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Organoids are emerging as a powerful tool to investigate complex biological structures in vitro. Vascularization of organoids is crucial to recapitulate the morphology and function of the represented human organ, especially in the case of the kidney, whose primary function of blood filtration is closely associated with blood circulation. Current in vitro microfluidic approaches have only provided initial vascularization of kidney organoids, whereas in vivo transplantation to animal models is problematic due to ethical problems, with the exception of xenotransplantation onto a chicken chorioallantoic membrane (CAM). Although CAM can serve as a good environment for vascularization, it can only be used for a fixed length of time, limited by development of the embryo. Here, we propose a novel lab on a chip design that allows organoids of different origin to be cultured and vascularized on a CAM, as well as to be transferred to in vitro conditions when required. Mouse embryonic kidneys cultured on the CAM showed enhanced vascularization by intrinsic endothelial cells, and made connections with the chicken vasculature, as evidenced by blood flowing through them. After the chips were transferred to in vitro conditions, the vasculature inside the organoids was successfully maintained. To our knowledge, this is the first demonstration of the combination of in vivo and in vitro approaches applied to microfluidic chip design. [ABSTRACT FROM AUTHOR]

The flow behavior of blood is determined mainly by red blood cell (RBC) deformation and aggregation as well as blood viscoelasticity. These intricately interdependent parameters should be monitored by healthcare providers to understand all aspects of circulatory flow dynamics under numerous cases including cardiovascular and infectious diseases. Current medical instruments and microfluidic systems lack the ability to quantify these parameters all at once and in physiologically relevant flow conditions. This work presents a handheld platform and a measurement method for quantitative analysis of multiple of these parameters from 50 μl undiluted blood inside a miniaturized channel. The assay is based on an optical transmission analysis of collective RBC deformation and aggregation under near-infrared illumination during a 1 s damped oscillatory flow and at stasis, respectively. Measurements with blood of different hemo-rheological properties demonstrate that the presented approach holds a potential for initiating simultaneous and routine on-chip blood flow analysis even in resource-poor settings. [ABSTRACT FROM AUTHOR]

Droplet-based microfluidic systems require a precise control of droplet physical properties; hence, measuring the morphological properties of droplets is critical to obtain high sensitivity analysis. The ability to perform such measurements in real-time is another demand which has not been addressed yet. In this study, we used coplanar electrodes configured in the differential measurement mode for impedimetric measurement of size and velocity. To obtain the size of the droplets, detailed 3D finite element simulations of the system were performed. The interaction of the non-uniform electric field and the droplet was investigated. Electrode geometry optimization steps were described and design guideline rules were laid out. User-friendly software was developed for real-time observation of droplet length and velocity together with in situ statistical analysis results. A comparison between impedimetric and optical measurement tools is given. Finally, to illustrate the benefit of having real-time analysis, iDM was used to synthesize particles with a predefined monodispersity limit and to study the response times of syringe pump and pressure pump driven droplet generation devices. This analysis allows one to evaluate the 'warm-up' time for a droplet generator system, after which droplets reach the desired steady-state size required by the application of interest. [ABSTRACT FROM AUTHOR]

The erythrocyte sedimentation rate (ESR) is a frequently used 30 min or 60 min clinical test for screening of several inflammatory conditions, infections, trauma, and malignant diseases, as well as non-inflammatory conditions including prostate cancer and stroke. Erythrocyte aggregation (EA) is a physiological process where erythrocytes form face-to-face linear structures, called rouleaux, at stasis or low shear rates. In this work, we proposed a method for ESR measurement from EA. We developed a microfluidic opto-electro-mechanical system, using which we experimentally showed a significant correlation (R2 = 0.86) between ESR and EA. The microfluidic system was shown to measure ESR from EA using fingerprick blood in 2 min. 40 μl of whole blood is filled in a disposable polycarbonate cartridge which is illuminated with a near infrared emitting diode. Erythrocytes were disaggregated under the effect of a mechanical shear force using a solenoid pinch valve. Following complete disaggregation, transmitted light through the cartridge was measured using a photodetector for 1.5 min. The intensity level is at its lowest at complete disaggregation and highest at complete aggregation. We calculated ESR from the transmitted signal profile. We also developed another microfluidic cartridge specifically for monitoring the EA process in real-time during ESR measurement. The presented system is suitable for ultrafast, low-cost, and low-sample volume measurement of ESR at the point-of-care. [ABSTRACT FROM AUTHOR]

