In Situ Magnetometry of Iron in Human Brain

Paramagnetic transition metals are crucial for cellular catalytic processes but can cause oxidative stress at high concentrations. Monitoring their concentrations and magnetic properties in cells is vital for medicine and biology. We present a novel multimodal method for in-cell magnetometry, enabling direct measurement of metal magnetic properties within individual cells in tissue at room temperature. The method combines superresolution MRI microscopy and cellular metal content quantification using synchrotron x-ray fluorescence. Iron susceptibility in human dopaminergic neurons was determined to be χρ 2.98±0.19×10−6m3/kg, revealing a low-affinity binding site in neuromelanin and suggesting its high neurotoxicity. This method links cellular iron concentration to MRI parameters measurable in vivo, enabling the detection of dopaminergic neuron density and iron load with clinical MRI. It holds promise for early Parkinson's disease diagnosis and advancing metal biology studies.