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Growing evidence demonstrates that cancer-associated fibroblasts (CAF) are responsible for tumor genesis, growth, metastasis, and treatment response. Therefore, targeting these cells may contribute to tumor control. It has been proposed that targeting key molecules and pathways of proliferative functions can be more effective than killing CAFs. In this regard, multicellular aggregates, like spheroids, can be used as human tumor models. Spheroids closely resemble human tumors and mimic many of their features. Microfluidic systems are ideal for cultivation and study of spheroids. These systems can be designed with different biological and synthetic matrices in order to have a more realistic simulation of the tumor microenvironment (TME). In this study, we investigated the effect of all-trans retinoic acid (ATRA) on 3D spheroid invasion of MDA-MB cells exposed to hydrogel matrix derived from CAFs. The number of invasive cells significantly decreased in CAF-ECM hydrogel treated with ATRA (p < 0.05), which indicates that ATRA could be effective for CAFs normalization. This experiment was done using an agarose-alginate microfluidic chip. As compared with common methods, such hydrogel casting is an easier method for chip fabrication and can even reduce costs. [ABSTRACT FROM AUTHOR]

Food safety is a significant issue that affects people worldwide and is tied to their lives and health. The issue of pesticide residues in food is just one of many issues related to food safety, which leave residues in crops and are transferred through the food chain to human consumption. Foods contaminated with pesticide residues pose a serious risk to human health, including carcinogenicity, neurotoxicity, and endocrine disruption. Although traditional methods, including gas chromatography, high-performance liquid chromatography, chromatography, and mass spectrometry, can be used to achieve a quantitative analysis of pesticide residues, the disadvantages of these techniques, such as being time-consuming and costly and requiring specialist staff, limit their application. Therefore, there is a need to develop rapid, effective, and sensitive equipment for the quantitative analysis of pesticide residues in food. Microfluidics is rapidly emerging in a number of fields due to its outstanding strengths. This paper summarizes the application of microfluidic techniques to pyrethroid, carbamate, organochlorine, and organophosphate pesticides, as well as to commercial products. Meanwhile, the study also outlines the development of microfluidics in combination with 3D printing technology and nanomaterials for detecting pesticide residues in food. [ABSTRACT FROM AUTHOR]

Overweight and obesity promote diabetes and heart disease onset. Triglycerides are key biomarkers for cardiovascular disease, strokes, and other health issues. Scientists have devised methods and instruments for the detection of these molecules in liquid samples. In this study, an enzymatic biosensor was developed using an Arduino-based microfluidic platform, wherein a lipolytic enzyme was immobilized on an ethylene-vinyl acetate polymer through physical adsorption. This low-cost optical biosensor employed a spectrophotometric transducer and was assessed in liquid samples to indirectly detect triglycerides and fatty acids using p-nitrophenol as an indicator. The average triglyceride level detected in the conducted experiments was 47.727 mg/dL. The biosensor exhibited a percentage of recovery of 81.12% and a variation coefficient of 0.791%. Furthermore, the biosensor demonstrated the ability to detect triglyceride levels without the need for sample dilution, ranging from 7.6741 mg/dL to 58.835 mg/dL. This study successfully developed an efficient and affordable enzymatic biosensor prototype for triglyceride and fatty acid detection. The lipolytic enzyme immobilization on the polymer substrate provided a stable and reproducible detection system, rendering this biosensor an exciting option for the detection of these molecules. [ABSTRACT FROM AUTHOR]

Drug nanonization and encapsulation efficiency enhancement are prerequisites for hydrophobic and hydrophilic drugs to be delivered at the targeted site. Microfluidic technology has emerged as an efficient technique to achieve these objectives due to its ability to provide intensive mixing and yield relatively uniform nanosized particles. Furthermore, microfluidic technology has been established as a promising method to develop novel drug delivery systems with uniform particle size and distribution, reducing batch variation with controlled drug delivery capabilities. This extensive review introduces various applications of microfluidic systems for synthesizing controlled-sized organic and inorganic nanoparticles, followed by a discussion on micromixers and their recent advancements in drug delivery systems. We have reviewed the vital role of spray and freeze-drying in nanoparticle production. In addition, we have highlighted the concept and compared a microreactor-assisted spray and freeze dryer for developing a new innovative drug delivery platform. Finally, a critical discussion is presented on several recent patents on microfluidics along with applicable drying technologies. [ABSTRACT FROM AUTHOR]

Electric split-ring metamaterial based microfluidic chip for label-free microparticles trapping and biosensing applications. (TS: trapping structure). [Display omitted] • An integration of terahertz (THz) electrical split-ring metamaterial (eSRM) with microfluidic chip is presented. • A label-free strategy in microparticle trapping and detecting is proposed for biosensing application. • eSRM-based microfluidic chip exhibits multiple resonances and selectively microparticle trapping characteristic. • eSRM-based microfluidic exhibits high sensitivity to detect microparticles in TE mode. In this work, an integration of terahertz (THz) electrical split-ring metamaterial (eSRM) with microfluidic chip is presented. This eSRM-based microfluidic chip exhibits multiple resonances in the THz spectrum and trapping selectively microparticle size characteristics. The arrangement of eSRM array is dislocation. It generates the fundamental inductive-capacitive (LC) resonant mode, quadrupole, and octupolar plasmon resonant modes and then exhibits high sensitivity to the environmental refraction index. The trapping structures of microparticles are elliptical barricades on eSRM surface. Thus, the electric field energy is strongly confined within the gap of eSRM in transverse electric (TE) mode and then the elliptical trapping structures are anchored on both sides of the split gap to ensure the microparticles can be trapped and located on the gap. To imitate the microparticle sensing ambient environment qualitatively and quantitatively in the THz spectrum, the microparticles are designed different feature sizes with different refraction index from 1.0 to 2.0 in ethanol medium. The results show the proposed eSRM-based microfluidic chip possesses the trapping and sensing abilities in single microparticle and high sensitivity for fungus, microorganism, chemical and environmental applications. [ABSTRACT FROM AUTHOR]

