Magnetic resonance imaging of isolated single liposome by magnetic resonance force microscopy

Magnetic resonance imaging (MRI) is very useful spectroscopy to visualize a three-dimensional (3D) real structure inside the sample without physical destruction. The spatial resolution of the readily available MRI spectrometer is, however, limited by a few ten to hundreds of microns due to a technological boundary of generating larger magnetic field gradient and to the insensitivity inherent to the inductive signal detection. Magnetic resonance force microscopy (MRFM) is new alternative MRI spectroscopy which is anticipated to significantly surpass the conventional MRI in both resolution and sensitivity. We report two imaging experiments on our MRFM spectrometer operated at room temperature and in vacuum similar to10(-3) pa. One is for similar to20 mum liposome membrane labeled entirely by a nitroxide imaging agent and the other for similar to15 mum DPPH particles, both are nearly the same size as that of human cell. The reconstructed images at spatial resolution similar to1 mum were in satisfactory agreement with the scanning electron microscope images. The potential capability of visualizing intrinsic radicals in the cell is suggested to investigate redox process from a microscopic point of view. (C) 2004 Elsevier Inc. All rights reserved.