A method for preparing monodisperse superparamagnetic carboxylated magnetic beads for immunoassay

The seed swelling/templating method remains a gold standard for producing monodisperse immunomagnetic beads, but it has several drawbacks. It cannot yield beads with high magnetic content, affecting their detection rates in immunodiagnostics. Conventional methods are inefficient and costly, often using nitro or amino groups for iron ion adsorption, which also raises safety and environmental concerns. Additionally, many commercially available beads have poor corrosion resistance, risking iron ion leakage during use. To address these issues, we improved the seed swelling method to achieve higher batch production and the following advantages: 1. The resulting immunomagnetic beads have uniform particle sizes and magnetic contents up to 40%; 2. Carboxylated porous microspheres were introduced for iron ion adsorption, improving experimental ease and environmental impact; 3. Enhancements in the encapsulation process significantly boosted corrosion resistance, allowing the beads to maintain stable magnetism for 16 h in a 5% EDTA solution.