Microfluidic cultivation devices that facilitate O2 control enable unique studies of the complex interplay between environmental O2 availability and microbial physiology at the single-cell level. Therefore, microbial single-cell analysis based on time-lapse microscopy is typically used to resolve microbial behavior at the single-cell level with spatiotemporal resolution. Time-lapse imaging then provides large image-data stacks that can be efficiently analyzed by deep learning analysis techniques, providing new insights into microbiology. This knowledge gain justifies the additional and often laborious microfluidic experiments. Obviously, the integration of on-chip O2 measurement and control during the already complex microfluidic cultivation, and the development of image analysis tools, can be a challenging endeavor. A comprehensive experimental approach to allow spatiotemporal single-cell analysis of living microorganisms under controlled O2 availability is presented here. To this end, a gas-permeable polydimethylsiloxane microfluidic cultivation chip and a low-cost 3D-printed mini-incubator were successfully used to control O2 availability inside microfluidic growth chambers during time-lapse microscopy. Dissolved O2 was monitored by imaging the fluorescence lifetime of the O2-sensitive dye RTDP using FLIM microscopy. The acquired image-data stacks from biological experiments containing phase contrast and fluorescence intensity data were analyzed using in-house developed and open-source image-analysis tools. The resulting oxygen concentration could be dynamically controlled between 0% and 100%. The system was experimentally tested by culturing and analyzing an E. coli strain expressing green fluorescent protein as an indirect intracellular oxygen indicator. The presented system allows for innovativemicrobiological research onmicroorganisms andmicrobial ecology with single-cell resolution. [ABSTRACT FROM AUTHOR]

[Display omitted] In recent decades, biotechnological drugs have emerged as relevant therapeutic tools. However, therapeutic molecules can exert their activity only if properly formulated and delivered into the body. In this regard, nano-sized drug delivery systems have been shown to provide protection, stability, and controlled release of payloads, increasing their therapeutic efficacy. In this work, a microfluidic mixing technique for the preparation of chitosan-based nanoparticles was established with the capability of easily exchanging macromolecular biological cargos such as the model protein β-Galactosidase, mRNA, and siRNA. The nanoparticles obtained showed hydrodynamic diameters ranging from 75 nm to 105 nm, low polydispersity of 0.15 to 0.22 and positive zeta potentials of 6 mV to 17 mV. All payloads were efficiently encapsulated (>80 %) and the well-known cytocompatibility of chitosan-based nanoparticles was confirmed. Cell culture studies demonstrated increased cellular internalization of loaded nano-formulations compared to free molecules as well as successful gene silencing with nano-formulated siRNA, suggesting the ability of these nanoparticles to escape the endosome. [ABSTRACT FROM AUTHOR]

Ultrathin hydrogel films composed of cross-linked polymer networks swollen by water, with soft and moisturized features similar to biological tissue, play a vital role in flexible biosensors and wearable electronics. However, achieving efficient and continuous fabrication of such films remains a challenge. Here, we present a microfluidic-based strategy for the continuous fabrication of free-standing ultrathin hydrogel films by using laminar flow, which can be precisely controlled in the micrometer scale. Compared with conventional methods, the microfluidic-based method shows advantages in producing hydrogel films with a high homogeneity as well as maintaining the structural integrity, without the need of supporting substrates and sophisticated equipment. This strategy allows the precise control over the thickness of the hydrogel films ranging from 15 ± 0.2 to 39 ± 0.5 μm, by adjusting the height of the microfluidic channels, with predictable opportunities for scaling up. Therefore, our strategy provides a facile route to produce advanced thin polymer films in a universal, steerable, and scalable manner and will promote the applications of thin polymer films in biosensors and wearable electronics. [ABSTRACT FROM AUTHOR]

The ongoing coronavirus disease 2019 (COVID-19) pandemic has boosted the development of antiviral research. Microfluidic technologies offer powerful platforms for diagnosis and drug discovery for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) diagnosis and drug discovery. In this review, we introduce the structure of SARS-CoV-2 and the basic knowledge of microfluidic design. We discuss the application of microfluidic devices in SARS-CoV-2 diagnosis based on detecting viral nucleic acid, antibodies, and antigens. We highlight the contribution of lab-on-a-chip to manufacturing point-of-care equipment of accurate, sensitive, low-cost, and user-friendly virus-detection devices. We then investigate the efforts in organ-on-a-chip and lipid nanoparticles (LNPs) synthesizing chips in antiviral drug screening and mRNA vaccine preparation. Microfluidic technologies contribute to the ongoing SARS-CoV-2 research efforts and provide tools for future viral outbreaks. Microfluidic technologies play an important role in virus pandemic. This review highlights the applications of microfluidic chip in severe acute respiratory syndrome coronavirus 2 detection and drug discovery. [Display omitted] [ABSTRACT FROM AUTHOR]

In recent years, the mechanism based on changing the cross-sectional shape of long and straight channels for increasing mixing efficiency has reached a bottleneck, while the vortex effect brought by curved channels has become a hot topic in current mixer research. The vortex effect should be fully utilized in the mixing process. Inspired by the spiral structure as well as splitting and reorganization, a passive three-dimensional double-helical structure micro-mixer was proposed. It is printed by FDM (fused deposition) technology. First, a model of the double-helix structure was printed with HIPS (high impact polystyrene) material, which was supported by PVA (polyvinyl alcohol) material. The mixing experiments showed that the three-dimensional (3D) double-helix structure could increase the mixing efficiency to 90.6%, while the mixing efficiency of the conventional two-dimensional (2D) T-shaped structure was only 78.5%. In this paper, the effects of the number of turns, pitch, diameter, staggering angle, and flow rate on the mixing effect are compared separately. The results show that the change of staggering angle has a better effect on the improvement of mixing efficiency. [ABSTRACT FROM AUTHOR]

