Simplified Fabrication of Magnetic Nanoparticles With Directly Adsorbed Antibodies for Bacteria Detection

Antigen-antibody reactions with conjugated magnetic nanoparticles (MNPs) are widely used for detecting viruses, bacteria, and proteins. In this study, we proposed a novel method for adsorbing antibodies directly on the surface of MNPs without coating any proteins. MNPs (Fe 3 O 4 ; average size 4 nm) were synthesized by a thermal decomposition method using oleyl amine as a surfactant, the fabricated MNPs exhibit superparamagnetic characteristics, and the antibodies (anti- Bifidobacterium longum ) were adsorbed. We found that 15 \mu \text{g} /mg of antibody adsorbed to MNPs and were able to detect the bacteria bound to the produced antibody-MNPs based on the antigen-antibody reaction, offering potential for highly sensitive bacteria detection.