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Nucleic acid amplification tests (NAATs)integrated on a chip hold great promise for point‐of‐care diagnostics. Currently, nucleic acid (NA) purification remains time‐consuming and labor‐intensive, and it takes extensive efforts to optimize the amplification chemistry. Using selective electrokinetic concentration, we report one‐step, liquid‐phase NA purification that is simpler and faster than conventional solid‐phase extraction. By further re‐concentrating NAs and performing polymerase chain reaction (PCR) in a microfluidic chamber, our platform suppresses non‐specific amplification caused by non‐optimal PCR designs. We achieved the detection of 5 copies of M. tuberculosis genomic DNA (equaling 0.3 cell) in real biofluids using both optimized and non‐optimal PCR designs, which is 10‐ and 1000‐fold fewer than those of the standard bench‐top method, respectively. By simplifying the workflow and shortening the development cycle of NAATs, our platform may find use in point‐of‐care diagnosis. [ABSTRACT FROM AUTHOR]

Nucleic acid amplification tests (NAATs)integrated on a chip hold great promise for point‐of‐care diagnostics. Currently, nucleic acid (NA) purification remains time‐consuming and labor‐intensive, and it takes extensive efforts to optimize the amplification chemistry. Using selective electrokinetic concentration, we report one‐step, liquid‐phase NA purification that is simpler and faster than conventional solid‐phase extraction. By further re‐concentrating NAs and performing polymerase chain reaction (PCR) in a microfluidic chamber, our platform suppresses non‐specific amplification caused by non‐optimal PCR designs. We achieved the detection of 5 copies of M. tuberculosis genomic DNA (equaling 0.3 cell) in real biofluids using both optimized and non‐optimal PCR designs, which is 10‐ and 1000‐fold fewer than those of the standard bench‐top method, respectively. By simplifying the workflow and shortening the development cycle of NAATs, our platform may find use in point‐of‐care diagnosis. [ABSTRACT FROM AUTHOR]

The regulation effect of surface charges on the transport of electrons in nanomaterials and ions in nanofluidic devices has been widely used to develop highly sensitive and label-free electrical biosensors. The intrinsic limitation to the clinical application of surface charge-effect nano-electrical biosensors is that they usually do not function in physiological conditions normally with high ionic concentrations (∼160 mM), in which the surface charges are screened within a short distance (＜1 nm at 160 mM). In this work, we developed a general strategy that enables surface charge-effect electrical biomolecular detection in physiological conditions with an integrated mechanism for enhancement of the limit of detection (LOD) by in situ preconcentration of target molecules during incubation and creation of a transient low ionic concentration environment during the signal read-out step using reconfigurable ion concentration polarization (ICP). We demonstrated the effectiveness of this strategy in a simple nanofluidic biosensor named a nanofluidic crystal (NFC), which can be prepared within hours and without expensive equipment. Our results indicate that the ion depletion effect of ICP could lower the ionic concentration by at least 200 fold and provide a stable ionic environment for over 15 s, enabling electrical detection of proteins and DNAs in serum and urine with LODs of 1–10 nM. We further reconfigured the device to preconcentrate target biomolecules before detection using the enrichment effect of ICP, obtaining LODs of 10–100 pM for proteins and DNAs in physiological conditions. By overcoming the inherent constraint on buffer conditions and the issues regarding fabrication, we believe that this work represents significant progress towards the practical application of surface charge-effect nano-electrical biosensors in point-of-care diagnostics and clinical medicine. [ABSTRACT FROM AUTHOR]

With various promising applications demonstrated, nanofluidics has been of broad research interest in the past decade. As nanofluidics matures from a proof of concept towards practical applications, it faces two major barriers: expensive nanofabrication and ultra-low throughput. To date, the only material that enables nanofabrication-free, high-throughput, yet precisely controllable nanofluidic systems is the close-packed nanoparticle array, i.e. nanofluidic crystals. Recently, significant progress in nanofluidics has been made using nanofluidic crystals, including high-current ionic diodes, high-power energy harvesters, efficient biomolecular separation, and facile biosensors. Nanofluidic crystals are seen as a key to applying nanofluidic concepts to real-world applications. In this review, we introduce the key concepts and models in nanofluidic crystals, summarize the fabrication methods, and discuss the various applications of nanofluidic crystals in depth, highlighting their advantages in terms of simple fabrication, low cost, flexibility, and high throughput. Finally, we provide our perspectives on the future of nanofluidic crystals and their potential impacts. [ABSTRACT FROM AUTHOR]

Microfabricated slanted nanofilter arrays are a promising technology for integrated biomolecule analysis systems such as online monitoring and point-of-care quality validation, due to their continuous-flow and one-step operation capability. However, an incomplete understanding of the system limits the performance and wider applications of slanted nanofilter arrays. In this paper, we present rigorous theoretical and experimental studies on macromolecule sieving in a slanted nanofilter array. From both stochastic and kinetic models, an explicit theoretical solution describing size-dependent molecule sieving was derived, which was validated using experimental sieving results obtained for various sieving conditions. Our results not only detail the relationship between sieving conditions and sieving efficiency but also demonstrate that sieving is affected by multiple hindrance effects (electrostatic hindrance), not steric hindrance alone. There is an optimal sieving condition for achieving the greatest separation efficiency for DNAs of a certain size range. Small DNA has great size selectivity in small nanofilters and in weak electric fields, whereas large DNA is present in large nanofilters and in strong electric fields. This study provides insights into designing a slanted nanofilter array for particular target applications and understanding the sieving principles in the nanofilter array. [ABSTRACT FROM AUTHOR]

We have developed novel protein gel electrophoresis techniques, sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) and isoelectric focusing (IEF) in short microchannels (∼millimeters) that take less than a minute. A photopatterning technique was used to cast in situ crosslinked polyacrylamide gel in a microchannel to perform SDS–PAGE. A fluorescent protein marker sample (Mr range of 20000–200000) was separated in less than 30s in less than 2mm of channel length. Crosslinked polyacrylamide gel, patterned in channels using UV light, provides higher sieving power and sample stacking effect, therefore yielding faster and higher-resolution separation in a chip. IEF of proteins was also achieved in a microchannel, and several proteins were focussed within tens of seconds in mm-length channels. As resolution in IEF is independent of separation distance, focusing in ultra-short channels results in not only faster separation but also more concentrated bands potentially allowing detection of low-concentration species. [Copyright &y& Elsevier]

Cytokines, crucial in immune modulation, impact disease progression when their secretion is dysregulated. Existing methods for profiling cytokine secretion suffer from time‐consuming and labor‐intensive processes and often fail to capture the dynamic nature of immune responses. Here, iSECRETE, an integrated platform that enables synchronous cell activation, wash‐free, and target‐responsive protein detection for single‐cell IFN‐γ cytokine secretion analysis within 30 min at room temperature is presented. By incorporating a DNA proximity assay (DPA) into a multifunctional microfluidic system, one‐pot homogenous cytokine signal amplification, with a limit of detection of ≈50 secreted molecules per cell is achieved. iSECRETE can robustly handle various sample types that are shown. Two distinct immune activation assay modalities are demonstrated on iSECRETE. Finally, the detection of single‐cell IFN‐γ secretion as an activation hallmark of chimeric antigen receptor T cells within 6 h of exposure to cancer targets is shown. iSECRETE represents the fastest single‐cell sample‐to‐result cytokine secretion assay to date, providing a powerful tool for advancing the understanding of biological phenotypes, functions, and pathways under in vivo‐like conditions. [ABSTRACT FROM AUTHOR]

