Capillary force-driven reverse-Tesla valve structure for microfluidic bioassays.

Biological assays involve the lysis of biological particles, enzyme reactions, and gene amplification, and require a certain amount of time for completion. Microfluidic chips are regarded as powerful devices for biological assays and in vitro diagnostics; however, they cannot achieve a high mixing efficiency, particularly in some time-consuming biological reactions. Herein, we introduce a microfluidic reverse-Tesla (reTesla) valve structure in which the fluid is affected by vortices and branch flow convergence, resulting in flow retardation and a high degree of mixing. The reTesla is passively operated by a microfluidic capillary force without any pumping facility. Compared with our previously developed micromixers, this innovative pumpless microfluidic chip exhibited high performance, with a mixing efficiency of more than 93%. The versatility of our reTesla chip will play a pivotal role in the study of various biological and chemical reactions.

Efficient separation of large particles and giant cancer cells using an isosceles trapezoidal spiral microchannel.

Polyploid giant cancer cells (PGCCs) contribute to the genetic heterogeneity and evolutionary dynamics of tumors. Their size, however, complicates their isolation from mainstream tumor cell populations. Standard techniques like fluorescence-activated cell sorting (FACS) rely on fluorescent labeling, introducing potential challenges in subsequent PGCC analyses. In response, we developed the Isosceles Trapezoidal Spiral Microchannel (ITSµC), a microfluidic device optimizing the Dean drag force (FD) and exploiting uniform vortices for enhanced separation. Numerical simulations highlighted ITSµC's advantage in producing robust FD compared to rectangular and standard trapezoidal channels. Empirical results confirmed its ability to segregate larger polystyrene (PS) particles (avg. diameter: 50 µm) toward the inner wall, while directing smaller ones (avg. diameter: 23 µm) outward. Utilizing ITSµC, we efficiently isolated PGCCs from doxorubicin-resistant triple-negative breast cancer (DOXR-TNBC) and patient-derived cancer (PDC) cells, achieving outstanding purity, yield, and viability rates (all greater than 90%). This precision was accomplished without fluorescent markers, and the versatility of ITSµC suggests its potential in differentiating a wide range of heterogeneous cell populations.

Enhanced enrichment of collected airborne coronavirus and influenza virus samples via a ConA-coated microfluidic chip for PCR detection.

The severe acute respiratory syndrome (SARS-CoV-2) outbreak triggered global concern and emphasized the importance of virus monitoring. During a seasonal influenza A outbreak, relatively low concentrations of 103-104 viral genome copies are available per 1 m3 of air, which makes detection and monitoring very challenging because the limit of detection of most polymerase chain reaction (PCR) devices is approximately 103 viral genome copies/mL. In response to the urgent need for the rapid detection of airborne coronaviruses and influenza viruses, an electrostatic aerosol-to-hydrosol (ATH) sampler was combined with a concanavalin A (ConA)-coated high-throughput microfluidic chip. The samples were then used for PCR detection. The results revealed that the enrichment capacity of the ATH sampler was 30,000-fold for both HCoV-229E and H1N1 influenza virus, whereas the enrichment capacities provided by the ConA-coated microfluidic chip were 8-fold and 16-fold for HCoV-229E and H1N1 virus, respectively. Thus, the total enrichment capacities of our combined ATH sampler and ConA-coated microfluidic chip were 2.4 × 105-fold and 4.8 × 105-fold for HCoV-229E and H1N1 virus, respectively. This methodology significantly improves PCR detection by providing a higher concentration of viable samples.

E2E-BPF microscope: extended depth-of-field microscopy using learning-based implementation of binary phase filter and image deconvolution.

