Indirect Magnetic Force Microscopy - A Multimodal Technique
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Date
2018-05
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The Ohio State University
Abstract
Magnetic micro- and nano-particles are widely used for labeling cells and tissues and for magneto-separation of biomolecules. Current approaches to detect these particles are limited to an ensemble of particles with poor spatial resolution at the single particle level. In this study we demonstrate how magnetism based microscopy can be utilized for detection of magnetic micro-particles in a label-free and multimodal manner. Earlier work from our laboratory had demonstrated how the atomic force microscopy (AFM) based technique, magnetic force microscopy (MFM), can map magnetic nano-particles and ferritin protein at nanoscale resolution. MFM has thus far been performed using direct MFM (D-MFM), where multiple passes of the probe over the sample are required to identify magnetic interactions between the sample and probe. The purpose of this study was to employ a novel indirect MFM (ID-MFM) technique that requires only one pass over the sample, reduces possible probe contamination, and enables multi-modal microscopy. In ID-MFM, an ultrathin silicon nitride window, commonly used for transmission electron microscopy (TEM) is utilized as a barrier between the sample and the probe. In this study ID-MFM was performed on commercially available paramagnetic and non-magnetic micro-particles. The paramagnetic micro-particles produced a distinct magnetic signature when imaged with the MFM probe as compared to an AFM probe. Non-magnetic particles produced no magnetic signature. All particles could be imaged with TEM and fluorescence microscopy as well, once mounted on the ID-MFM barrier, demonstrating the technique’s multimodal capabilities. ID-MFM thus holds the promise to serve as a high-throughput, ultrastructural, and multimodal technique for mapping micro- and nano-particles for a variety of applications.
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Keywords
magnetism, imaging, bioimaging, microscopy