Regenerative therapies, including the transplantation of spinal cord progenitor cells (SCPCs) derived from induced pluripotent stem cells (iPSCs), are promising treatment strategies for spinal cord injuries. However, the risk of tumorigenicity from residual iPSCs advocates an unmet need for rapid SCPCs safety profiling. Herein, a rapid (≈3000 cells min‐1) electrical‐based microfluidic biophysical cytometer is reported to detect low‐abundance iPSCs from SCPCs at single‐cell resolution. Based on multifrequency impedance measurements (0.3 to 12 MHz), biophysical features including cell size, deformability, membrane, and nucleus dielectric properties are simultaneously quantified as a cell is hydrodynamically stretched at a cross junction under continuous flow. A supervised uniform manifold approximation and projection (UMAP) model is further developed for impedance‐based quantification of undifferentiated iPSCs with high sensitivity (≈1% spiked iPSCs) and shows good correlations with SCPCs differentiation outcomes using two iPSC lines. Cell membrane opacity (day 1) is also identified as a novel early intrinsic predictive biomarker that exhibits a strong correlation with SCPC differentiation efficiency (day 10). Overall, it is envisioned that this label‐free and optic‐free platform technology can be further developed as a versatile cost‐effective process analytical tool to monitor or assess stem cell quality and safety in regenerative medicine. [ABSTRACT FROM AUTHOR]

Mesenchymal stromal cells (MSCs) are promising candidates for cartilage repair therapy due to their self-renewal, chondrogenic, and immunomodulatory capacities. It is widely recognized that a shift from fetal bovine serum (FBS)-containing medium toward a fully chemically defined serum-free (SF) medium would be necessary for clinical applications of MSCs to eliminate issues such as xeno-contamination and batch-to-batch variation. However, there is a notable gap in the literature regarding the evaluation of the chondrogenic ability of SF-expanded MSCs (SF-MSCs). In this study, we compared the in vivo regeneration effect of FBS-MSCs and SF-MSCs in a rat osteochondral defect model and found poor cartilage repair outcomes for SF-MSCs. Consequently, a comparative analysis of FBS-MSCs and SF-MSCs expanded using two SF media, MesenCult™-ACF (ACF), and Custom StemPro™ MSC SFM XenoFree (XF) was conducted in vitro. Our results show that SF-expanded MSCs constitute variations in morphology, surface markers, senescence status, differentiation capacity, and senescence/apoptosis status. Highly proliferative MSCs supported by SF medium do not always correlate to their chondrogenic and cartilage repair ability. Prior determination of the SF medium's ability to support the chondrogenic ability of expanded MSCs is therefore crucial when choosing an SF medium to manufacture MSCs for clinical application in cartilage repair. [ABSTRACT FROM AUTHOR]

[Display omitted] • Continuous, clogging-free, and ultra-high-throughput continuous microplastic removal. • A robust scaling-up of a mass-producible plastic device. • The first demonstration of 10-liter-scale high-throughput microplastic removal using a microfluidic system. The rapid increase in plastic consumption has accelerated microplastic pollution, raising concerns about potential ecological and health risks. Despite the development and application of various microplastic removal technologies, they exhibit inherent limitations, such as membrane fouling/clogging and low removal efficiency. In this study, we introduce a high-throughput membrane-free microplastic removal system utilizing a plastic spiral inertial microfluidic device. The continuous and clogging-free operational capabilities of spiral inertial microfluidics, coupled with a robust scaling-up of a mass-producible plastic device, allow us to overcome the limitations of conventional microplastic removal methods while meeting the throughput requirements for practical water treatment applications. Utilizing a multiplexed plastic spiral unit, we successfully demonstrated 10-liter-scale high-throughput microplastic removal with a high microparticle removal efficiency (up to ∼99%, depending on particle size) at a harvesting rate of purified water of ∼125 mL/min (not limited and can be further increased by utilizing multiple units in parallel) without any fouling/clogging issue. [ABSTRACT FROM AUTHOR]

Background: Articular cartilage degeneration can result from injury, age, or arthritis, causing significant joint pain and disability without surgical intervention. Currently, the only FDA cell-based therapy for articular cartilage injury is Autologous Chondrocyte Implantation (ACI); however, this procedure is costly, time-intensive, and requires multiple treatments. Mesenchymal stromal cells (MSCs) are an attractive alternative autologous therapy due to their availability and ability to robustly differentiate into chondrocytes for transplantation with good safety profiles. However, treatment outcomes are variable due to donor-to-donor variability as well as intrapopulation heterogeneity and unstandardized MSC manufacturing protocols. Process improvements that reduce cell heterogeneity while increasing donor cell numbers with improved chondrogenic potential during expansion culture are needed to realize the full potential of MSC therapy. Methods: In this study, we investigated the potential of MSC metabolic modulation during expansion to enhance their chondrogenic commitment by varying the nutrient composition, including glucose, pyruvate, glutamine, and ascorbic acid in culture media. We tested the effect of metabolic modulation in short-term (one passage) and long-term (up to seven passages). We measured metabolic state, cell size, population doubling time, and senescence and employed novel tools including micro-magnetic resonance relaxometry (µMRR) relaxation time (T2) to characterize the effects of AA on improved MSC expansion and chondrogenic potential. Results: Our data show that the addition of 1 mM L-ascorbic acid-2-phosphate (AA) to cultures for one passage during MSC expansion prior to initiation of differentiation improves chondrogenic differentiation. We further demonstrate that AA treatment reduced the proportion of senescent cells and cell heterogeneity also allowing for long-term expansion that led to a > 300-fold increase in yield of MSCs with enhanced chondrogenic potential compared to untreated cells. AA-treated MSCs with improved chondrogenic potential showed a robust shift in metabolic profile to OXPHOS and higher µMRR T2 values, identifying critical quality attributes that could be implemented in MSC manufacturing for articular cartilage repair. Conclusions: Our results suggest an improved MSC manufacturing process that can enhance chondrogenic potential by targeting MSC metabolism and integrating process analytic tools during expansion. [ABSTRACT FROM AUTHOR]

Acoustic fields have shown wide utility for micromanipulation, though their implementation in microfluidic devices often requires accurate alignment or highly precise channel dimensions, including in typical standing surface acoustic wave (SSAW) devices and resonant channels. In this work we investigate an approach that permits continuous microscale focusing based on diffractive acoustics, a phenomenon where a time-averaged spatially varying acoustic pressure landscape is produced by bounding a surface acoustic wave (SAW) transducer with a microchannel. By virtue of diffractive effects, this acoustic field is formed with the application of only a single travelling wave. As the field is dictated by the interplay between a propagating substrate-bound wave and a channel geometry, the pressure distribution will be identical for a given channel orientation regardless of its translation on a SAW substrate, and where small variations in channel size have no substantive effect on the pressure field magnitude or overall particle migration. Moreover, in the case of a channel with dimensions on the order of the diffractive fringe pattern spacing, the number of focusing positions will be identical for all channel orientations, with acoustic radiation forces pushing suspended particles to the channel edges. We explore this highly robust particle manipulation technique, determining two distinct sets of streaming and acoustic radiation dominant concentration positions, and show the continuous focusing of polystyrene 1 μm and 0.5 μm diameter particles and fluorescently labeled E. coli bacteria cells at flow rates exceeding those of previous microfluidic implementations for micron and submicron sized particles. [ABSTRACT FROM AUTHOR]

