Ultra-small lipid nanoparticles encapsulating sorafenib and midkine-siRNA selectively-eradicate sorafenib-resistant hepatocellular carcinoma in vivo

Hepatocellular carcinoma (HCC) is a fatal disease with limited therapeutic choices. The stroma-rich tumor microenvironment hinders the in vivo delivery of most nanomedicines. Ultra-small lipid nanoparticles (usLNPs) were designed for the selective co-delivery of the cytotoxic drug, sorafenib (SOR), and siRNA against the Midkine gene (MK-siRNA) to HCC in mice. The usLNPs composed of a novel pH-sensitive lipid, a diversity of phospholipids and a highly-selective targeting peptide. A microfluidic device, iLiNP, was used and a variety of factors were controlled to tune particle size aiming at maximizing tumor penetration efficiency. Optimizing the composition and physico-chemical properties of the usLNPs resulted in an enhanced tumor accumulation, selectivity and in vivo gene silencing. The optimized usLNPs exerted potent gene silencing in the tumor (median effective dose, ED₅₀~0.1 mg/Kg) with limited effect on the healthy liver. The novel combination synergistically-eradicated HCC in mice (~85%) at a surprisingly-low dose of SOR (2.5 mg/Kg) which could not be achieved via individual monotherapy. Toxicity studies revealed the biosafety of the usLNPs upon either acute or chronic treatment. Furthermore, the SOR-resistant HCC established in mice was eradicated by 70% using this approach. We conclude that our strategy is promising for potential clinical applications in HCC treatment.

Developing an integrated microfluidic and miniaturized electrochemical biosensor for point of care determination of glucose in human plasma samples

A cost-effective, point of care (POC) device based on highly oriented CNT arrays was developed as an electrochemical assay for real-time and sensitive detection of glucose in complex samples. A low-cost, microcontroller-based potentiostat consisting of Arduino Due and LMP9100-EVM was developed to perform electrochemical measurements such as cyclic voltammetry (CV) and amperometry. A syringe pump based on open-source electronics was designed to direct the flow through a microfluidic chip. Vertically aligned carbon nanotube (VACNT) sensor arrays, in combination with the miniature potentiostat and the syringe pumps, were utilized as a POC device for the rapid and accurate detection of glucose. The structure and morphology of samples were characterized by field emission scanning electron microscopy (FESEM) and attenuated total reflectance Fourier transform infrared spectrometry (ATR-FTIR). CV as well as electrochemical impedance spectroscopy (EIS) was performed to investigate the electrochemical behavior of the electrode with respect to different diffusion regimes. The mediator-less biosensor had a limit of detection of 23 μM and sensitivity of 1462 μA mM^-1 cm^-2 and 1050 μA mM^-1 cm^-2 at the linear range of 1.2-7.8 mM and 7.8-11.2 mM, respectively. The presence of other biological compounds such as uric acid (UA) and ascorbic acid (AA) did not interfere with the detection of glucose. Finally, the designed POC device was successfully applied for the determination of glucose in human blood plasma samples.

Mesenchymal glioblastoma-induced mature de-novo vessel formation of vascular endothelial cells in a microfluidic device

High vascularization is a biological characteristic of glioblastoma (GBM); however, an in-vitro experimental model to verify the mechanism and physiological role of vasculogenesis in GBM is not well-established. Recently, we established a self-organizing vasculogenic model using human umbilical vein endothelial cells (HUVECs) co-cultivated with human lung fibroblasts (hLFs). Here, we exploited this system to establish a realistic model of vasculogenesis in GBM. We developed two polydimethylsiloxane (PDMS) devices, a doughnut-hole dish and a 5-lane microfluidic device to observe the contact-independent effects of glioblastoma cells on HUVECs. We tested five patient-derived and five widely used GBM cell lines. Confocal fluorescence microscopy was used to observe the morphological changes in Red Fluorescent Protein (RFP)-HUVECs and fluorescein isothiocyanate (FITC)-dextran perfusion. The genetic and expression properties of GBM cell lines were analyzed. The doughnut-hole dish assay revealed KNS1451 as the only cells to induce HUVEC transformation to vessel-like structures, similar to hLFs. The 5-lane device assay demonstrated that KNS1451 promoted the formation of a vascular network that was fully perfused, revealing the functioning luminal construction. Microarray analysis revealed that KNS1451 is a mesenchymal subtype of GBM. Using a patient-derived mesenchymal GBM cell line, mature de-novo vessel formation could be induced in HUVECs by contact-independent co-culture with GBM in a microfluidic device. These results support the development of a novel in vitro research model and provide novel insights in the neovasculogenic mechanism of GBM and may potentially facilitate the future detection of unknown molecular targets.

