Highly sensitive paper-based immunoassay using photothermal laser speckle imaging.

Area of Science:

• Biomedical Engineering
• Analytical Chemistry
• Point-of-Care Diagnostics

Background:

• Paper-based lateral-flow assays (LFAs) are widely used but often lack the sensitivity for early disease biomarker detection.
• Existing LFAs are 10-100 times less sensitive than other molecular techniques.
• Low sensitivity limits LFA application in early disease diagnosis.

Purpose of the Study:

• To develop a highly sensitive and cost-effective LFA sensor.
• To improve the detection limit of LFAs for disease-relevant biomarkers.
• To validate the sensor's performance using clinically relevant targets.

Main Methods:

• Developed a lateral-flow assay sensor utilizing photothermal laser speckle imaging (PT-LSI).
• Employed gold nanoparticles (AuNPs) as signal transducers, absorbing light to generate heat.
• Measured heat-induced optical and thermal membrane changes via laser speckle imaging to quantify biomarker concentrations.

Main Results:

• The PT-LSI sensor demonstrated a 68-125× improvement in detection limit compared to colorimetric detection.
• Achieved highly sensitive detection of disease biomarkers.
• Validated the sensor's capability using U.S. FDA-approved cryptococcal antigen (CrAg) LFA kits.

Conclusions:

• PT-LSI offers a simple, cost-effective, and highly sensitive method to enhance LFA performance.
• This technology significantly expands the potential of LFAs for early disease diagnosis.
• The validated performance shows promise for clinical applications in detecting low-abundance biomarkers.