Several image-based biomedical diagnoses require high-resolution imaging capabilities at large spatial scales. However, conventional microscopes exhibit an inherent trade-off between depth-of-field (DoF) and spatial resolution, and thus require objects to be refocused at each lateral location, which is time consuming. Here, we present a computational imaging platform, termed E2E-BPF microscope, which enables large-area, high-resolution imaging of large-scale objects without serial refocusing. This method involves a physics-incorporated, deep-learned design of binary phase filter (BPF) and jointly optimized deconvolution neural network, which altogether produces high-resolution, high-contrast images over extended depth ranges. We demonstrate the method through numerical simulations and experiments with fluorescently labeled beads, cells and tissue section, and present high-resolution imaging capability over a 15.5-fold larger DoF than the conventional microscope. Our method provides highly effective and scalable strategy for DoF-extended optical imaging system, and is expected to find numerous applications in rapid image-based diagnosis, optical vision, and metrology.

An all-in-one platform to deplete pathogenic bacteria for rapid and safe enrichment of plant-derived extracellular vesicles.

Plant-derived extracellular vesicles (PDEVs) have exhibited several advantages, such as high biocompatibility, improvement of skin conditions, and the prevention of skin aging. However, traditional methods of extraction for plant substances, such as heating under reflux or solvent extraction, are complicated, time-consuming, and low in purity. Accordingly, a simple and efficient platform is necessary for purely isolating natural substances from plants. In this study, we report a newly designed platform for removing impurities to purify PDEVs. The proposed platform comprises three parts: (i) inflow of samples, (ii) depletion of impurities, and (iii) collection of PDEVs. The platform is designed to flow from top to bottom using gravity without the need for electric components. The platform allows the delimitation of impurities, such as the pathogenic bacteria in PDEVs, by capturing magnetic beads coated with Concanavalin A (Con A). We validate the practicality of our platform using extracellular vesicles derived from liquorice (LdEVs). Notably, the LdEVs purified using the Con A-coated magnetic beads provide better cell uptake and wound recovery than the commercialized extract LdEVs. This highlights the therapeutic potential of fresh LdEVs purified using our platform, particularly in preventing skin aging. The findings of this study hold significant practical implications for the cosmeceutical and therapeutic field, providing a promising approach for the extraction and purification of natural substances from plants to harness their benefits effectively.

Modularized dynamic cell culture platform for efficient production of extracellular vesicles and sequential analysis.

Extracellular vesicles (EVs) are nanometer-sized particles naturally secreted by cells for intercellular communication that encapsulate bioactive cargo, such as proteins and RNA, with a lipid bilayer. Tumor cell-derived EVs (tdEVs) are particularly promising biomarkers for cancer research because their contents reflect the cell of origin. In most studies, tdEVs have been obtained from cancer cells cultured under static conditions, thus lacking the ability to recapitulate the microenvironment of cells in vivo. Recent developments in perfusable cell culture systems have allowed oxygen and a nutrient gradient to mimic the physiological and cellular microenvironment. However, as these systems are perfused by circulating the culture medium within the unified structure, independently harvesting cells and EVs at each time point for analysis presents a limitation. In this study, a modularized cell culture system is designed for the perfusion and real-time collection of EVs. The system consists of three detachable chambers, one each for fresh medium, cell culture, and EV collection. The fresh medium flows from the medium chamber to the culture chamber at a flow rate controlled by the hydraulic pressure injected with a syringe pump. When the culture medium containing EVs exceeds a certain volume within the chamber, it overflows into the collection chamber to harvest EVs. The compact and modularized chambers are highly interoperable with conventional cell culture modalities used in the laboratory, thus enabling various EV-based assays.

Electrochemical detection and analysis of tumor-derived extracellular vesicles to evaluate malignancy of pancreatic cystic neoplasm using integrated microfluidic device.

