Title : Ultra-sensitive Detection of Superparamagnetic Nanoparticles

Speaker: Prof. Gunjan Agarwal, Ohio State University

Abstract: Superparamagnetic nanoparticles (SPIONs) are used in a multitude of biological applications such as: labeling of biomolecules and cells, cell tracking and sorting, and targeted drug delivery. In addition, nanoscale iron-deposits found in-vivo are superparamagnetic in nature. Currently existing biosensing modalities used for detection of SPIONs in-vivo or in-vitro can provide information only on an ensemble average of particles. Factors like spatial location, magnetic anisotropy and aggregation of SPIONs can complicate the ensemble average signal and thus confound their analysis. High sensitivity techniques to detect SPIONs at the single-particle level and spatially localize them in biological samples are not well-developed. We demonstrate how magnetic force microscopy (MFM) an atomic force microscopy (AFM) the based technique can be used to map SPIONs at the single particle level and ascertain their magnetic moment, aggregation state and magnetic anisotropy. We further present a novel indirect MFM technique, which preserves the high spatial resolution and sensitivity of the conventional or direct MFM but enables high-throughput detection of magnetic domains. In indirect MFM an ultrathin membrane separates the sample and the MFM probe, thus minimizing the effect of sample topography in MFM imaging. Samples prepared for indirect MFM are compatible with multimodal imaging using light and electron microscopy. We discuss the potential of direct and indirect MFM in analyzing SPION content in-vitro and in biology.