An integrated microfluidics for assessing the anti-aging effect of caffeic acid phenethylester in Caenorhabditis elegans

Aging is a fundamental and fascinating process. Anti-aging research tried to find the mysteries about the human lifespan. To investigate the longevity-extending role of caffeic acid phenethylester (CAPE) and reveal the possible regulation mechanism, the long-term cultivation under well-defined environments, real-time monitoring, and live imaging is highly desired. In this paper, a well-designed microfluidic device was proposed to analyze the anti-aging effect of CAPE in Caenorhabditis elegans. With the combined use of multiple functional units, including micro-pillar, worm responder, a branching network of distribution channels, and microchambers, the longitudinal measurements of the exact number of worms throughout the whole lifespans is possible. Meanwhile, the brief cooling function of temperature-controllable system can achieve temporary and repeated immobilization of nematodes for fluorescence imaging. Our research data showed that CAPE can increase the survival of worms under normal and stress condition, including heat stress and paraquat-induced oxidative stress. The further studies revealed the anti-aging mechanism of CAPE. This proposed strategy and device would be a useful platform to facilitate future anti-aging studies and the finding of new lead compounds.

Lipid nanoparticles loaded with ribonucleoprotein-oligonucleotide complexes synthesized using a microfluidic device exhibit robust genome editing and hepatitis B virus inhibition

The clustered regularly interspaced short palindromic repeats (CRISPR)-associated (Cas) system has considerable therapeutic potential for use in treating a wide range of intractable genetic and infectious diseases including hepatitis B virus (HBV) infections. While non-viral delivery technologies for the CRISPR/Cas system are expected to have clinical applications, difficulties associated with the clinically relevant synthesis of formulations and the poor efficiency of delivery severely hinder therapeutic genome editing. We report herein on the production of a lipid nanoparticle (LNP)-based CRISPR/Cas ribonucleoprotein (RNP) delivery nanoplatform synthesized using a clinically relevant mixer-equipped microfluidic device. DNA cleavage activity and the aggregation of Cas enzymes was completely avoided under the optimized synthetic conditions. The optimized formulation, which was identified through 2 steps of design of experiments, exhibited excellent gene disruption (up to 97%) and base substitution (up to 23%) without any apparent cytotoxicity. The addition of negative charges to the RNPs by complexing single-stranded oligonucleotide (ssON) significantly enhanced the delivery of both Cas9 and Cpf1 RNPs. The optimized formulation significantly suppressed both HBV DNA and covalently closed circular DNA (cccDNA) in HBV-infected human liver cells compared to adeno-associated virus type 2 (AAV2). These findings represent a significant contribution to the development of CRISPR/Cas RNP delivery technology and its practical applications in genome editing therapy.

Dawn of lipid nanoparticles in lymph node targeting: Potential in cancer immunotherapy

It is generally known that the lymph nodes (LNs) are important tissues in cancer immunotherapy. Therefore, delivering immune functional compounds to LNs is a useful strategy for enhancing cancer immunotherapy. Lipid-based nanocarriers have been widely used as delivery systems that target LNs, but lipid nanoparticle (LNP) technology has recently attracted increased interest. High levels of nucleic acids can be efficiently loaded in LNPs, they can be used to actively deliver nucleic acids into the cytoplasm, and they can be produced on an industrial scale. The use of microfluidic devices has been particularly valuable for producing small-sized LNPs, thus paving the way for successful LN targeting. In the review, we focus on the potential of LNP technology for targeting LNs.

A simplified PDMS microfluidic device with a built-in suction actuator for rapid production of monodisperse water-in-oil droplets

We previously established an automatic droplet-creation technique that only required air evacuation of a PDMS microfluidic device prior to use. Although the rate of droplet production with this technique was originally slow (∼10 droplets per second), this was greatly improved (∼470 droplets per second) in our recent study by remodeling the original device configuration. This improvement was realized by the addition of a degassed PDMS layer with a large surface area-to-volume ratio that served as a powerful vacuum generator. However, the incorporation of the additional PDMS layer (which was separate from the microfluidic PDMS layer itself) into the device required reversible bonding of five different layers. In the current study, we aimed to simplify the device architecture by reducing the number of constituent layers for enhancing usability of this microfluidic droplet generator while retaining its rapid production rate. The new device consisted of three layers. This comprised a degassed PDMS slab with microfluidic channels on one surface and tens of thousands of vacuum-generating micropillars on the other surface, which was simply sandwiched by PMMA layers. Despite its simplified configuration, this new device created monodisperse droplets at an even faster rate (>1000 droplets per second).