Alginate-based hydrogels are frequently employed in biomedical fields, where their size and uniformity are important for applications such as encapsulating pharmaceuticals or biological agents. In this paper, we study alginate droplet formation in a flow-focusing microfluidic device with a rectangular orifice of 30 × 100 microns in the presence of different types of surfactants in the continuous phase. This study looks at how surfactant type and concentration affect the generation of alginate microdroplets using droplet-based microfluidics, as well as how they affect the created alginate gel beads. To make alginate hydrogels, we used an external ionic cross-linking approach. Alginate hydrogels are formed by on-chip emulsifying a sodium alginate solution in an oil phase and collecting the emulsions in a bath containing calcium ions. Off-chip introduction of the cross-linking agents will reduce clogging issues that are common in droplet microfluidics. The diameter of microdroplets varies depending on the surfactant added to the continuous phase, either Span 80 or Tween 80, and the flow rate ratio between the dispersed and continuous phases. The conditions under which microdroplets form (the flow rate of the continuous phase and the surfactant supplied to it) determine the degree of gelation, shape, size, and monodipersity of hydrogels. Tween 80 emulsification results in the most homogeneous, totally gelled, tail-shaped hydrogels, whereas Span 80 emulsification results in smaller hydrogels with a more irregular size distribution. Using Span 80 resulted in partial gelation, necessitating a change in the collection bath (such as adding ethyl acetate to the oil phase). [ABSTRACT FROM AUTHOR]

Lung‐on‐chips have showed great promise as a tool to recapitulate the respiratory system for investigation of lung diseases in the past decade. However, the commonly applied artificial elastic membrane (e.g., polydimethylsiloxane, PDMS) in the chip failed to mimic the alveolar basal membrane in the composition and mechanical properties. Here we replaced the PDMS film by a thin, biocompatible, soft, and stretchable membrane based on F127‐DA hydrogel that well approached to the composition and stiffness of extracellular matrix in human alveoli for construction of lung‐on‐a‐chip. This chip well reconstructed the mechanical microenvironments in alveoli so that the epithelial/endothelial functions were highly expressed with a well established alveolar‐capillary barrier. In opposite to the unexpectedly accelerated fibrotic process on the PDMS‐based lung‐on‐a‐chip, HPAEpiCs on hydrogel‐based chip only presented fibrosis under nonphysiologically high strain, well reflecting the features of pulmonary fibrosis in vivo. This physiologically relevant lung‐on‐a‐chip would be an ideal model in investigation of lung diseases and for development of antifibrosis drugs. [ABSTRACT FROM AUTHOR]

Microfluidic chips have the advantages of miniaturization, integration, and portability, and are widely used in the early diagnosis of major diseases, personalized medical treatment, environmental detection, health quarantine, and other fields. The existing microfluidic chip manufacturing process is difficult to operate because of complex three-dimensional channels, complicated manufacturing steps, limited printing materials, the difficulty of operating the bonding process, and the need to purchase expensive new equipment. In this paper, an integrated molding method for microfluidic chips that integrates 3D printing and polymer dissolution technology is proposed. First, the channel mold of poly(vinyl alcohol) (PVA) or high impact polystyrene (HIPS) is dissolved to complete the manufacturing of the microfluidic chip channel. The integrated 3D-forming method of microfluidic chips proposed in this paper can manufacture microchannels inside the microfluidic chip, avoid the bonding process, and eliminate the need for rapid alignment of microchannels, material modification, and other operations, thus improving the stability of the process. Finally, by comparing the microchannels made by PVA and HIPS, it is concluded that the quality of the microchannels made by HIPS is obviously better than that made by PVA. This paper provides a new idea for the fabrication of microfluidic chips and the application of HIPS. [ABSTRACT FROM AUTHOR]

Featured Application: This study is a novel, simple, and low-cost device demonstration for cell separation applications. Simple and rapid fabrication of microfluidic devices can enable widespread implementation of lab-on-chip devices in resource-limited environments. However, currently most of the microfluidic devices are fabricated in cleanroom facilities that are well-funded and not accessible to most of the researchers in developing countries. Herein, a simple, low-cost, and reliable method is shown to fabricate microfluidic devices for separating cells and bacteria-size microparticles. For this purpose, serpentine and spiral microfluidic channels are designed and fabricated using rapid laser prototyping. This single inlet microfluidic device is shown to successfully separate yeast cells and smaller microparticles with an efficiency of 85% which is very promising for many lab-on-chip applications including cell-based diagnostics and therapeutics. [ABSTRACT FROM AUTHOR]

Copyright of International Journal of Engineering Research & Development (IJERAD) is the property of International Journal of Engineering Research & Development and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Protein biomarkers in nasal secretions can be used as a measure to differentiate between allergies, airway diseases and infections for non-invasive diagnostics. The point-of-care quantification of biomarker levels using flow-based microarray facilitates precise and rapid diagnosis and displays the potential for targeted and effective treatment. For the first time, we developed a flow-based chemiluminescence sandwich microarray immunoassay (CL-SMIA) for the quantification of nasal interferon-beta (IFN-β) on the Microarray Chip Reader-Research (MCR-R). Polycarbonate foils are used as a cost-effective surface for immobilizing capture antibodies. By using a commercially available set of anti-human IFN-β antibodies, the CL-SMIA can be compared directly to an enzyme-linked immunosorbent assay (ELISA) performed in microtiter plates concerning the bioanalytical performance and economic issues. Pre-incubation of the sample with detection antibodies facilitates the lower consumption of detection antibodies, as this allows for a longer interaction time between the antibody and the biomarker. The direct injection of pre-incubated samples into the microarray chips eliminates the adsorption of proteins in the tubing as well as the contamination of the tubing and valves of the MCR-R with clinical samples. The small flow cell allows for a low sample volume of 50 μL. The limit of detection of 4.53 pg mL−1 was slightly increased compared to a sandwich ELISA performed on microtiter plates which were 1.60 pg mL−1. The possibility to perform the CL-SMIA in a multiplexed mode makes it a promising assay for the rapid and cost-effective non-invasive detection of biomarkers in nasal secretions. [ABSTRACT FROM AUTHOR]

