Evaluation of Fluid Behaviors in a Pushbutton-Activated Microfluidic Device for User-Independent Flow Control

Although numerous studies have been conducted to realize ideal point-of-care testing (POCT), the development of a user-friendly and user-independent power-free microfluidic platform is still a challenge. Among various methods, the finger-actuation method shows a promising technique that provides a user-friendly and equipment-free way of delivering fluid in a designated manner. However, the design criteria and elaborate evaluation of the fluid behavior of a pushbutton-activated microfluidic device (PAMD) remain a critical bottleneck to be widely adopted in various applications. In this study, we have evaluated the fluid behavior of the PAMD based on various parameters, such as pressing velocity and depth assisted by a press machine. We have further developed a user-friendly and portable pressing block that reduces user variation in fluid behavior based on the evaluation.

Responsiveness and meaningful thresholds of PROMIS pain interference, fatigue, and physical function forms in adults with idiopathic inflammatory myopathies: Report from the OMERACT Myositis Working Group

BACKGROUND

A series of qualitative studies conducted by the OMERACT Myositis Working Group identified pain interference, fatigue, and physical function as highly important life impact domains for adults with idiopathic inflammatory myositis (IIM). In this study, our goal was to assess the responsiveness and minimal important difference of PROMIS pain interference (6a), fatigue (7a), and physical function (8b).

METHODS

Adults with IIM from USA, Netherlands, Korea, Sweden, and Australia with two "clinical" visits were enrolled in this prospective study. Anchor questions on a Likert scale were collected at baseline, and manual muscle testing (MMT), physician and patient reported global disease activity, and PROMIS instruments were collected at both visits. Responsiveness was assessed with i) ANOVA, ii) paired t-test, effect size and standardized response mean, and iii) Pearson correlation. Minimal important difference (MID), minimal important change (MIC) and minimal detectable change (MDC) values were calculated.

RESULTS

114 patients with IIM (median age 60, 60 % female) completed both visits. Changes in PROMIS instruments were significantly different among anchor categories. Patients who reported improvement had a significant improvement in their PROMIS scores with at least medium effect size, while patients who reported worsening and stability did not show a significant change with weak effect size. PROMIS instruments had weak to moderate correlations with MMT, patient and physician global disease activity. MID was approximately 2-3 points for Pain Interference and 3-4 points for Fatigue and Physical Function forms based on the method used. MIC was approximately 4-5 for improvement of all the instruments, while MDC was 1.7-2 points for Pain Interference and Physical Function and 3.2-3.9 for Fatigue.

CONCLUSION

This study provides evidence towards the responsiveness of the PROMIS instruments in a large international prospective cohort of adults with IIM supporting their use as PROMs in adult myositis.

Fabrication of a self-assembled and vascularized tumor array via bioprinting on a microfluidic chip

A tumor microenvironment (TME) is a complex system that comprises various components, including blood vessels that play a crucial role in supplying nutrients, oxygen, and growth factors, as well as delivering chemotherapy drugs to the tumor mass through the vascular endothelial barrier. To replicate the TME in vitro, several bioprinting and microfluidic organ-on-a-chip technologies have been developed. However, these technologies have not been fully exploited in terms of potential benefits of bioprinting and microfluidics, such as precise spatial control for biological samples, construction of multiple TMEs per microfluidic device, and the ability to adjust culture environments for better biological similarity. In addition, the complex transport phenomena within the vascular endothelial barrier and the aggregated tumor mass in the TME model should be considered before applying the model to drug treatment and screening. In this study, we describe a novel integrative technology that addresses these issues by introducing a self-organized TME array bioprinted on a microfluidic chip consisting of a vascular endothelial barrier surrounding breast cancer spheroids. To integrate the TME array onto the microfluidic platform, a microfluidic substrate for extrusion bioprinting was developed for a cell culture platform, which enables diffusivity control by microstructures and establishes a perfusion culture environment inside the culture channel. We also analyzed the cellular behaviors within the TME array to investigate the influence of the diffusivity on the self-organization process required to form the vascular endothelial barrier surrounding breast cancer spheroids.

Hybrid Biofabrication of Heterogeneous 3D Constructs Using Low-Viscosity Bioinks

The application of cytocompatible hydrogels supporting extensive cellular activities to three-dimensional (3D) bioprinting is crucial for recreating complex physiological environments with high biomimicry. However, the poor printability and tunability of such natural hydrogels diminish the versatility and resolution of bioprinters. In this study, we propose a novel approach for the hybrid biofabrication of complex and heterogeneous 3D constructs using low-viscosity bioinks. Poly(lactic acid) (PLA) filament is extruded by fused deposition modeling on a micromesh to create PLA-framed micromesh substrates onto which fibrinogen is printed by microextrusion bioprinting. The micromesh supports the printed hydrogel with a capillary pinning effect to enable high-resolution bioprinting. Accordingly, the micromesh-bioink layers are aligned and stacked to form volumetric constructs. This approach, called the 3D micromesh-bioink overlaid structure and interlocked culture (3D MOSAIC) platform, enables the fabrication of complicated and multimaterial 3D structures, including overhangs and voids. Endothelial cells cultured under vasculogenic conditions in the platform self-organize within the biologically functional hydrogel to form vascular networks, and cancer cell migration can be observed across the layers. The multidisciplinary 3D MOSAIC platform is an important step toward the biofabrication of complex constructs with high biological and structural significance and functionality.

Characterization of PDMS Microchannels Using Horizontally or Vertically Formed 3D-Printed Molds by Digital Light Projection

Three-dimensional (3D) printing is one of the promising technologies for the fabrication of microstructures due to its versatility, ease of fabrication, and low cost. However, the direct use of 3D-printed microstructure as a microchannel is still limited due to its surface property, biocompatibility, and transmittance. As an alternative, rapid prototyping of poly(dimethylsiloxane) (PDMS) from 3D-printed microstructures ensures both biocompatibility and efficient fabrication. We employed 3D-printed molds fabricated using horizontal and vertical arrangement methods with different slice thicknesses in a digital light projection (DLP)-based 3D printing process to replicate PDMS microchannels. The replicated PDMS structures were investigated to compare their optical transmittances and surface roughness. Interestingly, the optical transmittance of PDMS from the 3D-printed mold was significantly increased via bonding two single PDMS layers. To evaluate the applicability of the replicated PDMS devices from the 3D-printed mold, we performed droplet generation in the PDMS microchannels, comparing the same device from a conventional Si-wafer mold. This study provides a fundamental understanding of prototyping microstructures from the DLP-based 3D-printed mold.

On-chip microfluidic dual detection of amino acid metabolism disorders using cell-free protein synthesis

Various metabolic diseases are associated with the accumulation of specific amino acids due to abnormal metabolic pathways, and thus can be diagnosed by measuring the level of amino acids in body fluids. However, present methods for amino acid analysis are not readily accessible because they require a complex experimental setup, expensive equipment, and a long processing time. Here, we present a dual sensing microfluidic device that enables fast, portable, and quantitative analysis of target amino acids, harnessing the biological mechanism of protein synthesis. In this device, the working principle of a finger-actuated pumping unit is applied, and the microchannels are designed to perform cell-free synthesis of a reporter protein in response to the target amino acids in the assay samples. Multiple steps required for the translational assay are controlled by the simple operation of two pushbuttons on the device. It is demonstrated that the developed microfluidic device provides precise quantification of two amino acids (methionine and phenylalanine) within 30 min at room temperature. We expect that the application of the presented device can be readily extended to the point-of-care testing of other metabolic compounds.

