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Endothelial progenitor cell recruitment in a microfluidic vascular model
Daniel Lewis, Student, Johns Hopkins University
During vessel injury, endothelial progenitors cells(EPCs) are recruited from bone marrow and directed to the hypoxic injury site. The hypoxic conditions in the damaged blood vessel promote TNF- alpha, which upregulates intercellular adhesion molecule-1 (ICAM-1). EPCs attach to endothelial cell lining using ICAM-1. Here we aimed to examine EPC attachment to ECs in an injured-blood vessel conditions. We first determined ICAM-1 expression in stimulated HUVECs. We stimulated HUVECs with 21% oxygen (atmospheric), atmospheric with TNF-alpha-supplemented media, 1% oxygen (hypoxia), and hypoxia with TNF-alpha-supplemented media and found the highest ECFC attachment on HUVECs stimulated with TNF-alpha and hypoxia, correlating with the highest ICAM-1 expression. We next designed, fabricated and tested a three-dimensional microbioreactor(3D MBR)system with precise control and monitoring of dissolve oxygen and media flow rate in the cellular environment. We utilized a step-wise seeding approach, producing monolayer of HUVECs on all four walls. When stimulated with both TNF-alpha and hypoxia, ECFC retention on HUVECs was significantly increased under low shear stress compared to static controls. Overall, the 3D MBR system mimics the pathological oxygen tension and shear stress in the damaged vasculature, providing a platform to model vascular-related disorders.
A Random Access Memory for storing single living cells as data
Roozbeh Abedini Nassab, Student, Duke University
Single-cell Array (SCA) systems are emerging tools in medical research with applications in cancer therapy, immunology, and in studying cellular heterogeneity [1-3]. However, existing SCAs are neither sufficiently large nor automated to enable the study of rare cell behaviors and cell-cell interactions. In order to achieve these goals, we developed a novel SCA composed of magnetophoretic integrated circuit elements to manipulate and store single living cells [4-7], in analogous to random access memories (RAM), which store electrons (data) in computer systems.
These integrated circuits are based on overlaid magnetic and metallic patterns fabricated on silicon or glass substrates, coated by non-fouling PEOGMA layer. The driving force for transporting magnetically labeled cells to desired locations on the chip is provided by a rotating magnetic field, which shifts the local minima of the potential energy landscape along controlled directions, dragging the magnetically labeled cells along desired paths.
The new platform allows us to build significantly larger cell-based RAMs, capable of organizing >10,000 single-cells with operation times of less than an hour. We have the ability to store single-cells or cell pairs on specific storage sites and perform phenotypic study, over time. Moreover, we can selectively release them for follow-on transcriptomic analyses.
Evaluation of an integrated optic-fiber-microfluidic analyser for polyphenols measurement
Maria Cañizares-Macías, , National Autonomous University of Mexico
Absorbance detection has not been well investigated in conjunction with food microdevices because of its low sensitivity therefore complex strategies have had to be implemented to increase it, so in this paper a simple polydimetylsiloxane (PDMS) microdevice with precise optical alignment method using microchanneles to insert optical fibers based on Folin-Ciocalteau reaction to quantify polyphenols in white wine was development. A 6 V and 10 W halogen lamp as light source and a 7 mm path optical between the fibers were used increasing the sensitivity in the detection. The linear range was from 0.03 mmol/l to 018 mmol/L and the equation: Abs = 4.00(±0.16) [tannic acid] +0.17(±0.017). Repetibility and reproducibility intra laboratory were 2.95 %y 6.84 %, respectively. The results of polyphenols in wine were compared with those obtained by a flow injection analysis method based on the same reaction. The relative error between methods was less than 13 %. The determination was carried out within 20 s using reagent volumes lower than 11 µL.
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