review, we will summarize the evidence obtained exploring these different levels of complexity and highlighting advantages and limitations of each system used.

Microfluidic Platforms for Yeast-Based Aging Studies.

The budding yeast Saccharomyces cerevisiae has been a powerful model for the study of aging and has enabled significant contributions to our understanding of basic mechanisms of aging in eukaryotic cells. However, the laborious low-throughput nature of conventional methods of performing aging assays limits the pace of discoveries in this field. Some of the technical challenges of conventional aging assay methods can be overcome by use of microfluidic systems coupled to time-lapse microscopy. One of the major advantages is the ability of a microfluidic system to perform long-term cell culture under well-defined environmental conditions while tracking individual yeast. Here, recent advancements in microfluidic platforms for various yeast-based studies including replicative lifespan assay, long-term culture and imaging, gene expression, and cell signaling are discussed. In addition, emerging problems and limitations of current microfluidic approaches are examined and perspectives on the future development of this dynamic field are presented.

Miniaturized Redox Flow Batteries for Electronic Applications: CFD Modeling

Miniaturized redox flow batteries have seen interest in electronic applications because of their potential to simultaneously deliver electric power and remove heat. For these applications, the flow battery has to be constructed on a side of a computer chip, with components such as flow channels, manifolds, supply tubes, electrodes, membranes and current collectors. There are efforts underway to optimize the design of these components for different objectives such as maximum power density or maximum efficiency. Due to space constraints, design rules employed for classical redox flow batteries are only of limited use in microfluidic systems. Since experimentation with micro-scale components is especially expensive and time-consuming, there is a need to develop computational tools to understand trade-offs in the design and operation of these flow batteries. We have carried out computational fluid dynamics study of redox flow batteries using commercially available software. This paper analyses the effect of manifold and flow channel design on current and voltage distribution in the flow battery. The anolyte and catholyte fluid flows are modeled using Navier-Stokes equations of mass momentum and energy conservation. Species diffusion through porous electrodes is modeled using species-dependent diffusion coefficients, which are calculated based on the fluid state and the electrode geometry. The electrochemical reactions are modeled using the Butler-Volmer equation with a pre-defined exchange current density. The species concentrations, pressures and temperatures at various parts of the flow battery are solved using a multiphysics simulation software package. We find that the flow channel geometry and manifold design has an important effect on the flow distribution as well as current collection inside the flow battery. It also affects the pressure drop, thereby affecting the pumping power required to keep the battery operational. Based on these findings, we make observations regarding cell design and operation. We expect that these simulations, once validated with experiments, lead to a better understanding of the trade-offs involved in the design and operation of miniature redox flow batteries for electronic applications.

Increased Probability of Cell Membrane Breakdown by Use of Microfluidic System

This research shows the experiment results of cell membrane breakdown. We did the experiments by using plant protoplasts in a microfluidic system to increase the efficiency of membrane charging process. In the experiment, we apply 5 MHz of sine wave to attract the cell to target position and then apply 10–200 kHz to make breakdown occur. Under the experiment conditions (R = 10–25 μm, U = 10 VP, tL = 10 ms, σ = 45–55 mS/m), the use of microfluidic system with insulating wall and orifice increased breakdown probability. Breakdown probability is 86.8%, and the probabilities of fL at 10–100 kHz are higher than the probability of fL at 200 kHz.

Microfluidic model of angiogenic sprouting.

Microfluidic systems have emerged as an important technology for modeling cellular microenvironments in vitro. These systems enable unprecedented levels of control of chemical gradients, fluid flow, and localized 3-D extracellular matrices (ECM), all of which can be integrated to provide a physiologically relevant context for studying complex cellular processes such as angiogenesis. Here, we describe the design and use of microfluidic systems for reproducing the dynamic events of vascular morphogenesis.