Correlative optical photothermal infrared and X-ray fluorescence for chemical imaging of trace elements and relevant molecular structures directly in neurons

Alzheimer’s disease (AD) is the most common cause of dementia, costing about 1% of the global economy. Failures ofclinical trials targeting amyloid-βprotein (Aβ), a key trigger of AD, have been explained by drug inefficiency regardlessof the mechanisms of amyloid neurotoxicity, which are very difficult to address by available technologies. Here, wecombine two imaging modalities that stand at opposite ends of the electromagnetic spectrum, and therefore, can beused as complementary tools to assess structural and chemical information directly in a single neuron. Combininglabel-free super-resolution microspectroscopy for sub-cellular imaging based on novel optical photothermal infrared(O-PTIR) and synchrotron-based X-rayfluorescence (S-XRF) nano-imaging techniques, we capture elementaldistribution andfibrillary forms of amyloid-βproteins in the same neurons at an unprecedented resolution. Our resultsreveal that in primary AD-like neurons, iron clusters co-localize with elevated amyloidβ-sheet structures and oxidizedlipids. Overall, our O-PTIR/S-XRF results motivate using high-resolution multimodal microspectroscopic approaches tounderstand the role of molecular structures and trace elements within a single neuronal cell.