Background: The functional heterogeneity of culture-expanded mesenchymal stem cells (MSCs) has hindered the clinical application of MSCs. Previous studies have shown that MSC subpopulations with superior chondrogenic capacity can be isolated using a spiral microfluidic device based on the principle of inertial cell focusing. Hypothesis: The delivery of microfluidic-enriched chondrogenic MSCs that are consistent in size and function will overcome the challenge of the functional heterogeneity of expanded MSCs and will significantly improve MSC-based cartilage repair. Study Design: Controlled laboratory study. Methods: A next-generation, fully automated multidimensional double spiral microfluidic device was designed to provide more refined and efficient isolation of MSC subpopulations based on size. Analysis of in vitro chondrogenic potential and RNA sequencing was performed on size-sorted MSC subpopulations. In vivo cartilage repair efficacy was demonstrated in an osteochondral injury model in 12-week-old rats. Defects were implanted with MSC subpopulations (n = 6 per group) and compared with those implanted with unsegregated MSCs (n = 6). Osteochondral repair was assessed at 6 and 12 weeks after surgery by histological, micro–computed tomography, and mechanical analysis. Results: A chondrogenic MSC subpopulation was efficiently isolated using the multidimensional double spiral device. RNA sequencing revealed distinct transcriptomic profiles and identified differential gene expression between subpopulations. The delivery of a chondrogenic MSC subpopulation resulted in improved cartilage repair, as indicated by histological scoring, the compression modulus, and micro–computed tomography of the subchondral bone. Conclusion: We have established a rapid, label-free, and reliable microfluidic protocol for more efficient size-based enrichment of a chondrogenic MSC subpopulation. Our proof-of-concept in vivo study demonstrates the enhanced cartilage repair efficacy of these enriched chondrogenic MSCs. Clinical Relevance: The delivery of microfluidic-enriched chondrogenic MSCs that are consistent in size and function can overcome the challenge of the functional heterogeneity of expanded MSCs, resulting in significant improvement in MSC-based cartilage repair. The availability of such rapid, label-free enriched chondrogenic MSCs can enable better cell therapy products for cartilage repair with improved treatment outcomes. [ABSTRACT FROM AUTHOR]

Highlights • Uses the significant amplified local electric field induced by ICP to concentrate Li+ ions; • Separates enriched Li+ from Mg2+ by rich Na+ through competition of co-charged ions; • Continuously drives the concentrated Li+ from the microchannel. Abstract New technologies for efficient ion separation (e.g. extraction of lithium from salt lake brines) are highly desirable due to industrial and environmental concerns. A new ion concentration polarization (ICP)-based ion separation system, which is capable of extracting concentrated Li+ solutions continuously from high Mg2+/Li+ ratio brines is proposed. This system uses ICP-induced amplification of the electric field to concentrate Li+ ions and expel Mg2+, with external pressures applied to modulate the feeding flow of the brine in the microchannel and the bifurcated flow of concentrated Li+ through the branch. Through numerical simulations using a simplified two-dimensional model, effects of key operational parameters as well as same structural parameters are elaborated. It is demonstrated that the proposed system is able to continuously extract ∼38% of Li+ from the raw brine at a fluid flow velocity of ∼1 mm/s. The concentration of Li+ in the product solution is about ∼13 times of the raw brine, with a Li+/Mg2+ mass ratio of ∼10 (∼600 times of the raw brine). This work provides clear fundamental mechanism underlying the new method, offers important guidance for the design of relevant experiments, and paves the way for the potential industrialization of high efficiency Li+ extraction technologies. [ABSTRACT FROM AUTHOR]

Abstract Ion selective membrane (ISM) electrodes are widely used for selective ion sensing applications. Recently, new modalities have emerged whose operation involves active electrical polarization of the media, and current theoretical models are unsuitable to predict their behavior beyond near-equilibrium conditions. Here, we apply numerical modeling of physicochemical transport in such systems to study mechanisms of interfacial ion transfer and their role in limiting processes. Importantly, our analysis suggest that membrane-phase complexation (MC) has strong merits as a replacement for interfacial complexation (IC) in theoretical treatments. For our purpose, we have developed a highly detailed model based on Nernst–Planck–Poisson (NPP) with kinetic reactions of first-order. The solutions were derived in terms of logarithmically transformed concentration variables, allowing us to input experimentally determined stability coefficients. A unique process, referred to here as the reaction boundary layer (RBL), is a characteristic of MC, and we found it could have a significant impact on current–voltage (I–V) characteristics and transfer selectivity. Together with other well-known processes such as electrically driven diffusion, the RBL dictates the limits of ISM electrical polarization. Using our model, we demonstrate that operating outside these limits results in ingress of interfering ion species and concurrent loss of transfer selectivity. Highlights • Membrane complexation has strong merits as the intrinsic mechanism of interfacial ion transfer. • A reaction boundary layer effectively produces an intrinsic ISM current limit. • ISM over-limiting processes generally result in loss of transfer selectivity for the primary ion. [ABSTRACT FROM AUTHOR]

The growing interest in regenerative medicine has opened new avenues for novel cell therapies using stem cells. Bone marrow aspirate (BMA) is an important source of stromal mesenchymal stem cells (MSCs). Conventional MSC harvesting from BMA relies on archaic centrifugation methods, often leading to poor yield due to osmotic stress, high centrifugation force, convoluted workflow, and long experimental time (∼2–3 hours). To address these issues, we have developed a scalable microfluidic technology based on deterministic lateral displacement (DLD) for MSC isolation. This passive, label-free cell sorting method capitalizes on the morphological differences between MSCs and blood cells (platelets and RBCs) for effective separation using an inverted L-shaped pillar array. To improve throughput, we developed a novel multi-chip DLD system that can process 2.5 mL of raw BMA in 20 ± 5 minutes, achieving a 2-fold increase in MSC recovery compared to centrifugation methods. Taken together, we envision that the developed DLD platform will enable fast and efficient isolation of MSCs from BMA for effective downstream cell therapy in clinical settings. [ABSTRACT FROM AUTHOR]

Conventional water treatment process is composed of multiple stages, including desalination (salt removal) and pre/post-treatment of desalination to remove particles, chemicals, and other potential foulants for desalination. In this work, we developed a microfluidic proof-of-concept for a single device water treatment system, which removes both salt ions and non-salt contaminants. Our system combines electrocoagulation (EC), a versatile contaminant removal process, and ion concentration polarization (ICP) desalination, which is an electromembrane desalination process. We demonstrated a continuous EC–ICP operation that removed ＞95% of suspended solids and reduced the salinity from brackish range (20 mM NaCl) to a potable level (＜8.6 mM NaCl). We also demonstrated that our system is flexible in terms of the type and concentration of contaminants it can handle. Combining two different electrochemical processes into a single system, we can reduce unnecessary voltage drop by having a shared anode, and achieve both seamless integration and energy efficient operation. Our system will find applications as a small-scale water treatment system, if properly scaled up in the future. [ABSTRACT FROM AUTHOR]

