Magnetophoretic Refinement and Microdroplet Confinement for Magnetic Relaxation Biosensing
Jiaqing Duan1, Kaiyuan Jia1, Gaofei Lei1
1National Innovation Center for Digital Agricultural Products Circulation, Ministry of Agriculture and Rural Affairs, China Agricultural University, Beijing 100083, China.
Analytical Chemistry
|April 8, 2026
Summary
This study introduces microdroplet-confined magnetic relaxation biosensing (mc-MRB) to overcome noise limitations. The new method enhances signal stability and sensitivity for detecting Salmonella in food samples.
Area of Science:
- Biomedical Engineering
- Analytical Chemistry
- Microfluidics
Background:
- Magnetic relaxation biosensing (MRB) faces challenges from magnetic bead variations and diffusion in bulk solutions.
- These factors cause relaxation noise, limiting sensitivity and signal stability in current MRB techniques.
Purpose of the Study:
- To develop a microdroplet-confined magnetic relaxation biosensing (mc-MRB) strategy.
- To enhance signal stability and measurement sensitivity by controlling magnetic perturbers and their microenvironment.
Main Methods:
- Utilized a magnetophoretic-inertial microfluidic module for bead homogenization.
- Employed picoliter droplet confinement to restrict proton diffusion and stabilize magnetic fields.
- Applied low-field Nuclear Magnetic Resonance (NMR) for detection.
Main Results:
- Achieved quantitative detection of Salmonella from 5.2 × 10^1 to 5.2 × 10^5 CFU/mL.
- Established a limit of detection of 28 CFU/mL for Salmonella.
- Demonstrated robust specificity and performance in complex food matrices.
Conclusions:
- Microdroplet confinement significantly improves signal stability and sensitivity in MRB.
- Microenvironment engineering is a viable physical strategy for stabilizing magnetic relaxation signals.
- The mc-MRB system offers a sensitive and specific method for pathogen detection in food.
