Magnetic nanoparticles coated with zwitterionic copolymer as an advanced material for rapid and instrument-free biomolecular detection in human serum

The traditional agglutination assays especially those based on polystyrene beads have been recognized as convenient tools for disease diagnosis despite their limited detection range and low sensitivity. Unlike other particles namely polystyrene beads, SiO2 and gold nanoparticles having insignificant magnetic properties, magnetic nanoparticles (MNPs) offer unique advantages as their magnetic properties for agglutination methods. In the presence of magnet, not only can they be used to enrich the samples, but also their aggregation can also be induced, providing sensitive and rapid measurements. This work aims to develop MNPs for aggregation-based biomolecular detection. The MNPs were surface-modified with PMAMPC via an in situ coating method, then biotin as the target-specific probe was immobilized. The biotin-conjugated PMAMPC-MNPs were used for capturing and detecting the complementary protein, streptavidin in human serum samples. With the magnetic-induction, the nanoparticles would aggregate in the presence of streptavidin, resulting in a short detection time even in undiluted human serum. The concentration range for the detection was 35 nM to 150 nM and the lowest concentration of detection was 35 nM or equivalent to 2.5 mg⸳mL-1. The fact that this is simple, rapid and instrument-free method for biomolecular detection broadens their potential use in a variety of diagnostic applications.