New method for arbuscular mycorrhizal fungus spore separation using a microfluidic device based on manual temporary flow diversion

Arbuscular mycorrhizal fungi are beneficial components often included in biofertilizers. Studies of the biology and utilization of these fungi are key to their successful use in the biofertilizer industry. The acquisition of isolated spores is a required step in these studies; however, spore quality control and spore separation are bottlenecks. Filtered and centrifuged spores have to be hand-picked under a microscope. The conventional procedure is skill-demanding, labor-intensive, and time-consuming. Here, we developed a microfluidic device to aid manual separation of spores from a filtered and centrifuged suspension. The device is a single spore streamer equipped with a manual temporary flow diversion (MTFD) mechanism to select single spores. Users can press a switch to generate MTFD when the spore arrives at the selection site. The targeted spore flows in a stream to the collection chamber via temporary cross flow. Using the device, spore purity, the percentage of spore numbers against the total number of particles counted in the collecting chamber reached 96.62% (median, n = 10) which is greater than the spore purity obtained from the conventional method (88.89% (median, n = 10)).

Cancer cell detection device for the diagnosis of bladder cancer from urine

Bladder cancer is common and has one of the highest recurrence rates. Cystoscopy, the current gold standard diagnosis approach, has recently benefited from the introduction of blue light assisted photodynamic diagnostic (PDD). While blue light cystoscopy improves diagnostic sensitivity, it remains a costly and invasive approach. Here, we present a microfluidic-based platform for non-invasive diagnosis which combines the principle of PDD with whole cell immunocapture technology to detect bladder cancer cells shed in patient urine ex vivo. Initially, we demonstrate with model cell lines that our non-invasive approach achieves highly specific capture rates of bladder cancer cells based on their Epithelial Cell Adhesion Molecule expression (>90%) and detection by the intensity levels of Hexaminolevulinic Acid-induced Protoporphyrin IX fluorescence. Then, we show in a pilot study that the biosensor platform successfully discriminates histopathologically diagnosed cancer patients (n = 10) from non-cancer controls (n = 25). Our platform can support the development of a novel non-invasive diagnostic device for post treatment surveillance in patients with bladder cancer and cancer detection in patients with suspected bladder cancer.

Adhesive tape-assisted etching of silk fibroin film with LiBr aqueous solution for microfluidic devices

The regenerated silk fibroin (RSF)-based microfluidic device has attracted tremendous interests in recent years due to its excellent biocompatibility, mild processing conditions, and all aqueous casting production. However, the need of a micro-fabricated mold in the manufacture process greatly hinder its practical applications. Herein, we introduce an adhesive tape-assisted etching method with LiBr solution as the etchant to prepare RSF microfluidic devices. An engraved adhesive tape is used as the mask to cover on the surface of a RSF film. Then, LiBr solution is dropped on the mask to etch RSF in concentration- and duration-dependent manners. During this process, the LiBr-treated RSF transits from insoluble β-sheet crystallites to soluble conformations. The as-prepared RSF microfluidic devices possess good chemical resistance and excellent tolerance to mechanical deformation. RSF microfluidic systems with different patterns were fabricated to demonstrate the universality of the approach. A concentration gradient generator and a blood vessel-like channel were manufactured for the preparation of solutions with gradient pHs and the growth of living cells, respectively. The proposed strategy has great potentials in the facile fabrication of low-cost RSF microfluidic devices for tissue engineering and biomedical analysis.

