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Cancer-specific small extracellular vesicles (sEVs), known as exosomes, have shown a great promise to serve as novel biomarkers for cancer diagnosis and prognosis in liquid biopsies. However, the high heterogeneity of sEVs posed great technical challenges to acquiring their molecular information. A simple and reproducible method for isolating subpopulations of sEVs can significantly enhance the detection and stratification of these circulating biomarkers and their function. This study used the synergic effects of the immunoaffinity-based approach and inertial microfluidics (ImmunoInertial microfluidics) to isolate specific subpopulations of sEVs. At first, the cancer cell-derived sEVs were captured on microbeads of varying sizes which were functionalized with specific capture antibodies such as epithelial cell adhesion molecule (EpCAM), epidermal growth factor receptor (EGFR), and the programmed death-ligand 1 (PD-L1), facilitating the selective capture of sEVs. The sEVs-bearing microbeads were subsequently introduced to a series of inertial microfluidic channels, called iZExoSub (inertial zigzag microfluidics for exosome subpopulation separation), for size-based bead separation. Results revealed more than 90% efficiency in sEVs subpopulation separation, further proved via flow cytometry analysis data. Our approach is capable of selective isolation and quantitative detection of important biomarkers from sEVs subpopulations with high sensitivity and low cost and has the capacity to process samples of varying volumes, ranging from µL up to mL continuously. This system can outperform FACS machines in terms of sample throughput by orders of magnitudes. In addition, this study emphasized the necessity of using a consistent sEV marker (as capture and detector) across different samples for accurate assessment of subpopulations.

Most biorelated applications require homogeneous mixing, necessitating innovative approaches to design high-efficiency micromixers. In this study, for the first time, we have changed the straight structure of a base square-wave micromixer to include regular-polygon-designed mixing units coupled with convergent-divergent channels. The aim was to show that the designed mixing units can enhance mixing at low Reynolds (Re) numbers. Importantly, within the optimization process, the mixing volume and mixing length of the micromixers were kept intact. In this respect, the required numerical evaluations were conducted to obtain the optimized micromixers at Re = 0.1 and 2, where the mixing index for the base micromixer increased from 0.9187 to 0.9944 and from 0.1600 to 0.4043, respectively. Finally, to prove that the optimized micromixers possess a better practical performance than the base micromixer, RBC lysis, as a vital preprocessing step of many biological experiments, was compared at Re = 0.1 and 2 for the base and optimized micromixers.

This paper describes, in detail, a method that uses flow cytometry to quantitatively characterise the performance of continuous-flow microfluidic devices designed to separate particles. Whilst simple, this approach overcomes many of the issues with the current commonly utilised methods (high-speed fluorescent imaging, or cell counting via either a hemocytometer or a cell counter), as it can accurately assess device performance even in complex, high concentration mixtures in a way that was previously not possible. Uniquely, this approach takes advantage of pulse processing in flow cytometry to allow quantitation of cell separation efficiencies and resulting sample purities on both single cells as well as cell clusters (such as circulating tumour cell (CTC) clusters). Furthermore, it can readily be combined with cell surface phenotyping to measure separation efficiencies and purities in complex cell mixtures. This method will facilitate the rapid development of a raft of continuous flow microfluidic devices, will be helpful in testing novel separation devices for biologically relevant clusters of cells such as CTC clusters, and will provide a quantitative assessment of device performance in complex samples, which was previously impossible.

Microalgae are of commercial interest for their ability to produce high-value compounds and their potential to be used as feedstock across numerous industries. The production of algal biomass and other algal-based products involves different upstream and downstream processing steps, including cultivation, harvesting, and extraction. In particular, the harvesting process involves the extraction of a condensed algal slurry from a watery growth medium. This process accounts for 20 to 30 % of the biomass production costs, creating technological and economic barriers. The conventional harvesting methods suffer from high costs, cross-contamination, and low yield. This study explores the use of a microfluidic technique, in particular, the rigid spiral microchannel, for ultra-high-throughput algae harvesting. We have designed a novel spiral channel that enables microalgae separation at high flow rates and spatial resolution, taking advantage of inertial microfluidic principles. The results from trials with surrogate microparticles and algal cells reveal that the microchannel has the potential to operate at 12 mL/min with separation efficiency >99 %. Our inertial microfluidic device operates at high flow rates as a single channel, can be multiplexed, and shows excellent potential for large-scale processing of microalgae cultures. In addition, the lower number of loops provides the system with reduced back pressure, making it more desirable for operation using a range of different pumps. Since the overall cost of microalgae dewatering is substantial at the industrial scale, the design and fabrication of low-cost devices are of great importance, similar to the one we have developed in this study.

