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Microfluidic system is a single cell analysis (SCA) platform which is useful for cellular biological study. However, the system still needs further development and improvement for a complete high-throughput single cell analysis. The purpose of this study was to design and develop a microfluidic device for trapping and culturing single cells of human leukemia cell line. Trapping achievement and short-term culture capability were also evaluated. Polydimethylsiloxane (PDMS) microfluidic device consisted of two layers, one of which was a main channel with a dimension of 5 mm wide, 15 mm long, 70 µm high; and an array of 40 µm equilateral triangular microwells with 30 µm deep arranged in downward oblique direction. Trapping efficacy results were about 70.8% for single cells. The effects of different cell densities on cell trapping rates showed that the increment of cell density reduced the single cell trapping capability, and the trapping method was not harmful to the cells. Potential short-term culture of single cell trapping examined by Trypan blue dye assay and Calcein AM/EthD-1 fluorescent staining revealed 80% and 75% of cellular viability after 24 and 48 h of incubation, respectively. In summary, our developed PDMS microfluidic device succeeded in single cell trapping pattern and short-term culturing of leukemia cell line single cells. [ABSTRACT FROM AUTHOR]

Dynamic gut-on-a-chip platform allows better recreation of the intestinal environment in vitro compared to the traditional static cell culture. However, the underlying mechanism is still not fully discovered. In this study, the shear stress behavior in a gut-on-a-chip device with porous membrane subjected to peristalsis motion is numerically investigated using CFD simulation for three different pore sizes and two pattern layouts. The results reveal that, in the stationary microchannel, the average shear stress on the porous membrane is approximately 15% greater than that of the flat membrane, regardless of the pore size. However, when subjected to cyclic deformation, the porous membrane with smaller pore size experiences stronger variation of shear stress which is ±5.61%, ±10.12% and ±34.45% from its average for the pore diameters of 10 μm, 5 μm and 1 μm, respectively. The shear stress distribution is more consistent in case of the staggered pattern layout while the in-line pattern layout allows for a 32% wider range of shear stress at the identical pore size during a cyclic deformation. These changes in the shear stress caused by peristalsis motion, porous size and membrane pattern could be the key factors that promote cell differentiation in the deforming gut-on-a-chip model. [ABSTRACT FROM AUTHOR]

Membrane proteins are difficult to be extracted and to be coated on the substrate of the immunoassay reaction chamber because of their hydrophobicity. Traditional method to prepare membrane protein sample requires many steps of protein extraction and purification that may lead to protein structure deformation and protein dysfunction. This work proposes a simple technique to prepare and immobilize the membrane protein suspended in an unprocessed crude cell lysate sample. Membrane fractions in crude cell lysate were incorporated with the large unilamellar vesicle (LUV) that was mainly composed of POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) before coating in the polystyrene plate by passive adsorption technique. Immunofluorescence staining and the Enzyme-Linked Immunosorbent Assay (ELISA) examination of a strictly conformation-dependent integral membrane protein, Myelin Oligodendrocyte Glycoprotein (MOG), demonstrate that LUV incorporated cell lysate sample obviously promotes MOG protein immobilization in the microplate well. With LUV incorporation, the dose–response curve of the MOG transfected cell lysate coating plate can be 2–9 times differentiated from that of the untransfected cell lysate coating plate. The LUV incorporated MOG transfected cell lysate can be efficiently coated in the microplate without carbonate/bicarbonate coating buffer assistance. [ABSTRACT FROM AUTHOR]

A radiation biodosimeter is a measure of biological response to radiation that can help determine the exact dose received by using biological markers or radiation-damaged chromosomes using a blood sample as a surrogate tissue. Today, many researchers are interested in micro-technology known as microfluidics which is a device that deals with the theory of fluid flow in sub-millimeter sizes. This research demonstrates the design and fabrication of a microfluidic device for separation of lymphocytes from whole blood using a centrifugal technique. The device is made of a circular PMMA (Sumipex) sheet with a diameter of 90 mm and a thickness of 5 mm, consisting of 12 chambers, each a 3 mm deep hexagonal cavity with a capacity of 120 µL and a straight channel 20 mm long. Efficacy testing was performed by loading 120 µL of whole blood into a chamber and centrifuging at 3000 rpm for 5 min. A yellow layer was removed and overlaid on the Ficoll solution (1.077 g/mL) and centrifuged at the same speed. The peripheral blood mononuclear cells were then removed and stained with trypan blue before counting in the hemocytometer. The results show that the developed microfluidic device is able to separate lymphocytes efficiently, which is used as part of a radiation biodosimeter. [ABSTRACT FROM AUTHOR]