A paper-based device for the colorimetric determination of ammonia and carbon dioxide using thiomalic acid and maltol functionalized silver nanoparticles: application to the enzymatic determination of urea in saliva and blood

A colorimetric assay was developed which has the capability of determining urea in biological samples. It is an origami paper-based sensor consisting of silver nanoparticles that were synthesized by using two different capping agents: thiomalic acid and maltol. The function of the assay relied on hydrolysis of urea to ammonia and carbon dioxide in the presence of urease. The products interacted with nanoparticles which caused aggregation. Interestingly, thiomalic acid capped with silver nanoparticles were selective to ammonia, and the other nanoparticles synthesized by maltol responded to carbon dioxide. These interactions turned the color of nanoparticles from yellow to brown and red, respectively. The resulting colorations were captured by a floatable scanner. A routine image analysis software was utilized to provide the response of the assays. The method was applied to individually determine ammonia, carbon dioxide, and urea. The linear range was 0.06 mg.dL^-1-170.0 mg.dL^-1 for ammonia, 0.08 mg.dL^-1-220.0 mg.dL^-1 for carbon dioxide, and 0.5 mg.dL^-1-200.0 mg.dL^-1 for urea. The respective limits of detection were 0.03 mg.dL^-1, 0.06 mg.dL^-1, and 0.18 mg.dL^-1. No interferences were found in the detremination of urea. The method demonstrates a reliable performance for determination of urea in both saliva and blood samples. Graphical Abstract Schematic representation of paper based colorimetric sensor based on silver nanoparticles for both qualitative and quantitative analyses of urea in biological samples.

Application of microfluidic devices for glioblastoma study: current status and future directions

Glioblastoma (GBM) is one of the most malignant primary brain tumors. This neoplasm is the hardest to treat and has a bad prognosis. Because of the characteristics of genetic heterogeneity and frequent recurrence, a successful cure for the disease is unlikely. Increasing evidence has revealed that the GBM stem cell-like cells (GSCs) and microenvironment are key elements in GBM recurrence and treatment failure. To better understand the mechanisms underlying this disease and to develop more effective therapeutic strategies for treatment, suitable approaches, techniques, and model systems closely mimicking real GBM conditions are required. Microfluidic devices, a model system mimicking the in vivo brain microenvironment, provide a very useful tool to analyze GBM cell behavior, their correlation with tumor malignancy, and the efficacy of multiple drug treatment. This paper reviews the applications of microfluidic devices in GBM research and summarizes progress and perspectives in this field.

Co-culture of Murine Neurons Using a Microfluidic Device for The Study of Tau Misfolding Propagation

The deposition of misfolded, aggregated tau protein is a hallmark of several neurodegenerative diseases, collectively termed "tauopathies". Tau pathology spreads throughout the brain along connected pathways in a prion-like manner. The process of tau pathology propagation across circuits is a focus of intense research and has been investigated in vivo in human post-mortem brain and in mouse models of the diseases, in vitro in diverse cellular systems including primary neurons, and in cell free assays using purified recombinant tau protein. Here we describe a protocol that takes advantage of a minimalistic neuronal circuit arrayed within a microfluidic device to follow the propagation of tau misfolding from a presynaptic to a postsynaptic neuron. This assay allows high-resolution imaging as well as individual manipulation of the releasing and receiving neuron, and is therefore beneficial for investigating the propagation of tau and other misfolded proteins in vitro.

A single-view field filter device for rare tumor cell filtration and enumeration

In this work, we demonstrate a single-view field filter (SVFF) device for the efficient filtration and enumeration of rare tumor cells in the blood. In our device, the track-etched membrane is integrated within a low-cost polymer-film microfluidic chip, and multiplex microfiltration chambers are designed. Our device permits the performing of multiple sample tests on a single membrane and the dynamical observation of the entire filtration process in a single field of view. To characterize the device performance, our device is first tested using tumor cells, and three different cell behaviors are observed during the filtration process. Finally, we successfully apply our device for the separation of rare tumor cells from the lysed blood samples at various flow rates. The recovery rates of 93.3, 87.6, and 84.1% can be respectively achieved at the throughputs of 50, 100, and 150 μL/min. Our single-view field filter (SVFF) device offers the advantages of label-free filtration, efficient enumeration, easy integration, and low cost, and holds the potential to be used as an efficient tool for the filtration and enumeration of rare cells.