Tumor-derived extracellular vesicles (tdEVs) are one of the most promising biomarkers for liquid biopsy-based cancer diagnostics, owing to the expression of specific membrane proteins of their cellular origin. The investigation of epithelial-to-mesenchymal transition (EMT) in cancer using tdEVs is an alternative way of evaluating the risk of malignancy transformation. An ultra-sensitive selection and detection methodology is an essential step in developing a tdEVs-based cancer diagnostic device. In this study, we developed an indium-tin-oxide (ITO) sensor integrated microfluidic device consisting of two main parts: 1) a multi-orifice flow-fractionation (MOFF) channel for extraction of pure EVs by removing blood cellular debris, and 2) an ITO sensor coupled with a geometrically activated surface interaction (GASI) channel for enrichment and quantification of tdEV. The microfluidic channel and the ITO sensors are assembled with a 3D printed magnetic housing to prevent sample leakage and to easily attach/detach the sensors to/from the microfluidic channel. The tdEVs were successfully captured on the specific antibody modified ITO surfaces in the integrated microfluidic channel. The integrated sensors showed an excellent linear response between 103 and 109 tdEVs/mL. Simultaneous evaluation of the epithelial and mesenchymal markers on the tdEV surfaces successfully revealed the EMT index of the corresponding pancreatic cancer cells. Our ITO sensor integrated microfluidic device showed excellent detection in the clinically relevant tdEVs-concentration range for patients with pancreatic cystic neoplasms. Hence, this system is expected to open a new avenue for liquid biopsy-based cancer prognostics and diagnostics.

Coil spring-powered pump with inertial microfluidic chip for size-based isolation and enrichment of biological cells.

Microfluidic chips have been widely used for in vitro diagnostics using pretreatment of biological samples; however, biologists and clinical researchers have difficulties using them in resource-limited settings. Sample injection systems for microfluidic chips are bulky, expensive, electricity-powered, and complex. A coiled spring-powered device, which can be used to isolate variously sized cells with high efficiency continuously and passively, was developed for portable, low-cost, electricity-free, and simple sample injection. The flow driving power was provided by releasing the compression spring in the mechanical syringe driver with a one-click action. In general, a syringe pump generates a stable passive flow rate. However, the syringe pumps are large in size and expensive because they have many functions such as infusion/withdrawal flow injection and the use of syringes of various sizes, allowing them to be applied in a variety of applications performed in the laboratory. In addition, it is not suitable for portable devices because of the considerable amount of electric power required. To overcome these drawbacks, we developed a device prototype that sorts different-sized particles and separates rare tumor cells or blood cells from blood with high efficiency. The performance of the coiled spring-powered device was evaluated and found to be comparable with that of syringe pump-powered devices. In situations where trained personnel cannot handle microfluidic chips for isolating circulating biomarkers (CTCs, WBCs, or plasma) from blood samples, the coiled spring-powered device can provide diagnostic tools, especially in resource-limited countries.

A modular microfluidic platform for serial enrichment and harvest of pure extracellular vesicles.

Extracellular vesicles (EVs) are recognized as promising biomarkers for several diseases. However, their conventional isolation methods have several drawbacks, such as poor yields, low purity, and time-consuming operations. Therefore, a simple, low-cost, and rapid microfluidic platform has been extensively developed to meet the requirement in biomedical applications. Herein, a modular microfluidic platform is demonstrated to isolate and enrich EVs directly from plasma, in a combination of continuous capture and purification of EVs. The EVs were selectively captured by target-specific antibody-coated beads in a horseshoe-shaped orifice micromixer (HOMM) chip within 2 min. A fish-trap-shaped microfilter unit was subsequently used to elute and purify the affinity-induced captured EVs from the microbeads. The ability of the modular chip to capture, enrich, and release EVs was demonstrated in 5 min (100 µL sample) at high throughput (100 µL min-1). The two chips can be modularized or individually operated, depending on the clinical applications such as diagnostics and therapeutics. For the diagnostic applications, the EVs on microbeads can be directly subjected to the molecular analysis whereas the pure EVs should be released from the microbeads for the therapeutic treatments. This study reveals that the fabricated modular chip can be appropriately employed as a platform for EV-related research tools.

Electrochemical biosensor for nucleic acid amplification-free and sensitive detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA via CRISPR/Cas13a trans-cleavage reaction.