Perioperative risk and benefit of antiplatelet therapy in patients undergoing non-cardiac surgery within 1 year after percutaneous coronary intervention with second-generation drug-eluting stents

Background

Antiplatelet therapy (APT) in patients undergoing non-cardiac surgery (NCS) after percutaneous coronary intervention (PCI) is still on debate due to its opposite effects which are to prevent from cardiovascular events and to cause bleeding. There is no apparent consensus on how to determine perioperative APT strategy within 1 year after PCI. Therefore, we investigated the risk and benefit of APT in NCS within 1 year after PCI.

Methods

Patients undergoing NCS after PCI with second-generation drug-eluting stents are retrospectively included from multicenter cohort of 8 medical centers in Korea. Perioperative clinical event within 30 days after NCS was recorded. Net adverse clinical event (NACE) including all cause death, major adverse cardiac event (MACE, a composite of cardiac death, myocardial infarction, and stent thrombosis) and major bleeding were evaluated. To overcome bias, propensity score covariate adjustment was performed using logistic regression analysis to generate propensity scores for patients of both APT strategies.

Results

Total 1130 patients (median age 69 years, female 30.5%) undergoing NCS within 1 year after PCI were eligible in the cohort. Study population included 55.1% patients suffered from ACS and 22.5% underwent complex PCI. NCS included 45.8% intermediate-to-high risk surgery and 10.7% urgent or emergent surgery. APT was continued during NCS in 62.7% of the patients. More patients continued DAPT (48% vs. 32%, p<0.001) among the patients who underwent NCS within 6 months after PCI than those who underwent NCS after 6 months. There were 49 NACE (4.3%), 16 MACE (1.4%) and 23 major bleeding events (2.0%), respectively. Continuing APT was associated with a lower risk of NACE (Adjusted hazard ratio [HR], 0.49; 95% confidence interval [CI], 0.27–0.89; p=0.020)) and MACE (Adjusted HR, 0.35; 95 CI, 0.12–0.96; p=0.042). Subgroup analysis showed a tendency that continuing APT might be favorable than discontinuing APT in terms of MACE in patients who were diagnosed with ACS, underwent complex PCI, or underwent NCS within 6 months after PCI.

Conclusions

About two thirds of the patients were continuing APT during NCS. Our findings may support a careful consideration of APT continuation for some of the patients who are undergoing NCS within 1 year after PCI.

Funding Acknowledgement

Type of funding sources: None.

Oral anticoagulation therapy in atrial fibrillation patients with advanced chronic kidney disease: CODE-AF Registry

Background and objectives

Advanced chronic kidney disease (CKD), including end-stage renal disease (ESRD) on dialysis, increases thromboembolic risk among patients with atrial fibrillation (AF). This study examined the comparative safety and efficacy of direct-acting oral anticoagulant (DOAC) compared to warfarin or no OAC among AF patients with advanced CKD or ESRD on dialysis.

Methods

Using data from the COmparison study of Drugs for symptom control and complication prEvention of AF (CODE-AF) registry, 260 non-valvular AF patients with advanced CKD (defined as estimated glomerular filtration rate [eGFR] <3 0ml/min per 1.73 m2) or ESRD on dialysis were enrolled from June 2016 to July 2020. The study population was categorized into DOAC, warfarin, and no OAC group, and differences in major or clinically relevant non-major (CRNM) bleeding, stroke/systemic embolism (SE), myocardial infarction/critical limb ischemia (CLI), and death were assessed.

Results

During a median 24 months of follow-up, major or CRNM bleeding risk was significantly reduced in the DOAC group compared to the warfarin group (hazard ratio [HR] 0.21, 95% confidence interval [CI] 0.05 to 0.95, p=0.042). In addition, the risk of composite adverse clinical outcome (major or CRNM bleeding, stroke/SE, myocardial infarction/CLI, and death) was significantly reduced in the DOAC group compared to the no OAC group (HR 0.32, 95% CI 0.11 to 0.96, p=0.043).

Conclusion

Among AF patients with advanced CKD or ESRD on dialysis, DOAC was associated with a lower risk of major or CRNM bleeding compared to warfarin and a lower risk of composite adverse clinical outcome compared to no OAC.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Korean Healthcare Technology R&D project funded by the Ministry of Health & Welfare (HI15C1200, HC19C0130)

Bioprinting of heterogeneous and multilayered cell-hydrogel constructs using continuous multi-material printing and aerosol-based crosslinking

Bioprinting is a powerful biofabrication technique that mimics physiological environments and functions. Here, we describe a protocol to set up a continuous multiple-material bioprinting system that can replicate structurally complex and biologically functional microphysiological systems such as a tumor microenvironment. Although this bioprinting system uses a limited crosslinking agent, it is a versatile and advanced continuous multi-material printing technique.

For complete details on the use and execution of this protocol, please refer to Lee et al. (2021).

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Set up a continuous multi-bioink printer to print a complex biological construct

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Printing procedures of multilayered and heterogeneous constructs

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Form a tumor microenvironment with four bioinks containing three cell types

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Analyze cancer cell migration and vascular network formation

Resting heart rate and cardiovascular outcomes in patients with atrial fibrillation: CODE-AF registry

Funding Acknowledgements

Type of funding sources: None.

Background

The prognostic significance of resting heart rate and its therapeutic target in atrial fibrillation (AF) is uncertain.

Purpose

The aim of this study was to investigate the relationships between resting heart rate and cardiovascular outcomes in patients with AF.

Methods

A total of 8,886 patients with AF was included from the COmparison study of Drugs for symptom control and complication prEvention of AF (CODE-AF) registry. Patients were categorized according to baseline heart rate, and cardiovascular outcomes were accessed during a median follow-up of 30 months. The primary outcome was a composite of cardiovascular death, hospitalization due to heart failure, and myocardial infarction/critical limb ischemia.

Results

Compared to heart rate ≥100 beats per minute (bpm), heart rate 80-99 bpm was associated with the lowest risk of primary outcome (adjusted hazard ratio [HR] 0.56, 95% confidence interval [CI] 0.40-0.79, p=0.001). In subgroup of patients with heart failure with preserved ejection fraction (HFpEF), heart rate between 80-99 bpm was associated with reduced risk of primary outcome compared to heart rate ≥100 bpm (HR 0.40, 95% CI 0.16-0.98, p=0.045). However, in patients with heart failure with reduced ejection fraction (HFrEF), there was no association between resting heart rate and cardiovascular outcomes (P for interaction 0.001).

Conclusion

Resting heart rate was associated with cardiovascular outcomes in patients with AF, and those with a resting heart rate between 80-99 bpm had the lowest risk of adverse events. The impact of resting heart rate on adverse events persisted in patients with concomitant HFpEF but was not apparent in those with concomitant HFrEF.

