Distance-Based Tear Lactoferrin Assay on Microfluidic Paper Device Using Interfacial Interactions on Surface-Modified...

Area of Science:

• Analytical Chemistry
• Biomaterials Science
• Point-of-Care Diagnostics

Background:

• Microfluidic paper-based analytical devices (μPADs) offer potential for low-cost diagnostics.
• Distance-based detection on μPADs enables instrument-free quantitative analysis.
• Lactoferrin is a key biomarker in tear fluid for diagnosing ocular conditions.

Purpose of the Study:

• To develop a cost-effective, calibration-free, distance-based assay for lactoferrin in human tear fluid using μPADs.
• To avoid reliance on antibodies or enzymes for lactoferrin detection.
• To investigate the fluidic mobilities of lactoferrin and Tb(3+) on surface-modified cellulosic paper.

Main Methods:

• Surface modification of cellulosic filter paper with ι-carrageenan.
• Chromatographic elution experiments using a tear-like sample matrix.
• Development of a distance-based fluorescence assay for lactoferrin quantification.
• Validation against the Enzyme-Linked Immunosorbent Assay (ELISA) method.

Main Results:

• The ι-carrageenan modification overcame electrostatic interactions, enabling effective lactoferrin and Tb(3+) mobility control.
• The developed μPAD successfully quantified lactoferrin in the range of 0-4 mg mL(-1) with a limit of detection of 0.1 mg mL(-1).
• Assay results showed excellent correlation with ELISA (slope=0.997, R^2=0.948) for human tear samples.
• The assay demonstrated good batch-to-batch reproducibility using printing methods.

Conclusions:

• A novel, antibody/enzyme-free, distance-based lactoferrin assay on μPADs was successfully developed.
• The assay provides a simple, visual, and calibration-free method for lactoferrin quantification in human tears.
• This technology holds promise for accessible point-of-care diagnostics for ocular diseases.