The outbreak of the COVID-19 pandemic has led to millions of fatalities worldwide. For preventing epidemic transmission, rapid and accurate virus detection methods to early identify infected people are urgently needed in the current situation. Therefore, an electrochemical biosensor based on the trans-cleavage activity of CRISPR/Cas13a was developed in this study for rapid, sensitive, and nucleic-acid-amplification-free detection of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Herein, a redox probe conjugated with ssRNA is immobilized on the electrode surface modified with a nanocomposite (NC) and gold nanoflower (AuNF) for enhancing the sensing performance. The SARS-CoV-2 RNA is captured by the Cas13a-crRNA complex, which triggers the RNase function of Cas13a. The enzymatically activated Cas13a-crRNA complex is subsequently introduced to the reRNA-conjugated electrochemical sensor, and consequently cleaves the reRNA. A change in current occurs due to the release of the redox molecule labeled on the reRNA, which is trans-cleaved from the Cas13a-crRNA complex. The biosensor can detect as low as 4.4 × 10-2 fg/mL and 8.1 × 10-2 fg/mL of ORF and S genes, respectively, over a wide dynamic range (1.0 × 10-1 to 1.0 × 105 fg/mL). Moreover, the biosensor was evaluated by measuring SARS-CoV-2 RNA spiked in artificial saliva. The recovery of the developed sensor was found to be in an agreeable range of 96.54-101.21%. The designed biosensor lays the groundwork for pre-amplification-free detection of ultra-low concentrations of SARS-CoV-2 RNA and on-site and rapid diagnostic testing for COVID-19.

Multi-miRNA panel of tumor-derived extracellular vesicles as promising diagnostic biomarkers of early-stage breast cancer.

Extracellular vesicles (EV) have been emerging as potential biomarkers for disease monitoring. In particular, tumor-derived EV (TDE) are known to carry oncogenic miRNA, so they can be used for diagnosis of early cancer by analyzing the expression levels of EV-miRNA circulating in the blood. Here, using our novel microfluidic device, we rapidly and selectively isolate cancerous EV expressing breast cancer-derived surface markers CD49f and EpCAM within 2 minutes. Based on seven candidates of miRNA nominated from The Cancer Genome Atlas (TCGA) database, the expression levels of miRNA in TDE were validated in a total of 82 individuals, including 62 breast cancer patients and 20 healthy controls. Among seven candidates, four miRNAs (miR-9, miR-16, miR-21, and miR-429) from the EV were highly elevated in early-stage breast cancer patients compared with healthy donors. The combination of significant miRNAs from specific EV has high sensitivities of 0.90, 0.86, 0.88, and 0.84 of the area under the receiver operating characteristic curve (AUC) in each subtype (luminal A, luminal B, HER-2, and triple-negative) of early-stage breast cancer. Our results suggest that the combination of four miRNA signatures of specific EV could serve as a sensitive and specific biomarker and enable early diagnosis of breast cancer using liquid biopsy.

Microfluidic chip for rapid and selective isolation of tumor-derived extracellular vesicles for early diagnosis and metastatic risk evaluation of breast cancer.

The epithelial-to-mesenchymal transition (EMT) index in cancer is a complementary approach for estimating metastatic risk. Considering the demand for evaluating metastatic risk based on liquid biopsies, tumor-derived extracellular vesicles (EVs) can be exploited to generate the EMT index. For the generation of EVs-based EMT index, it is essential to selectively isolate each epithelial cell and mesenchymal cell-derived EVs. This study proposes a novel microfluidic chip for selectively separating two types of EVs in an efficient and timely manner. The microfluidic chip is fully integrated with a micromixer for the creation of efficient collision between EVs and specific antibody-coated microbeads (7 and 15 µm in diameter) and a hydrodynamic particle separator for the stratification of EVs bound microbeads according to the sizes of microbeads. Using this chip, over 90% of EVs expressing the epithelial marker (epithelial cell adhesion molecule, EpCAM) and the mesenchymal marker (CD49f) can be selectively isolated within 6.7 min per 100 µL of sample volume. The clinical relevance of EMT is investigated using plasma samples from 20 breast cancer patients and 10 age-matched controls. The EMT index produced from the microfluidic chip is in a good agreement with the conventional tissue-based EMT index and is significantly high in patients with aggressive breast cancer subtypes, compared with healthy controls. In addition, the patients with high scores on the EMT index (≥5) shows recurrence within 5 years after adjuvant treatment. Predicting EMT-index-based metastatic risk using our microfluidic chip can be beneficial for cancer diagnosis and prognosis.