Despite increasing demand in the manipulation of nanoscale objects for next generation biological and industrial processes, there is a lack of methods for reliable separation, concentration and purification of nanoscale objects. Acoustic methods have proven their utility in contactless manipulation of microscale objects mainly relying on the acoustic radiation effect, though the influence of acoustic streaming has typically prevented manipulation at smaller length scales. In this work, however, we explicitly take advantage of the strong acoustic streaming in the vicinity of a highly focused, high frequency surface acoustic wave (SAW) beam emanating from a series of focused 6 μm substrate wavelength interdigital transducers patterned on a piezoelectric lithium niobate substrate and actuated with a 633 MHz sinusoidal signal. This streaming field serves to focus fluid streamlines such that incoming particles interact with the acoustic field similarly regardless of their initial starting positions, and results in particle displacements that would not be possible with a travelling acoustic wave force alone. This streaming-induced manipulation of nanoscale particles is maximized with the formation of micro-vortices that extend the width of the microfluidic channel even with the imposition of a lateral flow, occurring when the streaming-induced flow velocities are an order of magnitude larger than the lateral one. We make use of this acoustic streaming to demonstrate the continuous and differential focusing of 100 nm, 300 nm and 500 nm particles. [ABSTRACT FROM AUTHOR]

This in vitro study evaluated the effects of the infiltration of F- and Ca2+ ions into human enamel by electrokinetic flow (EKF) on the enamel microhardness and F- content. Sound human enamel ground sections of unerupted third molars were infiltrated with de-ionized water by EKF and with F- ion by EKF respectively. All samples were submitted to two successive transverse acid-etch biopsies (etching times of 30 s and 20 min) to quantify F- ion infiltrated deep into enamel. Remarkably, sound enamel showed a large increase in microhardness (MH) after infiltration of NaF (p < 0.00001) and CaCl2 (p = 0.013) by EKF. Additionally, NaF-EKF increased the remineralization in the lesion body of artificial enamel caries lesions compared to controls (p < 0.01). With the enamel biopsy technique, at both etching times, more F- ions were found in the EKF-treated group than the control group (p << 0.05), and more fluoride was extracted from deeper biopsies in the NaF-EKF group. In conclusion, our results show that EKF treatment is superior in transporting Ca2+ and F− ions into sound enamel when compared to molecular diffusion, enhancing both the mineralization of sound enamel and the remineralization of artificial enamel caries. [ABSTRACT FROM AUTHOR]

The correction notice for the article "Metabolic modulation to improve MSC expansion and therapeutic potential for articular cartilage repair" in Stem Cell Research & Therapy addresses the correction of co-author Kiesar Sideeq Bhat's name. The updated version of the original article can be accessed online. The correction was made by Ching Ann Tee, Daniel Ninio Roxby, Rashidah Othman, Vinitha Denslin, Kiesar Sideeq Bhat, Zheng Yang, Jongyoon Han, Lisa Tucker-Kellogg, and Laurie A. Boyer. [Extracted from the article]

Selective ion extraction is a vital element of many resource recovery systems. Carrier-based membranes offer the ability to remove specific, targeted ions from brine and waste streams, but these materials have delivered inconsistent outcomes in their active transport applications. To study non-ideal behaviors of target-ion selective membranes, we introduce a direct, real-time system for selectively measuring concentrations within electro-membrane boundary layers. In a carrier-based membrane system, we applied our method to monitor adverse, current-limiting behaviors. During its operation, we detected loss of transport selectivity and counter-ion discharge. It provided sufficient evidence to identify the mechanism underlying these adverse, over-limiting effects—the internal concentration polarization of free-carrier. Our method may raise new prospects for direct experimental characterization of nonlinear transport phenomena in electro-membrane systems. [ABSTRACT FROM AUTHOR]

We present a novel continuous-flow nanofluidic biomolecule/cell concentrator, utilizing the ion concentration polarization (ICP) phenomenon. The device has one main microchannel which bifurcates into two channels, one for a narrow, concentrated stream and the other for a wider but target-free stream. A nanojunction [cation-selective material (Nafion)] is patterned along the tilted concentrated channel. Application of an electric field generates the ICP zone near the nanojunction so that biomolecules and cells are guided into the narrow, concentrated channel by hydrodynamic force. Once biomolecules from the main channel are continuously streamed out to the concentrated channel, one can achieve a continuous flow of the same sample solution but with higher concentrations up to 100-fold. By controlling hydrodynamic resistance of the main and concentrated channel, the concentration factors can be adjusted. We demonstrated the continuous-flow concentration with various targets, such as bacteria [fluorescein sodium salt, recombinant green fluorescence protein (rGFP), red blood cells (RBCs), and Escherichia coli (E. coli)]. Specially, fluorescein isothiocyanate (FITC)-conjugated lectin from Lens culinaris (lentil) (FITC-lectin) was tested on the different buffer conditions to clarify the effect of polarities of the target sample. This system is ideally suited for a generic concentration front-end for a wide variety of biosensors, with minimal integration-related complications. [ABSTRACT FROM AUTHOR]

Patterned regular sieves and filters with comparable molecular dimensions hold great promise as an alternative to conventional polymeric gels and fibrous membranes to improve biomolecule separation. Recent developments of microfabricated nanofluidic sieves and filters have demonstrated superior performance for both analytical and preparative separation of various physiologically relevant macromolecules, including proteins. The insights gained from designing these artificial molecular sieves and filters, along with the promising results gathered from their first applications, serve to illustrate the impact that they can have on improving future separation of complex biological samples. Further development of artificial sieves and filters with more elaborate geometrical constraints and tailored surface functionality is believed to provide more promising ideals and results for biomolecule separation, which has great implications for proteomic research and biomarker discovery. [Copyright &y& Elsevier]

Here, we propose a fully-automated platform using a spiral inertial microfluidic device for standardized semen preparation that can process patient-derived semen samples with diverse fluidic conditions without any pre-washing steps. We utilized the multi-dimensional double spiral (MDDS) device to effectively isolate sperm cells from other non-sperm seminal cells (e.g., leukocytes) in the semen sample. The recirculation platform was employed to minimize sample dependency and achieve highly purified and concentrated (up to tenfold) sperm cells in a rapid and fully-automated manner (~ 10 min processing time for 50 mL of diluted semen sample). The clinical (raw) semen samples obtained from healthy donors were directly used without any pre-washing step to evaluate the developed separation platform, which showed excellent performance with ~ 80% of sperm cell recovery, and > 99.95% and > 98% removal of 10-μm beads (a surrogate for leukocytes) from low-viscosity and high-viscosity semen samples, respectively. We expect that the novel platform will be an efficient and automated tool to achieve purified sperm cells directly from raw semen samples for assisted reproductive technologies (ARTs) as an alternative to density centrifugation or swim-up methods, which often suffer from the low recovery of sperm cells and labor-intensive steps. [ABSTRACT FROM AUTHOR]

Inertial microfluidics has enabled many impactful high throughput applications. However, devices fabricated in soft elastomer (i.e., polydimethylsiloxane (PDMS)) suffer reliability issues due to significant deformation generated by the high pressure and flow rates in inertial microfluidics. In this paper, we demonstrated deformation-free and mass-producible plastic spiral inertial microfluidic devices for high-throughput cell separation applications. The design of deformable PDMS spiral devices was translated to their plastic version by compensating for the channel deformation in the PDMS devices, analyzed by numerical simulation and confocal imaging methods. The developed plastic spiral devices showed similar performance to their original PDMS devices for blood separation and Chinese hamster ovary (CHO) cell retention. Furthermore, using a multiplexed plastic spiral unit containing 100 spirals, we successfully demonstrated ultra-high-throughput cell clarification (at a processing rate of 1 L min−1) with a high cell-clarification efficiency of ∼99% (at the cell density changing from ∼2 to ∼10 × 106 cells mL−1). Benefitting from the continuous and clogging-free separation with an industry-level throughput, the cell clarification device could be a critical breakthrough for the production of therapeutic biologics such as antibodies or vaccines, impacting biomanufacturing in general. [ABSTRACT FROM AUTHOR]

