Magnetic nanoparticles dynamics investigated via X-ray photon correlation spectroscopy

Purpose and goal:

NanoEcho, a pioneer in cancer diagnostics, uses MNPs for magnetomotive ultrasound imaging. This project aimed to better understand MNPs’ response to NanoEchos probe magnetic fields using operando mode. These results can certainly enhance the magnetomotive technique since the in-operando analysis provides insights into process parameters that could improve image contrast, boosting diagnostic tool efficacy and healthcare outcomes. These experiments were conducted at the ESRF - Grenoble using XPCS.

Expected results and effects:

The project aimed to perform XPCS measurements of how MNPs behave in a tissue-like test object (polyvinyl alcohol-gel matrix) under the influence of Nanoecho´s prototype probe. The experiment was successful, with autocorrelation functions matching the expected periodic behavior based on the impact of the prototype probe. Extracted parameters such as relaxation frequency provided clues about the motion of the nanoparticles and shed light onto anisotropic effects and variations of relaxation rate as function of process parameters.

Approach and implementation:

The beam line geometry was adapted for the prototype probe and used 3D printed sample holders. Each sample was placed in a 40 µm focused X-ray beam and the resulting speckle pattern was collected at 10 ms intervals. Radiation damage required frequent sample renewal to new positions.

Series of such patterns were collected for different samples (MNP types and concentrations) and parameters (probe magnetic field intensity and frequency). For each time series, speckle patterns were correlated to obtain the time-averaged temporal autocorrelation function of the scattered intensity.