Authors: L. De Silva, Q. Hu, Y. Wang, S.-J. Xu
Affilation: University of Houston, United States
Pages: 451 - 454
Keywords: force spectroscopy, atomic magnetometers, magnetic particles, molecular diagnositics
Molecular imaging usually employs a labeling technique, mainly optical labeling or magnetic labeling, to highlight target molecules. While optical labeling uses a wavelength parameter to achieve molecular specificity, there is no analogous parameter in magnetic labeling to achieve molecular specificity. To solve this problem, we develop a spectroscopic technique based on the binding force between the probe molecules labeled with magnetic nanoparticles and the receptor molecules. This force-induced remnant magnetization spectroscopy (FIRMS) measures the magnetization of the magnetic nanoparticles as a function of the binding force between the magnetically-labeled probe molecules and the target molecules. Atomic magnetometers are used for detection, which are the most sensitive sensors for measuring magnetic fields. We have investigated specific cell uptake of ligand-conjugated magnetic particles, in which the physisorbed particles and specifically bound particles are resolved without sample separation. In addition, the high force resolution of 1 pN allows us to distinguish different subclass antibodies and DNA duplexes with a single-basepair difference. Re-binding experiments are performed to confirm the specific molecular bonds, a unique advantage over single-molecule techniques such as optical tweezers and atomic force microscopy. We will discuss broad applications of this technique in molecular diagnostics.