The influence of electrolyte concentration on nanofractures fabricated in a 3D-printed microfluidic device by controlled dielectric breakdown

A three-dimensional-printed microfluidic device made of a thermoplastic material was used to study the creation of molecular filters by controlled dielectric breakdown. The device was made from acrylonitrile butadiene styrene by a fused deposition modeling three-dimensional printer and consisted of two V-shaped sample compartments separated by 750 µm of extruded plastic gap. Nanofractures were formed in the thin piece of acrylonitrile butadiene styrene by controlled dielectric breakdown by application voltage of 15-20 kV with the voltage terminated when reaching a defined current threshold. Variation of the size of the nanofractures was achieved by both variation of the current threshold and by variation of the ionic strength of the electrolyte used for breakdown. Electrophoretic transport of two proteins, R-phycoerythrin (RPE; <10 nm in size) and fluorescamine-labeled BSA (f-BSA; 2-4 nm), was used to monitor the size and transport properties of the nanofractures. Using 1 mM phosphate buffer, both RPE and f-BSA passed through the nanofractures when the current threshold was set to 25 µA. However, when the threshold was lowered to 10 µA or lower, RPE was restricted from moving through the nanofractures. When we increased the electrolyte concentration during breakdown from 1 to 10 mM phosphate buffer, BSA passed but RPE was blocked when the threshold was equal to, or lower than, 25 µA. This demonstrates that nanofracture size (pore area) is directly related to the breakdown current threshold but inversely related to the concentration of the electrolyte used for the breakdown process.

Legionella pneumophila sg1-sensing signal enhancement using a novel electrochemical immunosensor in dynamic detection mode

This work presents a comparison between static and dynamic modes of biosensing using a novel microfluidic assay for continuous and quantitative detection of Legionella pneumophila sg1 in artificial water samples. A self-assembled monolayer of 16-amino-1-hexadecanethiol (16-AHT) was covalently linked to a gold substrate, and the resulting modified surface was used to immobilize an anti-Legionella pneumophila monoclonal antibody (mAb). The modified surfaces formed during the biosensor functionalization steps were characterized using electrochemical measurements and microscopic imaging techniques. Under static conditions, the biosensor exhibited a wide linear response range from 10 to 10⁸ CFU/mL and a detection limit of 10 CFU/mL. Using a microfluidic system, the biosensor responses exhibited a linear relationship for low bacterial concentrations ranging from 10 to 10³ CFU/mL under dynamic conditions and an enhancement of sensing signals by a factor of 4.5 compared to the sensing signals obtained under static conditions with the same biosensor for the detection of Legionella cells in artificially contaminated samples.

ZnO Nanowire-Anchored Microfluidic Device With Herringbone Structure Fabricated by Maskless Photolithography

The integration of nanomaterials in microfluidic devices has emerged as a new research paradigm. Microfluidic devices composed of ZnO nanowires have been developed for the collection of urine extracellular vesicles (EVs) at high efficiency and in situ extraction of various microRNAs (miRNAs). The devices can be used for diagnosing various diseases, including kidney diseases and cancers. A major research need for developing micro total analysis systems is to enhance extraction efficiency. This article presents a novel fabrication method for a herringbone-patterned microfluidic device anchored with ZnO nanowire arrays. The substrates with herringbone patterns were created by maskless photolithography. The ZnO nanowire arrays were grown on the substrates by chemical bathing. The patterned design was to introduce turbulent flows as opposed to laminar flow in traditional devices to increase the mixing and contact of the urine sample with ZnO nanowires. The device showed reduced flow rates compared with conventional planar microfluidic channels and successfully extracted urine EV-encapsulated miRNAs.

Separating mouse malignant cell line (EL4) from neonate spermatogonial stem cells utilizing microfluidic device in vitro

BACKGROUND

Some children who have survived cancer will be azoospermic in the future. Performing isolation and purification procedures for spermatogonial stem cells (SSC) is very critical. In this regard, performing the process of decontamination of cancerous cells is the initial step. The major objective of the present study is to separate the malignant EL4 cell line in mice and spermatogonial stem cells in vitro.

METHODS

The spermatogonial stem cells of sixty neonatal mice were isolated, and the procedure of co-culturing was carried out by EL4 which were classified into 2 major groups: (1) the control group (co-culture in a growth medium) and (2) the group of co-cultured cells which were separated using the microfluidic device. The percentage of cells was assessed using flow cytometry technique and common laboratory technique of immunocytochemistry and finally was confirmed through the laboratory technique of reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

The actual percentage of EL4 and SSC after isolation was collected at two outlets: the outputs for the smaller outlet were 0.12% for SSC and 42.14% for EL4, while in the larger outlet, the outputs were 80.38% for SSC and 0.32% for EL4; in the control group, the percentages of cells were 21.44% for SSC and 23.28% for EL4 (based on t test (p ≤ 0.05)).

CONCLUSIONS

The present study demonstrates that the use of the microfluidic device is effective in separating cancer cells from spermatogonial stem cells.