Methods are described to achieve more efficient multi- dimensional protein separation in a microfluidic channel. The new methods couple isoelectric focusing (lEF) with high ionic strength electrophoretic separations by active microvalve control in a microchip. Several experiments demonstrating independent 2D separation were performed, and critical parameters for optimal chip performance were identified, including channel passivation, electroosmosis control, and IEF linearity control. This strategy can be used for integration of different heterogeneous separation techniques, such as IEF, capillary electrophoresis, and liquid chromatography. This new device can be ideal for preseparation and preconcentration of complex biomolecule samples for a streamlined biomolecule analysis using mass spectrometry. [ABSTRACT FROM AUTHOR]

• The effect of hydrodynamic convective flow on the development of diffusion layers was experimentally and numerically evaluated. • The loss of the ion exchange membrane's perm-selectivity resulted from the co-ion leakage due to the accumulated concentrated plug. • The higher flow in the concentrate side drastically improved the current utilization drop in high operating current. In electromembrane processes such as electrodialysis (ED) and ion concentration polarization (ICP), the diffusion layers on both diluate and concentrate sides influence permselectivity of the ion-exchange membrane and current utilization. The diffusion layer in the diluate stream, due to lower salinity and higher resistivity, has been regarded as the primary source of energy loss. In contrast, very few studies have focused on the diffusion layer in the concentrate stream. In this paper, we evaluate the influence of hydrodynamic convective flow on the development of diffusion layers on both concentrate and diluate sides, specifically in the ICP desalination process. Interestingly, the higher convective flow in the concentrate side was shown to drastically improve the current utilization drop in high operating current, which has been a recurring challenge in electromembrane processes. We attribute this to the prevention of co-ion leakage into the membrane, confirmed by both experimentation and numerical modeling. This new insight has a clear design implication for optimizing electromembrane processes for higher energy efficiency. [ABSTRACT FROM AUTHOR]

Ion selective membrane (ISM) is widely used in electrochemical engineering and micro-fluidic processes, yet accurate modeling of the ISM is still challenging due to many scientific issues. So far, assumptions on the "ideal ISM" have been used in most simulation studies involving ion transport and electrokinetic flow in ion concentration polarization systems, but the validity or accuracy of those assumptions has never been investigated. In this paper, using a two-dimensional nanochannel system with practical significance, we verify the validity of the ideal ISM model by making comparisons between the idealized ISM system and a more realistic permselective nanochannel system in terms of simplifications over the electrical potential, counter-ion concentration, and zero co-ion flux. Our results show that the simplifications of fixed voltage and fixed counter-ion concentration in the ideal ISM model are largely accurate in most situations, especially under high applied voltage and/or with high charge density inside the ISM. However, zero co-ion flux simplification is not exactly accurate in most occasions. Significant errors may be incurred by the zero co-ion flux assumption when steady state solutions are sought using the ISM model. Some discussions over the influences of structures of the nanochannel system are also added. The obtained results will help in obtaining detailed understanding of the transport features inside the nanoporous ISM, especially when the comparison between simulation and experimental data is necessary. [ABSTRACT FROM AUTHOR]

Acquired multidrug resistance in tumors is a big challenge in cancer therapy. As an important physical stimulus in the tumor microenvironment, elevated interstitial fluid pressure has been reported to inhibit drug delivery and promote metastasis in solid tumors. However, the direct influence of this fluid pressure on anticancer drug resistance remains unclear. Here, we develop a pressurized in vitro circulating tumor cell (CTC) culture platform for anticancer drug screening. By using human breast cancer cell line MCF-7 and MDA-MB-231, we find that doxorubicin resistance can be increased by up to 2.5 times under 30 mmHg culture condition, through ABCC1 overexpression that reduces intracellular doxorubicin concentration. A similar chemoresistance change is also observed in clinical metastatic circulating tumor cells samples. These findings provide a new insight into the chemoresistance mechanism of metastatic human breast cancer cells and elucidate the significance of abnormal hydrostatic pressure in cancer progression. [ABSTRACT FROM AUTHOR]

Chinese hamster ovary (CHO) cells have been the most commonly used mammalian host for large-scale commercial production of therapeutic proteins, such as monoclonal antibodies. Enhancement of productivity of these CHO cells is one of the top priorities in the biopharmaceutical industry to reduce manufacturing cost. Although there are many different methods (e.g. temperature, pH, feed) to improve protein production in CHO cells, the role of physiologically relevant hydrostatic pressure in CHO cell culture has not been reported yet. In this study, four different hydrostatic pressures (0, 30, 60, and 90 mmHg) were applied to batch CHO cells, and their cell growth/metabolism and IgG1 production were examined. Our results indicate that hydrostatic pressure can increase the maximum cell concentration by up to 50%. Moreover, overall IgG1 concentration on Day 5 showed that 30 mmHg pressure can increase IgG1 production by 26%. The percentage of non-disulphide-linked antibody aggregates had no significant change under pressure. Besides, no significant difference was observed between 30 mmHg and no pressure conditions in terms of cell clumping formation. All these findings are important for the optimization of fed-batch or perfusion culture for directing cell growth and improving antibody production. [ABSTRACT FROM AUTHOR]

A fully-automated and portable leukocyte separation platform was developed based on a new type of inertial microfluidic device, multi-dimensional double spiral (MDDS) device, as an alternative to centrifugation. By combining key innovations in inertial microfluidic device designs and check-valve-based recirculation processes, highly purified and concentrated WBCs (up to >99.99% RBC removal, ∼80% WBC recovery, >85% WBC purity, and ∼12-fold concentrated WBCs compared to the input sample) were achieved in less than 5 minutes, with high reliability and repeatability (coefficient of variation, CV < 5%). Using this, one can harvest up to 0.4 million of intact WBCs from 50 μL of human peripheral blood (50 μL), without any cell damage or phenotypic changes in a fully-automated operation. Alternatively, hand-powered operation is demonstrated with comparable separation efficiency and speed, which eliminates the need for electricity altogether for truly field-friendly sample preparation. The proposed platform is therefore highly deployable for various point-of-care applications, including bedside assessment of the host immune response and blood sample processing in resource-limited environments. [ABSTRACT FROM AUTHOR]

