No abstract

Alzheimer’s disease (AD) is the most common cause of dementia, costing about 1% of the global economy. Failures of clinical trials targeting amyloid-β protein (Aβ), a key trigger of AD, have been explained by drug inefficiency regardless of the mechanisms of amyloid neurotoxicity, which are very difficult to address by available technologies. Here, we combine two imaging modalities that stand at opposite ends of the electromagnetic spectrum, and therefore, can be used as complementary tools to assess structural and chemical information directly in a single neuron. Combining label-free super-resolution microspectroscopy for sub-cellular imaging based on novel optical photothermal infrared (O-PTIR) and synchrotron-based X-ray fluorescence (S-XRF) nano-imaging techniques, we capture elemental distribution and fibrillary forms of amyloid-β proteins in the same neurons at an unprecedented resolution. Our results reveal that in primary AD-like neurons, iron clusters co-localize with elevated amyloid β-sheet structures and oxidized lipids. Overall, our O-PTIR/S-XRF results motivate using high-resolution multimodal microspectroscopic approaches to understand the role of molecular structures and trace elements within a single neuronal cell.

No abstract

Planar photonic waveguides enable ultrathin sample illumination in fluorescence microscopy over exceedingly large fields of view. Their fabrication has been based on hard coatings requiring sputter deposition and ion-beam lithography, making volume production cumbersome and thereby limiting their availability. Additionally, they are typically fabricated on top of opaque silicon wafers, which restricts the use to upright microscopes. Here, we present a low-cost photonic waveguide chip based on standard 170 μm thick glass coverslips coated with a micrometer-thin layer of EpoCore, a photoresist polymer with a high refractive index. These chips enable wide-field excitation for fluorescence microscopy and nanoscopy on inverted microscopes using fluorescence detection through the transparent substrate. Channel waveguides with varying widths provide uniform near-field illumination by evanescent waves for fields of view up to the millimeter scale. We demonstrate multicolor fluorescence excitation resulting in high-contrast immunofluorescence and super-resolution imaging with a resolution of approximately 60 nm.