Double-end clamped beam is one of the most important miniaturized structures in microelectromechanical systems (MEMS). In recent years, they have achieved extensive application in a variety of fields, including environmental monitoring, food detection, and disease diagnosis, since they have high sensitivity, high throughput, good specification and fast response. To meet the market demand for precise three-dimensional microstructures and tiny device sizes, the rationalization of the process design of micro-nano technology is essential. In previous research, the function of the microcantilever sensor was finally realized through eight lithography cycles. High performance piezoresistive microcantilever arrays were successfully developed with a yield of 90% in our work. In this paper, a hollow composite microfluidic double-end clamped beam structure is proposed, a reasonable process flow is developed. Simulations show that the hollow microfluidic structure's sensitivity can reach the order of 10-12 g, and the quality factor is nearly stable above 10,000. It is crucial for the development of double-end clamped beam sensors because it offers a low-cost, portable, and rapid detection method for the detection of biomolecules. [ABSTRACT FROM AUTHOR]

Background: Neuronal networks receive and deliver information to regulate bodily functions while the vascular network provides oxygen, nutrients, and signaling molecules to tissues. Neurovascular interactions are vital for both tissue development and maintaining homeostasis in adulthood; these two network systems align and reciprocally communicate with one another. Although communication between network systems has been acknowledged, the lack of relevant in vitro models has hindered research at the mechanistic level. For example, the current used in vitro neurovascular models are typically established to be short-term (≤ 7 days) culture models, and they miss the supporting vascular mural cells. Methods: In this study, we utilized human induced pluripotent stem cell (hiPSC) -derived neurons, fluorescence tagged human umbilical vein endothelial cells (HUVECs), and either human bone marrow or adipose stem/stromal cells (BMSCs or ASCs) as the mural cell types to create a novel 3D neurovascular network-on-a-chip model. Collagen 1–fibrin matrix was used to establish long-term (≥ 14 days) 3D cell culture in a perfusable microphysiological environment. Results: Aprotinin-supplemented endothelial cell growth medium-2 (EGM-2) supported the simultaneous formation of neuronal networks, vascular structures, mural cell differentiation, and the stability of the 3D matrix. The formed neuronal and vascular networks were morphologically and functionally characterized. Neuronal networks supported vasculature formation based on direct cell contacts and by dramatically increasing the secretion of angiogenesis-related factors in multicultures in contrast to cocultures without neurons. Both utilized mural cell types supported the formation of neurovascular networks; however, the BMSCs seemed to boost neurovascular networks to greater extent. Conclusions: Overall, our study provides a novel human neurovascular network model that is applicable for creating in vivo-like tissue models with intrinsic neurovascular interactions. The 3D neurovascular network model on chip forms an initial platform for the development of vascularized and innervated organ-on-chip and further body-on-chip concepts and offers the possibility for mechanistic studies on neurovascular communication both under healthy and in disease conditions. DtMPMfM_nPvk_pFj8pUo8r Video Abstract [ABSTRACT FROM AUTHOR]

Fluorescence-based detection techniques are part of an ever-expanding field and are widely used in biomedical and environmental research as a biosensing tool. These techniques have high sensitivity, selectivity, and a short response time, making them a valuable tool for developing bio-chemical assays. The endpoint of these assays is defined by changes in fluorescence signal, in terms of its intensity, lifetime, and/or shift in spectrum, which is monitored using readout devices such as microscopes, fluorometers, and cytometers. However, these devices are often bulky, expensive, and require supervision to operate, which makes them inaccessible in resource-limited settings. To address these issues, significant effort has been directed towards integrating fluorescence-based assays into miniature platforms based on papers, hydrogels, and microfluidic devices, and to couple these assays with portable readout devices like smartphones and wearable optical sensors, thereby enabling point-of-care detection of bio-chemical analytes. This review highlights some of the recently developed portable fluorescence-based assays by discussing the design of fluorescent sensor molecules, their sensing strategy, and the fabrication of point-of-care devices. [ABSTRACT FROM AUTHOR]

Fraunhofer EMFT's research and manufacturing portfolio includes piezoelectrically actuated silicon micro diaphragm pumps with passive flap valves. Research and development in the field of microfluidics have been dedicated for many years to the use of micropumps for generating positive and negative pressures, as well as delivering various media. However, for some applications, only small amounts of fluid need to be pumped, compressed, or evacuated, and until now, only macroscopic pumps with high power consumption have been able to achieve the necessary flow rate and pressure, especially for compressible media such as air. To address these requirements, one potential approach is to use a multistage of high-performing micropumps optimized to negative pressure. In this paper, we present several possible ways to cascade piezoelectric silicon micropumps with passive flap valves to achieve these stringent requirements. Initially, simulations are conducted to generate negative pressures with different cascading methods. The first multistage option assumes pressure equalization over the piezo-actuator by the upstream pump, while for the second case, the actuator diaphragm operates against atmospheric pressure. Subsequently, measurement results for the generation of negative gas pressures down to −82.1 kPa relative to atmospheric pressure (19.2 kPa absolute) with a multistage of three micropumps are presented. This research enables further miniaturization of many applications with high-performance requirements for micropumps, achievable with these multistage systems. [ABSTRACT FROM AUTHOR]

The development of microelectronic devices has increased the need for a power supply with high power density for long-term operation. In this article, microfluidic fuel cells (MFCs) are first introduced, and second, due to the significant effect of mass transfer on their performance, mass transfer in these fuel cells is investigated. MFCs have small dimensions and simple geometry, and formic acid and oxygen dissolved in sulfuric acid are usually used as fuel and oxidizers, respectively. The equations of continuity, momentum, and mass transfer have been solved in three dimensions using Open-Foam open-source software to model the MFC and then validated, with the results available in the references. Fick's equation was used to calculate the rate of diffusion, and the Butler-Volmer equation was used to calculate the rates of electrochemical reactions in catalyst layers. Preliminary results indicated that the performance of this fuel cell is greatly limited by poor fuel utilization, which is consistent with the experimental data. The flow is fully developed in this short distance from the inlet, and in the fully developed area, the ratio Umax/U is equal 2.1. The mixing zone located at the interface of fuel and oxidizer is in the shape of an hourglass in the cross-section, and as the inlet velocity increases, its thickness decreases along the channel. Also, as the flow moves along the channel, the thickness of the layer with a low concentration near the electrodes increases. [ABSTRACT FROM AUTHOR]

