Sensitivity enhancement for colorimetric glucose assays on whole blood by on-chip beam-guidance
University of Freiburg, Freiburg, Baden-Württemberg, Germany Biomedical Microdevices
(Impact Factor: 2.88).
10/2006; 8(3):209-14. DOI: 10.1007/s10544-006-8172-x
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( composite function) 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 microM) 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.
Available from: Peter Clark
- "For microscale devices, Reynolds numbers are very low (<1) and thus mixing is accomplished only by molecular diffusion. There have been many attempts to create active mixing in microfluidic environment . Among these methods , electrokinetic mixing techniques particularly electrothermal effect (ETE) seem to be appropriate for enhancing biosensor kinetics in a microchannel environment. "
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ABSTRACT: We present a microfabricated quantum dot-linked immuno-diagnostic assay (μQLIDA) biosensor with an embedded mixing element. We adapted our previous capillary-based system into a microfabricated planar microchannel, which has been integrated with an active, electrothermal mixing component. With the active mixing element, the detection time was significantly reduced from about 3.5 h to 30 min in a case study of detecting myeloperoxidase (MPO). MPO is an inflammatory biomarker that is over-expressed in inflammatory conditions including inflammatory bowel disease and cardiovascular disease. The μQLIDA biosensor presented here is a low-cost, rapid immunofluorescence sensor that can detect nanomolar concentrations of MPO, with a working volume of 2 μl.
Sensors and Actuators B Chemical 03/2015; 209:722 - 728. DOI:10.1016/j.snb.2014.12.033 · 4.10 Impact Factor
Available from: PubMed Central
- "Some of these use passive working principles [3–5], others apply dielectrophoresis [6,7], acoustic standing waves [8–11], segmented flow [12–14], or magnetophoresis [15,16]. Applying centrifugal force is one of the most powerful candidates for the passive steady-non pulsatile-flow in microfluidic systems  for continuous fully automated processing such as cell arrangement , DNA concentration , biomolecular separation , and also a compact disc (CD) microfluidic chip based enzyme-linked immunosorbent assay (ELISA) , whole blood glucose analysis , and hybridization assay for phenylketonuria (PKU) screening . Especially, extraction of plasma from whole blood exploiting microfluidic pathways with centrifugal pumping  and cell trapping exploiting reagent-impregnated agarose-made micro holes with centrifugal liquid pumping  were examined for practical applications. "
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ABSTRACT: We have demonstrated the efficacy of a microfluidic medium exchange method for single cells using passive centrifugal force of a rotating microfluidic-chip based platform. At the boundary of two laminar flows at the gathering area of two microfluidic pathways in a Y-shape, the cells were successfully transported from one laminar flow to the other, without mixing the two microfluidic mediums of the two laminar flows during cell transportation, within 5 s with 1 g (150 rpm) to 36.3 g (900 rpm) acceleration, with 93.5% efficiency. The results indicate that this is one of the most simple and precise tools for exchanging medium in the shortest amount of time.
International Journal of Molecular Sciences 12/2012; 13(1):819-27. DOI:10.3390/ijms13010819 · 2.86 Impact Factor
Available from: Ruey-Jen Yang
- "In performing glucose concentration detection, the most commonly used biorecognition element is immobilized glucose oxidase (Ivnitski et al. 2008; Ammam and Fransaer 2009). Glucose detection is generally performed using either electrochemical methods (Garcia and Henry 2004) or optical absorbance methods (Grumann et al. 2006). Suzuki and Kumagai (2003) developed a disposable glucose sensor in which the glucose concentration was visualized directly in a manner similar to that of a mercury-or alcohol-loaded thermometer. "
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ABSTRACT: A novel three-dimensional (3D) disposable glucose concentration detection chip is presented. The chip comprises a four-layer
polymethyl methacrylate (PMMA) structure and is fabricated using a commercial CO2 laser and a hot-press bonding technique. In the proposed device, the glucose solution is injected into a double parallel
connection micromixer (DPCM) and is mixed with DNS reagent by means of a self-rotation effect. An experimental platform has
been created for multiple reaction process by integrating chip and micro-heater. The fluid streams exiting the two circular
mixing chambers of the DPCM are then combined and mixed further at a T-type microchannel outlet before passing to a collection
chamber. Numerical simulations are performed to analyze the vortex streamline distribution within the DPCM and to estimate
the mixing performance. The numerical results show that a mixing efficiency as high as 92.5% can be obtained at low Reynolds
numbers (Re=12). It is found a good linear relation of R
2=0.9953 from the chip detection method comparing to the traditional method of R
2=0.9976 at DNS reagent and glucose solution volume ratio of 1:1. In addition, the experimental results show that the accuracy
of the glucose concentration measurements obtained using the proposed microfluidic chip is comparable with that of the measurements
obtained using a conventional large-scale detection method. Overall, the results presented in this study indicate that the
DPCM chip provides a rapid and low-cost means of detecting the concentration of glucose solutions.
KeywordsMicromixer–DNS method–CO2 laser machining–Microfluidics
Microfluidics and Nanofluidics 10/2011; 11(4):479-487. DOI:10.1007/s10404-011-0813-6 · 2.53 Impact Factor
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