Femtomolar sensitivity using a channel-etched thin film waveguide fluoroimmunosensor

Area of Science:

• Biomedical Engineering
• Analytical Chemistry
• Optoelectronics

Background:

• Accurate detection of low-concentration analytes is crucial in diagnostics and research.
• Existing immunosensing technologies often struggle to reach femtomolar detection levels.
• Integrated optical waveguides offer potential for sensitive biosensing applications.

Purpose of the Study:

• To develop and validate a novel evanescent fluoroimmunoassay for ultra-sensitive analyte detection.
• To demonstrate femtomolar (sub-part-per-trillion) detection capabilities using an integrated optical waveguide.
• To evaluate sensor performance using both direct and indirect immunoassay formats.

Main Methods:

• Utilized a dual-channel, evanescent fluoroimmunoassay on a silicon oxynitride thin film optical waveguide.
• Employed a red-emitting cyanine dye (Cy-5) to minimize optical interference.
• Tested direct and indirect sandwich assay formats for protein ligand detection.

Main Results:

• Achieved femtomolar (less than 1 part per trillion [w/w]) analyte detection limits.
• Demonstrated dose-response behavior in both direct and indirect assay configurations.
• Reported the first instance of femtomolar sensitivity in an immunosensing instrument.

Conclusions:

• The developed evanescent fluoroimmunoassay platform enables unprecedented sensitivity for analyte detection.
• Integrated optical waveguides are highly effective for achieving ultra-low detection limits in biosensing.
• This technology represents a significant advancement in immunosensing instrumentation.