Human red blood cells (RBCs) are highly studied by researchers and clinicians alike because RBCs play an essential role in medical diagnostics. RBCs are the most abundant component of whole blood. The accurate analysis of blood samples for blood cells is crucial to help diagnose and management of several life-threatening diseases. Current techniques for analyzing blood cell counts are time-consuming and expensive, requiring a highly trained technician. Implementing a portable, label-free method enables analysis at small clinics and remote locations with reduced times of analysis and cost. The development of miniature, handheld shear-horizontal surface acoustic wave (SH-SAW) biosensors capable of accurately counting RBCs in liquid samples will improve medical diagnostics in resourcelimited regions of the United States and parts of the world where access to centralized clinical laboratories is limited. A shear-horizontal surface acoustic wave is a horizontally polarized surface acoustic wave that is produced by a transducer that is fabricated onto a piezoelectric substrate such as lithium tantalate, lithium niobite, or quartz. We report a lithium tantalate SH-SAW biosensor and method for monitoring the RBC level (hematocrit level) from a whole blood sample using a shear-horizontal surface acoustic wave (SH-SAW) biosensor that uses a 500-picoliter sample well. Samples were introduced by directly pipetting whole blood onto the sample reservoir and washing away any excess material. The SH-SAW biosensor uses an immunoassay, where the antibody anti-glycophorin A is coated on the surface of the active area of the sensor. The sample is compared to a reference sample. Using Microsoft Excel statistical tools, we showed that the results demonstrate the concentration dependence of the samples with an average coefficient of variance (CV) within a sample group was 10% or less for all samples analyzed. Our successful demonstration offers proof of concept for handheld blood cell monitors for remote and resource-limited applications. To our knowledge, this is the first demonstration of an SH-SAW device being used for monitoring red blood cell counts. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central China Normal University is the property of Huazhong Normal University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

One of the key thrusts in three-dimensional (3D) printing and direct writing is to seamlessly vary composition and functional properties in printed constructs. Most inks used for extrusion-based printing, however, are compositionally static and available approaches for dynamic tuning of ink composition remain few. Here, we present an approach to modulate extruded inks at the point of print, using droplet inclusions. Using a glass capillary microfluidic device as the printhead, we dispersed droplets in a polydimethylsiloxane (PDMS) continuous phase and subsequently 3D printed the resulting emulsion into a variety of structures. The mechanical characteristics of the 3D-printed constructs can be tuned in situ by varying the spatial distribution of droplets, including aqueous and liquid metal droplets. In particular, we report the use of poly(ethylene glycol) diacrylate (PEGDA) aqueous droplets for local PDMS chemistry alteration resulting in significant softening (85% reduced elastic modulus) of the 3D-printed constructs. Furthermore, we imparted magnetic functionality in PDMS by dispersing ferrofluid droplets and rationally designed and printed a rudimentary magnetically responsive soft robotic actuator as a functional demonstration of our droplet-based strategy. Our approach represents a continuing trend of adapting microfluidic technology and principles for developing the next generation of additive manufacturing technology.

Human neural stem and progenitor cells (hNSPCs) have therapeutic potential to treat neural diseases and injuries since they provide neuroprotection and differentiate into astrocytes, neurons, and oligodendrocytes. However, cultures of hNSPCs are heterogeneous, containing cells linked to distinct differentiated cell fates. HNSPCs that differentiate into astrocytes are of interest for specific neurological diseases, creating a need for approaches that can detect and isolate these cells. Astrocyte-biased hNSPCs differ from other cell types in electrophysiological properties, namely membrane capacitance, and we hypothesized that this could be used to enrich these cells using dielectrophoresis (DEP). We implemented a two-step DEP sorting scheme, consisting of analysis to define the optimal sorting frequency followed by separation of cells at that frequency, to test whether astrocyte-biased cells could be separated from the other cell types present in hNSPC cultures. We developed a novel device that increased sorting reproducibility and provided both enriched and depleted cell populations in a single sort. Astrocyte-biased cells were successfully enriched from hNSPC cultures by DEP sorting, making this the first study to use electrophysiological properties for label-free enrichment of human astrocyte-biased cells. Enriched astrocyte-biased human cells enable future experiments to determine the specific properties of these important cells and test their therapeutic efficacy in animal models of neurological diseases.

Droplet microfluidics enables studying large cell populations in chemical isolation, at a single-cell resolution. Applications include studying cellular response to drugs, cell-to-cell interaction studies. Such applications need a reliable and repeatable droplet generation with high monodispersity. Most systems used in research rely on manual tuning of flow parameters on off-the-shelf instruments. Setups are highly customized, limiting reproduction of experimental results. We propose an integrated, modular system for automated aqueous droplet generation with high monodispersity. The system provides dynamic feedback control of droplet size and input pressure. Input pressure is generated by two piezoelectric micropumps. Droplet sizes are determined via light intensity measurement in an LED-photodiode setup. The system is capable of wireless communication and has a low enough power consumption for battery-powered operation. We report on the assembly and the underlying working principle, as well as an in-depth experimental evaluation of the performance of the proof-of-concept prototype in aqueous droplet generation. Evaluation was performed on a modular as well as on a system level. During module-level evaluations, aqueous droplets were generated in a light mineral oil + Span 80 surfactant carrier medium, using 3 different flow-focusing junction geometries. The presented prototype had a significantly faster pressure stabilization time (10 s) compared to a syringe pump-based reference setup (120 s). During system-level evaluation, deionized water droplets were generated in a carrier medium of HFE7500 + PEG-PFPE triblock surfactant. Resultant droplet sizes were benchmarked with microscopy. The system was able to repeatedly generate mono- and polydisperse droplets on demand, with CVs between 5-10% in the $\sim $ 50- $200 \mu \text{m}$ droplet diameter range.

