The blood-brain barrier (BBB) is a unique feature of the human body, preserving brain homeostasis and preventing toxic substances to enter the brain. However, in various neurodegenerative diseases, the function of the BBB is disturbed. Mechanisms of the breakdown of the BBB are incompletely understood and therefore a realistic model of the BBB is essential. We present here the smallest model of the BBB yet, using a microfluidic chip, and the immortalized human brain endothelial cell line hCMEC/D3. Barrier function is modulated both mechanically, by exposure to fluid shear stress, and biochemically, by stimulation with tumor necrosis factor alpha (TNF-α), in one single device. The device has integrated electrodes to analyze barrier tightness by measuring the transendothelial electrical resistance (TEER). We demonstrate that hCMEC/D3 cells could be cultured in the microfluidic device up to 7 days, and that these cultures showed comparable TEER values with the well-established Transwell assay, with an average (± SEM) of 36.9 Ω.cm(2) (± 0.9 Ω.cm(2)) and 28.2 Ω.cm(2) (± 1.3 Ω.cm(2)) respectively. Moreover, hCMEC/D3 cells on chip expressed the tight junction protein Zonula Occludens-1 (ZO-1) at day 4. Furthermore, shear stress positively influenced barrier tightness and increased TEER values with a factor 3, up to 120 Ω.cm(2). Subsequent addition of TNF-α decreased the TEER with a factor of 10, down to 12 Ω.cm(2). This realistic microfluidic platform of the BBB is very well suited to study barrier function in detail and evaluate drug passage to finally gain more insight into the treatment of neurodegenerative diseases.

In this article high-yield (77%) and high-speed (2700 cells s(-1)) single cell droplet encapsulation is described using a Dean-coupled inertial ordering of cells in a simple curved continuous microchannel. By introducing the Dean force, the particles will order to one equilibrium position after travelling less than 1 cm. We use a planar curved microchannel structure in PDMS to spatially order two types of myeloid leukemic cells (HL60 and K562 cells), enabling deterministic single cell encapsulation in picolitre drops. An efficiency of up to 77% was reached, overcoming the limitations imposed by Poisson statistics for random cell loading, which yields only 37% of drops containing a single cell. Furthermore, we confirm that > 90% of the cells remain viable. The simple planar structure and high throughput provided by this passive microfluidic approach makes it attractive for implementation in lab on a chip (LOC) devices for single cell applications using droplet-based platforms.

In this article, we present a microfluidic device capable of successive high-yield single-cell encapsulation in droplets, with additional droplet pairing, fusion, and shrinkage. Deterministic single-cell encapsulation is realized using Dean-coupled inertial ordering of cells in a Yin-Yang-shaped curved microchannel using a double T-junction, with a frequency over 2000 Hz, followed by controlled droplet pairing with a 100% success rate. Subsequently, droplet fusion is realized using electrical actuation resulting in electro-coalescence of two droplets, each containing a single HL60 cell, with 95% efficiency. Finally, volume reduction of the fused droplet up to 75% is achieved by a triple pitchfork structure. This droplet volume reduction is necessary to obtain close cell-cell membrane contact necessary for final cell electrofusion, leading to hybridoma formation, which is the ultimate aim of this research.

This paper presents the design, fabrication and first results of a microfluidic cell trap device for analysis of apoptosis. The microfluidic silicon-glass chip enables the immobilization of cells and real-time monitoring of the apoptotic process. Induction of apoptosis, either electric field mediated or chemically induced with tumour necrosis factor (TNF-alpha), in combination with cycloheximide (CHX), was addressed. Exposure of cells to the appropriate fluorescent dyes, FLICA and PI, allows one to discriminate between viable, apoptotic and necrotic cells. The results showed that the onset of apoptosis and the transitions during the course of the cell death cascade were followed in chemically induced apoptotic HL60 cells. For the case of electric field mediated cell death, the distinction between apoptotic and necrotic stage was not clear. This paper presents the first results to analyse programmed cell death dynamics using this apoptosis chip and a first step towards an integrated apoptosis chip for high-throughput drug screening on a single cellular level.

Today, droplet based microfluidics has become a standard platform for high-throughput single cell experimentation and analysis. However, until now no label-free, integrated single cell detection and discrimination method in droplets is available. We present here a microfluidic chip for fast (>100 Hz) and label-free electrical impedance based detection of cells in droplets. The microfluidic glass-PDMS device consists of two main components, the droplet generator and the impedance sensor. The planar electrode pair in the main channel allows the detection of only cells and cell containing droplets passing the electrodes using electrical impedance measurements. At a measurement frequency of 100 kHz non-viable cells, in low-conducting (LC) buffer, show an increase in impedance, due to the resistive effect of the membrane. The opposite effect, an impedance decrease, was observed when a viable cell passed the electrode pair, caused by the presence of the conducting cytoplasm. Moreover, we found that the presence of a viable cell in a droplet also decreased the measured electrical impedance. This impedance change was not visible when a droplet containing a non-viable cell or an empty droplet passed the electrode pair. A non-viable cell in a droplet and an empty droplet were equally classified. Hence, droplets containing (viable) cells can be discriminated from empty droplets. In conclusion, these results provide us with a valuable method to label-free detect and select viable cells in droplets. Furthermore, the proposed method provides the first step towards additional information regarding the encapsulated cells (e.g., size, number, morphology). Moreover, this all-electric approach allows for all-integrated Lab on a Chip (LOC) devices for cell applications using droplet-based platforms.