Construction of a Fibroblast-Associated Tumor Spheroid Model Based on a Collagen Drop Array Chip

Spheroid, a 3D aggregate of tumor cells in a spherical shape, has overcome the limitations of conventional 3D cell models to accurately mimic the in-vivo environment of a human body. The spheroids are cultured with other primary cells and embedded in collagen drops using hang drop plates and low-attachment well plates to construct a spheroid–hydrogel model that better mimics the cell–cell and cell–extracellular matrix (ECM) interactions. However, the conventional methods of culturing and embedding spheroids into ECM have several shortcomings. The procedure of transferring a single spheroid at a time by manual pipetting results in well-to-well variation and even loss or damage of the spheroid. Based on the previously introduced droplet contact-based spheroid transfer technique, we present a poly(dimethylsiloxane) and resin-based drop array chip and a pillar array chip with alignment stoppers, which enhances the alignment between the chips for uniform placement of spheroids. This method allows the facile and stable transfer of the spheroid array and even eliminates the need for a stereomicroscope while handling the cell models. The novel platform demonstrates a homogeneous and time-efficient construction and diverse analysis of an array of fibroblast-associated glioblastoma multiforme spheroids that are embedded in collagen.

Development of the micro-patterned 3D neuronal-hydrogel model using soft-lithography for study a 3D neural network on a microelectrode array. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021;2021:1234-1237. [PMID: 34891510 DOI: 10.1109/embc46164.2021.9629822]

In vitro patterned neuronal models have been studied as one of the strategies to investigate the relationship between structural connectivity and functional activity of neural network. Despite the importance of three-dimensional (3D) cell models, most of these studies have been performed on two-dimensional models. In this study, we present a technique to construct the micro-pattern to 3D neuronal-hydrogel model using a micromolding in capillaries (MIMIC) technique on microelectrode array (MEA). Our technique was suitable to prevent the deformation of micro-patterned collagen model against the neuronal contracted tension during the network formation. The relationship between the growth directions of glial cells and micro-pattern direction was investigated. Lastly, we confirmed that our 3D model had synchronized activity among neurons in 3D. This model is expected to be used as a tool to study the relationship between structural connectivity and functional activity in the 3D environment.

Label-free monitoring of 3D cortical neuronal growth in vitro using optical diffraction tomography

The highly complex central nervous systems of mammals are often studied using three-dimensional (3D) in vitro primary neuronal cultures. A coupled confocal microscopy and immunofluorescence labeling are widely utilized for visualizing the 3D structures of neurons. However, this requires fixation of the neurons and is not suitable for monitoring an identical sample at multiple time points. Thus, we propose a label-free monitoring method for 3D neuronal growth based on refractive index tomograms obtained by optical diffraction tomography. The 3D morphology of the neurons was clearly visualized, and the developmental processes of neurite outgrowth in 3D spaces were analyzed for individual neurons.

Droplet contact-based spheroid transfer technique as a multi-step assay tool for spheroid arrays

Hanging drop plates and low-attachment well plates are suitable for a high throughput screening model of a spheroid, because each drop (or well) contains a single spheroid and the spheroid environment are separated from each other. However, uniform spheroid culture on these devices is difficult as the liquid around the spheroid is replaced by direct pipetting, which can cause spheroid damage or loss, and well-to-well variation. If spheroids need to be cultured for a long time or analyzed through chemical treatment of immunostaining, it becomes a more considerable problem as the number of pipetting action increases. To address these problems, we have developed a poly(dimethylsiloxane) (PDMS)-based drop array chip (DAC) and a pillar array chip (PAC) that can apply a droplet contact-based spheroid transfer (DCST) technique to multiple reagent change or washing steps of spheroid assays. Unlike previous DCST devices, 3D-printed mold-based DCST devices showed stable spheroid manipulation during repetitive drop contact and facile transfer of spheroid arrays to the next reagent-loaded DAC while minimizing cross-contamination of the reagents. Compared to the conventional manual or machine pipetting method, the DCST method showed lower user-to-user variation and a higher spheroid retention rate in the manipulation of the spheroid array. Live/dead staining, hypoxia staining, and immunofluorescence staining of the spheroid array were performed on a breast cancer cell line, BT-474. Furthermore, four clearing methods were applied to the spheroid array as a proof of concept, and we have identified the applicability of the DCST platform as a pretreatment platform for whole spheroid analysis.

Associations between changing patterns of ST-T waves morphologies in rest electrocardiography and cardiovascular risk in an asymptomatic low risk population: a report from Ansan-Ansung cohort study

Background

While clinical significance of ST-T wave abnormalities (STA) in rest electrocardiography (ECG) on long-term cardiovascular outcomes has been on debate, few studies have been reported on the association between the changes in ST-T waves in rest ECG and cardiovascular outcomes in low risk populations. We investigate the changing patterns of STA in rest ECG and the predictive value of the changes in ST-T wave in rest ECG for cardiovascular events in an asymptomatic general population.

Methods

A longitudinal community-based cohort study was conducted for 12 years. Koreans aged 40–69 years were followed biennially through scheduled revisit for comprehensive assessments. Among 10,030 participants, 6,648 participants who did not have any cardiovascular diseases, angina-related symptoms or pathologic Q waves in rest ECG at baseline were included for analysis. Changes in STAs were defined using the changes between ECG at baseline and that at the first revisit. A major adverse cardiovascular events was defined as a composite of cardiac death, myocardial infarction, clinical diagnosis of coronary artery disease and stroke.

Results

Among 5,924 participants without STA at baseline, only 187 participants (3.2%) developed new STA. Among 724 patients (10.9%) with STA at baseline, 274 patients (37.8%) persistently showed STA at the first revisit. MACEs occurred more frequently in the participants persistently with STA and those with newly-developed STA than in the participants persistently without STA (Figure 1). Multivariate Cox-proportional hazard models showed that a higher risk of MACE was only associated with the persisted STA (HR 1.69; 95% CI 1.10–2.63). In participants with baseline STA, persisted T-wave flattening was associated with a higher risk of MACE, whereas T-wave inversion, either persisted or fluctuated was not associated with a higher risk of MACE, compared with persistent absence of STA (Figure 2). In the participants without baseline STAs, multivariate Cox-proportional hazard model showed that newly-developed T-wave flattening (HR 1.85; 95% CI 0.20–2.84), not T-wave inversion (HR 1.50; 95% CI 0.85–2.65) was associated with a higher risk of MACE. Survival receiver operating curve analysis showed that the changes in STAs had a C-index of 0.538 (95% CI 0.511–0.558), a sensitivity of 13.0% and a specificity of 92.5% and add only a small value to the predictive power of 10-year atherosclerotic cardiovascular diseases risk estimator (C-index without STA changes 0.708 [0.681–0.736] vs. C-index with STA changes 0.721 [0.694–0.748]).