Giardia is one of the most common waterborne pathogens causing around 200 × 106 diarrheal infections annually. It is of great interest to microbiological research as it is among the oldest known eukaryotic cells. Purifying Giardia from fecal samples for both research and diagnostic purposes presents one of the most difficult challenges. Traditional purification methods rely on density gradient centrifugation, membrane-based filtration, and sedimentation methods, which suffer from low recovery rates, high costs, and poor efficiency. Here, we report on the use of microfluidics to purify Giardia cysts from mouse feces. We propose a rigid spiral microfluidic device with a trapezoidal cross section to effectively separate Giardia from surrounding debris. Our characterizations reveal that the recovery rate is concentration-dependent, and our proposed device can achieve recovery rates as high as 75% with 0.75 ml/min throughput. Moreover, this device can purify Giardia from extremely turbid samples to a level where cysts are visually distinguishable with just one round of purification. This highly scalable and versatile 3D printed microfluidic device is then capable of further purifying or enhancing the recovery rate of the samples by recirculation. This device also has the potential to purify other gastrointestinal pathogens of similar size, and throughput can be significantly increased by parallelization.

Microbial populations play a crucial role in human health and the development of many diseases. These diseases often arise from the explosive proliferation of opportunistic bacteria, such as those in the nasal cavity. Recently, there have been increases in the prevalence of these opportunistic pathogens displaying antibiotic resistance. Thus, the study of the nasal microbiota and its bacterial diversity is critical in understanding pathogenesis and developing microbial-based therapies for well-known and emerging diseases. However, the isolation and analysis of these populations for clinical study complicates the already challenging task of identifying and profiling potentially harmful bacteria. Existing methods are limited by low sample throughput, expensive labeling, and low recovery of bacteria with ineffective removal of cells and debris. In this study, we propose a novel microfluidic channel with a zigzag configuration for enhanced isolation and detection of bacteria from human clinical nasal swabs. This microfluidic zigzag channel separates the bacteria from epithelial cells and debris by size differential focusing. As such, pure bacterial cell fractions devoid of large contaminating debris or epithelial cells are obtained. DNA sequencing performed on the separated bacteria defines the diversity and species present. This novel method of bacterial separation is simple, robust, rapid, and cost-effective and has the potential to be used for the rapid identification of bacterial cell populations from clinical samples.

Separation and enrichment of target cells prior to downstream analyses is an essential pre-treatment step in many biomedical and clinical assays. Separation techniques utilizing simple, cost-effective, and user-friendly devices are highly desirable, both in the lab and at the point of need. Passive microfluidic approaches, especially inertial microfluidics, fit this brief perfectly and are highly desired. Using an optimized additive manufacturing technique, we developed a zigzag microchannel for rigid inertial separation and enrichment, hereafter referred to as Z-RISE. We empirically showed that the Z-RISE device outperforms equivalent devices based on curvilinear (sinusoidal), asymmetric curvilinear, zigzag with round corners, or square-wave formats and modelled this behavior to gain a better understanding of the physics underpinning the improved focusing and separation performance. The comparison between rigid and soft zigzag microchannels reveals that channel rigidity significantly affects and enhances the focusing performance of the microchannel. Compared to other serpentine microchannels, zigzag microfluidics demonstrates superior separation and purity efficiency due to the sudden channel cross-section expansion at the corners. Within Z-RISE, particles are aligned in either double-side or single-line focusing positions. The transition of particles from a double-focusing line to a single focusing line introduced a new phenomenon referred to as the plus focusing position. We experimentally demonstrated that Z-RISE could enrich leukocytes and their subtypes from diluted and RBC lysed blood while depleting dead cells, debris, and RBCs. Z-RISE was also shown to yield outstanding particle or cell concentration with a concentration efficiency of more than 99.99%. Our data support the great potential of Z-RISE for applications that involve particle and cell manipulations and pave the way for commercialization perspective in the near future.

Cryopreservation is the final step of stem cell production before the cryostorage of the product. Conventional methods of adding cryoprotecting agents (CPA) into the cells can be manual or automated with robotic arms. However, challenging issues with these methods at industrial-scale production are the insufficient mixing of cells and CPA, leading to damage of cells, discontinuous feeding, the batch-to-batch difference in products, and, occasionally, cross-contamination. Therefore, the current study proposes an alternative way to overcome the abovementioned challenges; a highly efficient micromixer for low-cost, continuous, labour-free, and automated mixing of stem cells with CPA solutions. Our results show that our micromixer provides a more homogenous mixing of cells and CPA compared to the manual mixing method, while the cell properties, including surface markers, differentiation potential, proliferation, morphology, and therapeutic potential, are well preserved.

