Amplified flow-cytometric separation-free fluorescence immunoassays

Area of Science:

• Biochemistry
• Immunology
• Analytical Chemistry

Background:

• Traditional immunoassays often require complex separation steps to distinguish between free and bound labels, impacting efficiency and sensitivity.
• Developing highly sensitive and precise analytical methods is crucial for early disease detection and monitoring.

Purpose of the Study:

• To describe a novel equilibrium-type competitive-binding fluorescence immunoassay.
• To demonstrate a method that obviates the need for separating free from bound labels.
• To achieve high sensitivity and precision in antigen detection using dual-sphere technology.

Main Methods:

• Utilized antibody-coated non-fluorescent particles (10 microns) and antigen-coated fluorescent latex particles (0.10 microns).
• Employed a competitive-binding mechanism where soluble antigen competes with microsphere-bound antigen for antibody sites.
• Measured fluorescence distribution of large spheres using a flow cytometer after equilibrium was reached.

Main Results:

• Achieved a sensitivity of 10(-12) mol/L for horseradish peroxidase detection in a prototype assay.
• Demonstrated that undiluted serum can be assayed without compromising sensitivity.
• Showed potential for ultra-high sensitivity (10(-14) mol/L) in double-antibody 'sandwich'-type assays using the dual-sphere concept.

Conclusions:

• The described dual-sphere fluorescence immunoassay offers a sensitive, precise, and efficient alternative to traditional methods.
• The technology eliminates the need for label separation, simplifying assay procedures.
• This approach holds significant promise for developing advanced diagnostic tools in clinical settings.