Conclusions

STAs uncommonly developed while frequently disappeared spontaneously in the asymptomatic general population. Persisted STA and newly developed STA in rest ECG were predictive of future cardiovascular events in the asymptomatic general population. However, the changes in STAs did not significantly improve the predictive value of the conventional risk estimator, when added.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Research Foundation of Korea Figure 1Figure 2

Simulation and validation for count-based binary decision of target blood pressure achievement in home blood pressure monitoring data analysis for clinical practice

Introduction

Home blood pressure monitoring (HBPM) is a useful tool to identify hypertension and to decide whether a patient's blood pressure (BP) is controlled. The use of automatized oscillometric BP measurement devices has become increasingly popular with help of information technology and internet of things to the devices. However, applying HBPM to daily clinical practices is still challenging, because most patients with hypertension are in age groups not familiar to digital devices and internet and high BP criteria using average home BP values are often useless in outpatient clinics without easily accessible average BP calculation tools. Therefore, we developed a simple and straightforward method to interpret HBPM through counts of BP ≥135/85 mmHg.

Methods

We simulated 400 cases of HBPM using a random number generator function in statistical software. The simulated average home systolic BP (SBP) and its standard deviation (SD) were 125±15 mmHg and 12±5 mmHg and the number of HBP readings was 24 times. The simulated diastolic BP (DBP) was randomly selected to 50–75% of the SBP. The validation of the binary interpretation method was conducted using actual HBPM data from 386 subjects in a rural area of South Korea. Receiver operating characteristics curve analysis was conducted, and linear regression and logarithmic models were fitted between the numbers of home BP ≥135/85 mmHg and mean BP. Hypertension was defined with average home BP ≥135/85 mmHg.

Results

In the simulated cohort, hypertension was presented in 197 cases (49.3%). The C-index of the numbers of BP readings ≥135/85 mmHg was 0.994 (95% confidence interval [CI] 0.990–0.998), and ≥12 of 24 BP readings ≥135/85 mmHg showed a sensitivity of 95.4%, a specificity of 95.1% and an accuracy of 95.3% for the diagnosis of hypertension. In validation cohort, the numbers of home BP measurements varied from 8 to 81 times. The validation cohort similarly showed that the C-index of the ratio between the number of high BP readings (≥135/85 mmHg) to the number of BP measurements (R-NHBP/NBP) was 0.985 (95% CI, 0.976–0.994) and the best accuracy was shown at R-NHBP/NBP of ≥0.45. R-NHBP/NBP of ≥0.5 showed a sensitivity of 0.957, a specificity of 0.907 and an accuracy of 0.927. The accuracy of the R-NHBP/NBP of ≥0.5 decreased as SD and the range of SBP increased, whereas it did not change with the number of measurements (Figure 1). R-NHBP/NBP <0.2 predicted normotension and R-NHBP/NBP >0.8 predicted hypertension in 95% confidence. Mean widths of the 95 prediction intervals for the average SBP and DBP were 18.2 mmHg and 12.6 mmHg, respectively (Figure 2).

Conclusion

Counting the number of BP ≥135/85 mmHg can provide accurate assessments for the BP levels. R-NHBP/NBP of ≥0.5 is a simple and accurate marker of high BP in HBPM, and R-NHBP/NBP could be a useful tool to assess BP levels in patients practicing HBPM.

Funding Acknowledgement

Type of funding sources: None. Figure 1Figure 2

Multilayered and heterogeneous hydrogel construct printing system with crosslinking aerosol

Microextrusion bioprinting has been used to recreate the complex architecture and composition of a physiological system through the quick and accurate handling of various biomaterials. However, existing techniques are limited in precisely fabricating complex constructs, including multilayers and heterogeneous patterns with distinct regions, because the extruded bioink spreads rapidly upon contact with the substrate and is partially mixed with subsequently printed bioinks. This issue leads to difficulties in accurately and stably constructing multi-material structures with clear interfaces for prolonged printing before gelation. To fabricate multilayered and heterogeneous constructs, a bioprinting system should be able to continuously extrude various biomaterials and simultaneously crosslink the extruded bioink to stabilize the printed construct. In this study, a multiple-bioink printing system was developed by integrating a multibarrel nozzle for extruding multiple bioinks with a nebulizer for simultaneous crosslinking. The crosslinking aerosol sprayed from the nebulizer was able to gelate the various hydrogel bioinks as they were extruded through the multibarrel nozzle. Such aerosol-based crosslinking improved printing resolution and stability. The developed bioprinting system showed the possibility of recapitulating the physiological complex architecture such as a cancer microenvironment with well-defined interfaces between regions of different mechanical properties and cellular compositions. Using the integrated bioprinting system, a multilayered and heterogeneous construct was printed with four bioinks, including three types of cells (breast cancer cells, stromal cells, and vascular endothelial cells). The printed biological model was characterized by analyzing cancer cell migration and vascular network formation. The developed multiple-bioink printing system is expected to be highly efficient in recapitulating complex tissues and their environments with compartmentalized regions.

Biomarker barcodes: multiplexed microfluidic immunohistochemistry enables high-throughput analysis of tissue microarray

We present a multiplexed microfluidic immunohistochemistry (IHC) technology that enables high-throughput analysis of tissue microarrays (TMAs) using the patterns of biomarker barcodes, which consist of a series of expressed linear patterns of specific biomarkers. A multichannel poly(dimethylsiloxane) microfluidic device was reversibly assembled by the pressure of simple equipment for multiplexed IHC on each core of TMA or cell microarray (CMA) section slides. By injecting primary antibodies from different biomarkers independently into each channel, multiplexed immunostaining can be performed on each core of TMA. We confirmed the equal immunostaining quality regardless of the channel orders and core positions in the slide. Four different biomarkers (ER, PR, HER2, and Ki67) were used for the demonstration of distinctive expression patterns on CMAs which consist of six different breast cancer cell lines, and it was confirmed that these bar-like signals could be a biomarker barcode for the TMA core. A biomarker barcode of breast cancer patient-derived TMA was quickly scanned by a slide scanner and compared to the conventional method for breast cancer diagnosis. This "barcode-IHC" concept, which has been verified by performing multiplexed microfluidic IHC on CMA and TMA samples, provides high reproducibility and the potential of high-throughput screening with molecular diagnostic capability.

Pushbutton-activated microfluidic cartridge as a user-friendly sample preparation tool for diagnostics

Microfluidic technologies have several advantages in sample preparation for diagnostics but suffer from the need for an external operation system that hampers user-friendliness. To overcome this limitation in microfluidic technologies, a number of user-friendly methods utilizing capillary force, degassed poly(dimethylsiloxane), pushbutton-driven pressure, a syringe, or a pipette have been reported. Among these methods, the pushbutton-driven, pressure-based method has a great potential to be widely used as a user-friendly sample preparation tool for point-of-care testing or portable diagnostics. In this Perspective, we focus on the pushbutton-activated microfluidic technologies toward a user-friendly sample preparation tool. The working principle and recent advances in pushbutton-activated microfluidic technologies are briefly reviewed, and future perspectives for wide application are discussed in terms of integration with the signal analysis system, user-dependent variation, and universal and facile use.