In vitro erythroid cultures from human hematopoietic stem cells produce immature red blood cells (RBCs) called reticulocytes, which are important for RBCs production, and are widely used in scientific studies of malaria pathology, hematological diseases and protein translation. However, in vitro reticulocyte cultures contain expelled cell nuclei and erythroblasts as undesirable by-products and current purification methods such as density gradient centrifugation and fluorescence-activated cell sorting (FACS) are not optimal for integrated bioprocessing and downstream therapeutic applications. Developments in Dean flow fractionation (DFF) and deterministic lateral displacement (DLD) microfluidic sorting methods are ideal alternatives due to label-free size sorting, throughput scalability and low manufacturing cost. DFF sorting of reticulocytes from whole erythroid culture showed a 2.4-fold increase in cell recovery compared to FACS albeit with a lower purity; DLD sorting showed comparable cell recovery and purity with FACS using an inverse-L pillar structure to emphasize size and deformability sorting of reticulocytes. The viability and functional assurance of purified reticulocytes showed conserved cell deformability and supported the propagation of malaria parasites. Collectively, our study on label-free RBCs isolation represents a significant technical advancement towards developing in vitro generated viable human RBCs, opening opportunities for close-loop cell manufacturing, downstream therapeutic and research purposes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cell cluster removal device based on spiral inertial microfluidics. • Cell cluster removal with high volumetric throughput, removal efficiency, and biocompatibility. • The first demonstration of the selective removal of large CHO cell clusters from bioreactors using microfluidics. • The first report on the large-particle trapping effect in spiral inertial microfluidic devices. Suspension cultures of Chinese hamster ovary (CHO) cells are extensively employed in biopharmaceutical production. During cultivation, CHO cell clusters often form due to cell death and other irregularities, substantially reducing cell growth and productivity. In this study, we introduce a novel method for the selective removal of large CHO cell clusters from bioreactors, utilizing the large-particle trapping effect in spiral inertial microfluidics. A single spiral inertial microfluidic device effectively removed large clusters from CHO cell culture, demonstrating high volumetric throughput, removal efficiency, and biocompatibility. This straightforward, agent-free, and continuous-flow approach can be applied to remove large mammalian cell clusters across various scales and modes of operation (discontinuous or continuous) during cell line development, bioprocess optimization, and biomanufacturing. [ABSTRACT FROM AUTHOR]

Tooth whitening, a routine procedure in dentistry, is one of the examples of medical procedures that are limited by the challenge of delivering molecules into various types of nanoporous tissues. Current bleaching methods rely on simple diffusion of peroxides into enamel nano channels, therefore requires sufficient contact time with peroxides. In-office treatments often involve enamel etching or light activation which often results in patient sensitivity and potential soft tissue damage. To demonstrate a robust method to transport hydrogen peroxide to greater depths into enamel nanopores through nanofluidic flows driven by electrokinetics, with the intention to increase efficacy while reducing treatment time. Freshly extracted human teeth were subjected to electrokinetic flow treatment with hydrogen peroxide under different electric fields with varying operation times. Pre- and post-operative shade matching was done using a photospectrometer. It is demonstrated that the operation time for the same concentration of hydrogen peroxide can be shortened by 10 times. The proposed method showed significant improvements in whitening effects over control groups and thus offers promising clinically-viable chairside applications with efficacy. The demonstrated nanofluidic transport of hydrogen peroxide into enamel has a potential to be applied for enhancing tooth whitening, compared to simple diffusion, without heating the hard dental tissues. [ABSTRACT FROM AUTHOR]

In electromembrane desalination processes such as electrodialysis (ED) and ion concentration polarization (ICP) desalination, ion-depleted boundary layers constitute the desalted, product stream, yet also cause high resistivity and voltage drop. Directly manipulating fluid flow streams is a new method to break this fundamental trade-off for electromembrane desalination. In this work, we are introducing a novel electromembrane desalination architecture that allows a feed stream to return to the feed inlet side of the membrane (hereby named as return-flow (RF) architecture) to improve the energy efficiency by re-distributing and controlling the depleted boundary layer, even at high current values. The technical feasibility of this idea was examined in ICP desalination process (RF-ICP) with a wide range of feed salinity from 10 to 70 g/L. For a partial desalination, RF-ICP (∼75 cm2 of membrane area) has achieved similar power consumption compared to batch-ED with 3 times bigger membrane area (200 cm2) with a higher area efficiency for salt removal, which translates into lower optimal desalination cost. The techno-economic analysis of RF-ICP have been performed for the treatment of 70 g/L brine waste. For partial desalination of 70 g/L brine down to 35 g/L, RF-ICP desalination achieved overall water cost as low as $2.57/m3 ($0.41/barrel). This could translate into reduction in total water cost up to 31% for zero brine release scenarios, depending on the concentrated brine treatment cost. These results show that return-flow architecture can improve the performance of electromembrane desalination, enabling more flexible water treatment for many real-world applications. • A novel channel architecture, RF-ICP, was first developed for electromembrane desalination. • RF-ICP allowed the feedwater stream to return to the feed inlet side of the membrane. • RF-ICP improved the energy efficiency by re-distributing and controlling the depleted boundary layer. • RF-ICP was adopted for the ICP desalination with a wide range of feed salinity (10–70 g/L). • The techno-economic analysis was performed for partial desalination of brine. [ABSTRACT FROM AUTHOR]

A techno-economic analysis is used to evaluate the economic feasibility of ion concentration polarization (ICP) desalination for seawater desalination and brine management. An empirical optimization model based on a limited set of experimental data, which was obtained from a lab-scale ICP desalination prototype, was established to calculate the required energy and membrane area for a given set of operating parameters. By calculating operating and capital expenses in various feed and product cases, the optimal levelized cost of water is determined over a range of feed salinities, mostly above seawater salinity (35 g/kg). Through these analyses, we study the economic feasibility of three applications: 1) partial desalination of brine discharge by ICP (feed varied from 35 to 75 g/kg) to common seawater RO feed level (35 g/kg) in a hybrid ICP-RO system; 2) the concentration of seawater desalination brine for salt production, and 3) partial desalination of oilfield wastewater. The economic feasibility of ICP desalination processes has been evaluated and the rough cost of treatment has been generated for several relevant applications. The approach taken in this work could be employed for other new and existing desalination processes, where a priori process modeling and optimization is scientifically and/or numerically challenging. Graphical abstract Image 1 Highlights • We performed techno-economic analysis of ICP desalination. • An empirical model based on experimental data on brine separation was established to calculate the optimized water cost. • Three application scenarios are presented for partial desalination of brine and brine concentration. • ICP-RO hybrid can be economically competitive for salinity above the technical limit of RO. • Electrodialysis may be more suitable than multi-stage ICP for salt production. [ABSTRACT FROM AUTHOR]

Precise measurement of mechanical and electrical properties of single cells can yield useful information on the physiological and pathological state of cells. In this work, we develop a differential multiconstriction microfluidic device with self-aligned 3D electrodes to simultaneously characterize the deformability, electrical impedance and relaxation index of single cells at a high throughput manner (>430 cell/min). Cells are pressure-driven to flow through a series of sequential microfluidic constrictions, during which deformability, electrical impedance and relaxation index of single cells are extracted simultaneously from impedance spectroscopy measurements. Mechanical and electrical phenotyping of untreated, Cytochalasin B treated and N-Ethylmaleimide treated MCF-7 breast cancer cells demonstrate the ability of our system to distinguish different cell populations purely based on these biophysical properties. In addition, we quantify the classification of different cell types using a back propagation neural network. The trained neural network yields the classification accuracy of 87.8% (electrical impedance), 70.1% (deformability), 42.7% (relaxation index) and 93.3% (combination of electrical impedance, deformability and relaxation index) with high sensitivity (93.3%) and specificity (93.3%) for the test group. Furthermore, we have demonstrated the cell classification of a cell mixture using the presented biophysical phenotyping technique with the trained neural network, which is in quantitative agreement with the flow cytometric analysis using fluorescent labels. The developed concurrent electrical and mechanical phenotyping provide great potential for high-throughput and label-free single cell analysis. fx1 • Concurrent electrical and mechanical phenotyping of single cells. • High-throughput single cell analysis based on three biophysical properties. • Microfluidic cytometry with self-aligned 3D electrodes. • A neural network algorithm for improved cell differentiation. [ABSTRACT FROM AUTHOR]

