Three-dimensional Microfluidic Device Research Articles

3D Microfluidic Devices in a Single Piece of Paper for the Simultaneous Determination of Nitrite and Thiocyanate.

The concentrations of nitrite and thiocyanate in saliva can be used as the biomarkers of the progression of periodontitis disease and environmental tobacco smoke exposure, respectively. Therefore, it is particularly necessary to detect these two indicators in saliva. Herein, the three-dimensional single-layered paper-based microfluidic analytical devices (3D sl-μPADs) were, for the first time, fabricated by the spraying technique for the colorimetric detection of nitrite and thiocyanate at the same time. The conditions for 3D sl-μPADs fabrication were optimized in order to well control the penetration depth of the lacquer in a paper substrate. Then, the developed 3D sl-μPADs were utilized to simultaneously detect nitrite and thiocyanate and the limits of detection are 0.0096 and 0.074 mM, respectively. What is more, the μPADs exhibited good specificity, good repeatability, and acceptable recoveries in artificial saliva. Therefore, the developed 3D sl-μPADs show a great potential to determine nitrite and thiocyanate for the assessment of the human health.

An Integrated Paper-Based Microfluidic Device for Real-Time Sweat Potassium Monitoring

Wearable electrochemical sensors have attracted tremendous attention in recent years. Here, an integrated three-dimensional paper-based microfluidic electrochemical device (3D-PMED) with flexible wireless circuits is demonstrated for real-time monitoring of sweat potassium. The paper-based microfluidic pad is fabricated by printing wax patterns on cellulose paper and then folding the pre-patterned paper four times to form a five-layer stacked structure: sweat collector, vertical channel, transverse channel, electrode layer, and sweat evaporator. Also, we have discussed the different properties with three swear collector types. The sweat monitoring device is realized by integrating a screen-printed potassium ion-selective sensor on the PET substrate with the fabricated paper microfluidic pad. The sweat flow in 3D-PMED is modeled with red ink to generate the flow pathway of sweat and the capability of sweat storage. The detection range of the potassium ion-selective sensor is 1-32 mM, and the electrode response potential is 61.79 mV per decade of K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> concentration. The device has a small size that is suitable for everywhere on the body, and also have shown good selectivity for both anion and cation, and a stable performance within 1 week. This 3D-PMED has provided a simple, low-cost way for real-time dynamic sweat potassium monitoring when exercising.

Development of a parallel three-dimensional microfluidic device for high-throughput cytometry

Microflow cytometry was previously pursued to achieve high-throughput cell analyses. It has advantages of parallelization and miniaturization capabilities that allow fewer detecting elements to simultaneously observe multiple channels. However, the major disadvantage is that it is difficult to precisely control parallel cell positions in each channel when cells pass through the detection area. In this study, we developed a multilayer microfluidic device, which has one sample flow inlet, two sheath flow inlets, and one flow outlet, which can achieve parallel sheath 3D flow focusing and fluorescence detection in 32 channels. The sample flow in each channel is focused and allows the cells or particles to pass through the detection zone one by one. Optimized flow rate ratios of the sample flow, lateral sheath flow, and circular sheath flow were found. The highest throughput of 106 cells/s was obtained using mammalian cells. The current cytometer, which incorporates a microoptic-integrated microfluidic device and newly developed optical system, was proven to have multicolor detection ability.

Symmetry-based nonperturbative micromanipulation in a three-dimensional microfluidic device

A three-dimensional microfluidic device with embedded symmetries enables rich flow controls for complex manipulations of particles. These flow characteristics, especially a strain-free flow with uniform flow velocities, are protected by symmetries. This nonperturbative capability serves as a supplement to current perturbative micromanipulation approaches.

Three-Dimensional Microporous Hollow Fiber Membrane Microfluidic Device Integrated with Selective Separation and Capillary Self-Driven for Point-of-Care Testing.

