Real‐Time Detection of Single Magnetic Nanoparticle with Interferometric Scattering Microscopy

Magnetic nanoparticles (MNPs) have extensive applications in multimodal imaging, drug delivery, and cell therapy techniques due to the magnetic and chemical properties. However, existing magnetic particle imaging (MPI) can only detect the signal of hundreds of MNPs, making it difficult to track the dynamics of single MNP. Fluorescence labeling methods can achieve single-particle detection, but the restrictions, such as weak signal, photobleaching, and limited temporal resolution, may make them unsuitable for real-time tracking of MNPs. In this study, we propose an interferometric scattering (iSCAT) microscopy based method to track the motion of single MNP in pure water. In our method, we induce directional displacement of MNPs with applying a magnetic field gradient. Experimental results show that the motion of MNPs is consistently aligned with the magnetic field direction, validating the feasibility of the proposed method. The proposed method provides a promising approach to reveal the microscopic motion of MNPs.