A tunable high-gradient magnetic separation system based on an ordered wire-array column

Area of Science:

• Biomagnetic separation
• Microfluidics
• Analytical chemistry

Background:

• Upstream sample preparation challenges sensitivity and reproducibility in bioanalysis, especially for rare or weakly magnetic targets.
• Existing magnetic separation methods often lack tunability and quantitative interpretation.

Purpose of the Study:

• To present a tunable high-gradient magnetic separation (HGMS) system using an ordered iron-nickel (Fe-Ni) wire-array column.
• To demonstrate the system's ability to generate stable, quantifiable local high-gradient magnetic fields.
• To systematically regulate and interpret separation conditions using the Mason number (Mn).

Main Methods:

• Utilized an ordered Fe-Ni wire-array column to create tunable high-gradient magnetic regions.
• Independently adjusted magnetic flux density (B) and volumetric flow rate (Q).
• Employed magnetically homogeneous methemoglobin-red blood cells (metHb-RBCs) and heterogeneous superparamagnetic iron oxide nanoparticle (SPION)-labeled RAW264.7 macrophages as model systems.

Main Results:

• Demonstrated tunable capture and enrichment of magnetic targets under varying magnetic field and flow rate conditions.
• Validated the use of the Mason number (Mn) as a force-flow descriptor for homogeneous magnetic cells (metHb-RBCs).
• Showed preferential enrichment of higher-moment cells and consistent enrichment trends for heterogeneous magnetic cells (SPION-labeled macrophages) under matched apparent Mn conditions.

Conclusions:

• The ordered wire-array column provides a geometry-defined and quantitatively interpretable HGMS microenvironment for magnetic cell enrichment.
• The tunable system enhances sensitivity and reproducibility in bioanalysis sample preparation.
• The platform offers potential for future studies on diverse magnetic targets.