Background: Emergence of drug-resistant cancer phenotypes is a challenge for anti-cancer therapy. Cancer stem cells are identified as one of the ways by which chemoresistance develops.Method: We investigated the anti-inflammatory combinatorial treatment (DA) of doxorubicin and aspirin using a preclinical microfluidic model on cancer cell lines and patient-derived circulating tumour cell clusters. The model had been previously demonstrated to predict patient overall prognosis.Results: We demonstrated that low-dose aspirin with a sub-optimal dose of doxorubicin for 72 h could generate higher killing efficacy and enhanced apoptosis. Seven days of DA treatment significantly reduced the proportion of cancer stem cells and colony-forming ability. DA treatment delayed the inhibition of interleukin-6 secretion, which is mediated by both COX-dependent and independent pathways. The response of patients varied due to clinical heterogeneity, with 62.5% and 64.7% of samples demonstrating higher killing efficacy or reduction in cancer stem cell (CSC) proportions after DA treatment, respectively. These results highlight the importance of using patient-derived models for drug discovery.Conclusions: This preclinical proof of concept seeks to reduce the onset of CSCs generated post treatment by stressful stimuli. Our study will promote a better understanding of anti-inflammatory treatments for cancer and reduce the risk of relapse in patients. [ABSTRACT FROM AUTHOR]

Cancer is the leading cause of death worldwide. The complex and disorganized tumor microenvironment makes it very difficult to treat this disease. The most common in vitro drug screening method now is based on 2D culture models which poorly represent actual tumors. Therefore, many 3D tumor models which are more physiologically relevant have been developed to conduct in vitro drug screening and alleviate this situation. Among all these models, the microfluidic tumor model has the unique advantage of recapitulating the tumor microenvironment in a comparatively easier and representative fashion. While there are many review papers available on the related topic of microfluidic tumor models, in this review we aim to focus more on the possibility of generating “clinically actionable information” from these microfluidic systems, besides scientific insight. Our topics cover the tumor microenvironment, conventional 2D and 3D cultures, animal models, and microfluidic tumor models, emphasizing their link to anti-cancer drug discovery and personalized medicine. [ABSTRACT FROM AUTHOR]

Plunging jets are used in many environmental and industrial applications to enhance mixing and mass transfer rates. One of the current challenges in applying plunging jet reactors for brine dispersal from desalination plants is that the density of brine causes the jet to drop straight to the seafloor. This hypoxic fluid disperses slowly and elicits a toxic effect on the local marine ecosystem. To provide new insights and improvements, we have developed a numerical model that considers the co-transport of brine in a two-phase air–fluid system. In our model, Navier–Stokes describes the transport of fluid, and Nernst–Planck describes the transport of dissolved brine. One of the key observations we made is that brine convection is characterized by competition between the positive buoyancy of air–fluid mixtures and the negative buoyancy of brine–fluid mixtures. Depending on the jet flow rate, the brine would either (1) ascend radially from the plume or (2) drop straight downwards. In our experiments, we demonstrate the same behaviors. Ultimately, it may be possible to reduce the destructive effects of high-density brine impinging on the seafloor by optimizing the jet to promote air entrainment, thus maintaining the system in its radial mixing regime. [Display omitted] • We applied the finite element method to study brine transport in a plunging jet. • Our model reproduced gravity-driven impingement of brine on the floor of a pool. • We identified two regimes of brine transport with different mixing performances. • By enhancing air mass transfer, we could promote a favorable transport regime. • Effective jet mixing will help prevent deterioration of marine ecosystems. [ABSTRACT FROM AUTHOR]

Removing nonviable cells from a cell suspension is crucial in biotechnology and biomanufacturing. Label-free microfluidic cell separation devices based on dielectrophoresis, acoustophoresis, and deterministic lateral displacement are used to remove nonviable cells. However, their volumetric throughputs and test cell concentrations are generally too low to be useful in typical bioreactors in biomanufacturing. In this study, we demonstrate the efficient removal of small (＜10 μm) nonviable cells from bioreactors while maintaining viable cells using inertial microfluidic cell sorting devices and characterize their performance. Despite the size overlap between viable and nonviable cell populations, the devices demonstrated 3.5–28.0% dead cell removal efficiency with 88.3–83.6% removal purity as well as 97.8–99.8% live cell retention efficiency at 4 million cells per mL with 80% viability. Cascaded and parallel configurations increased the cell concentration capacity (10 million cells per mL) and volumetric throughput (6–8 mL min−1). The system can be used for the removal of small nonviable cells from a cell suspension during continuous perfusion cell culture operations. [ABSTRACT FROM AUTHOR]

A novel ion concentration polarization-based microfluidic device is proposed for continuous extraction of Li + from high Mg 2+ /Li + ratio brines. With simultaneous application of the cross-channel voltage that drives electroosmotic flow and the cross-membrane voltage that induces ion depletion, Li + is concentrated much more significantly than other cations in front of the membrane in the microchannel. The application of external pressure produces a fluid flow that drags a portion of Li + (and Na + ) to flow through the microchannel, while keeping most of Mg 2+ (and K + ) blocked, thus implementing continuous Li + extraction. Two-dimensional numerical simulation using a microchannel of 120 µm length and 4 µm height and a model, highly concentrated brine, shows that the system may produce a continuous flow rate of 1.72 mm/s, extracting 25.6% of Li + , with a Li + /Mg 2+ flux ratio of 2.81 × 10 3 , at an external pressure of 100 Pa and cross-membrane voltage of 100 times of thermal voltages (25.8 mV). Fundamental mechanisms of the system are elaborated and effects of the cross-membrane voltage and the external pressure are analyzed. These results and findings provide clear guidance for the understanding and designing of microfluidic devices not only for Li + extraction, but also for other ionic or molecular separations. [ABSTRACT FROM AUTHOR]

Current clinical approaches for articular cartilage repair have not been able to restore the tissue with zonal architecture, and its biomechanical and functional properties. Mimicking the zonal organization of articular cartilage in neo-tissue by implanting zonal chondrocyte subpopulations in multilayer construct could enhance the functionality of the graft, engineering of stratified tissue has not yet been realized due to lack of efficient and specific zonal chondrocyte isolation protocol. We show that by using a spiral microchannel device, the superficial, middle and deep zone chondrocytes can be separated based on cell size, and enriched from full thickness porcine cartilage in a high-throughput, label-free manner. The size-sorted cells show zone-specific characteristics in RT-PCR analysis of zonal cartilage markers. Both freshly sorted and two-passage expanded zonal chondrocytes formed cartilage tissue in 3D hydrogel, bearing respective zonal characteristics, indicated by RT-PCR, histology, extracellular matrix proteins, and mechanical compression test. In the proof-of-concept in vivo study using a rodent cartilage defect model, the size-sorted zonal chondrocytes when delivered in bi-layered hydrogel construct, facilitated better cartilage repair with mechanically enhanced cartilage tissue, in comparison to conventional chondrocytes implantation. This study provides an effective approach to obtain large numbers of zonal chondrocytes, and demonstrates the translational potential of stratified zonal chondrocyte implantation for clinical repair of critical size cartilage defects. [ABSTRACT FROM AUTHOR]

