We report the development of enhanced optical platforms for fluorescence-based biosensors. A prev... more We report the development of enhanced optical platforms for fluorescence-based biosensors. A previous analysis by us has shown that the emission of fluorescence in such a system is highly anisotropic and is preferentially emitted into the substrate over a well-defined angular range, with the result that the light is guided along the substrate via total internal reflection. However, conventional optical biosensors based on fluorescence detection typically employ a detector that is positioned either directly above or directly below the biochip. As a consequence, only a small fraction of the total emitted fluorescence is detected, which impacts adversely on sensor performance. The enhanced biosensor presented here is based on a novel, generic platform specifically designed to overcome the inherent limitations of planar substrates. The platform incorporates custom-designed optical elements, the purpose of which is to redirect the emitted fluorescence onto a detector positioned beneath the biochip. Platforms were fabricated using the polymer processing technique of microinjection moulding. In this paper we demonstrate the ability of this optical system to achieve a 80-fold luminescence capture enhancement. We also demonstrate its effectiveness as an enhanced biosensor platform by carrying out a proof of principle BSA/antiBSA competitive assay. This work has significant implications for the development of mass-producible, highly efficient optical biosensors.
We report a microfluidic chip-based hydrodynamic focusing approach that minimizes sample volume f... more We report a microfluidic chip-based hydrodynamic focusing approach that minimizes sample volume for the analysis of cell-surface interactions under controlled fluid-shear conditions. Assays of statistically meaningful numbers of translocating platelets interacting with immobilized von Willebrand factor at arterial shear rates (∼1500 s(-1)) are demonstrated. By controlling spatial disposition and relative flow rates of two contacting fluid streams, e.g., sample (blood) and aqueous buffer, on-chip hydrodynamic focusing guides the cell-containing stream across the protein surface as a thin fluid layer, consuming ∼50 μL of undiluted whole blood for a 2-min platelet assay. Control of wall shear stress is independent of sample consumption for a given flow time. The device design implements a mass-manufacturable fabrication approach. Fluorescent labeling of cells enables readout using standard microscopy tools. Customized image-analysis software rapidly quantifies cellular surface coverage and aggregate size distributions as a function of time during blood-flow analyses, facilitating assessment of drug treatment efficacy or diagnosis of disease state.
We report the development of enhanced optical platforms for fluorescence-based biosensors. A prev... more We report the development of enhanced optical platforms for fluorescence-based biosensors. A previous analysis by us has shown that the emission of fluorescence in such a system is highly anisotropic and is preferentially emitted into the substrate over a well-defined angular range, with the result that the light is guided along the substrate via total internal reflection. However, conventional optical biosensors based on fluorescence detection typically employ a detector that is positioned either directly above or directly below the biochip. As a consequence, only a small fraction of the total emitted fluorescence is detected, which impacts adversely on sensor performance. The enhanced biosensor presented here is based on a novel, generic platform specifically designed to overcome the inherent limitations of planar substrates. The platform incorporates custom-designed optical elements, the purpose of which is to redirect the emitted fluorescence onto a detector positioned beneath the biochip. Platforms were fabricated using the polymer processing technique of microinjection moulding. In this paper we demonstrate the ability of this optical system to achieve a 80-fold luminescence capture enhancement. We also demonstrate its effectiveness as an enhanced biosensor platform by carrying out a proof of principle BSA/antiBSA competitive assay. This work has significant implications for the development of mass-producible, highly efficient optical biosensors.
We report a microfluidic chip-based hydrodynamic focusing approach that minimizes sample volume f... more We report a microfluidic chip-based hydrodynamic focusing approach that minimizes sample volume for the analysis of cell-surface interactions under controlled fluid-shear conditions. Assays of statistically meaningful numbers of translocating platelets interacting with immobilized von Willebrand factor at arterial shear rates (∼1500 s(-1)) are demonstrated. By controlling spatial disposition and relative flow rates of two contacting fluid streams, e.g., sample (blood) and aqueous buffer, on-chip hydrodynamic focusing guides the cell-containing stream across the protein surface as a thin fluid layer, consuming ∼50 μL of undiluted whole blood for a 2-min platelet assay. Control of wall shear stress is independent of sample consumption for a given flow time. The device design implements a mass-manufacturable fabrication approach. Fluorescent labeling of cells enables readout using standard microscopy tools. Customized image-analysis software rapidly quantifies cellular surface coverage and aggregate size distributions as a function of time during blood-flow analyses, facilitating assessment of drug treatment efficacy or diagnosis of disease state.
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