With the development of modern medicine, the research methods of occurrence, development and treatment of orthopedic diseases are developing rapidly. The microenvironment provided by traditional orthopedic research methods differ considerably from the human body, resulting in poor or inconsistent conclusions in previous studies. Microfluidic technology has shown its advantages in the field of orthopedic research, especially in providing bionic mechanical stimulation environment. The microfluidic device can simulate the complex internal environment through the fine and complex structure and perfusion control system, and provide a stable, controllable and efficient culture system. Moreover, it can serve as a manufacturing device, which can produce bone grafts or bone like organs for tissue engineering with bionic structure. It can also simultaneously act as a detection device, which can realize high-throughput detection of small samples at low cost. In addition, we can establish in vitro physiological or pathological models on microfluidic systems to assist in the diagnosis and treatment of orthopedic diseases. This paper reviews the medical application of microfluidic devices in orthopedics.

In this study, a more efficient, convenient, and cost-effective way was proposed to design and fabricate a polydimethylsiloxane (PDMS) microfluidic device using 3D printing and transfer techniques. Typically, sensor measurements can only be conducted by immersing the sensor in a solution under static conditions. However, in this study, a newly designed microfluidic device combined with a microfluidic system enables dynamic measurements with sensors. By controlling the flow and temperature of the test liquid, the physiological environment of the human body under various conditions can be simulated, resulting in more accurate and realistic data. During the dynamic condition, an average sensitivity of 6.396 mV/(mg/dL) and linearity of 0.999 were obtained at a flow rate of $75.0 \mu \text{L}$ /min. When the temperature was at 37°C, the biosensor achieved an average sensitivity of 4.381 mV/(mg/dL) and a linearity of 0.999. The dynamic response time was 7 seconds, and the drift rate was 1.47 mV/hr. The experimental results obtained under dynamic conditions showed a significant improvement in the sensing characteristics of the urea biosensor compared with the results obtained under static conditions.

Abstract Background Astrocytes play a crucial, yet not fully elucidated role in the selective motor neuron pathology in amyotrophic lateral sclerosis (ALS). Among other responsibilities, astrocytes provide important neuronal homeostatic support, however this function is highly compromised in ALS. The establishment of fully human coculture systems can be used to further study the underlying mechanisms of the dysfunctional intercellular interplay, and has the potential to provide a platform for revealing novel therapeutic entry points. Methods In this study, we characterised human induced pluripotent stem cell (hiPSC)-derived astrocytes from FUS-ALS patients, and incorporated these cells into a human motor unit microfluidics model to investigate the astrocytic effect on hiPSC-derived motor neuron network and functional neuromuscular junctions (NMJs) using immunocytochemistry and live-cell recordings. FUS-ALS cocultures were systematically compared to their CRISPR-Cas9 gene-edited isogenic control systems. Results We observed a dysregulation of astrocyte homeostasis, which resulted in a FUS-ALS-mediated increase in reactivity and secretion of inflammatory cytokines. Upon coculture with motor neurons and myotubes, we detected a cytotoxic effect on motor neuron-neurite outgrowth, NMJ formation and functionality, which was improved or fully rescued by isogenic control astrocytes. We demonstrate that ALS astrocytes have both a gain-of-toxicity and loss-of-support function involving the WNT/β-catenin pathway, ultimately contributing to the disruption of motor neuron homeostasis, intercellular networks and NMJs. Conclusions Our findings shine light on a complex, yet highly important role of astrocytes in ALS, and provides further insight in to their pathological mechanisms. Graphical Abstract

Abstract Background In 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. Results Here 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. Conclusion The 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 Abstract

Yuri Sugimoto,1,2,&ast; Tadaharu Suga,1,&ast; Naoya Kato,1 Mizuki Umino,1 Asako Yamayoshi,2 Hidefumi Mukai,1,3 Shigeru Kawakami1 1Department of Pharmaceutical Informatics, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan; 2Department of Chemistry of Functional Molecules, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan; 3Laboratory for Molecular Delivery and Imaging Technology, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan&ast;These authors contributed equally to this workCorrespondence: Shigeru Kawakami, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, Nagasaki-shi, Nagasaki, 852-8588, Japan, Tel/Fax +81 95 819 8563, Email skawakam@nagasaki-u.ac.jpIntroduction: Targeted liposomes using ligand peptides have been applied to deliver therapeutic agents to the target sites. The post-insertion method is commonly used because targeted liposomes can be prepared by simple mixing of ligand peptide-lipid and liposomes. A large-scale preparation method is required for the clinical application of ligand-peptide-modified liposomes. Large-scale preparation involves an increase in volume and a change in the preparation conditions. Therefore, the physicochemical properties of liposomes may change owing to large alterations in the preparation conditions. To address this issue, we focused on a microfluidic device and developed a novel ligand peptide modification method, the microfluidic post-insertion method.Methods: We used integrin αvβ 3-targeted GRGDS (RGD) and cyclic RGDfK (cRGD)-modified high functionality and quality (HFQ) lipids, which we had previously developed. First, the preparation conditions of the total flow rate in the microfluidic device for modifying HFQ lipids to polyethylene glycol (PEG)-modified (PEGylated) liposomes were optimized by evaluating the physicochemical properties of the liposomes. The targeting ability of integrin αvβ 3-expressing colon 26 murine colorectal carcinoma cells was evaluated by comparing the cellular association properties of the liposomes prepared by the conventional post-insertion method.Results: When the RGD-HFQ lipid was modified into PEGylated liposomes by varying the total flow rate (1, 6, and 12 mL/min) of the microfluidic device, as the total flow rate increased, the polydispersity index also increased, whereas the particle size did not change. Furthermore, the RGD- and cRGD-modified PEGylated liposomes prepared at a total flow rate of 1 mL/min showed high cellular association properties equivalent to those prepared by the conventional post-insertion method.Conclusion: Microfluidic post-insertion method of HFQ lipids might be useful for clinical application and large-scale preparation of targeted liposomes.Keywords: liposomes, targeting, post-insertion method, polyethylene glycol, microfluidic