The novel 3D microfluidic concept of "lab-on-hollow fiber membrane (HFM)" was presented for multifunctional and rapid biological assays, integrating sample size sieving and colorimetric quantification in an HFM. Herein, microporous HFMs with a gradient pore size and high hydrophilic flux were used as microfluidic device substrates. The membrane pores selectively trapped macromolecules within the inner surface, while allowing free diffusion of smaller molecules, including glucose and protein. The microfluidic flow rate in HFM closely followed the Lucas-Washburn and Laplace's models, indicating that the microfluidics facilitated the upward flow of the fluid by microcapillary action without external pumping. Subsequently, for sensing of different biomolecules, a highly sensitive fluorescent or optical chromogenic reagent was immobilized in HFM by an electrostatic interaction. Pyronin G fluorescence reagent was quenched by blood glucose, and the quenching efficiency showed a good linear correlation with glucose concentration (1-22 mM, R2 = 0.997). Moreover, this sensing platform was then further applied for the analysis of urine protein or glucose in the visible spectrum, with a wide testing range. Compared to traditional 2D flat membrane devices, this 3D-HFM microfluidic device exhibited excellent sensing versatility and color rendering uniformity with enhanced sensitivity. Target molecules screening, conditioning, enzymatic recognition, and signal readout of biomolecules have all been implemented on this device, which has paved the way to highly sensitive assays on point-of-care testing (POCT).

A three-dimensional origami microfluidic device for paper chromatography: Application to quantification of Tartrazine and Indigo carmine in food samples

Herein, we report three-dimensional paper chromatography (3D-PC) as a micro-chromatographic platform. The method was based on applying the origami microfluidic device for separation, coupled by colorimetric methods for simultaneous determination. The microfluidic device fabrication was a facile printing approach. Two azo food dyes, Tartrazine (E102) and Indigo carmine (E132), were selected as a model analyte, while carbonate-bicarbonate buffer was used as the mobile phase. Our micro-chromatographic device is associated with two big advantages including needing very small volume of mobile phase ( ~12 µL) and ultrafast separation time (~35 s). Under the optimal conditions, the method provided acceptable linear ranges of 0. 0 g L1–18.0 g L1 (R2 = 0.997) for E102 and 0.070 g L1–10.0 g L1 for E132 and the limits of detection (3σ/slope) were evaluated as 0.620 and 0.060 g L1, respectively. The proposed method was successfully applied in the separation and quantification of these dyes in commercial food products such as jelly, candy, and four kinds of drink samples without any sample preparation prior to analysis. The mean recovery values for the real sample analysis were in the range of 100.14%–102.38% for E132 and E102 respectively. The inter-device relative standard deviations were in the ranges of 1.5%–11.8%. In total, our chromatographic μPAD is small (1.0 cm × 1.0 cm × 0.5 cm), portable, inexpensive, no need of specialized user, requires low volumes of sample (0.5 μL), and can perform separation using 12 μL of aqueous mobile phase in very short time.

Research on healthcare and external medicine based on nano biochip technology

The first step in the development of biochips is to prepare biochip carriers. In this process, the surface of the carrier needs to be chemically treated to enable rapid and efficient immobilisation of the various probes. The quality of the carrier directly affects the performance of the microarray and is critical to the preparation of the chip. In this paper, the surface-smoothed slides were used to assemble nanofilms with large specific surface area and super-adsorption properties on the slides, and then functionalised surface modification, giving full play to the dual advantages of physical adsorption and chemical coupling. The glass cuboid is used as the chip substrate, and the cylindrical glass capillary is used as the microfluidic channel. By simply combining it with the flow pump, a three-dimensional microfluidic immunoassay device is constructed. By comparing the properties of protein immobilisation, immune response efficiency and signal-to-noise ratio in three-dimensional devices, it is compared with traditional two-dimensional microfluidic chips. The scores in the experimental group and the control group were significantly lower than those in the initial diagnosis, P 0.04, indicating that there was no statistical difference between the two groups. The use of topical drugs to treat chronic localisation problems can effectively alleviate the patient's discomfort and reduce the symptoms of skin lesions. At the same time, it has high safety and good promotion value.

