Nanoscale Magnetic Imaging of Ferritin Nanoclusters Using Nitrogen-Vacancy Magnetometry

Nitrogen-vacancy (NV) centers in diamond provide a powerful platform for nanoscale magnetic imaging under ambient conditions [1]. Here, we employ wide-field optically detected magnetic resonance (ODMR) microscopy to image stray magnetic fields generated by ferritin nanoclusters drop-casted on a diamond surface [2,3]. Ferritin, a natural iron-storage protein containing an ∼8 nm ferrihydrite-like core within a protein shell [4], forms nanoscale magnetic dipoles whose static fields are detected by near-surface NV centers. The magnetic field patterns produced by ferritin clusters are imaged as a function of applied magnetic field and correlated with scanning electron microscopy (SEM) to directly link magnetic contrast with cluster morphology. Distinct ODMR resonance shifts and linewidth broadening reveal spatial variations in local magnetic fields associated with ferritin aggregation. This work demonstrates NV-based magnetic imaging as a quantitative, label-free approach for probing nanoscale magnetic behavior in biomolecular systems. [1] R. Schirhagl et al., Annu. Rev. Phys. Chem. 65, 83 (2014). [2] Fescenko et al., Phys. Rev. Appl. 11, 034029 (2019). [3] S. Lamichhane et al., ACS Nano 17, 8694 (2023). [4] N. D. Chasteen and P. M. Harrison, J. Struct. Biol. 126, 182 (1999).