Microfluidic recapitulation of circulating tumor cell-neutrophil clusters via double spiral channel-induced deterministic encapsulation.

Circulating tumor cell (CTC)-neutrophil clusters are highly potent precursors of cancer metastasis. However, their rarity in patients' blood has restricted research thus far, and moreover, studies on in vitro methods for mimicking cell clusters have generally neglected in vivo conditions. Here, we introduce an inertial-force-assisted droplet microfluidic chip that allows the recapitulation of CTC-neutrophil clusters in terms of physical as well as biochemical features. The deterministic encapsulation of cells via double spiral channels facilitates the pairing of neutrophils and cancer cells with ratios of interest (from 1 : 1 to 1 : 3). The encapsulated cells are spontaneously associated to form clusters, achieving the physical emulation of CTC-neutrophil clusters. Furthermore, the molecular signatures of CTC-neutrophil clusters (e.g., their E-cadherin, VCAM-1, and mRNA expressions) were well defined. Our novel microfluidic platform for exploring CTC-neutrophil clusters can therefore play a promising role in cancer-metastasis studies.

Detachable microfluidic device implemented with electrochemical aptasensor (DeMEA) for sequential analysis of cancerous exosomes.

The quantification of cancer-derived exosomes has a strong potential for minimally invasive diagnosis of cancer during its initial stage. As cancerous exosomes form a small fraction of all the exosomes present in blood, ultra-sensitive detection is a prerequisite for the development of exosome-based cancer diagnostics. Herein, a detachable microfluidic device implemented with an electrochemical aptasensor (DeMEA) is introduced for highly sensitive and in-situ quantification of cancerous exosomes. To fabricate the aptasensor, a nanocomposite was applied on the electrode surface followed by electroplating of gold nanostructures. Subsequently, an aptamer against an epithelial cell adhesion molecule is immobilized on the electrode surface to specifically detect cancer-specific exosomes. A microfluidic vortexer is then constructed and implemented in the sensing system to increase the collision between the exosomes and sensing surface using hydrodynamically generated transverse flow. The microfluidic vortexer was integrated with the aptasensor via a 3D printed magnetic housing. The detachable clamping of the two different devices provides an opportunity to subsequently harvest the exosomes for downstream analysis. The DeMEA has high sensitivity and specificity with an ultra-low limit of detection of 17 exosomes/µL over a wide dynamic range (1 × 102 to 1 × 109) exosomes/µL in a short period. As proof of the concept, the aptasensor can be separated from the 3D printed housing to harvest and analyze the exosomes by real-time polymerase chain reaction. Moreover, the DeMEA quantifies the exosomes from plasma samples of patients with breast cancer at different stages of the disease. The DeMEA provides a bright horizon for the application of microfluidic integrated biosensors for the early detection of cancerous biomarkers.

Automatically Controlled Microfluidic System for Continuous Separation of Rare Bacteria from Blood.