Microfluidic channel-integrated hanging drop array chip operated by pushbuttons for spheroid culture and analysis

Although the hanging drop methods have a number of advantages for spheroid culture, they suffer from reagent exchange procedures that depend on tedious and accurate liquid handling by manual pipetting or robotic arms. To simplify these procedures, we developed a method for liquid handling in a hanging drop array (HDA) chip for spheroid culture and analysis by integrating microfluidic channels operated by pushbuttons. Six finger-actuated microfluidic pumping units connected to a 3 × 3 HDA can draw or replenish reagents in an HDA chip without any external equipment. The initial cell seeding, medium exchange, and staining for further analysis can be simply done by pushing the buttons in the programmed order. After the assessment of the reagent exchange ratio of the device, BT474 spheroids of various sizes were cultured in the device for 7 days by exchanging the medium once a day and stained on the same device by exchanging the medium with staining reagents for the LIVE/DEAD assay. Furthermore, the cultured spheroids were embedded into collagen by exchanging the medium with a collagen solution to mimic a cancer metastasis environment.

Pushbutton-activated microfluidic dropenser for droplet digital PCR

Here, we report a portable microfluidic device to generate and dispense droplets simply operated by pushbutton for droplet digital polymerase chain reaction (ddPCR), which is named pushbutton-activated microfluidic dropenser (droplet dispenser) (PAMD). After loading the PCR mixtures and the droplet generation oil to PAMD, digitized PCR mixtures are prepared in PCR tubes after the actuation of a pushbutton. Multiple droplet generation units are simultaneously operated by a single pushbutton, and the size of droplets is controllable by adjusting the geometry of the droplet generation channel. To examine the performance of PAMD, digitized PCR mixtures containing genomic DNA of Escherichia coli (E. coli) O157:H7 prepared by PAMD were assessed by a fluorescence signal analyzer after PCR with a thermal cycler. As a result, PAMD can produce analytical droplets for ddPCR as much as a conventional droplet generator even though any external equipment is not required.

Controlled 3D co-culture of beta cells and endothelial cells in a micropatterned collagen sheet for reproducible construction of an improved pancreatic pseudo-tissue

The co-culture of beta cells and endothelial cells in constructing a pancreatic pseudo-tissue can provide a functional advancement for in vitro diabetic-related drug testing and biological studies or in vivo transplantation. In order to mimic the pancreatic tissue more similar to in vivo, it is necessary to control the microenvironment, including cell-cell and cell-extracellular matrix interactions. In this study, we report a geometrically controlled three-dimensional (3D) pancreatic model where MIN6 and MS1 cells are co-cultured within a micropatterned collagen sheet. In 4-10 days, depending on the cell seeding concentration, the MIN6 cells formed islet-like clusters surrounded by an endothelial MS1 cell monolayer. The MS1 cells also formed monolayers at the edge of the micropatterns connecting between the clusters, resulting in a blood vessel-like structure in which no cells were found. It was confirmed that the 3D co-culture structure was not formed in a non-patterned sheet and the structure also helped insulin secretion of MIN6 cells. By simply embedding the cell mixture and the hexagonal micropattern into the collagen sheet, we were also able to achieve the highly reproducible fabrication of a 3D pancreatic pseudo-tissue construct for in vivo and in vitro applications.

Reciprocating flow-assisted nucleic acid purification using a finger-actuated microfluidic device

Molecular diagnostics can provide a powerful diagnostic tool since it can detect pathogens with high sensitivity, but complicated sample preparation procedures limit its widespread use as an on-site detection tool that relies on the skilled person and external equipment. To resolve these limitations, we report a solid-phase nucleic acid purification using a finger-actuated microfluidic device, which can control a set amount of flow regardless of differences in end-users. To increase the recovery rate, a finger-actuated reciprocator was newly developed and integrated into the microfluidic device that can efficiently react with silica microbeads and reagents. After verifying the finger-actuated microfluidic reciprocator, the effect of the reciprocating flow on the recovery rate was assessed to purify the standard DNA of the hepatitis B virus (HBV). The recovery rate was increased up to ∼50% and 955 to 955 000 IU mL^-1 of HBV standard DNA was successfully purified and detected by a real-time polymerase chain reaction. Furthermore, the proposed microfluidic device was exploited to purify the HBV DNA from the patient's blood plasma samples.

Towards practical sample preparation in point-of-care testing: user-friendly microfluidic devices

Microfluidic technologies offer a number of advantages for sample preparation in point-of-care testing (POCT), but the requirement for complicated external pumping systems limits their wide use. To facilitate sample preparation in POCT, various methods have been developed to operate microfluidic devices without complicated external pumping systems. In this review, we introduce an overview of user-friendly microfluidic devices for practical sample preparation in POCT, including self- and hand-operated microfluidic devices. Self-operated microfluidic devices exploit capillary force, vacuum-driven pressure, or gas-generating chemical reactions to apply pressure into microchannels, and hand-operated microfluidic devices utilize human power sources using simple equipment, including a syringe, pipette, or simply by using finger actuation. Furthermore, this review provides future perspectives to realize user-friendly integrated microfluidic circuits for wider applications with the integration of simple microfluidic valves.

Chips-on-a-plate device for monitoring cellular migration in a microchannel-based intestinal follicle-associated epithelium model

This paper describes a chips-on-a-plate (COP) device for monitoring the migration of Raji cells in the Caco-2/Raji coculture. To generate a model of the human intestinal follicle-associated epithelium (FAE), the coculture method using a conventional Transwell cell culture insert was established. Due to the structural limitations of the Transwell insert, live-cell tracking studies have not been performed previously using the existing FAE model. In this study, we designed a COP device to conduct long-term live-cell tracking of Raji cell migration using a microchannel-based FAE model. The COP device incorporates microfluidic chips integrated on a standard well plate, consistent humidity control to allow live-cell microscopy for 2 days, and microchannels connecting the two cell culture chambers of the COP device, which serve as a monitoring area for cellular migration. Using the COP device, we provide the first analysis of various migratory characteristics of Raji cells, including their chemotactic index in the microchannel-based FAE model. We showed that the migration of Raji cells could be controlled by modulating the geometry of the connecting microchannels. Cellular treatments with cytokines revealed that the cytokines increased the permeability of an FAE model with a detachment of Caco-2 cells. Live-cell monitoring of Raji cells treated with a fluorescent reagent also indicated exocytosis as a key agent of the Caco-2/Raji interaction. The COP device allows live-cell tracking analyses of cocultured cells in the microchannel-based FAE model, providing a promising tool for investigating cellular behavior associated with the recruitment of Raji to Caco-2 cells.

P5298Influence of the changes in body fat on all-cause and cardiovascular mortality in a general population: a report from Ansan-Ansung cohort in the Korean genome environment study

Background

Paradoxical beneficial effects of obesity on all-cause and cardiovascular mortality have been reported in multiple cohort studies based on patients with cardiovascular disease as well as general populations. However, the association between the presence of obesity at baseline and the better survival rates could not be directly interpreted into the beneficial effect of gain in obesity or fatness on the mortality, which makes it difficult to provide any recommendation for the management of obesity. Therefore, we investigated the influence of the changes in body fat on all-cause and cardiovascular mortality in a general population.

Methods

A population-based cohort study has been conducted for 12 years (from 2001 to 2012). A total of 5,259 subjects in whom body compositions using a bio-impedance method were measured at least 2 times during the observational period were included. The causes of death was identified from the nation-wide database in KOSTAT. I20-I82 and R99 in the International Classification of Disease-10 codes were defined as a cardiovascular death. The subjects were evenly divided into 3 groups by the percentages of the changes in body fat (Δ%BF; decreased [Δ%BF <0.0%] vs. increased [Δ%BF 0.0–13.7%] vs. highly increased [Δ%BF ≥13.7%]). Inverse probability of treatment weighting was applied to balance the covariate differences among the groups.

