Journal
BIOMEDICAL MICRODEVICES
Volume 8, Issue 3, Pages 209-214Publisher
SPRINGER
DOI: 10.1007/s10544-006-8172-x
Keywords
glucose; optical beam-guidance; lab-on-a-disk; colorimetric assay; total internal reflection
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In this paper, we present a novel concept for optical beam-guidance to significantly enhance the sensitivity of colorimetric assays by extending the optical path length through the detection cell which linearly impacts the resulting attenuation of a probe beam according to the law of Beer-Lambert. In our setup, the incident probe beam is deflected by 90 degrees into the chip plane at monolithically integrated V-grooves to pass a flat detection cell at its full width (i.e., with a path length of 10 mm) instead of its usually much smaller height. Afterwards, the attenuated beam is redirected by another V-groove towards an external detector. The general beam-guidance concept is demonstrated by a glucose assay on human whole blood on a centrifugal microfluidic lab-on-a-disk platform made of COC. We achieve an excellent linearity with a correlation coefficient (R-2) of 0.997 paired with a lower limit of detection (200 mu M) and a good reproducibility with a coefficient of variation (CV) of 4.0% over nearly three orders of magnitude. With an accelerated sedimentation of cellular constituents by centrifugal forces, the sample of whole blood can be analyzed in a fully integrated fashion within 210 s. This time-to-result can even be improved by the numerical extrapolation of the saturation value. Additionally, the direct assay on whole blood also shows a negligible correlation with the hematocrit of the blood sample.
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