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Beads-on-a-Tip testing for ultrasensitive antigen detection across a large dynamic range
Ziwei Wu1, Yangjian Cai1, Yitong Zhao1,2
1Institute for Biomedical Materials and Devices (IBMD), Faculty of Science University of Technology Sydney Sydney New South Wales Australia.
Smart Molecules : Open Access
|April 27, 2026
Summary
This study introduces a novel Beads-on-a-Tip design for ultra-sensitive antigen detection, significantly improving lateral flow immunoassay (LFIA) sensitivity for point-of-care testing (POCT). The new method achieves a lower limit of detection than existing LFIAs.
Area of Science:
- Biomedical Engineering
- Analytical Chemistry
- Point-of-Care Diagnostics
Background:
- Lateral flow immunoassays (LFIAs) are widely used for point-of-care testing (POCT) due to their low cost and ease of use.
- Current LFIAs often lack quantitative capabilities and suffer from limited sensitivity (nanogram range) due to passive fluidics and non-specific binding.
- Nitrocellulose membranes in traditional LFIAs contribute to high background noise and reduced assay performance.
Purpose of the Study:
- To develop an enhanced LFIA platform with improved sensitivity and quantitative capabilities for antigen detection.
- To overcome the limitations of passive capillary fluidics and non-specific binding in conventional LFIAs.
- To establish a novel diagnostic system for ultra-sensitive detection of biomarkers, using SARS-CoV-2 spike antigen as a model.
Main Methods:
- A novel 'Beads-on-a-Tip' design was developed, replacing nitrocellulose membranes with magnetic beads in a pipette tip.
- Capture antibodies were conjugated to magnetic beads for sandwich immunoassay, enabling active washing and enrichment of low-abundant antigens.
- Upconversion nanoparticles (UCNPs) were utilized as luminescent reporters to enhance detection sensitivity.
Main Results:
- The Beads-on-a-Tip design achieved a significantly reduced limit of detection (LOD) of 706 fg/mL for SARS-CoV-2 spike antigen.
- The assay demonstrated a broad dynamic range spanning over 7 orders of magnitude (500 fg/mL to 10 μg/mL).
- Optimization of incubation time and UCNP-to-bead ratio was crucial for enhancing immunocomplex formation and signal-to-noise ratio.
Conclusions:
- The developed Beads-on-a-Tip LFIA system offers a substantial improvement in sensitivity and quantitative accuracy for POCT.
- This novel approach effectively mitigates non-specific binding and background noise, leading to superior assay performance.
- The system presents a promising solution for ultra-sensitive, quantitative diagnostics, particularly for low-abundant biomarkers.