In-situ oral delivery of therapeutic antibodies, like monoclonal antibody, for chronic inflammation treatment is the most convenient approach compared with other administration routes. Moreover, the abundant links between the gut microbiota and colonic inflammation indicate that the synergistic or antagonistic effect of gut microbiota to colonic inflammation. However, the antibody activity would be significantly affected while transferring through the gastrointestinal tract due to hostile conditions. Moreover, these antibodies have short serum half-lives, thus, require to be frequently administered with high doses to be effective, leading to low patient tolerance. Here, we develop a strategy utilizing thin shell hydrogel microcapsule fabricated by microfluidic technique as the oral delivering carrier. By encapsulating antibodies in these microcapsules, antibodies survive in the hostile gastrointestinal environment and rapidly release into the small intestine through oral administration route, achieving the same therapeutic effect as the intravenous injection evaluated by a colonic inflammation disease model. Moreover, the abundance of some intestinal microorganisms as the indication of the improvement of inflammation has remarkably altered after in-situ antibody-laden microcapsules delivery, implying the restoration of micro-ecology of the intestine. These findings prove our microcapsules are exploited as an efficient oral delivery agent for antibodies with programmable function in clinical application.

Abstract A contiguous carbonate‐rich hydroxyapatite microcoating in a microfluidic device represents a substrate that has chemical and structural similarity to bone mineral. The present work describes a low‐temperature method to deposit a carbonate‐rich hydroxyapatite microcoating on a glass slide and its incorporation within the microchannels of a microfluidic device. A glass slide is covered/masked with polypropylene‐based tape and CaCO3 nanoparticles are deposited on exposed areas by convective self assembly. The precursor CaCO3 is converted to carbonate‐rich hydroxyapatite by dissolution‐recrystallization in phosphate‐buffered saline. The microcoating is aligned/incorporated within a microchannel when the underlying glass is bonded to a polydimethylsiloxane structure with the device layout. X‐ray diffraction, laser Raman microspectroscopy, and X‐ray photoelectron spectroscopy indicate that the microcoating was comprised of carbonate‐rich hydroxyapatite. Scanning electron microscopy and 3D laser confocal microscopy showed that was comprised of nanocrystalline rod‐like clusters that collectively exhibit a thickness of ∼20 µm. Monocultures/cocultures of osteoblast‐lineage (MC3T3‐E1, MG63) and preosteoclast‐lineage (RAW 264.7) cells were performed. Osteoblast‐lineage cells adhered to the microcoating and deposited an extracellular matrix of collagen fibrils and mineral accretions. Mineralization was detected in/near the inlet wells. The microcoating is analogous to bone mineral and could be applied to various layouts and mineral systems.

Postmenopausal osteoporosis is one of the most prevalent skeletal disorders in women and is featured by the imbalance between intraosseous vascularization and bone metabolism. In this study, a pH‐responsive shell–core structured micro/nano‐hydrogel microspheres loaded with polyhedral oligomeric silsesquioxane (POSS) using gas microfluidics and ionic cross‐linking technology are developed. This micro/nano‐hydrogel microsphere system (PDAP@Alg/Cs) can achieve oral delivery, intragastric protection, intestinal slow/controlled release, active targeting to bone tissue, and thus negatively affecting intraosseous angiogenesis and osteoclastogenesis. According to biodistribution data, PDAP@Alg/Cs can successfully enhance drug intestinal absorption and bioavailability through intestine adhesion and bone targeting after oral administration. In vitro and in vivo experiments reveal that PDAP@Alg/Cs promoted type H vessel formation and inhibited bone resorption, effectively mitigating bone loss by activating HIF‐1α/VEGF signaling pathway and promoting heme oxygenase‐1 (HO‐1) expression. In conclusion, this novel oral micro/nano‐hydrogel microsphere system can simultaneously accelerate intraosseous vascularization and decrease bone resorption, offering a brand‐new approach to prevent postmenopausal osteoporosis. [ABSTRACT FROM AUTHOR]

A concept of a microfluidic fluorescent chemical sensing system is presented and demonstrated as a sensor for measurement of dissolved oxygen in water. The system utilizes on-line mixing of a fluorescent reagent with the analyzed sample, while it measures the fluorescence decay time of the mixture. The system is built entirely out of silica capillaries and optical fibers, and allows for very low consumption of the reagent (of the order of mL/month) and the analyzed sample (of the order of L/month). The proposed system can, thus, be applied to continuous on-line measurements, while utilizing a broad variety of different and proven fluorescent reagents or dyes. The proposed system allows for the use of relatively high-excitation light powers, as the flow-through concept of the system reduces the probability of the appearance of bleaching, heating, or other unwanted effects on the fluorescent dye/reagent caused significantly by the excitation light. The high amplitudes of fluorescent optical signals captured by an optical fiber allow for low-noise and high-bandwidth optical signal detection, and, consequently, the possibility for utilization of reagents with nanosecond fluorescent lifetimes. [ABSTRACT FROM AUTHOR]

The pumping mechanism in multi‐inlet microfluidic channels usually requires multiple micropumps to be separately attached to each inlet. Unfortunately, this may create fluid leakage resulting from a considerably high internal pressure. To address this, a passive sub‐atmospheric pressure‐inducing micropump is proposed and its performance is characterized as a function of the flow rate and the gauge pressure. With this pump, a sufficiently high flow rate is generated, comparable to some active‐piezoelectric micropumps. The gauge pressure is exponentially descending with time and can be crudely classified into three regions of high, moderate, and slow pressure‐release times. Overall, the stabilized pressure is identified within 70 s < t ≤ 300 s for slow rate mixing while rapid mixing is applicable at t ≤ 70 s. [ABSTRACT FROM AUTHOR]