Prostate cancer (PCa) diagnosis is primarily based on prostate-specific antigen (PSA) testing and prostate tissue biopsies. However, PSA testing has relatively low specificity, while tissue biopsies are highly invasive and have relatively low sensitivity at early stages of PCa. As an alternative, we developed a technique of liquid biopsy, based on isolation of circulating tumor cells (CTCs) from seminal fluid (SF). The recovery of PCa cells from SF was demonstrated using PCa cell lines, achieving an efficiency and throughput as high as 89% (±3.8%) and 1.7 mL min-1, respectively, while 99% (±0.7%) of sperm cells were disposed of. The introduced approach was further tested in a clinical setting by collecting and processing SF samples of PCa patients. The yield of isolated CTCs measured as high as 613 cells per SF sample in comparison with that of 6 cells from SF of healthy donors, holding significant promise for PCa diagnosis. The correlation analysis of the isolated CTC numbers with the standard prognostic parameters such as Gleason score and PSA serum level showed correlation coefficient values at 0.40 and 0.73, respectively. Taken together, our results show promise in the developed liquid biopsy technique to augment the existing diagnosis and prognosis of PCa.

Microfluidic devices have shown promising applications in the bioprocessing industry. However, the lack of modularity and high cost of testing and error limit their implementation in the industry. Advances in 3D printing technologies have facilitated the conversion of microfluidic devices from research output to applicable industrial systems. Here, for the first time, we presented a 3D printed modular microfluidic system consisting of two micromixers, one spiral microfluidic separator, and one microfluidic concentrator. We showed that this system can detach and separate mesenchymal stem cells (MSCs) from microcarriers (MCs) in a short time while maintaining the cell’s viability and functionality. The system can be multiplexed and scaled up to process large volumes of the industry. Importantly, this system is a closed system with no human intervention and is promising for current good manufacturing practices. Graphical Abstract: [Figure not available: see fulltext.]

Microfluidics is a promising approach for the facile and large-scale fabrication of monodispersed droplets for various applications in biomedicine. This technology has demonstrated great potential to address the limitations of regenerative medicine. Microfluidics provides safe, accurate, reliable, and cost-effective methods for encapsulating different stem cells, gametes, biomaterials, biomolecules, reagents, genes, and nanoparticles inside picoliter-sized droplets or droplet-derived microgels for different applications. Moreover, microenvironments made using such droplets can mimic niches of stem cells for cell therapy purposes, simulate native extracellular matrix (ECM) for tissue engineering applications, and remove challenges in cell encapsulation and three-dimensional (3D) culture methods. The fabrication of droplets using microfluidics also provides controllable microenvironments for manipulating gametes, fertilization, and embryo cultures for reproductive medicine. This review focuses on the relevant studies, and the latest progress in applying droplets in stem cell therapy, tissue engineering, reproductive biology, and gene therapy are separately evaluated. In the end, we discuss the challenges ahead in the field of microfluidics-based droplets for advanced regenerative medicine.

Background Evidence recommends that vitamin D might be a crucial supportive agent for the immune system, mainly in cytokine response regulation against COVID-19. Hence, we carried out a systematic review and meta-analysis in order to maximise the use of everything that exists about the role of vitamin D in the COVID-19. Methods A systematic search was performed in PubMed, Scopus, Embase and Web of Science up to December 18, 2020. Studies focused on the role of vitamin D in confirmed COVID-19 patients were entered into the systematic review. Results Twenty-three studies containing 11 901 participants entered into the meta-analysis. The meta-analysis indicated that 41% of COVID-19 patients were suffering from vitamin D deficiency (95% CI, 29%-55%), and in 42% of patients, levels of vitamin D were insufficient (95% CI, 24%-63%). The serum 25-hydroxyvitamin D concentration was 20.3 ng/mL among all COVID-19 patients (95% CI, 12.1-19.8). The odds of getting infected with SARS-CoV-2 are 3.3 times higher among individuals with vitamin D deficiency (95% CI, 2.5-4.3). The chance of developing severe COVID-19 is about five times higher in patients with vitamin D deficiency (OR: 5.1, 95% CI, 2.6-10.3). There is no significant association between vitamin D status and higher mortality rates (OR: 1.6, 95% CI, 0.5-4.4). Conclusion This study found that most of the COVID-19 patients were suffering from vitamin D deficiency/insufficiency. Also, there is about three times higher chance of getting infected with SARS-CoV-2 among vitamin-D-deficient individuals and about five times higher probability of developing the severe disease in vitamin-D-deficient patients. Vitamin D deficiency showed no significant association with mortality rates in this population.