Liquid-infused porous surfaces inspired by Nepenthes pitcher plant were fabricated on polyurethane. Five different micro-structures, including pillar (PIL), Sharklet ® (SHK), continuous discrete ridge (DIR), hole (HOL) and networking (NET), were fabricated by soft lithography. Effects of micro-structural geometry on lubricant infiltration capability were investigated by infiltration the micro-structures with two lubricants of different viscosity, Krytox-103 (η : 0.131 Pa ⋅ s) and Krytox-105 (η : 0. 7 3 7 Pa ⋅ s). The lubricant infiltration and retention capability were determined using a confocal laser scanning micro-scopy, and properties of the infused surfaces were evaluated by measuring the speed of water droplet motion at various tilting angles. The results revealed that, for the 80 μ m-high micro-structures, infiltration with a less viscous Krytox-103 resulted in more complete infiltration and retention, particularly for the PIL micro-structure. The infused surface exhibited a slippery behavior signified by low sliding angle and good anti-adhesion against chlorophyll fluid and milk yogurt. The lubricant retention capability was significantly reduced for the 7 μ m-high micro-structures due to lower aspect ratio and low capillary force. In this case, the PIL infused with a more viscous Krytox-105 provided a slippery surface. [ABSTRACT FROM AUTHOR]

Polydimethylsiloxane (PDMS) is a hydrophobic elastomer commonly used for microfluidic fabrication. PDMS has to be modified to improve its hydrophilicity and thus inhibits non-specific protein adsorption. This work evaluates the modification materials for the development of microfluidic cell-based immunofluorescence (IF) assay. In cell-based IF assay, PDMS is modified not just to inhibit the adsorption of non-specific florescent-conjugated protein that causes the elevation of background signal, but also to firmly support cell adhesion for subsequent immunostaining procedure. PDMS materials modified by three regular modification materials consisting of an extracellular matrix (poly-L-lysine; PLL), a hydrophilic polymer (polyvinyl alcohol; PVA) and a non- ionic surfactant (pluronic F127) were compared with each other based on hydrophilicity improvement, minimization of non-specific background signal, and enhancement of human embryonic kidney (HEK) cell adhesion. Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) analysis confirms that all modification materials are successfully immobilized on the PDMS surfaces. Due to its antifouling mechanism, pluronic modification greatly improves the hydrophilicity of the PDMS and inhibits non-specific protein adsorption. Even though the hydrophilicity and non-specific protein adsorption resistivity of the PDMS modified with PLL did not significantly differ from those of the unmodified PDMS, PLL modification obviously promotes HEK cell adhesion. Negative control and Myelin Oligodendrocyte Glycoprotein (MOG) expressing HEK cells were immobilized in microfluidics for IF assay evaluation. Results demonstrate that positive MOG expressing cells can be selectively stained by anti-MOG IgG antibody within 1 h at room temperature. Microfluidic platforms also enhance immobilized cell distribution, which compatibly supports single-cell analysis technique. [ABSTRACT FROM AUTHOR]

Our laboratory has the fundamental responsibility to study cancer stem cells (CSC) in various models of human and animal neoplasms. However, the major impediments that spike our accomplishment are the lack of universal biomarkers and cellular heterogeneity. To cope with these restrictions, we have tried to apply the concept of single cell analysis, which has hitherto been recommended throughout the world as an imperative solution pack for resolving such dilemmas. Accordingly, our first step was to utilize a predesigned spiral microchannel fabricated by our laboratory to perform size-based single cell separation using mast cell tumor (MCT) cells as a model. However, the impact of hydrodynamic shear stresses (HSS) on mechanical cell injury and viability in a spiral microchannel has not been fully investigated so far. Intuitively, our computational fluid dynamics (CFD) simulation has strongly revealed the formations of fluid shear stress (FSS) and extensional fluid stress (EFS) in the sorting system. The panel of biomedical assays has also disclosed cell degeneration and necrosis in the model. Therefore, we have herein reported the combinatorically detrimental effect of FSS and EFS on the viability of MCT cells after sorting in our spiral microchannel, with discussion on the possibly pathogenic mechanisms of HSS-induced cell injury in the study model. [ABSTRACT FROM AUTHOR]