Droplet-based microfluidic systems offer tremendous benefits for high throughput biochemical assays. Despite the wide use of electrical detection for microfluidic systems, application of impedimetric sensing for droplet systems is very limited. This is mainly due to the insulating oil-based continuous phase used for most aqueous samples of interest. We present modelling and experimental verification of impedimetric detection of hemagglutination in microdroplets. We have detected agglutinated red blood cells in microdroplets and screened whole blood samples for multiple antibody sera using conventional microelectrodes. We were able to form antibody and whole blood microdroplets in PDMS microchannels without any tedious chemical surface treatment. Following the injection of a blood sample into antibody droplets, we have detected the agglutination-positive and negative droplets in an automated manner. In order to understand the characteristics of impedimetric detection inside microdroplets, we have developed the lumped electrical circuit equivalent of an impedimetric droplet content detection system. The empirical lumped element values are in accordance with similar models developed for single phase electrical impedance spectroscopy systems. The presented approach is of interest for label-free, quantitative analysis of droplets. In addition, the standard electronic equipment used for detection allows miniaturized detection circuitries that can be integrated with a fluidic system for a quantitative microdroplet-based hemagglutination assay that is conventionally performed in well plates. [ABSTRACT FROM AUTHOR]

Phenylketonuria (PKU) is characterized by an autosomal recessive mutation in the phenylalanine hydroxylase (PAH) gene. Impaired PAH enzyme activity leads to the accumulation of phenylalanine (Phe) and its metabolites in the bloodstream, which disrupts the central nervous system and causes psychomotor retardation. Early diagnosis of PKU is essential for timely intervention. Moreover, continuous monitoring of blood Phe levels is indispensable for prognosis, requiring a robust and reliable monitoring system. This study presents an automated lab-on-a-CD-based system for early diagnosis and monitoring of PKU treatment. This miniaturised system contains CD-shaped disposable cartridges, a mini centrifuge, and an electrochemical sensing unit. Modified screen-printed gold electrodes were used for the electrochemical measurements in cartridges. Electrode modification was conducted by electrochemical graphene oxide reduction and deposition on the electrode surface, which increased the sensitivity of the measurement 1.5 fold. The system used amperometric detection to measure Phe in the blood through oxidation of NAD + to NADH by the enzyme phenylalanine dehydrogenase. The limit of detection (LOD), limit of quantification (LOQ), and sensitivity of the system were 0.0524, 0.1587 mg dL -1 and 0.3338 μA mg -1 dL, respectively, within the 0-20 mg dL -1 measurement range ( R 2 = 0.9955). The performance of the lab-on-a-CD system was compared to the gold standard HPLC method. The accuracy was 83.1% for HPLC and 84.1% for the lab-on-a-CD system. In conclusion, this study successfully developed a portable diagnostic device for rapid (under 20 min), accurate and highly sensitive detection of Phe in whole blood.

When droplets enter a junction they sort to the channel with the highest flow rate at that instant. Transport is regulated by a discrete time-delayed feedback that results in a highly periodic behavior where specific patterns can continue to cycle indefinitely. Between these highly ordered regimes are chaotic structures where no pattern is evident. Here we develop a model that describes droplet sorting under various asymmetries: branch geometry (length, cross-section), droplet resistance and pressures. First, a model is developed based on the continuum assumption and then, with the assistance of numerical simulations, a discrete model is derived to predict the length and composition of the sorting pattern. Furthermore we derive all unique sequences that are possible for a given distribution and develop a preliminary estimation of why chaotic regimes form. The model is validated by comparing it to numerical simulations and results from microfluidic experiments in PDMS chips with good agreement.

This study presents a microfluidic system that incorporates electroosmotic pumps, a concentration gradient generator and a fish cell line (rainbow trout gill) to perform toxicity testing on fish cells seeded in the system. The system consists of three mechanical components: (1) a toxicity testing chip containing a microfluidic gradient generator which creates a linear concentration distribution of toxicant in a cell test chamber, (2) an electroosmotic (EO) pump chip that controls the flow rate and operation of the toxicity chip, and (3) indirect reservoirs that connect the two chips allowing for the toxicant solution to be pumped separately from the electroosmotic pump solution. The flow rate and stability of the EO pumps was measured and tested by monitoring the gradient generator using fluorescence microscopy. Furthermore, a lethality test was performed with this system setup using a rainbow trout gill cell line (RTgill-W1) as the test cells and sodium dodecyl sulfate as a model toxicant. A gradient of sodium dodecyl sulfate, from 0 to 50 microg mL(-1), was applied for 1 hr to the attached cells, and the results were quantified using a Live/Dead cell assay. This work is a preliminary study on the application of EO pumps in a living cell assay, with the potential to use the pumps in portable water quality testing devices with RTgill-W1 cells as the biosensors.