Exosomes belong to the class of extracellular vesicles of endocytic origin, which are regarded as a promising source of cancer biomarkers in liquid biopsy. As a result, an accurate, sensitive, and specific quantification of these nano-sized particles is of significant importance. Affinity-based approaches are recognized as the most valuable technique for exosome isolation and characterization. Indeed, Affibody biomolecules are a type of protein scaffold engineered with small size and enjoy the features of high thermal stability, affinity, and specificity. While the utilization of antibodies, aptamers, and other biologically active substances for exosome detection has been reported widely, there are no reports describing Affibody molecules’ usage for exosome detection. In this study, for the first time, we have proposed a novel strategy of using Affibody functionalized microbeads (AffiBeads) for exosome detection with a high degree of efficiency. As a proof-of-concept, anti-EGFR-AffiBeads were fabricated and applied to capture and detect human lung A549 cancer cell-derived EGFR-positive exosomes using flow cytometry and fluorescent microscopy. Moreover, the capture efficiency of the AffiBeads were compared with its counterpart antibody. Our results showed that the Affibody probe had a detection limit of 15.6 ng exosomes per mL (~12 exosomes per AffiBead). The approach proposed in the current study can be used for sensitive detection of low expression level markers on tumor-derived exosomes, providing a basis for early-stage cancer diagnosis.

Electrospinning is a promising method to fabricate bioengineered scaffolds, thanks to utilizing various types of biopolymers, flexible structures, and also the diversity of output properties. Mechanical properties are one of the major components of scaffold design to fabricate an efficacious artificial substitute for the natural extracellular matrix. Additionally, fiber orientations, as one of the scaffold structural parameters, could play a crucial role in the application of fabricated fibrous scaffolds. In this study, gelatin was used as a highly biocompatible polymer in blend with cellulose acetate (CA), a polysaccharide, to enhance the achievable range of mechanical characteristics to fabricated fibrous electrospun scaffolds. By altering input variables, such as polymers concentration, weight ratio, and mandrel rotation speed, scaffolds with various mechanical and morphological properties could be achieved. As expected, the electrospun scaffold with a higher mandrel rotation speed shows higher fiber alignment. A wide range of mechanical properties were gained through different values of polymer ratio and total concentration. A general improvement in mechanical strength was observed by increasing the concentration and CA content in the solution, but contradictory effects, such as high viscosity in more concentrated solutions, influenced the mechanical characteristics as well. A response surface method was applied on experimental results in order to describe a continuous variation of Young's modulus, yield stress, and strain at rupture. A full quadratic version of equations with the 95% confidence level was applied for the response modeling. This model would be an aid for engineers to adjust mandrel rotation speed, solution concentration, and gelatin/CA ratio to achieve desired mechanical and structural properties.

The COVID-19 pandemic has changed people's lives and has brought society to a sudden standstill, with lockdowns and social distancing as the preferred preventative measures. To lift these measurements and reduce society's burden, developing an easy-to-use, rapid, and portable system to detect SARS-CoV-2 is mandatory. To this end, we developed a portable and semi-automated device for SARS-CoV-2 detection based on reverse transcription loop-mediated isothermal amplification followed by a CRISPR/Cas12a reaction. The device contains a heater element mounted on a printed circuit board, a cooler fan, a proportional integral derivative controller to control the temperature, and designated areas for 0.2 mL Eppendorf® PCR tubes. Our system has a limit of detection of 35 copies of the virus per microliter, which is significant and has the capability of being used in crisis centers, mobile laboratories, remote locations, or airports to diagnose individuals infected with SARS-CoV-2. We believe the current methodology that we have implemented in this article is beneficial for the early screening of infectious diseases, in which fast screening with high accuracy is necessary.