In blood samples from patients with viral infection, it is often important to separate viral particles from human cells, for example, to minimize background in performing viral whole genome sequencing. Here, we present a microfluidic device that uses spiral inertial microfluidics with continuous circulation to separate host cells from viral particles and free nucleic acid. We demonstrate that this device effectively reduces white blood cells, red blood cells, and platelets from both whole blood and plasma samples with excellent recovery of viral nucleic acid. Furthermore, microfluidic separation leads to greater viral genome coverage and depth, highlighting an important application of this device in processing clinical samples for viral genome sequencing. [ABSTRACT FROM AUTHOR]

Mesenchymal stem cells (MSCs) have been shown as potential candidates for cell-based therapies for a diverse range of tissue regenerative applications. Therapeutic use of MSCs usually requires culture expansion, which increases the heterogeneity of MSCs in vitro, thus affecting the potency of the MSCs for more specific indications. The capacity for identifying and isolating special subsets of MSCs for treatment of specific diseases therefore holds great clinical significance. An important therapeutic application of MSC is for the regeneration of cartilage tissue. We and others have previously developed label-free microfluidic means to isolate subpopulations of culture expanded MSCs based on distinct biophysical characteristics. Here we utilize a spiral micro-channel device to separate culture expanded MSCs into five subgroups according to cell size, and study their proliferation and chondrogenesis at early, middle and late passages. Results show that in all passages, the medium-size subpopulation (cell size of 17–21 μm), compared to other subpopulations, displays significantly higher proliferation rate and chondrogenic capacity in terms of cartilage extracellular matrix formation. Also, the small cell subpopulation (average cell size of 11–12 μm) shows lower viability, and large cell subpopulation (average cell size 23–25 μm) expresses higher level of senescence-associated β-galactosidase. Finally, we show that repeated microfluidic exclusion of MSCs larger than 21 μm and smaller than 17 μm at every passage during continuous culture expansion result in selected MSCs with faster proliferation and better chondrogenic potential as compared to MSC derived from conventional expansion approach. This study demonstrates the significant merit and utility of size-based cell selection for the application of MSCs in cartilage regeneration. [ABSTRACT FROM AUTHOR]

In this study, we report the use of a high-throughput microfluidic spiral chip to screen out eggs from a mixed age nematode population, which can subsequently be cultured to a desired developmental stage. For the sorting of a mixture containing three different developmental stages, eggs, L1 and L4, we utilized a microfluidic spiral chip with a trapezoidal channel to obtain a sorting efficiency of above 97% and a sample purity (SP) of above 80% for eggs at different flow rates up to 10 mL min−1. The result demonstrated a cost-effective, simple, and highly efficient method for synchronizing C. elegans at a high throughput (∼4200 organisms per min at 6 mL min−1), while eliminating challenges such as clogging and non-reusability of membrane-based filtration. Due to its simplicity, our method can be easily adopted in the C. elegans research community. [ABSTRACT FROM AUTHOR]

In this paper, technical and economic feasibility of partial desalination of hypersaline brine by ion concentration polarization (ICP) desalination is examined. We engineered a lab-scale ICP desalination system producing flow rate up to 96 mL/min, which represents the largest scale-up of ICP desalination process so far. With highly saline brine feed water (NaCl, 70,000 mg/L of TDS) and utilizing two different cation exchange membranes, we measured electrical responses of unit fluidic cell, and monitored the product water salinity changes over a wide ranges of flow velocities and electric current densities. Based on these, realistic power consumption and expected cost of brine treatment can be calculated, for the economic validation of partial brine desalination by ICP process. For the salt removal ratio of 50%, the optimal water cost is obtained as $3.08/m 3 while the least power consumption is achieved as 5.6 kWh/m 3 . Our results also show that the partial desalination could be more economically preferable than complete desalination for the brine management. Yet, ICP desalination should be further improved and optimized, with significant potential to be applied in many different desalination applications and hybrid scenarios. [ABSTRACT FROM AUTHOR]

Acoustic streaming has emerged as a promising technique for refined microscale manipulation, where strong rotational flow can give rise to particle and cell capture. In contrast to hydrodynamically generated vortices, acoustic streaming is rapidly tunable, highly scalable and requires no external pressure source. Though streaming is typically ignored or minimized in most acoustofluidic systems that utilize other acoustofluidic effects, we maximize the effect of acoustic streaming in a continuous flow using a high-frequency (381 MHz), narrow-beam focused surface acoustic wave. This results in rapid fluid streaming, with velocities orders of magnitude greater than that of the lateral flow, to generate fluid vortices that extend the entire width of a 400 μm wide microfluidic channel. We characterize the forces relevant for vortex formation in a combined streaming/lateral flow system, and use these acoustic streaming vortices to selectively capture 2 μm from a mixed suspension with 1 μm particles and human breast adenocarcinoma cells (MDA-231) from red blood cells. [ABSTRACT FROM AUTHOR]

Assessment of airway secretion cells, both for research and clinical purposes, is a highly desired goal in patients with acute and chronic pulmonary diseases. However, lack of proper cell isolation and enrichment techniques hinder downstream evaluation and characterization of cells found in airway secretions. Here, we demonstrate a novel enrichment method to capture immune-related cells from clinical airway secretions using closed-loop separation of spiral inertial microfluidics (C-sep). By recirculating the output focusing stream back to the input reservoir and running continuously with a high flow processing rate, one can achieve optimal concentration, recovery and purity of airway immune cells from a large volume of diluent, which was not readily possible in the single-pass operation. Our method reproducibly recovers 94.0% of polymorphonuclear leukocytes (PMNs), with up to 105 PMNs in clear diluted buffer from 50 μL of airway secretions obtained from mechanically ventilated patients. We show that C-sep isolated PMNs show higher neutrophil elastase (NE) release following activation by phorbol 12-myristate 13-acetate (PMA) than cells isolated by conventional mucolytic method. By capturing cells without chemically disrupting their potential function, our method is expected to expand the possibility of clinical in vitro cell based biological assays for various pulmonary diseases such as acute respiratory distress syndrome, pneumonia, cystic fibrosis, and bronchiectasis. [ABSTRACT FROM AUTHOR]

In an electrochemical system, ion transport near ion exchange membranes or electrodes induces inevitable concentration polarization ( i.e. , formation of diffusion boundaries), which impedes the mass transport and worsens the energy efficiency. To mitigate the effect of concentration polarization (CP), various efforts towards mass transport enhancement employed structures, often called spacers, which promote mixing and modify the flow velocity distribution in the channel. In this work, we employed an electrodialysis (ED) system as a model to investigate the mass transport effects of embedded microstructures, which can redistribute the local flow velocity. We placed a row of cylindrical posts inside the diluate channel and varied the distance from the posts to the membranes. We studied the effect of this post-to-membrane distance on the mass transport by measuring the current-voltage responses and visualizing ion concentration and flow velocity profiles. The study was done through microfluidic ED model experiments and direct numerical simulation based on the coupled Navier-Stokes and Poisson-Nernst-Planck equations. Our results indicate that when the posts are positioned near the center of the channel, the mass transport is enhanced due to the increase in local convection near the concentration boundary layers. More importantly, we discovered that the mass transport is maximized when the location of the posts is slightly off-centered, due to the asymmetry of the cation/anion diffusivity (D Na+