Human Induced Pluripotent Stem-Cardiac-Endothelial-Tumor-on-a-Chip to Assess Anticancer Efficacy and Cardiotoxicity

Cancer remains a leading health threat in the United States, and cardiovascular drug toxicity is a primary cause to eliminate a drug from FDA approval. As a result, the demand to develop new anticancer drugs without cardiovascular toxicity is high. Human induced pluripotent stem (iPS) cell-derived tissue chips provide potentially a cost-effective preclinical drug testing platform, including potential avenues for personalized medicine. We have developed a three-dimensional microfluidic device that simultaneously cultures tumor cell spheroids with iPS-derived cardiomyocytes (iPS-CMs) and iPS-derived endothelial cells (iPS-EC). The iPS-derived cells include a GCaMP6 fluorescence reporter to allow real-time imaging to monitor intracellular calcium transients. The multiple-chambered tissue chip features electrodes for pacing of the cardiac tissue to assess cardiomyocyte function such as the maximum capture rate and conduction velocity. We measured the inhibition concentration (IC50) of the anticancer drugs, Doxorubicin (0.1 μM) and Oxaliplatin (4.2 μM), on the tissue chip loaded with colon cancer cells (SW620). We simultaneously evaluated the cardiotoxicity of these anticancer drugs by assessing the drug effect on the spontaneous beat frequency and conduction velocity of iPS-derived cardiac tissue. Consistent with in vivo observations, Doxorubicin reduced the spontaneous beating rate and maximum capture rate at or near the IC50 (0.04 and 0.22 μM, respectively), whereas the toxicity of Oxaliplatin was only observed at concentrations beyond the IC50 (33 and 9.9 μM, respectively). Our platform demonstrates the feasibility to simultaneously assess cardiac toxicity and antitumor effects of drugs and could be used to enhance personalized drug testing safety and efficacy. Impact statement Drug development using murine models for preclinical testing is no longer adequate nor acceptable both financially for the pharmaceutical industry as well as for generalized or personalized assessment of safety and efficacy. Innovative solutions using human cells and tissues provide exciting new opportunities. In this study, we report on the creation of a 3D microfluidic device that simultaneously cultures human tumor cell spheroids with cardiomyocytes and endothelial cells derived from the same induced pluripotent stem cell line. The platform provides the opportunity to assess efficacy of anticancer agents while simultaneously screening for potential cardiovascular toxicity in a format conducive for personalized medicine.

Development of a microfluidic route for the formation of gellan-based microgels incorporating jabuticaba (Myrciaria cauliflora) extract

Gellan microgels incorporated with jabuticaba extract were produced by external gelation of monodisperse water-in-oil (W/O) emulsions. This extract, rich in anthocyanins, has shown antioxidant effect and benefits associated to intestinal issues. The W/O emulsions were produced using a three-dimensional microfluidic device operated in an intermittent dripping regime flow. Microgels were obtained from external gelation of emulsions by calcium ions present in the continuous phase. Our results showed how to produce and control the microgel diameter and polydispersity by varying the flow rate of continuous and dispersed phases. Diameter of microgels ranged from 185 μm to 342 μm, and coefficient of variation values varied between 1.6 and 8.6%. The low stability of microgels loaded with jabuticaba extract was mainly associated with both the low gellan concentration and the osmotic pressure difference during storage. In spite of this, the microfluidic route proposed can potentially be used to incorporate and protect anthocyanins extracts and might be extended for other hydrophilic molecules.

A microfluidic device enabling surface-enhanced Raman spectroscopy at chip-integrated multifunctional nanoporous membranes.