Mixing at the microscale is of great importance for various applications ranging from biological and chemical synthesis to drug delivery. Among the numerous types of micromixers that have been developed, planar passive spiral micromixers have gained considerable interest due to their ease of fabrication and integration into complex miniaturized systems. However, less attention has been paid to non-planar spiral micromixers with various cross-sections and the effects of these cross-sections on the total performance of the micromixer. Here, mixing performance in a spiral micromixer with different channel cross-sections is evaluated experimentally and numerically in the Re range of 0.001 to 50. The accuracy of the 3D-finite element model was first verified at different flow rates by tracking the mixing index across the loops, which were directly proportional to the spiral radius and were hence also proportional to the Dean flow. It is shown that higher flow rates induce stronger vortices compared to lower flow rates; thus, fewer loops are required for efficient mixing. The numerical study revealed that a large-angle outward trapezoidal cross-section provides the highest mixing performance, reaching efficiencies of up to 95%. Moreover, the velocity/vorticity along the channel length was analyzed and discussed to evaluate channel mixing performance. A relatively low pressure drop (<130 kPa) makes these passive spiral micromixers ideal candidates for various lab-on-chip applications.

In modern life, several factors such as genetics, exposure to toxins, and aging have resulted in significant levels of male infertility, estimated to be approximately 18% worldwide. In response, substantial progress has been made to improve in vitro fertilization treatments (e.g. microsurgical testicular sperm extraction (m-TESE), intra-cytoplasmic sperm injection (ICSI), and round spermatid injection (ROSI)). Mimicking the structure of testicular natural extracellular matrices (ECM) outside of the body is one clear route toward complete in vitro spermatogenesis and male fertility preservation. Here, a new wave of technological innovations is underway applying regenerative medicine strategies to cell-tissue culture on natural or synthetic scaffolds supplemented with bioactive factors. The emergence of advanced bioengineered systems suggests new hope for male fertility preservation through development of functional male germ cells. To date, few studies aimed at in vitro spermatogenesis have resulted in relevant numbers of mature gametes. However, a substantial body of knowledge on conditions that are required to maintain and mature male germ cells in vitro is now in place. This review focuses on advanced bioengineering methods such as microfluidic systems, bio-fabricated scaffolds, and 3D organ culture applied to the germline for fertility preservation through in vitro spermatogenesis.

Intracellular delivery is considered an indispensable process for various studies, ranging from medical applications (cell-based therapy) to fundamental (genome-editing) and industrial (biomanufacture) approaches. Conventional macroscale delivery systems critically suffer from such issues as low cell viability, cytotoxicity, and inconsistent material delivery, which have opened up an interest in the development of more efficient intracellular delivery systems. In line with the advances in microfluidics and nanotechnology, intracellular delivery based on micro- and nanoengineered platforms has progressed rapidly and held great promises owing to their unique features. These approaches have been advanced to introduce a smorgasbord of diverse cargoes into various cell types with the maximum efficiency and the highest precision. This review differentiates macro-, micro-, and nanoengineered approaches for intracellular delivery. The macroengineered delivery platforms are first summarized and then each method is categorized based on whether it employs a carrier- or membrane-disruption-mediated mechanism to load cargoes inside the cells. Second, particular emphasis is placed on the micro- and nanoengineered advances in the delivery of biomolecules inside the cells. Furthermore, the applications and challenges of the established and emerging delivery approaches are summarized. The topic is concluded by evaluating the future perspective of intracellular delivery toward the micro- and nanoengineered approaches.

Obstructive sleep apnoea (OSA) is a chronic disorder that involves a decrease or complete cessation of airflow during sleep. It occurs when the muscles supporting the soft tissues in the throat relax during sleep, causing narrowing or closure of the upper airway. Sleep apnoea is a serious medical condition with an increased risk of cardiovascular complications and impaired quality of life. Continuous positive airway pressure (CPAP) is the most effective treatment for moderate to severe cases of OSA and is effective in mild sleep apnoea. However, CPAP therapy is associated with the development of several nasal side effects and is inconvenient for the user, leading to low compliance rates. The effects of CPAP treatment on the upper respiratory system, as well as the pathogenesis of side effects, are incompletely understood and not adequately researched. To better understand the effects of CPAP treatment on the upper respiratory system, we developed an in vitro 3D-printed microfluidic platform. A nasal epithelial cell line, RPMI 2650, was then exposed to certain conditions to mimic the in-vivo environment. To create these conditions, the microfluidic device was utilized to expose nasal epithelial cells grown and differentiated at the air-liquid interface. The airflow was similar to what is experienced with CPAP, with pressure ranging between 0-20 cm of H20. Cells exposed to pressure showed decreased barrier integrity, change in cellular shape, and increased cell death (lactate dehydrogenase release into media) compared to unstressed cells. Stressed cells also showed increased secretions of inflammatory markers IL-6 and IL-8 and had increased production of ATP. Our results suggest that stress induced by airflow leads to structural, metabolic, and inflammatory changes in the nasal epithelium, which may be responsible for developing nasal side-effects following CPAP treatment.

