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Experimental Microsystems Platforms

MicroFluidics

Monitoring the immune response in single host cells challenged with pathogens is required in order to understand the stochasticity of immune response in a population of cells. We have developed a microfluidic platform for optical interrogation of an array of single host cells.  We have also developed an electrofluidic platform for impedimetric interrogation of single host cells during pathogenic challenges.

Impedimetric Monitoring of Immune Response in Single Host Cells

Monitoring the immune response in single host cells challenged with pathogens is required in order to understand the stochasticity of immune response in a population of cells. We have developed a microfluidic platform for optical interrogation of an array of single host cells. The single cell array (SCA) chip utilizes fluid constrictions to place host cells in pre-defined traps (T1-T50) for high-resolution confocal imaging. DRIE is used to define through-holes and channel features in silicon wafers (i-iii), and the chip is anodically bonded to a glass coverslip (iv). After capture, cells are then exposed to a pathogenic challenge consisting of bacteria or purified lipopolysaccharide (LPS) that is shed by bacteria is delivered to the captured cell.

Monitoring the immune response in single host cells challenged with pathogens is required in order to understand the stochasticity of immune response in a population of cells. We have developed a microfluidic platform for optical interrogation of an array of single host cells (C.D. James et al., Biomed. Microdev. 2009, in press). The single cell array (SCA) chip utilizes fluid constrictions to place host cells in pre-defined traps (T1-T50) for high-resolution confocal imaging. DRIE is used to define through-holes and channel features in silicon wafers i-iii), and the chip is anodically bonded to a glass coverslip (iv). After capture, cells are then exposed to a pathogenic challenge consisting of bacteria or purified lipopolysaccharide (LPS) that is shed by bacteria is delivered to the captured cell. Host cells contain a GFP reporter construct to identify the location of the transcription factor NF-kappaB.

Schematic of the (a) SCA chip fabrication and (b) optical micrograph of the chip.    b

Fig. 1: (left) Schematic of the (a) SCA chip fabrication and (b) optical micrograph of the chip. (right) (a-d) Macrophage held in a trap during an exposure to LPS. (e) Fluorescence intensity across the cell and (f) the ratio of nuclear to cytoplasm fluorescence as a function of time.

Optical Monitoring of Immune Response in Single Host Cells

femtostat coupled to the platform

 

 

 

 

 

Fig. 2 Electrofluidic platform for impedimetric interrogation of single cells.

We have also developed an electrofluidic platform for impedimetric interrogation of single host cells during pathogenic challenges (C.D. James et al., Biosens Bioelec 2008, 23, 845). A cell is captured to a micro-pore (<3 mm diameter) under negative pressure. Then, the cell is exposed to a pathogenic challenge which results in signaling events that can alter cell membrane properties, as well as the adherence of the cell to the chip. A femtostat coupled to the platform is then used to monitor changes in impedance across the captured cell in real-time (sampled every 6s). The device can also be used to perform live/dead assays on cells.
a
Fig. 3 (left) Real and imaginary components of the impedance across a single macrophage as a function of time during an LPS challenge. (right) Nyquist plot of the macrophage before and after LPS exposure.

For additional information or questions, please email us at Biosensors and Nanomaterials

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