Bloodstream infection by microorganisms is a major public health concern worldwide. Millions of people per year suffer from microbial infections, and current blood culture-based diagnostic methods are time-consuming because of the low concentration of infectious microorganisms in the bloodstream. In this study, we introduce an efficient automated microfluidic system for the continuous isolation of rare infectious bacteria (Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa) from blood. Bacteria received a balanced force between a fluidic drag force and a periodically controlled dielectrophoretic (DEP) force from tilted electrodes to minimize cell adhesion to the electrodes, which prevented the loss of rare infectious bacteria. Target bacteria were efficiently segregated from the undesired blood cells to ensure that only the bacteria received the DEP force under the hypotonic condition, while the blood cells received no DEP force and exited the channel via a laminar flow. Thus, the bacteria were successfully extracted from the blood with a high recovery yield of 91.3%, and the limit of the bacteria concentration for isolation was 100 cfu/ml. We also developed an automated system that performed every step from blood-sample loading to application of electricity to the microfluidic chip for bacteria separation. It reduced the standard deviation of the bacteria recovery yield from 6.16 to 2.77 compared with the conventional batch process, providing stable bacteria-extraction performance and minimizing errors and bacteria loss caused by user mistakes. © 2019 International Society for Advancement of Cytometry.

On-chip isolation and enrichment of circulating cell-free DNA using microfluidic device.

Circulating cell-free DNA (cfDNA), containing cancer-specific DNAs derived from tumor cells, plays an important role in real-time monitoring of disease progression. Due to the abnormal growth of cancer and the promotion of cancer cell apoptosis by chemotherapy, the higher cfDNA concentration than healthy individuals is closely correlated with the diagnosis and treatment of cancer. Also, the mutation detection in tumor cell-derived cfDNA can be used to predict tumor progression. Human blood contains many blood cells (red blood cells, white blood cells, and platelets), proteins, extracellular vesicles, and so on. These blood components act as the inhibitors when the cfDNA is analyzed using polymerase chain reaction. So, analysis of cfDNA using whole blood directly may affect the sensitivity of the analysis or result in false-negative. The conventional methods of cfDNA isolation, such as silica absorption and polymer-mediated enrichment, are labor-intensive and time-consuming processes that can also lead to the loss of cfDNA in cumbersome procedures. Here, we designed an integrated microfluidic chip capable of on-chip cfDNA extracting to reduce sample loss and processing time. Our proposed device minimizes the number of experimental steps from 5 to 1, the total processing time from 42 to 19 min, and the required volume of washing reagents from 2 to 0.4 ml for cfDNA enrichment compared to the conventional method.

Highly sensitive and accurate estimation of bloodstain age using smartphone.

The estimation of bloodstain age is an important factor in forensic analysis. Previously, we have reported a smartphone-based colorimetric system for age estimation of bloodstain, in which Whole blood and EDTA whole blood were dropped on 4 different materials (700 µL) and captured using a smartphone for 72 h. In order to enhance sensitivity and accuracy of the previous system, the current work is dedicated towards the application of pattern recognition and classification of bloodstain images based on a smartphone. Three detection methods (blood pool, crack ratio, and colorimetric analysis) in terms of 6 steps of drying process of the bloodstain (coagulation, gelation, edge desiccation, center desiccation, crack propagation, and final desiccation) were applied to estimate age of the bloodstain accurately. Three parameters from the bloodstain images were then classified as comparing to those of stored reference images with similar trends in database. The bloodstain age was successfully determined by 9 h, 18 h, and 48 h with respect to the three detection methods mentioned above, respectively. The differences in bloodstain images were clearly distinguished every hour by using smartphone-based pattern recognition analysis. Therefore, our system is expected to shed a light on the field of forensic science by estimating bloodstain age in real time.

Salivary Exosome and Cell-Free DNA for Cancer Detection.

