Liposome immunoassay by long-lived fluorescence detection

Area of Science:

• Biochemistry
• Analytical Chemistry
• Biotechnology

Background:

• Liposomes are versatile nanocarriers with applications in drug delivery and diagnostics.
• Fluorescence energy transfer (FRET) is a powerful technique for studying molecular interactions.
• Developing sensitive and specific immunoassays is crucial for disease diagnosis and monitoring.

Purpose of the Study:

• To develop a novel immunoassay utilizing fluorescence energy transfer (FRET) between a europium chelate and allophycocyanin (APC).
• To investigate the feasibility of using liposomes as a platform for this FRET-based immunoassay.
• To evaluate the assay's performance in detecting biotinylated molecules and free biotin.

Main Methods:

• Liposomes encapsulating a europium chelate (2-naphthoyltrifluoroacetone) were prepared.
• Streptavidin or anti-biotin antibody was immobilized onto the liposome surface.
• Allophycocyanin conjugated to biotin (APC-BT) was added, and FRET was measured via long-lived fluorescence.
• The assay's response to varying concentrations of APC-BT and free biotin was analyzed using a flow system.

Main Results:

• A linear increase in fluorescence intensity was observed with increasing concentrations of APC-BT (1-10 µg/mL), indicating efficient FRET.
• The fluorescence intensity decreased competitively with increasing concentrations of free biotin (0.1-100 µM), demonstrating specific binding.
• The assay demonstrated sensitive detection capabilities for biotinylated analytes.

Conclusions:

• The developed liposome-based FRET immunoassay is a viable method for quantifying biotinylated molecules.
• This assay offers a sensitive and specific platform for diagnostic applications.
• The use of long-lived fluorescence enhances assay robustness and reduces background interference.