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A two bead immunoassay in a micro fluidic device using a flat laser intensity profile for illumination
Pieter Roos1, Cameron D Skinner
1cskinner@alcor.concordia.ca
The Analyst
|July 18, 2003
Summary
A novel optical system maintains a flattop laser beam profile in a confocal detection system. This enables sensitive antigen detection in multiplex immunoassays, comparable to standard ELISA methods.
Area of Science:
- Optics and Photonics
- Biomedical Engineering
- Analytical Chemistry
Background:
- Gaussian beams are commonly used in optical systems but have limitations for precise illumination.
- Keplerian beam reshapers can convert Gaussian beams to flattop beams, improving illumination uniformity.
- Confocal detection systems require tightly focused beams for high-resolution imaging.
Purpose of the Study:
- To demonstrate the maintenance of a flattop beam profile within a confocal detection system.
- To evaluate the performance of this system in a microfluidic device for biological assays.
- To assess the detection limits for specific antigens using a multiplex immunoassay.
Main Methods:
- Utilized a Keplerian beam reshaper with two aspheric lenses to convert a Gaussian beam to a flattop beam.
- Integrated the reshaped beam into a confocal detection system, focusing the beam to a 33-micrometer diameter.
- Imaged fluorescein excitation in a microfluidic device using a CCD camera to characterize the beam's intensity profile.
- Performed a two-bead multiplex immunoassay to detect tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6).
Main Results:
- The flattop beam profile was successfully maintained within the confocal detection system.
- The reshaped beam exhibited a uniform intensity profile with a 6.38% relative standard deviation (RSD).
- The multiplex immunoassay achieved detection limits for TNF-alpha and IL-6 comparable to standard enzyme-linked immunosorbent assays (ELISA).
Conclusions:
- The demonstrated optical system effectively generates and maintains a uniform flattop illumination profile in a high-resolution confocal detection setup.
- This technology offers a robust platform for sensitive and specific antigen detection in microfluidic-based multiplex immunoassays.
- The comparable detection limits suggest potential for this method to replace or augment existing immunoassay techniques.