A three-dimensional microfluidic chip that combines sample manipulation and SERS detection on-chip was developed. This was successfully achieved by chip integration of a nanoporous polycarbonate track-etched (PCTE) membrane which connects microfluidic channels on two different levels with each other. The membrane fulfills two functions at the same time. On the one hand, it enables sample enrichment by selective electrokinetic transport processes through the membrane. On the other hand, the silver nanoparticle-coated backside of the same membrane enables SERS detection of the enriched analytes. The SERS substrate performance and the electrokinetic transport phenomena were studied using Rhodamine B (RhB) by Raman microscopy and fluorescence video microscopy. After system validation, the approach was attested by on-chip processing of a complex food sample. In a proof-of-concept study, the microfluidic device with the SERS substrate membrane was used to detect a concentration of 1 ppm melamine (705 cm-1) in whole milk. Electrokinetic transport across the nanoporous SERS substrate facilitates the extraction of analyte molecules from a sample channel into a detection channel via a potential gradient, thus easily removing obscuring compounds present in the sample matrix. The SERS signal of the analyte could be significantly increased by on-target sample drying. This was achieved by guiding an additional gas flow over the membrane which further extends the microfluidic functionality of the chip device. The proposed method possesses the advantages of combining a rapid (within 15 min) sample clean-up using electrokinetic transport in a three-dimensional microfluidic device which is highly suitable for sensitive and selective SERS detection of chemical and biological analytes. Graphical Abstract.

Chemiluminescence Immunoassays for Simultaneous Detection of Three Heart Disease Biomarkers Using Magnetic Carbon Composites and Three-Dimensional Microfluidic Paper-Based Device

Chemiluminescence (CL) immunoassays for simultaneous detection of early acute myocardial infarction (AMI) biomarkers, including copeptin, heart-type fatty acid binding protein (h-FABP), and cardiac troponin I (cTnI), were developed by using Co2+/N-(aminobutyl)-N-(ethylisoluminol) (ABEI) functionalized magnetic carbon composite (Co2+-ABEI-Fe3O4@void@C) as an interface and a three-dimensional microfluidic paper-based device (3D μPAD) as a detection system. For CL immunoassays, Co2+-ABEI-Fe3O4@void@C was assembled with chitosan (CS) and gold nanoparticle-conjugated antibody (Au-Ab) sequentially to form the sensing platform (Co2+-ABEI-Fe3O4@void@C-CS/Au-Ab). In the presence of antigen (Ag), Ag was captured by the sensing interface to form an immunocomplex, leading to an increase in CL intensity due to the catalysis of -COO- existing in Ag. A 3D μPAD with three detection zones for simultaneous detection of copeptin, h-FABP, and cTnI was designed and fabricated to obtain time-resolved CL signals. Three kinds of immunocomplexes formed with copeptin, h-FABP, and cTnI were added to three detection zones of 3D μPAD, respectively. After injecting H2O2, three time-resolved CL signals were generated in one CL detection run by virtue of time-delayed transport of H2O2 to different detection zones. The three time-resolved CL signals were used for the simultaneous determination of copeptin, h-FABP, and cTnI. The detection limit of copeptin, h-FABP, and cTnI was 0.40 pg/mL, 0.32 pg/mL, and 0.50 pg/mL, respectively, which is at least 1 order of magnitude lower than most of the reported immunoassays. The immunoassays could be directly used for the detection of copeptin, h-FABP, and cTnI in human serum samples. The proposed immunoassays are simple, fast, sensitive, and selective, and are of great application potential in early diagnosis and treatment of AMI.

Three-Dimensional Paper-Based Microfluidic Analytical Devices Integrated with a Plasma Separation Membrane for the Detection of Biomarkers in Whole Blood.