BACKGROUND:Measurement of serum human epidermal growth factor receptor-2 (HER-2/neu) levels might play an essential role as a diagnostic/screening marker for the early selection of therapeutic approaches and predict prognosis in breast cancer patients. We aimed to undertake a systematic review and meta-analysis focusing on the diagnostic/screening value of serum HER-2 levels in comparison to routine methods. METHODS:We performed a systematic search via PubMed, Scopus, Cochrane-Library, and Web of Science databases for human diagnostic studies reporting the levels of serum HER-2 in breast cancer patients, which was confirmed using the histopathological examination. Meta-analyses were carried out for sensitivity, specificity, accuracy, area under the ROC curve (AUC), positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR), and negative likelihood ratio (NLR). RESULTS:Fourteen studies entered into this investigation. The meta-analysis indicated the low sensitivity for serum HER2 levels (Sensitivity: 53.05, 95%CI 40.82-65.28), but reasonable specificity of 79.27 (95%CI 73.02-85.51), accuracy of 72.06 (95%CI 67.04-77.08) and AUC of 0.79 (95%CI 0.66-0.92). We also found a significant differences for PPV (PPV: 56.18, 95%CI 44.16-68.20), NPV (NPV: 76.93, 95%CI 69.56-84.31), PLR (PLR: 2.10, 95%CI 1.69-2.50) and NLR (NLR: 0.58, 95%CI 0.44-0.71). CONCLUSION:Our findings revealed that although serum HER-2 levels showed low se nsitivity for breast cancer diagnosis, its specificity, accuracy and AUC were reasonable. Hence, it seems that the measurement of serum HER-2 levels can play a significant role as a verification test for initial negative screening test results, especially in low-income regions due to its cost-effectiveness and ease of implementation.

© 2020 Elsevier B.V. Telomerase activity has been demonstrated in a wide variety of most solid tumors and considered as a well-known cancer biomarker. The commonly utilized method for its detection is polymerase chain reaction (PCR)-based telomeric repeat amplification protocol (TRAP). However, the TRAP technique suffers from false-negative results caused by the failure of PCR step. Moreover, it requires advanced equipment with a tedious and time-consuming procedure. Herein, we presented a portable nitrocellulose paper-based nanobiosensing platform for ultrafast and equipment-free detection of telomerase activity based on a simple colorimetric assay that enabled naked-eye visualization of the color change in response to enzyme activity. In this platform, hybridization was initially performed between telomere complementary oligonucleotide immobilized on gold nanoparticles (GNPs) and telomerase elongated biotinylated probe. Thereafter, the assembly was attached on activated paper strip via avidin-biotin interaction. The signal amplification was carried out by enlargement of the attached GNPs on the paper strip, forming tightly compact rod-shaped submicron structures of gold representing a visual color formation. Thanks to significant sensitivity enhancement, the color change was occurred for down to 6 cells, which can be easily observed by the naked eye. Due to the desired aspects of the developed assay including PCR-free, low cost, simple, and high sensitivity, it can be used for evaluation of telomerase activity in cell extracts for future clinical applications. Furthermore, this design has the ability to be easily integrated into lab-on-chip devices for point-of-care telomerase sensing.

High throughput particle/cell concentration is crucial for a wide variety of biomedical, clinical, and environmental applications. In this work, we have proposed a passive spiral microfluidic concentrator with a complex cross-sectional shape, i.e., a combination of rectangle and trapezoid, for high separation efficiency and a confinement ratio less than 0.07. Particle focusing in our microfluidic system was observed in a single, tight focusing line, in which higher particle concentration is possible, as compared with simple rectangular or trapezoidal cross-sections with similar flow area. The sharper focusing stems from the confinement of Dean vortices in the trapezoidal region of the complex cross-section. To quantify this effect, we introduce a new parameter, complex focusing number or CFN, which is indicative of the enhancement of inertial focusing of particles in these channels. Three spiral microchannels with various widths of 400 µm, 500 µm, and 600 µm, with the corresponding CFNs of 4.3, 4.5, and 6, respectively, were used. The device with the total width of 600 µm was shown to have a separation efficiency of ~98%, and by recirculating, the output concentration of the sample was 500 times higher than the initial input. Finally, the investigation of results showed that the magnitude of CFN relies entirely on the microchannel geometry, and it is independent of the overall width of the channel cross-section. We envision that this concept of particle focusing through complex cross-sections will prove useful in paving the way towards more efficient inertial microfluidic devices.

