Parallelization of chip-based fluorescence immuno-assays with quantum-dot labelled beads

Abstract

This paper presents a novel optical concept for the readout of a parallel, bead-based fluorescence immunoassay conducted on a lab-on-a-disk platform. The reusable part of thc modular setup comprises a detection unit featuring a single LED as light source, two emissionfilters, and a color CCD-camera as standard components together with a spinning drive as actuation unit. The miniaturized lab-on-a-disk is devised as a disposable. In the read-out process of the parallel assay, beads are first identified by the color of incorporated quantum dots (QDs). Next, the reaction-specific fluorescence signal is quantified with FluoSpheres-labeled detection antibodies. To enable a fast and automated read-out, suitable algorithms have been implemented in this work. Based on this concept, we successfully demonstrated a Hepatitis-A assay on our disk-based lab-on-a-chip.

The centrifugal microfluidic Bio-Disk platform

“…Fluorescence detection. We also evaluated schemes for bead-based fluorescence detection [67][68][69]. On the one hand, the detection on a bead phase allows us to introduce the sensitive capture molecules after the sealing of the substrate, possibly requiring thermally and/or chemically harsh conditions.…”

Integrated Sample Preparation, Reaction, and Detection on a High-Frequency Centrifugal Microfluidic Platform

“…By spinning of the disk, centrifugal forces F n control flow rates and thus incubation times at high accuracy to carry out the standard steps of a fluorescence immunoassay, that is, the delivery of the sample, detection of antibodies, and washing. In a two-step read-out procedure 41 using the same camera and LED, a fluorescence image of the bead-incorporated QDs is first captured while using a long pass filter. An image processor localizes the beads and identifies their respective color tag in a (statistically) very reliable manner.…”

“…28 –32 The disk characteristically features inlet ports for the sample and reagent uptake as well as microchannels and microstructures where the sample is transported and processed 33 –40 by the interplay of centrifugal (volume) forces and capillary (surface) forces. The nature of the final step can be the collection of the processed substance or the read-out of an assay result, depending on whether an analytical assay, 41 –43 a preparative procedure, 44,45 or a synthesis has been implemented in a lab-on-a-disk system. Numerous “lab-on-a-disk” products have already been launched in the market.…”

CMAS: fully integrated portable centrifugal microfluidic analysis system for on-site colorimetric analysis

“…17,18 They demonstrated a bench-top device for a fully integrated processing and read-out of the hemoglobin assay, which comprises a PC-controlled actuation unit, a synchronised free-droplet dispenser unit to load the reagents, a low-cost laser and a spectrophotometer as components for the optical detection. The use of a spectrophotometer ensures a flexible read-out of additional colorimetric assays or even fluorescence immunoassays (FIA), 19 allowing different types of assays to be run on the same disc, either simultaneously or sequentially. Also techniques for on-board-storage and release of liquid reagents have been successfully integrated in the meantime.…”