Paper-based microfluidic analytical devices (μPADs) have recently attracted attention as a point-of-care test kit because of their low cost and nonrequirement for external forces. To directly detect biomarkers in whole blood, however, they need to be assembled with a filter such as a plasma separation membrane (PSM) because the color of the blood cells interferes with the colorimetric assay. However, this assembly process is rather complicated and cumbersome, and the fluid does not uniformly move to the detection zone when the adhesion between the paper and PSM is not perfect. In this study, we report a simple three-dimensional (3D) printing method for fabricating PSM-integrated 3D-μPADs made of plastics without the need for additional assembly. In detail, PSM was coated with parylene C to prevent its dissolution from organic solvent during 3D printing. Then, the coated PSM was superimposed on the paper. Detection zones and a reservoir were printed on the paper and PSM via liquid photopolymerization, using a digital light processing printer. The limit of detection of the PSM-integrated 3D-μPADs for glucose in whole blood was 0.3 mM, and these devices demonstrated clinically relevant performance on diabetes patient blood samples. Our 3D-μPADs can also simultaneously detect multiple metabolic disease markers including glucose, cholesterol, and triglycerides in whole blood. Our results suggest that our printing method is useful for fabricating 3D-μPADs integrated with PSM for the direct detection of biomarkers in whole blood.

Multiplexed chemiluminescence determination of three acute myocardial infarction biomarkers based on microfluidic paper-based immunodevice dual amplified by multifunctionalized gold nanoparticles

Acute myocardial infarction (AMI) causes significant mortality and morbidity. The determination of multiple AMI biomarkers is very important for the timely diagnosis of AMI. In this work, simultaneous determination of three AMI biomarkers were achieved by virtue of a three-dimensional (3D) microfluidic paper-analytical device (μPAD) with temporally resolved chemiluminescence (CL) emissions for the first time. A dual-signal amplification strategy was introduced including by employing primary antibody functionalized gold nanoparticles (Ab1-GNPs) immobilized on the detection zone as amplified capture probes, and Co(II) catalyst, secondary antibody, luminol multifunctionalized gold nanoparticles (Co(II)-Ab2-luminol-GNPs) with excellent CL activity as amplified signal probes. CL immunoreactions were performed at three detection zone of the fabricated 3D μPAD by assembling Ab1-GNPs, antigen, and Co(II)-Ab2-luminol-GNPs to form sandwich-type immunocomplexes. Auto separated CL signals with temporal resolution were obtained by time delayed transport of H2O2 to different detection zones for multiplexed analysis. The CL signal obtained by using Co(II)-Ab2-luminol-GNPs as signal probe (10576 a.u.) were about 20-fold higher than that by using conventional horseradish peroxidase labeled antibody modified luminol-GNPs as signal probe (531 a.u.). Finally, three AMI biomarkers including heart-type fatty acid-binding protein (H-FABP), cardiac troponin I (cTnI) and copeptin were quantitatively analyzed in one CL detection run by reading the CL intensity of the obtained three CL emission peaks. The detection range were ultra-wide ranged from 0.1 pg/mL to 1 μg/mL, 0.5 pg/mL to 1 μg/mL and 1 pg/mL to 1 mg/mL with the detection limits down to 0.06 pg/mL, 0.3 pg/mL and 0.4 pg/mL for H-FABP, cTnI and copeptin detection, respectively. The developed μPAD based immunoassay performing multiplexed analysis ability, high sensitivity, ultra-wide dynamic range, favorable selectivity, accessible accuracy and reproducibility, have great application potential for the early diagnosis of AMI.

Three-Dimensional Modeling of Avascular Tumor Growth in Both Static and Dynamic Culture Platforms.

Microfluidic cell culture platforms are ideal candidates for modeling the native tumor microenvironment because they can precisely reconstruct in vivo cellular behavior. Moreover, mathematical modeling of tumor growth can pave the way toward description and prediction of growth pattern as well as improving cancer treatment. In this study, a modified mathematical model based on concentration distribution is applied to tumor growth in both conventional static culture and dynamic microfluidic cell culture systems. Apoptosis and necrosis mechanisms are considered as the main inhibitory factors in the model, while tumor growth rate and nutrient consumption rate are modified in both quiescent and proliferative zones. We show that such modification can better predict the experimental results of tumor growth reported in the literature. Using numerical simulations, the effects of the concentrations of the nutrients as well as the initial tumor radius on the tumor growth are investigated and discussed. Furthermore, tumor growth is simulated by taking into account the dynamic perfusion into the proposed model. Subsequently, tumor growth kinetics in a three-dimensional (3D) microfluidic device containing a U-shaped barrier is numerically studied. For this case, the effect of the flow rate of culture medium on tumor growth is investigated as well. Finally, to evaluate the impact of the trap geometry on the tumor growth, a comparison is made between the tumor growth kinetics in two frequently used traps in microfluidic cell culture systems, i.e., the U-shaped barrier and microwell structures. The proposed model can provide insight into better predicting the growth and development of avascular tumor in both static and dynamic cell culture platforms.