Liquid biopsies are easier to acquire patient derived samples than conventional tissue biopsies, and their use enables real-time monitoring of the disease through continuous sampling after initial diagnosis, resulting in a paradigm shift to customized treatment according to the patient's prognosis. Among the various liquid biopsy samples, saliva is easily obtained by spitting or swab sucking without needing an expert for sample collection. In addition, it is known that disease related biomarkers that exist in the blood and have undergone extensive research exist in saliva even at a lower concentration than the blood. Thus, interest in the use of saliva as a liquid biopsy has increased. In this review, we focused on the salivary exosome and cell-free DNA (cfDNA) among the various biomarkers in saliva. Since the exosome and cfDNA in saliva are present at lower concentrations than the biomarkers in blood, it is important to separate and concentrate them before conducting down-stream analyses such as exosome cargo analysis, quantitative polymerase chain reaction (qPCR), and sequencing. However, saliva is difficult to apply directly to microfluidics-based systems for separation because of its high viscosity and the presence of various foreign substances. Therefore, we reviewed the microfluidics-based saliva pretreatment method and then compared the commercially available kit and the microfluidic chip for isolation and enrichment of the exosome and cfDNA in saliva.

Progress in Circulating Tumor Cell Research Using Microfluidic Devices.

Circulating tumor cells (CTCs) are a popular topic in cancer research because they can be obtained by liquid biopsy, a minimally invasive procedure with more sample accessibility than tissue biopsy, to monitor a patient's condition. Over the past decades, CTC research has covered a wide variety of topics such as enumeration, profiling, and correlation between CTC number and patient overall survival. It is important to isolate and enrich CTCs before performing CTC analysis because CTCs in the blood stream are very rare (0⁻10 CTCs/mL of blood). Among the various approaches to separating CTCs, here, we review the research trends in the isolation and analysis of CTCs using microfluidics. Microfluidics provides many attractive advantages for CTC studies such as continuous sample processing to reduce target cell loss and easy integration of various functions into a chip, making "do-everything-on-a-chip" possible. However, tumor cells obtained from different sites within a tumor exhibit heterogenetic features. Thus, heterogeneous CTC profiling should be conducted at a single-cell level after isolation to guide the optimal therapeutic path. We describe the studies on single-CTC analysis based on microfluidic devices. Additionally, as a critical concern in CTC studies, we explain the use of CTCs in cancer research, despite their rarity and heterogeneity, compared with other currently emerging circulating biomarkers, including exosomes and cell-free DNA (cfDNA). Finally, the commercialization of products for CTC separation and analysis is discussed.

A microfluidic electrochemical aptasensor for enrichment and detection of bisphenol A.

Bisphenol A (BPA) is an organic monomer used to make common consumer goods such as plastic containers, sports equipment, and cosmetics which are heavily produced worldwide. A growing interest has been drawn to general public as BPA is one of the major endocrine disrupting chemicals threating human health. To date, numerous BPA sensors have been attempted to be developed but important challenges still remained such as limited linearity range, easy to use, and long term response time. To address the present issues, a microfluidic channel should be integrated into an electrochemical aptasensor and it is called Geometrically Activated Surface Interaction (GASI) chip. The vigorous generation of the micro-vortex in the GASI fluidic chamber provides the high collision chances between BPA and anti-BPA aptamer (BPAPT) and consequently more BPA molecules can be captured on the aptasensor surface, which finally results in high sensitivity of the aptasensor. To construct the integrated aptasensor, a miniaturized gold electrode is fabricated using shadow mask and e-beam evaporation process. Afterward, BPAPT is immobilized on a nanostructured gold electrode via thiol chemistry, and other terminus of the aptamer is labeled with a ferrocene (Fc) redox probe. Then, the microfluidic channel is mounted over the miniaturized gold electrode to introduce and enrich BPA to the aptasensor. Upon the specific interaction between BPA and its aptamer, configuration of aptamer is changed so that Fc tag approaches to the electrode surface and direct oxidation signal of Fc and BPA are followed as analytical signals. The unique microfluidic integrated electrochemical aptasensor delivers a wide linear dynamic range over 5 × 10-12 to 1 × 10-9 M, with a limit of detection 2 × 10-13 M. This aptasensor provides a precise platform for simple, selective and more importantly rapid detection of BPA. Such kind of sensing platforms can serve as a fertile ground for designing miniaturized portable sensors.