Experimental Investigation of Air Compliance Effect on Measurement of Mechanical Properties of Blood Sample Flowing in Microfluidic Channels

Air compliance has been used effectively to stabilize fluidic instability resulting from a syringe pump. It has also been employed to measure blood viscosity under constant shearing flows. However, due to a longer time delay, it is difficult to quantify the aggregation of red blood cells (RBCs) or blood viscoelasticity. To quantify the mechanical properties of blood samples (blood viscosity, RBC aggregation, and viscoelasticity) effectively, it is necessary to quantify contributions of air compliance to dynamic blood flows in microfluidic channels. In this study, the effect of air compliance on measurement of blood mechanical properties was experimentally quantified with respect to the air cavity in two driving syringes. Under periodic on–off blood flows, three mechanical properties of blood samples were sequentially obtained by quantifying microscopic image intensity (<I>) and interface (α) in a co-flowing channel. Based on a differential equation derived with a fluid circuit model, the time constant was obtained by analyzing the temporal variations of β = 1/(1–α). According to experimental results, the time constant significantly decreased by securing the air cavity in a reference fluid syringe (~0.1 mL). However, the time constant increased substantially by securing the air cavity in a blood sample syringe (~0.1 mL). Given that the air cavity in the blood sample syringe significantly contributed to delaying transient behaviors of blood flows, it hindered the quantification of RBC aggregation and blood viscoelasticity. In addition, it was impossible to obtain the viscosity and time constant when the blood flow rate was not available. Thus, to measure the three aforementioned mechanical properties of blood samples effectively, the air cavity in the blood sample syringe must be minimized (V_{air, R} = 0). Concerning the air cavity in the reference fluid syringe, it must be sufficiently secured about V_{air, R} = 0.1 mL for regulating fluidic instability because it does not affect dynamic blood flows.

Deterministic paracrine repair of injured myocardium using microfluidic-based cocooning of heart explant-derived cells

While encapsulation of cells within protective nanoporous gel cocoons increases cell retention and pro-survival integrin signaling, the influence of cocoon size and intra-capsular cell-cell interactions on therapeutic repair are unknown. Here, we employ a microfluidic platform to dissect the impact of cocoon size and intracapsular cell number on the regenerative potential of transplanted heart explant-derived cells. Deterministic increases in cocoon size boosted the proportion of multicellular aggregates within cocoons, reduced vascular clearance of transplanted cells and enhanced stimulation of endogenous repair. The latter being attributable to cell-cell stimulation of cytokine and extracellular vesicle production while also broadening of the miRNA cargo within extracellular vesicles. Thus, by tuning cocoon size and cell occupancy, the paracrine signature and retention of transplanted cells can be enhanced to promote paracrine stimulation of endogenous tissue repair.

A Microfluidic E-Tongue System Using Layer-by-Layer Films Deposited onto Interdigitated Electrodes Inside a Polydimethylsiloxane Microchannel

An electronic tongue (e-tongue) is a multisensory system employed in the analysis of liquid samples, transforming the raw data into specific recognition patterns through computational and statistical analysis. Distinct types of e-tongues have been reported in the literature, with a plethora of applications in several areas of research. Recently, e-tongues have been integrated into microfluidic devices, which offer advantages such as the use of continuous flow for faster and more accurate analysis, and reduction in size of the devices and volumes for sampling and discharge, which in turn reduces waste and cost. Here we describe the procedures and methodologies recently used in our research group in the development of a microfluidic e-tongue sensing system.

Engineering magnetic nanoparticles and their integration with microfluidics for cell isolation

Isolation of cancer cells, bacteria, and viruses from peripheral blood has important applications in cancer diagnosis, therapy monitoring, and drug development. Magnetic particles functionalized with antibodies that target receptors of cancer cells have been shown to isolate such entities using magnetic field gradients. Here, we report enhancement in capture efficiency and specificity by engineering magnetic nanoparticles and integrating them with microfluidics for the enumeration of tumor cells. Nanoparticles were made from iron oxide, coated with poly(ethylene glycol), and conjugated through avidin-biotin chemistry with antibody specifically against epithelial cell adhesion molecule (EpCAM). On exposure of targeted nanoparticles to tumor cells, specific uptake by EpCAM-expressing tumor cells (e.g., BxPC3, a pancreatic cancer cell) was observed, whereas there was negligible uptake by cells with low EpCAM expression (e.g., CCRF-CEM, a leukemia cell). Using an arrangement of magnets called a Halbach array, capture efficiency and specificity towards BxPC3 cells tagged with magnetic nanoparticles were enhanced, compared to conditions without the magnetic field gradient and/or without magnetic nanoparticles, either in buffer or in whole blood. These results illustrate that engineered magnetic nanoparticles and their integration with microfluidics have great potential for tumor cell enumeration and cancer prognosis.