Three-dimensional microfluidic paper-based device for multiplexed colorimetric detection of six metal ions combined with use of a smartphone.

A simple double-layered three-dimensional (3D) microfluidic paper-based analytical device (μPAD) was designed for the simultaneous determination of six metal ions-Fe(III), Ni(II), Cr(VI), Cu(II), Al(III), and Zn(II)-for the first time. The 3D μPAD was composed of two paper layers: a top pretreatment layer and a bottom colorimetric detection layer. The sample solution added to the central sample reservoir of the 3D μPAD could be automatically divided into eight flow pathways and be automatically pretreated while flowing through the pretreatment zones located in the microfluidic channels, and automatically carried out the chromogenic reactions after reaching the detection zones. Random diffusion of the chromogenic reagents was effectively prevented by transport of the pretreated sample solution to the detection zones through 3D microfluidic channels with an L-type circuitous flow route design, resulting in highly increased color uniformity and reproducibility. Combined with use of a flat LED lamp as an upward lighting source and a smartphone as a convenient detector, improved color perception, highly enhanced sensitivity, and an extended detection range were obtained. Finally, the double-layered 3D μPAD was applied to the multiplexed determination of the six metal ions in mixtures and environmental samples with satisfactory results. Detection limits as low as 0.2, 0.3, 0.1, 0.03, 0.08, and 0.04 mg/L for Fe(III), Ni(II), Cr(VI), Cu(II), Al(III), and Zn(II) detection, respectively, were achieved, which are about one order of magnitude lower than obtained with previously reported μPADs for the detection of metal ions. The present 3D μPAD is simple, fast, selective, sensitive, and user-friendly, and holds great application potential for multiplexed on-site analysis.

Patterning and Modeling Three-Dimensional Microfluidic Devices Fabricated on a Single Sheet of Paper.

This work describes a method to fabricate three-dimensional paper microfluidic devices in one step, without the need of stacking layers of paper, glue, or tape. We used a nontransparent negative photoresist that allows patterning selectively (vertically) the paper, creating systems of two or three layers, including channels. To demonstrate the capabilities of this methodology, we designed, fabricated, and tested a six-level diluter. The performance of the device was also simulated using a simple numerical model implemented in the program PETSc-FEM. The resulting μPAD is small (1.6 cm × 2.2 cm), inexpensive, requires low volumes of sample (5 μL), and is able to perform mixing and dilution in 2 min.

Flow controllable three-dimensional paper-based microfluidic analytical devices fabricated by 3D printing technology

In most cases, three-dimensional paper-based microfluidic analytical devices (3D-μPADs) were fabricated manually by stacking or folding methods. For the first time, digital light processing stereolithography (DLP-SLA) 3D printing technology was adopted to automatically make 3D-μPADs. In the fabrication process, a printing pause was set between two layers to allow paper to be placed in the resin tank. The resin on the fresh paper spontaneously bonded to the former cured paper layer during curing, thus realizing the automatic bonding and alignment between different layers of paper and avoiding the human participation and errors as in stacking and folding methods. There was a gap between two vertical aligned flow paths, therefore the liquid did not flow spontaneously from the upper layer to the lower layer. Most of the fluid flow in 3D-μPADs was spontaneous or manually activated, which was not conducive to complex assays that require different regents to be delivered sequentially. Herein, we used an electric field or airflow to trigger the fluid flow and demonstrated the flow controllability by a proof-of-concept colorimetric assay. The limits of detection of glucose and albumin were 0.8 mM and 3.5 μM, respectively, which were sufficient for clinical requirements. Given the characteristic of flow controllability, we believe that the proposed 3D-μPADs have great potential to make paper-based complex assays automated and programmable.

