Droplet-based fluorescence anisotropy insulin immunoassay

Area of Science:

• Biomedical Engineering
• Endocrinology
• Analytical Chemistry

Background:

• Continuous flow microfluidic systems face challenges with diffusion-limited mixing, causing signal dispersion and reduced temporal resolution for hormone measurements.
• Peptides and proteins, crucial in biological signaling, exhibit large diffusion coefficients, exacerbating mixing issues in conventional microfluidic assays.
• Droplet microfluidics offers a solution by compartmentalizing reactions, minimizing dispersion and enhancing temporal resolution for biological molecule analysis.

Purpose of the Study:

• To develop and validate a droplet microfluidic platform for high-temporal-resolution fluorescence anisotropy immunoassay of insulin.
• To overcome the limitations of diffusion-based mixing in continuous flow systems for analyzing rapid hormonal changes.
• To improve the precision and speed of insulin secretion measurements from pancreatic islets.

Main Methods:

• Integration of a fluorescence anisotropy immunoassay for insulin into a droplet microfluidic system.
• Online mixing of insulin with assay reagents followed by rapid capture into discrete droplets.
• Utilized a double-etched glass microfluidic device with a 200 mm incubation channel for optimized reagent flow and incubation.
• Implemented droplet microfluidics to minimize dispersion and enhance temporal resolution.

Main Results:

• Achieved high precision for fluorescence anisotropy measurements with relative standard deviations < 2% across tested insulin concentrations.
• Absolute fluorescence intensity precision ranged from 5% to 6%.
• Obtained a limit of detection of 3 nM for insulin, comparable to conventional systems.
• Demonstrated a significantly improved response time of 9.8 ± 2.6 seconds, surpassing previous continuous flow systems.

Conclusions:

• The droplet microfluidic FA immunoassay system provides precise and rapid measurement of insulin.
• This platform enhances temporal resolution, enabling better capture of rapid signaling events in pancreatic islet research.
• The developed system represents a significant advancement for studying dynamic biological processes at the cellular level.