Applications of machine learning for simulations of red blood cells in microfluidic devices

Background

For optimization of microfluidic devices for the analysis of blood samples, it is useful to simulate blood cells as elastic objects in flow of blood plasma. In such numerical models, we primarily need to take into consideration the movement and behavior of the dominant component of the blood, the red blood cells. This can be done quite precisely in small channels and within a short timeframe. However, larger volumes or timescales require different approaches. Instead of simplifying the simulation, we use a neural network to predict the movement of the red blood cells.

Results

The neural network uses data from the numerical simulation for learning, however, the simulation needs only be run once. Alternatively, the data could come from video processing of a recording of a biological experiment. Afterwards, the network is able to predict the movement of the red blood cells because it is a system of bases that gives an approximate cell velocity at each point of the simulation channel as a linear combination of bases.In a simple box geometry, the neural network gives results comparable to predictions using fluid streamlines, however in a channel with obstacles forming slits, the neural network is about five times more accurate.The network can also be used as a discriminator between different situations. We observe about two-fold increase in mean relative error when a network trained on one geometry is used to predict trajectories in a modified geometry. Even larger increase was observed when it was used to predict trajectories of cells with different elastic properties.

Conclusions

While for uncomplicated box channels there is no advantage in using a system of bases instead of a simple prediction using fluid streamlines, in a more complicated geometry, the neural network is significantly more accurate. Another application of this system of bases is using it as a comparison tool for different modeled situations. This has a significant future potential when applied to processing data from videos of microfluidic flows.

A new microfluidic device for separating circulating tumor cells based on their physical properties by using electrophoresis and dielectrophoresis forces within an electrical field

BACKGROUND AND OBJECTIVE

The presence of circulating tumor cells in the patient's blood is a clinical factor that indicates the initiation of metastasis.

METHODS

In this paper, a microfluidic device is designed to separate, enumerate, and to diagnose cancer cells from the patient's blood sample. Here, we present a new microfluidic device that is capable of separating circulating tumor cells based on their physical properties by using electrophoresis and dielectrophoresis forces within an electrical field. Cells are modeled as spherical particles, each size as a representor of different cells.

RESULTS

The distance between cells has been increased, and by using a novel method of rolling up the convergent and divergent channels, the primary distance of elements, which was 50 µm, reached 142-178.5. Cells with different diameters sense a different force, and therefore, cancer cells can be separating from other cells in the blood, such as white blood cells. To make the current device, practical for clinical studies, a cell enumerator is designed for downstream of cell separator. In the cell enumerator, a change in impedance occurs when a cell passes through the sensor.

CONCLUSIONS

By measuring the electrical current between two electrodes of the cell enumerator sensor, the exact count of cells can be obtained.

A 3D printed microfluidic flow-cell for microscopy analysis of in situ-grown biofilms

Biofilm phenomena ranging from metabolic processes to attachment, detachment and quorum sensing are influenced by the fluid flow across the biofilm. A number of commercially available flow-cells allow for microscopy analysis of laboratory biofilms under flow, but there is a lack of shear controlled microfluidic devices that accommodate biofilms grown in situ on carriers or tissue samples. Therefore, we developed a flow-cell with adjustable geometry for microscopy analysis of in situ-grown biofilm samples under shear-controlled flow. The flow-cells were designed as one-piece disposable models, 3D-printed in resin and sealed with a coverslip after insertion of the biofilm sample. As a proof of concept, we studied the impact of stimulated saliva flow on pH developments in in situ-grown dental biofilms exposed to sucrose. Under static conditions, pH dropped in the biofilms, with pronounced differences between individual biofilms, but also between different microscopic fields of view within one biofilm. pH in the top layer of the biofilms tended to be lower than pH in the bottom layer. Under conditions of stimulated saliva flow (5 mm/min), pH rose to neutral or slightly alkaline values in all biofilms, and the vertical gradients were reversed, with the biofilm bottom becoming more acidic than the top. Hence, the present work demonstrates the importance of flow for the study of pH in dental biofilms.