Speaker
Description
The proper function of cells is directly related to the subcellular compartmentalization and spatial distribution of a broad range of molecular species, from enzymes to metabolites and signaling molecules. Determining the spatial distribution of biomolecules within cells is therefore crucial for understanding fundamental cellular mechanisms; yet there is a lack of technologies capable of in vivo, label-free chemical mapping of subcellular structures with the necessary high sensitivity, chemical specificity, and spatial resolution.
Field-resolved spectroscopy (FRS) has shown unprecedented sensitivity and dynamic range [1] and is therefore capable of detecting chemical species within a wide range of concentrations. We envision that FRS combined with near-field microscopy provides a uniquely well-suited configuration for subcellular, label-free chemical imaging of living cells. Spatially resolving the near-field field-resolved light-matter interactions via electro-optic sampling, as demonstrated for the first time down to the near-infrared spectral range [2], can deliver sensitivity to low chemical concentrations and spatial resolution beyond the diffraction limit.
To understand the complex near-field interactions, contrast, and resolution, we perform finite-difference time-domain simulations using the open-source nonlinear optics simulation software Lightwave Explorer [3]. Here, we define the subcellular structure and organelle material properties of the green alga C. reinhardtii based on experimental data from scattering-type scanning near-field optical microscopy (sSNOM) [4]. Namely, the internal cell structure is defined according to atomic force microscopy images, and the index of refraction and extinction coefficients are derived from scattered near-field spectra, each recorded on a specific organelle.
This numerical study is crucial for guiding our current efforts in setting up a near-field FRS microscope and subsequent FRS data analysis and interpretation.
