Non constriction based immobilization of polymer spheres for bio-sensing and scaffold based applications
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Date
2014-05
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The Ohio State University
Abstract
Microfluidic devices have been routinely used to perform multiplexed analysis at proteomic, genomic and cellular levels. Such analysis serves to probe fundamental biological questions as well as provide means for clinical diagnosis. At the proteomic and genomic levels, bead based assays are commonly used as solid phases to immobilize antigens for downstream detection. Functional cellular analysis such as proliferation studies use microbeads as scaffolds for cell culture. A significant majority of assay systems use constriction to immobilize beads while sample is flown through to utilize spatial-coding multiplexing strategies or divert maximal fluid flow through sensor beads. Spatial constriction however, results in non uniform flow of fluid across bead surface and substantially increases shear forces on bead surface. In a high-throughput context these limitations are detrimental in terms of assay reproducibility and flow rate limitation respectively. We demonstrate the use of a sandwiched polycarbonate membrane to trap microbeads in a bi-layer microfluidic chip to perform sandwiched ELISA based detection of murine IgG protein. Using flow-rates of 1 ml/hr we established a fluorescence limit of detection of 2 nanograms/ml. In order to validate the device for multimarker, we successfully detected EpCAM (Epithelial Cell Adhesion Marker) at concentration of 5 nanograms/ml using flow-rates of 1 ml/hr. We also explored the usability of our device for single-cell analysis using MCF-7 breast cancer cells as models for proliferation function analysis. Anti-EpCAM coated beads were used to anchor MCF-7 cells via the EpCAM receptor and serve as scaffold for cell growth. Beads in the chip supplied with growth media experienced viable cell growth as opposed to none of the beads with fixed cells. Growth was recorded for a maximum of 4 days and followed a sigmoid trend. In short, our study demonstrates the usability of a microfluidic chip with integrated membrane component to immobilize solid phase bead for proteomic biosensing and cell proliferation function analysis. Such assays could provide useful means to provide develop point-of-care diagnostic but also interrogate fundamental biologic questions in pathologies such as cancer.
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Keywords
bioprocessor, immunoassay, microfluidic, simulation, single cell