Results

The age was 51.2±8.5 years and 51.6% was male. Median observation duration was 163 (the interquartile range: 157–168) months. The all-cause death and cardiovascular death occurred most frequently in the decreased Δ%BF group and least frequent in the highly increased Δ%BF group in both unweighted and weighted cohort. Multivariate Cox proportional hazard models showed that the risk of all-cause death was lower in the increased and highly increased Δ%BF groups (hazard ratio [HR] 0.61 [0.47–0.80] and 0.24 [0.17–0.34], respectively) and the risk of cardiovascular death was lower in the highly increased Δ%BF group (HR 0.20 [0.08–0.48]), compared to those in the decreased Δ%BF group after adjustment for all covariates including physical activities and the changes in muscle mass. The risk of all-cause death and cardiovascular death linearly decreased with increasing Δ%BF (HR 0.72 [0.67–0.77] and 0.70 [0.60–0.82], respectively).

Conclusion

The increase in body fat is associated with a lower risk of all-cause death and cardiovascular death in a middle-age general population, independently with physical activities and the changes in muscle mass.

P5665The independent effect of insulin resistance on incidence of atrial fibrillation in non-diabetics

Purpose

Patients with diabetes mellitus have an elevated risk of atrial fibrillation (AF). However, whether insulin resistance may elevate risk of AF incidence in non-diabetic is inconsistent. The aim of our study was to verify the association between insulin resistance and incidence of AF in non-diabetics.

Methods

We evaluated population-based cohorts embedded in the Korean Genome Epidemiology Study. Insulin resistance was expressed as Homeostasis Model Assessment for Insulin resistance (HOMA-IR). Baseline data including HOMA-IR and electrocardiography (ECG) were obtained at 2001. Subsequent biennial ECG was performed for identification of AF until 2016.

Results

Among the 8220 participants (46.8% male; median age 49 years), 25 participants had AF (0.3%) at baseline and 101 participants developed AF (1.2%) during follow up of 12 years. In multivariate Cox regression analysis, high HOMA-IR (≥1.4) was significantly associated with incident AF compared with low HOMA-IR (<1.40) (adjusted hazard ratio [HR] 1.9, 95% confidence interval [CI] 1.3–3.0). In subgroup analysis, these association was consistent regardless of obesity (BMI<25; adjust HR 1.8, 95% CI 1.1–3.0, BMI≥25; adjust HR 2.3, 95% CI 1.3–4.0)

Subgroup analysis

Conclusion

Based on prospective cohort study, insulin resistance (HOMA-IR) was associated with AF independently of obesity in non-diabetics.

Integrated microfluidic pumps and valves operated by finger actuation

Here, we report an integrated operation of microfluidic pumps and valves only by finger actuation. As the working principle of the finger-actuated microfluidic pumps includes deflection of the poly(dimethylsiloxane) (PDMS) membrane, the pneumatic valves for controlling the flow direction can be easily integrated with the pumps. Using a single button, the flow path can be determined and flow generation can be achieved. We also verified the integrated operation of finger-actuated pumps and valves by demonstrating nucleic acid purification.

Finger-Actuated Microfluidic Display for Smart Blood Typing

Accurate blood typing is required before transfusion. A number of methods have been developed to improve blood typing, but these are not user-friendly. Here, we have developed a microfluidic smart blood-typing device operated by finger actuation. The blood-typing result is displayed by means of microfluidic channels with the letter and the symbol of the corresponding blood type. To facilitate the mixing of blood and reagents, the two sample inlets are connected to a single actuation chamber. According to the agglutination aspect in the mixture, the fluids are directed to both the microslit filter channels and bypass channels, or only to the bypass channels. The dimension of the microslit filter being clogged by the red blood cell aggregates was optimized to achieve reliable blood-typing results. The flow rate ratio between two channels in the absence of agglutination was subjected to numerical analysis. With this device, blood typing was successfully performed by seven button pushes using less than 10 μL of blood within 30 s.

Finger-Actuated Microfluidic Concentration Gradient Generator Compatible with a Microplate

The generation of concentration gradients is an essential part of a wide range of laboratory settings. However, the task usually requires tedious and repetitive steps and it is difficult to generate concentration gradients at once. Here, we present a microfluidic device that easily generates a concentration gradient by means of push-button actuated pumping units. The device is designed to generate six concentrations with a linear gradient between two different sample solutions. The microfluidic concentration gradient generator we report here does not require external pumps because changes in the pressure of the fluidic channel induced by finger actuation generate a constant volume of fluid, and the design of the generator is compatible with the commonly used 96-well microplate. Generation of a concentration gradient by the finger-actuated microfluidic device was consistent with that of the manual pipetting method. In addition, the amount of fluid dispensed from each outlet was constant when the button was pressed, and the volume of fluid increased linearly with respect to the number of pushing times. Coefficient of variation (CV) was between 0.796% and 13.539%, and the error was between 0.111% and 19.147%. The design of the microfluidic network, as well as the amount of fluid dispensed from each outlet at a single finger actuation, can be adjusted to the user’s demand. To prove the applicability of the concentration gradient generator, an enzyme assay was performed using alkaline phosphatase (ALP) and para-nitrophenyl phosphate (pNPP). We generated a linear concentration gradient of the pNPP substrate, and the enzyme kinetics of ALP was studied by examining the initial reaction rate between ALP and pNPP. Then, a Hanes–Woolf plot of the various concentration of ALP was drawn and the V_max and K_m value were calculated.

Vertically sheathing laminar flow-based immunoassay using simultaneous diffusion-driven immune reactions

Simultaneous infusion of primary and secondary antibodies of different diffusivity into vertical laminar flows enables the improved immune reactions.

Microfluidic on-chip immunohistochemistry directly from a paraffin-embedded section

We present here a novel microfluidic platform that can perform microfluidic on-chip immunohistochemistry (IHC) processes on a formalin-fixed paraffin-embedded section slide. Unlike previous microfluidic IHC studies, our microfluidic chip made of organic solvent-resistant polyurethane acrylate (PUA) is capable of conducting on-chip IHC processes consecutively. A narrow channel wall structure of the PUA chip shows effective sealing by pressure-based reversible assembly with a section slide. We performed both on-chip IHC and conventional IHC processes and compared the IHC results based on the immunostaining intensity. The result showed that the effects of the on-chip deparaffinization, antigen retrieval, and immunoreaction processes on the IHC result were equivalent to conventional methods while reducing the total process time to less than 1/2. The experiment with breast cancer tissue shows that human epidermal growth factor receptor 2 (HER2) classification can be performed by obtaining a clearly distinguishable immunostaining intensity according to the HER2 expression level. We expect our on-chip microfluidic platform to provide a facile technique suitable for miniaturized, automated, and precise diagnostic devices, including a point-of-care device.

