Magnetic properties and electron oxidation state transition of immunomagnetic nanoparticles specifically captured with the target bacteria

Abstract

Immunomagnetic nanoparticles (IMNPs) have been widely applied for the capture and concentration in the rapid detection of target bacteria. In this research, the focus was on studying the changes in magnetic properties changes of the IMNPs when they were attached to bacterial cells. These alterations in properties could facilitate an even rapid detection of the target bacteria and eliminate the need for culturing on plating media. The variation of magnetizing values, including saturated magnetization (Ms), remanent magnetization (Mr), coercivity force (Hc), and magnetic susceptibility (χm), was analysed through M-H loops. It was observed that the magnetizing properties of the IMNPs underwent changes based on the concentrations of Salmonella Typhimurium cells in the test solution. The correlation of this phenomenon was confirmed by the results of synchrotron x-ray absorption spectroscopy (XAS), which revealed electronic transition changes in the IMNPs after capturing the bacteria cells. Additionally, the electronic bands of the magnetite nanoparticle [Fe(II) and Fe(III)] were detected, indicating an electronic transformation between the Salmonella cells and the bound IMNPs. The XAS change was further verified using different cell types, such as Campylobacter jejuni which also showed electronic transformation after attaching to IMNPs. These findings suggest that IMNP-cell attachment triggered the change in the magnetic properties of IMNPs. Such insights could serve as valuable information for the development of novel rapid bacteria detection assays/devices using magnetic sensing techniques.