Mid-infrared Chemical Imaging of Intracellular Tau Fibrils using Fluorescence-guided Computational Photothermal Microscopy

TL;DR

This paper introduces a novel fluorescence-guided computational microscopy technique that enables 3D chemical imaging and spectroscopic analysis of intracellular tau fibrils, revealing their structure and relation to lipids in native cells.

Contribution

The development of FBS-IDT, a low-cost, label-free 3D imaging method combining mid-IR photothermal and fluorescence imaging for intracellular amyloid analysis.

Findings

Successful 3D visualization of tau fibril structures.

Correlation between lipid accumulation and tau aggregation.

Revealed protein secondary structure of tau fibrils.

Abstract

Amyloid proteins are associated with a broad spectrum of neurodegenerative diseases. However, it remains a grand challenge to extract molecular structure information from intracellular amyloid proteins in their native cellular environment. To address this challenge, we developed a computational chemical microscope integrating 3D mid-infrared photothermal imaging with fluorescence imaging, termed Fluorescence-guided Bond-Selective Intensity Diffraction Tomography (FBS-IDT). Based on a low-cost and simple optical design, FBS-IDT enables chemical-specific volumetric imaging and 3D site-specific mid-IR fingerprint spectroscopic analysis of tau fibrils, an important type of amyloid protein aggregates, in their intracellular environment. Label-free volumetric chemical imaging of human cells with/without seeded tau fibrils is demonstrated to show the potential correlation between lipid accumulation and tau aggregate formation. Depth-resolved mid-infrared fingerprint spectroscopy is performed to reveal the protein secondary structure of the intracellular tau fibrils. 3D visualization of the \b{eta}-sheet for tau fibril structure is achieved.