High-throughput culture and embedment of spheroid array using droplet contact-based spheroid transfer

Spheroids are one of the most representative models of 3D cell culture, which can be easily formed using conventional hanging drop method. However, medium change and spheroid transferring process are the bottlenecks that reduce the throughput of the entire process in the hanging drop culture. In addition, the embedment of spheroid into hydrogel still depends on the individual pipetting process. To overcome these issues, we present poly(dimethylsiloxane) (PDMS)-based simple devices which can exploit droplet contact-based spheroid transfer using a drop array chip (DAC) having an array of well structures and peripheral rims. When the upper spheroid-containing drops were in contact with the lower liquid drops, the air-liquid interface disappeared at the merged surface and the spheroids settled down due to gravitational force. This method was applied to repetitive medium change and live/dead staining of spheroids cultured with the hanging drop method. To simultaneously embed the spheroids into the corresponding collagen hydrogel drops, a PDMS-based pillar array chip (PAC) was contacted in advance with the spheroid-containing DAC. The contacted PAC then contained the spheroids trapped in small drops of liquid reduced in volume to around 0.5 μl. Consequently, the spheroids were embedded into the collagen drops at once by contacting the spheroid-containing PAC with the collagen-loaded DAC. The embedded spheroids using the DAC-PAC contacting method showed a reliable invasion behavior compared to the embedded spheroids using conventional manual pipetting.

Finger-actuated microfluidic device for the blood cross-matching test

A blood cross-matching test should be carried out to prevent a hemolytic transfusion reaction as the final verification step. To simplify complicated procedures of a conventional blood cross-matching test requiring bulky systems and skilled people, we present a finger-actuated microfluidic device for the blood cross-matching test. Although finger actuation is a simple action that anyone can easily accomplish, there would be a variation in the individual finger actuation that may induce the user-dependent errors of the device. Therefore, the working principle of the finger-actuated microfluidic device is newly designed to reduce the user-dependent errors by indirectly controlling the pressure of fluidic channels. The constant volume was repeatedly dispensed by pushing and releasing a pressure chamber regardless of the different pushed depths of the pressure chamber, the pushing time interval, and the end-users. The dispensed volume was linearly increased according to the number of pushing times applied to the pressure chamber and determined by adjusting the diameter of an actuation chamber. In addition, multiple fluids can be dispensed with a desirable ratio by pushing and releasing the pressure chamber. Finally, a finger-actuated microfluidic device for the blood cross-matching test was developed, which can simultaneously actuate four fluidic channels. After loading 50 μL of whole blood samples from a donor and a recipient into two inlets of the device, the blood plasma from each individual was separated through the two plasma separation membranes. The blood cross-matching test results can be achieved by cross-reacting the donor's blood plasma with the recipient's whole blood as well as the donor's whole blood with the recipient's blood plasma by pushing and releasing only a single pressure chamber within 10 min.

Multiplexed Detection of Foodborne Pathogens from Contaminated Lettuces Using a Handheld Multistep Lateral Flow Assay Device

This paper presents a handheld device that is capable of simplifying multistep assays to perform sensitive detection of foodborne pathogens. The device is capable of multiplexed detection of Escherichia coli (E. coli) O157:H7, Salmonella Typhimurium (S. Typhimurium), Staphylococcus aureus, and Bacillus cereus. The limit of detection for each bacterium was characterized, and then, the detection of bacteria from contaminated fresh lettuces was demonstrated for two representative foodborne pathogens. We employed a sample pretreatment protocol to recover and concentrate target bacteria from contaminated lettuces, which can detect 1.87 × 104 CFU of E. coli O157:H7 and 1.47 × 104 CFU of S. Typhimurium/1 g of lettuce without an enrichment process. Lastly, we demonstrated that the limit of detection can be reduced to 1 CFU of E. coli O157:H7 and 1 CFU of S. Typhimurium/1 g of lettuce by including a 6 h enrichment of contaminated lettuces in growth media before pretreatment.

Plant array chip for the germination and growth screening of Arabidopsis thaliana

A screening process for the germination and growth of seed is generally required for plant research. Such a repetitive screening process is costly and time-consuming, and its bulky setup requires a lot of space. In particular, the control of the variables, such as light, nutrients, hormones and temperature, is difficult due to the limited space for incubation. In addition, small seeds such as Arabidopsis thaliana are difficult to handle as they are hundreds of microns in diameter and require a more precisely controllable screening environment. However, conventional screening methods involve the seeding of multiple seeds on a single agarose plate without physical partitions. Such methods need to be improved because they lack control over the growth environment and the results are highly dependent on the researchers. To overcome the above-mentioned limitations, a novel seeding array chip has been developed which can be filled with conventional solid agarose while enabling more efficient screening. Individual seeds can be partitioned from each other and a number of different agarose conditions can be tested in a single plant array chip. As a demonstration, we tested the effect of various concentrations of Murashige and Skoog medium and a plant hormone (e.g., abscisic acid) on the growth of Arabidopsis. The chip can efficiently save the space required for screening by providing different conditions for ∼400 seeds in a 59 × 55 mm chip, and it also provides easy observation and analysis of seed growth. The proposed plant array chip is expected to contribute to more efficient screening of essential phenotypes such as germination and growth for both academic and industrial purposes.

Onion (Allium cepa L.) peel extract (OPE) regulates human sperm motility via protein kinase C-mediated activation of the human voltage-gated proton channel

Onion (Allium cepa L.) and quercetin protect against oxidative damage and have positive effects on multiple functional parameters of spermatozoa, including viability and motility. However, the associated underlying mechanisms of action have not yet been identified. The aim of this study was to investigate the effect of onion peel extract (OPE) on voltage-gated proton (Hv1) channels, which play a critical role in rapid proton extrusion. This process underlies a wide range of physiological processes, particularly male fertility. The whole-cell patch-clamp technique was used to record the changes in Hv1 currents in HEK293 cells transiently transfected with human Hv1 (HVCN1). The effects of OPE on human sperm motility were also analyzed. OPE significantly activated the outward-rectifying proton currents in a concentration-dependent manner, with an EC₅₀ value of 30 μg/mL. This effect was largely reversible upon washout. Moreover, OPE induced an increase in the proton current amplitude and decreased the time constant of activation at 0 mV from 4.9 ± 1.7 to 0.6 ± 0.1 sec (n = 6). In the presence of OPE, the half-activation voltage (V_1/2 ) shifted in the negative direction, from 20.1 ± 5.8 to 5.2 ± 8.7 mV (n = 6), but the slope was not significantly altered. The OPE-induced current was profoundly inhibited by 10 μm Zn²⁺ , the most potent Hv1 channel inhibitor, and was also inhibited by treatment with GF109203X, a specific protein kinase C (PKC) inhibitor. Furthermore, sperm motility was significantly increased in the OPE-treated groups. OPE exhibits protective effects on sperm motility, at least partially via regulation of the proton channel. Moreover, similar effects were exerted by quercetin, the major flavonoid in OPE. These results suggest OPE, which is rich in the potent Hv1 channel activator quercetin, as a possible new candidate treatment for human infertility.