© 2020, © 2020 Informa UK Limited, trading as Taylor & Francis Group. Recently, organ-on-a-chip models, which are microfluidic devices that mimic the cellular architecture and physiological environment of an organ, have been developed and extensively investigated. The chips can be tailored to accommodate the disease conditions pertaining to many organs; and in the case of this review, the lung. Lung-on-a-chip models result in a more accurate reflection compared to conventional in vitro models. Pharmaceutical drug testing methods traditionally use animal models in order to evaluate pharmacological and toxicological responses to a new agent. However, these responses do not directly reflect human physiological responses. In this review, current and future applications of the lung-on-a-chip in the respiratory system will be discussed. Furthermore, the limitations of current conventional in vitro models used for respiratory disease modeling and drug development will be addressed. Highlights of additional translational aspects of the lung-on-a-chip will be discussed in order to demonstrate the importance of this subject for medical research.

The recent outbreak of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its associated serious respiratory disease, coronavirus disease 2019 (COVID-19), poses a major threat to global public health. Owing to the lack of vaccine and effective treatments, many countries have been overwhelmed with an exponential spread of the virus and surge in the number of confirmed COVID-19 cases. Current standard diagnostic methods are inadequate for widespread testing as they suffer from prolonged turn-around times (>12 h) and mostly rely on high-biosafety-level laboratories and well-trained technicians. Point-of-care (POC) tests have the potential to vastly improve healthcare in several ways, ranging from enabling earlier detection and easier monitoring of disease to reaching remote populations. In recent years, the field of POC diagnostics has improved markedly with the advent of micro- and nanotechnologies. Due to the COVID-19 pandemic, POC technologies have been rapidly innovated to address key limitations faced in existing standard diagnostic methods. This review summarizes and compares the latest available POC immunoassay, nucleic acid-based and clustered regularly interspaced short palindromic repeats- (CRISPR)-mediated tests for SARS-CoV-2 detection that we anticipate aiding healthcare facilities to control virus infection and prevent subsequent spread.

Inertial microfluidics has been broadly investigated, resulting in the development of various applications, mainly for particle or cell separation. Lateral migrations of these particles within a microchannel strictly depend on the channel design and its cross-section. Nonetheless, the fabrication of these microchannels is a continuous challenging issue for the microfluidic community, where the most studied channel cross-sections are limited to only rectangular and more recently trapezoidal microchannels. As a result, a huge amount of potential remains intact for other geometries with cross-sections difficult to fabricate with standard microfabrication techniques. In this study, by leveraging on benefits of additive manufacturing, we have proposed a new method for the fabrication of inertial microfluidic devices. In our proposed workflow, parts are first printed via a high-resolution DLP/SLA 3D printer and then bonded to a transparent PMMA sheet using a double-coated pressure-sensitive adhesive tape. Using this method, we have fabricated and tested a plethora of existing inertial microfluidic devices, whether in a single or multiplexed manner, such as straight, spiral, serpentine, curvilinear, and contraction-expansion arrays. Our characterizations using both particles and cells revealed that the produced chips could withstand a pressure up to 150 psi with minimum interference of the tape to the total functionality of the device and viability of cells. As a showcase of the versatility of our method, we have proposed a new spiral microchannel with right-angled triangular cross-section which is technically impossible to fabricate using the standard lithography. We are of the opinion that the method proposed in this study will open the door for more complex geometries with the bespoke passive internal flow. Furthermore, the proposed fabrication workflow can be adopted at the production level, enabling large-scale manufacturing of inertial microfluidic devices.

Since the discovery of inertial focusing in 1961, numerous theories have been put forward to explain the migration of particles in inertial flows, but a complete understanding is still lacking. Recently, computational approaches have been utilized to obtain better insights into the underlying physics. In particular, fundamental aspects of particle focusing inside straight and curved microchannels have been explored in detail to determine the dependence of focusing behavior on particle size, channel shape, and flow Reynolds number. In this review, we differentiate between the models developed for inertial particle motion on the basis of whether they are semi-analytical, Navier-Stokes-based, or built on the lattice Boltzmann method. This review provides a blueprint for the consideration of numerical solutions for modeling of inertial particle motion, whether deformable or rigid, spherical or non-spherical, and whether suspended in Newtonian or non-Newtonian fluids. In each section, we provide the general equations used to solve particle motion, followed by a tutorial appendix and specified sections to engage the reader with details of the numerical studies. Finally, we address the challenges ahead in the modeling of inertial particle microfluidics for future investigators.

