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Issue 5, 2011
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Lensless CCD-based fluorometer using a micromachined optical Söller collimator

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In this paper, we describe a simple charge-coupled device (CCD) based lensless fluorometer with sensitivity in the range of current ELISA plate readers. In our lensfree fluorometer, a multi-wavelength LED light source was used for fluorophore excitation. To collimate the light, we developed a simple optical Söller collimator based on a “stack of pinholes” (a stack of black PMMA with array of pinholes machined with laser) enabling the light to be collimated from the LED through the filters and the assay's microfluidics directly onto the CCD without a lens. The elimination of the lens that is used in almost all other current CCD based detection systems has four major advantages: (1) It simplifies the device design and fabrication while reducing cost. (2) It reduces the distance between the sample and the measuring device (without a lens the distance needed to focus the image on the CCD is reduced and the fluorometer can be more compact). (3) It couples the CCD and the detected surface by using an optical Söller Collimator which allows the use of filters for fluorescence detection. (4) It also uncouples the CCD and the microfluidics to enable the use of interchangeable fluidics while protecting the delicate CCD. The lensless CCD-based fluorometer is capable of detecting 16 samples simultaneously, and was used for in vitrodetection of botulinum neurotoxin serotype A (BoNT-A) activity with a FRET assay that measures cleavage of a fluorophore-tagged peptide substrate specific for BoNT-A (SNAP-25) by the toxin light chain (LcA). The limit of detection (LOD) of our lensless fluorometer is 1.25 nM, which is similar to the LOD of a modern ELISA plate reader. Combined with microfluidics, this simple low cost point-of-care (POC) medical diagnostic system may be useful for the performance of many other complex medical diagnostic assays without a laboratory and thus potentially enhancing the accessibility and the quality of health care delivery in underserved populations.

Graphical abstract: Lensless CCD-based fluorometer using a micromachined optical Söller collimator

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Publication details

The article was received on 21 Sep 2010, accepted on 22 Dec 2010 and first published on 17 Jan 2011

Article type: Paper
DOI: 10.1039/C0LC00431F
Citation: Lab Chip, 2011,11, 941-949
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    Lensless CCD-based fluorometer using a micromachined optical Söller collimator

    J. Balsam, M. Ossandon, Y. Kostov, H. A. Bruck and A. Rasooly, Lab Chip, 2011, 11, 941
    DOI: 10.1039/C0LC00431F

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