Catheter probe endoscopic ultrasonography by using cold lubricating jelly-filled method for esophageal subepithelial tumors

Catheter probe endoscopic ultrasonography (C-EUS) by ultrasonographic jelly-filled method has been used to evaluate esophageal subepithelial tumors (SETs). Ultrasonographic jelly is safe on the skin, but its internal safety has not been demonstrated. The jelly stored at room temperature is easily injected into the esophagus through the instrument channel of the endoscope. However, using jelly stored at room temperature remains problematic because the jelly is drained rapidly. We used cold lubricating jelly and an intravenous extension tube to resolve these problems. In this study, we evaluated the safety and efficacy of cold lubricating jelly-filled method. The medical records of patients who underwent C-EUS by using water or cold lubricating jelly-filled method for esophageal SETs from March 2013 to September 2016 in Gangneung Asan hospital were reviewed. Clinical characteristics and EUS findings were evaluated retrospectively. Image quality and procedure time between water and cold lubricating jelly-filled method were compared retrospectively. This study included 138 patients (74 males, 64 females) with esophageal SET with a mean age of 57.1 ± 11.1 years. Thirty-four patients had lesions in the upper esophagus, 58 patients had lesions in the middle esophagus, and 46 patients had lesions in the lower esophagus. The EUS diagnoses were leiomyoma (82.6%), hemangioma (4.3%), extrinsic compressive lesion (3.6%), granulosa cell tumor (2.9%), ectopic calcification (1.4%), cyst (1.4%), lipoma (0.7%), varix (0.7%), and inconclusive lesion (2.2%). The mean image score in the cold lubricating jelly filled-method group was higher than that in the water-filled method group (3.2 ± 0.7 vs. 2.8 ± 0.7, P = 0.002). The procedure time in the cold lubricating jelly filled-method group was shorter than that in the water-filled method group (10 minutes 27 seconds ± 4 minutes 22 seconds versus 13 minutes 20 seconds ± 6 minutes 20 seconds, P = 0.045). No procedure-related complication was observed. C-EUS using the cold lubricating jelly-filled method seems to provide better image quality and shorter procedure time compared with C-EUS using the water-filled method.

Visualization and label-free quantification of microfluidic mixing using quantitative phase imaging

Microfluidic mixing plays a key role in various fields, including biomedicine and chemical engineering. To date, although various approaches for imaging microfluidic mixing have been proposed, they provide only quantitative imaging capability and require exogenous labeling agents. Quantitative phase imaging techniques, however, circumvent these problems and offer label-free quantitative information about concentration maps of microfluidic mixing. We present the quantitative phase imaging of microfluidic mixing in various types of polydimethylsiloxane microfluidic channels with different geometries; the feasibility of the present method was validated by comparing it with the results obtained by theoretical calculation based on Fick's law.

Effects of eupatilin on the contractility of corpus cavernosal smooth muscle through nitric oxide-independent pathways

Eupatilin (5,7-dihydroxy-3,4,6-trimethoxyflavone) is one of the main compounds present in Artemisia species. Eupatilin has both antioxidative and anti-inflammatory properties and a relaxation effect on vascular contraction regardless of endothelial function. We evaluated the relaxant effects of eupatilin on the corpus cavernosum (CC) of rabbits and the underlying mechanisms of its activity in human corpus cavernosum smooth muscle (CCSM) cells. Isolated rabbit CC strips were mounted in an organ bath system. A conventional whole-cell patch clamp technique was used to measure activation of calcium-sensitive K⁺ -channel currents in human CCSM cells. The relaxation effect of eupatilin was evaluated by cumulative addition (10^-5  m ~ 3 × 10^-4  m) to CC strips precontracted with 10^-5  m phenylephrine. Western blotting analysis was performed to measure myosin phosphatase targeting subunit 1 (MYPT1) and protein kinase C-potentiated inhibitory protein for heterotrimeric myosin light chain phosphatase of 17-kDa (CPI-17) expression and to evaluate the effect of eupatilin on the RhoA/Rho-kinase pathway. Eupatilin effectively relaxed the phenylephrine-induced tone in the rabbit CC strips in a concentration-dependent manner with an estimated EC₅₀ value of 1.2 ± 1.6 × 10^-4  m (n = 8, p < 0.05). Iberiotoxin and tetraethylammonium significantly reduced the relaxation effect (n = 8, p < 0.001 and p = 0.003, respectively). Removal of the endothelium or the presence of L-NAME or indomethacin did not affect the relaxation effect of eupatilin. In CCSM cells, the extracellular application of eupatilin 10^-4  m significantly increased the outward currents, and the eupatilin-stimulated currents were significantly attenuated by treatment with 10^-7  m iberiotoxin (n = 13, p < 0.05). Eupatilin reduced the phosphorylation level of MYPT1 at Thr853 of MLCP and CPI-17 at Thr38. Eupatilin-induced relaxation of the CCSM cells via NO-independent pathways. The relaxation effects of eupatilin on CCSM cells were partially due to activation of BK_Ca channels and inhibition of RhoA/Rho-kinase.

Lateral flow assay-based bacterial detection using engineered cell wall binding domains of a phage endolysin

The development of a cost-effective and efficient bacterial detection assay is essential for diagnostic fields, particularly in resource-poor settings. Although antibodies have been widely used for bacterial capture, the production of soluble antibodies is still expensive and time-consuming. Here, we developed a nitrocellulose-based lateral flow assay using cell wall binding domains (CBDs) from phage as a recognition element and colloidal gold nanoparticles as a colorimetric signal for the detection of a model pathogenic bacterium, Bacillus cereus (B. cereus). To improve conjugation efficiency and detection sensitivity, cysteine-glutathione-S-transferase-tagged CBDs and maltose-binding protein-tagged CBDs were produced in Escherichia coli (E. coli) and incorporated in our assays. The sensitivity of the strip to detect B. cereus was 1×10⁴ CFU/mL and the overall assay time was 20min. The assay showed superior results compared to the antibody-based approach, and did not show any significant cross-reactivity. This proof of concept study indicates that the lateral flow assay using engineered CBDs hold considerable promise as simple, rapid, and cost-effective biosensors for whole cell detection.

Demonstration of Interposed Modular Hydrogel Sheet for Multicellular Analysis in a Microfluidic Assembly Platform

Hydrogel sheets have emerged as a promising biomaterial scaffold for the encapsulation and transfer of multicellular structures. Although the improvement of the chemical interactions and the design of micro-scaled geometry have contributed to the development of multipurpose hydrogel scaffolds, the application of hydrogel sheets to assess multicellular structures is still challenging. To expand the technical applicability of hydrogel sheets, we here demonstrate that a single layer of the hydrogel sheet can be integrated as an interposed module in a microfluidic device for multicellular analysis. As a cell culture unit, encapsulated pancreatic insulinoma (MIN6) cells in the hydrogel sheet were labeled and examined via multiple microchannels. After obtaining simultaneously multi-labeled cells in the hydrogel sheet that had been incorporated into the microfluidic device, each modular hydrogel sheet was also recoverable and re-cultured without any distortion. The modular hydrogel sheet can be simply manipulated and conserved as a multicellular module in a three-dimensional (3D) in vitro culture platform. Using the modular concept of hydrogel sheets capable of cell culture and/or assay, an integrated multicellular analysis in the microfluidic device is expected to improve accessibility, scalability, and practicality for end users.