© 2019 Elsevier B.V. Expression of programmed death-ligand 1 (PD-L1) in cancer cells plays an important role in cancer-immune cell interaction. The emerging evidence suggests regulation of PD-L1 expression by several tumor microenvironmental cues. However, the association of PD-L1 expression with chemical and mechanical features of the tumor microenvironment, specifically epidermal growth factor receptor (EGFR) signaling and matrix stiffness, remains elusive. Herein, we determine whether EGFR targeting and substrate stiffness affect the regulation of PD-L1 expression. Breast carcinoma cell lines, MCF7 and MDA-MB-231, were cultured under different conditions targeting EGFR and exposing cells to distinct substrate stiffness to evaluate PD-L1 expression. Furthermore, the ability to form aggregates in short-term culture of breast carcinoma cells and its effect on expression level of PD-L1 was probed. Our results indicated that PD-L1 expression was altered in response to both EGFR inhibition and substrate stiffness. Additionally, a positive association between the formation of multicellular aggregates and PD-L1 expression was observed. MDA-MB-231 cells expressed the highest PD-L1 level on a stiff substrate, while inhibition of EGFR reduced expression of PD-L1. The results suggested that both physical and chemical features of tumor microenvironment regulate PD-L1 expression through alteration of tumor aggregate formation potential. In line with these results, the in-silico study highlighted a positive correlation between PD-L1 expression, EGFR signaling, epithelial to mesenchymal transition related transcription factors (EMT-TFs) and stemness markers in metastatic breast cancer. These findings improve our understanding of regulation of PD-L1 expression by tumor microenvironment leading to evasion of tumor cells from the immune system.

© 2019, Controlled Release Society. Dexamethasone is a widely used drug in medical and biological applications. Since the systematic and controllable release of this drug is of significant importance, encapsulation of this anti-inflammatory drug in poly(lactic-co-glycolic acid) (PLGA) nanoparticles can minimize uncontrolled issues. As dexamethasone-encapsulated PLGA nanoparticles are synthesized in the presence of organic solvents, poly(dimethylsiloxane) (PDMS)-based microchannels collapse due to the swelling problem. In present study, PTFE nanoparticles were used for the surface modification of the microchannels to prevent absorption and adhesion of solvents into the microchannels’ wall. The contact angle analysis of microchips after coating showed that the surface of microchannels bear the superhydrophobicity feature (140.30°) and SEM images revealed that PTFE covered the surface of PDMS, favorably. Then, the prepared microchip was tested for the synthesis of dexamethasone-loaded nanoparticles. SEM and atomic force microscopy (AFM) images of the synthesized nanoparticles represented that there was not any evidence of adhesion or absorption of nanoparticles. Furthermore, the monodispersity of nanoparticles was discernible. As AFM results revealed, the average diameters of 47, 63, and 82 nm were achieved for flow ratios of 0.01, 0.05, and 0.1, respectively. To evaluate the drug efficiency, cumulative release and encapsulation efficiency were analyzed which showed much more efficiency than the synthesized nanoparticles in the bulk mode. In addition, MTT test revealed that nanoparticles could be considered as a non-toxic material. Since the synthesis of drug-loaded nanoparticles is ubiquitous in laboratory experiments, the approach presented in this study can render more versatility in this regard.

DNA is a molecule and assortment of fruitful information of organisms and a wide range of viruses. Polymerase chain reaction (PCR) is a process used to amplify DNA strands in order to generate millions of them and extract the applicable information. Although conventional methods for PCR are flourishing to a certain extent, they have such major drawbacks as contamination, high material consumption, and low-speed function. By the combination of PCR devices with the microfluidic approach and integrating them with droplet generation technology, the mentioned problems can be eliminated. In this study, a novel two-step rapid-cycle dropletbased PCR (dPCR) device, considering the design of microchannel and heat transfer system, has been presented. First, numerous studies have been conducted to select the proper droplet generator for the integration of the droplet generation with the PCR device. Then, with the careful attention to the requirements of a PCR device, the geometry of different zones of the PCR device has been, meticulously, designed. In the next and last step, the heat transfer system for the designed zones of the PCR device has been planned. Afterward, results are examined carefully which indicate that in a cycle of PCR, they are not any major discrepancies between the designed dPCR and the ideal one-the one that is intended to be created.