Renal cell carcinoma (RCC) presents as metastatic disease in one third of cases. Research on circulating tumor cells (CTCs) and liquid biopsies is improving the understanding of RCC biology and metastases formation. However, a standardized, sensitive, specific, and cost-effective CTC detection technique is lacking. The use of platforms solely relying on epithelial markers is inappropriate in RCC due to the frequent epithelial-mesenchymal transition that CTCs undergo. This study aimed to test and clinically validate RUBYchip™, a microfluidic label-free CTC detection platform, in RCC patients. The average CTC capture efficiency of the device was 74.9% in spiking experiments using three different RCC cell lines. Clinical validation was performed in a cohort of 18 patients, eight non-metastatic (M0), five metastatic treatment-naïve (M1TN), and five metastatic progressing-under-treatment (M1TP). An average CTC detection rate of 77.8% was found and the average (range) total CTC count was 6.4 (0–27), 101.8 (0–255), and 3.2 (0–10), and the average mesenchymal CTC count (both single and clustered cells) was zero, 97.6 (0–255), and 0.2 (0–1) for M0, M1TN, and M1TP, respectively. CTC clusters were detected in 25% and 60% of M0 and M1TN patients, respectively. These results show that RUBYchip™ is an effective CTC detection platform in RCC. [ABSTRACT FROM AUTHOR]

Microbial pathogens have threatened the world due to their pathogenicity and ability to spread in communities. The conventional laboratory‐based diagnostics of microbes such as bacteria and viruses need bulky expensive experimental instruments and skilled personnel which limits their usage in resource‐limited settings. The biosensors‐based point‐of‐care (POC) diagnostics have shown huge potential to detect microbial pathogens in a faster, cost‐effective, and user‐friendly manner. The use of various transducers such as electrochemical and optical along with microfluidic integrated biosensors further enhances the sensitivity and selectivity of detection. Additionally, microfluidic‐based biosensors offer the advantages of multiplexed detection of analyte and the ability to deal with nanoliters volume of fluid in an integrated portable platform. In the present review, we discussed the design and fabrication of POCT devices for the detection of microbial pathogens which include bacteria, viruses, fungi, and parasites. The electrochemical techniques and current advances in this field in terms of integrated electrochemical platforms that include mainly microfluidic‐ based approaches and smartphone and Internet‐of‐things (IoT) and Internet‐of‐Medical‐Things (IoMT) integrated systems have been highlighted. Further, the availability of commercial biosensors for the detection of microbial pathogens will be briefed. In the end, the challenges while fabrication of POC biosensors and expected future advances in the field of biosensing have been discussed. The integrated biosensor‐based platforms with the IoT/IoMT usually collect the data to track the community spread of infectious diseases which would be beneficial in terms of better preparedness for current and futuristic pandemics and is expected to prevent social and economic losses. [ABSTRACT FROM AUTHOR]

A new microfluidic device to enhance the enrichment factor in miniaturized systems is proposed. The microfluidic system was design for liquid phase microextractions, and it was applied to the simultaneous extraction of acidic compounds of a wide range of polarity (0.5 < log P < 3). The device operated under stagnant acceptor phase conditions and all the operational parameters involved were optimized. Tributyl phosphate was found to be a new highly efficient supported liquid membrane to simultaneously extract analytes of very different polarities. The optimal donor and acceptor phase were pH 2 and pH 13, respectively. The donor flow rate and the extraction time were investigated simultaneously, offering great versatility with high enrichment factors (EFs). Limits of quantitation were within 0.02 and 0.09 µg mL−1 for all compounds at 10 µL min−1 as donor flow rate and 20-min extractions, offering EFs between 11 and 18 with only 200-µL sample volume consumption. The method was successfully applied to human urine samples, observing recoveries between 47 and 90% for all compounds. This new proposed microfluidic system increases the wide range of applications, especially when the analytes are present in lower concentrations in the sample. [ABSTRACT FROM AUTHOR]

Loop-mediated isothermal amplification (LAMP) is a rapid and high-yield amplification technology for specific DNA or RNA molecules. In this study, we designed a digital loop-mediated isothermal amplification (digital-LAMP)-functioning microfluidic chip to achieve higher sensitivity for detection of nucleic acids. The chip could generate droplets and collect them, based on which we could perform Digital-LAMP. The reaction only took 40 min at a constant temperature of 63 °C. The chip enabled highly accurate quantitative detection, with the limit of detection (LOD) down to 102 copies μL−1. For better performance while reducing the investment of money and time in chip structure iterations, we used COMSOL Multiphysics to simulate different droplet generation ways by including flow-focusing structure and T-junction structure. Moreover, the linear structure, serpentine structure, and spiral structure in the microfluidic chip were compared to study the fluid velocity and pressure distribution. The simulations provided a basis for chip structure design while facilitating chip structure optimization. The digital-LAMP-functioning chip proposed in the work provides a universal platform for analysis of viruses. [ABSTRACT FROM AUTHOR]

Intracortical neural probes are both a powerful tool in basic neuroscience studies of brain function and a critical component of brain computer interfaces (BCIs) designed to restore function to paralyzed patients. Intracortical neural probes can be used both to detect neural activity at single unit resolution and to stimulate small populations of neurons with high resolution. Unfortunately, intracortical neural probes tend to fail at chronic timepoints in large part due to the neuroinflammatory response that follows implantation and persistent dwelling in the cortex. Many promising approaches are under development to circumvent the inflammatory response, including the development of less inflammatory materials/device designs and the delivery of antioxidant or anti-inflammatory therapies. Here, we report on our recent efforts to integrate the neuroprotective effects of both a dynamically softening polymer substrate designed to minimize tissue strain and localized drug delivery at the intracortical neural probe/tissue interface through the incorporation of microfluidic channels within the probe. The fabrication process and device design were both optimized with respect to the resulting device mechanical properties, stability, and microfluidic functionality. The optimized devices were successfully able to deliver an antioxidant solution throughout a six-week in vivo rat study. Histological data indicated that a multi-outlet design was most effective at reducing markers of inflammation. The ability to reduce inflammation through a combined approach of drug delivery and soft materials as a platform technology allows future studies to explore additional therapeutics to further enhance intracortical neural probes performance and longevity for clinical applications. [ABSTRACT FROM AUTHOR]