Cryptococcal infections are often characterized by a paucity of leukocytes in the infected tissues. Previous research has shown that the capsular polysaccharide glucuronoxylomannan (GXM) inhibits leukocyte migration. In this study we investigated whether the capsular polysaccharide GXM affects the migration of neutrophils (polymorphonuclear leukocytes [PMN]) through the endothelium by interfering with adhesion in a static adhesion model. Pretreatment of PMN with GXM inhibited PMN adhesion to tumor necrosis factor alpha (TNF-␣)-stimulated endothelium up to 44%. Treatment of TNF-␣-stimulated endothelium with GXM led to a 27% decrease in PMN adhesion. GXM treatment of both PMN and endothelium did not have an additive inhibitory effect. We demonstrated that GXM-induced L-selectin shedding does not play an important role in the detected inhibition of adhesion. L-selectin was still present on PMN in sufficient amounts after GXM treatment, since it could be further inhibited by blocking antibodies. Furthermore, blocking of GXM-related L-selectin shedding did not abolish the GXM-related inhibition of adhesion. GXM most likely exerts its effect on PMN by interfering with E-selectin-mediated binding. The use of blocking monoclonal antibodies against E-selectin, which was shown to decrease adhesion in the absence of GXM, did not cause additive inhibition of PMN adhesion after GXM pretreatment. The use of blocking antibodies also demonstrated that the inhibiting effect found after GXM treatment of endothelium probably involves interference with both intercellular adhesion molecule-1 and E-selectin binding.Cryptococcus neoformans is an encapsulated yeast that can cause life-threatening meningitis in immunocompromised patients. Compared to bacterial meningitis, cryptococcal meningitis is usually characterized by a relative paucity of leukocytes in the cerobrospinal fluid and infected tissues (4, 6), despite adequate stimulation of cytokine production (6,7,12,46,60,65,67). Previous research has shown that the immunomodulatory effects of cryptococcal capsular polysaccharides contribute to the scant leukocyte infiltrates often observed. Cryptococcal culture filtrate, the isolated capsular polysaccharide glucuronoxylomannan (GXM), and mannoprotein 4 (10) all inhibit the influx of leukocytes into inflammation sites (10, 17, 48). Since GXM and mannoprotein 4 have intrinsic chemoattracting properties (10, 15, 16) and high titers of both are found in the bloodstream during infections (10, 13, 25), it has been hypothesized that these compounds, by cross-desensitization, prevent leukocytes from properly responding to chemoattractants, thereby contributing to the scant infiltrate often reported in cryptococcal infections. This has already been demonstrated for GXM in humans as well as in experimental infections in animal models (17,48,49,50). Another mechanism for the diminished leukocyte transendothelial migration, one not yet analyzed in detail in the literature, could be the interference with leukocyte adhesion to the endothelium at ...

Apoptotic turnover rate depends on the stimulus used to induce apoptosis, while the type of the cell determines the way of the transition within the apoptotic cascade.

Breast cancer is the leading cause of cancer deaths among non-smoking women worldwide. At the moment the treatment regime is such that patients receive different chemotherapeutic and/or hormonal treatments dependent on the hormone receptor status, the menopausal status and age. However, in vitro sensitivity testing of tumor biopsies could rationalize and improve the choice of chemo-and hormone therapy. Lab-on-a-Chip devices, using microfluidic techniques, make detailed cellular analysis possible using fewer cells, enabling working with a patients' own cells and performing chemo-and hormone sensitivity testing in an ex vivo setting. This article describes the development of two microfluidic devices made in poly(dimethylsiloxane) (PDMS) to validate the cell culture properties and analyze the chemosensitivity of MCF-7 cells (estrogen receptor positive human breast cancer cells) in response to the drug staurosporine (SSP). In both cases, cell viability was assessed using the life-stain Calcein-AM (CAAM) and the death dye propidium iodide (PI). MCF-7 cells could be statically cultured for up to 7 days in the microfluidic chip. A 30 min flow with SSP and a subsequent 24 h static incubation in the incubator induced apoptosis in MCF-7 cells, as shown by a disappearance of the aggregate-like morphology, a decrease in CAAM staining and an increase in PI staining. This work provides valuable leads to develop a microfluidic chip to test the chemosensitivity of tumor cells in response to therapeutics and in this way improve cancer treatment towards personalized medicine.