Melamine promotes calcium crystal formation in three-dimensional microfluidic device

Melamine, which induces proximal tubular (PT) cell damage has a greater nephrotoxic effect when combined with cyanuric and uric acids; however, it is unknown whether such effect can stimulate calcium phosphate (CaP)/calcium oxalate (CaOx) stone formation. Here, we show that melamine acts as an inducer of CaP, CaOx and CaP + CaOx (mixed) crystal formations in a time and concentration-dependent manner by stabilizing those crystals and further co-aggregating with melamine. To explore the physiological relevance of such melamine-augmented calcium crystal formation, we used 2-dimensional (2D) and 3D microfluidic (MF) device, embedded with PT cells, which also resembled the effect of melamine-stimulated CaP, CaOx and mixed crystal formation. Significantly, addition of preformed CaP and/or CaOx crystal in the presence of melamine, further potentiated those crystal formations in 3D MFs, which helped the growth and aggregation of mixed crystals. Our data show that the mechanism of such predisposition of stone formation could be largely due to co-crystallization between melamine and CaP/CaOx and pronounced effect on induction of stone-forming pathway activation in 3D MF. Taken together, melamine-induced CaP and/or CaOx crystal formation ex-vivo will help us in understanding the larger role of melamine as an environmental toxicant in producing the pathology in similar cellular microenvironments.

3D Droplet-Based Microfluidic Device Easily Assembled from Commercially Available Modules Online Coupled with ICPMS for Determination of Silver in Single Cell.

More recently, single-cell analysis based on ICPMS has made considerable headway while a challenge remains to differentiate single cell from doublets during the analysis. One burgeoning solution is to encapsulate single cell into droplets on the platform of the microfluidic chip. However, the manufacture of the droplet-based microfluidic chip requires sophisticated fabrication and limits its potential application. In this paper, we presented an off-the-shelf three-dimensional (3D) microfluidic device by assembling commercially available parts without any proficient manufacturing process. Uniform monodisperse microdroplet was generated from the 3D microfluidic device with a size variation of 1.5%, and the innner diameter of the 3D microfluidic device was the same as the nebulizer (150 μm). The proposed 3D microfluidic device-time-resolved ICPMS system was applied to detect silver in single AgNPs (51 nm), and the result is in good agreement with conventional acid digestion method, demonstrating the accuracy of the method. Silver uptake behaviors in HepG2 cells were then studied by incubating with Ag+ or AgNPs under biocompatible conditions. The results revealed that the cell-to-cell variability in terms of the diversity of cells incubated with AgNPs was wider than those cells incubated with Ag+ from the aspect of the content distribution of silver at the single-cell level.

Human Cellular Models for the Investigation of Lung Inflammation and Mucus Production in Cystic Fibrosis.

Chronic inflammation, oxidative stress, mucus plugging, airway remodeling, and respiratory infections are the hallmarks of the cystic fibrosis (CF) lung disease. The airway epithelium is central in the innate immune responses to pathogens colonizing the airways, since it is involved in mucociliary clearance, senses the presence of pathogens, elicits an inflammatory response, orchestrates adaptive immunity, and activates mesenchymal cells. In this review, we focus on cellular models of the human CF airway epithelium that have been used for studying mucus production, inflammatory response, and airway remodeling, with particular reference to two- and three-dimensional cultures that better recapitulate the native airway epithelium. Cocultures of airway epithelial cells, macrophages, dendritic cells, and fibroblasts are instrumental in disease modeling, drug discovery, and identification of novel therapeutic targets. Nevertheless, they have to be implemented in the CF field yet. Finally, novel systems hijacking on tissue engineering, including three-dimensional cocultures, decellularized lungs, microfluidic devices, and lung organoids formed in bioreactors, will lead the generation of relevant human preclinical respiratory models a step forward.