Chem-SIM: Super-resolution Chemical Imaging via Photothermal Modulation of Structured-Illumination Fluorescence

TL;DR

Chem-SIM is a novel super-resolution chemical imaging technique combining structured illumination fluorescence with mid-infrared photothermal microscopy, enabling detailed chemical mapping of live cells and microorganisms.

Contribution

It introduces Chem-SIM, a new method that preserves vibrational fingerprints and achieves high-resolution, high-throughput chemical imaging in biological samples.

Findings

Distinguishes bacterial growth phases via chemical content mapping.

Reports deuterated fatty-acid incorporation in ovarian cancer cells.

Resolves lipid-droplet dynamics in live cells.

Abstract

Structured illumination microscopy (SIM) has attained high spatiotemporal delineation of subcellular architecture, yet offers limited insight into chemical composition. We develop Chem-SIM, a structured-illumination fluorescence detected mid-infrared photothermal microscopy, for super-resolved chemical imaging of microorganisms and mammalian cells. Poisson maximum-likelihood demodulation and spectral normalization across wavenumber recover the weak IR-induced fluorescence intensity change under low photon budgets and convert the fluorescence intensity modulation to chemical fingerprints. Photothermal gating further rejects water backgrounds in aqueous samples, while the IR pump maintains cellular activity at near-physiological temperature. Chem-SIM preserves full vibrational fingerprints, achieves SIM-grade lateral resolution in a high-throughput camera-based format. Here, we show that this platform distinguishes stationary- from log-phase bacteria through chemical content mapping, reports deuterated fatty-acid incorporation in ovarian cancer cells, and resolves lipid-droplet dynamics in live cells, establishing a high-throughput route to super-resolved imaging of organelle chemistry, metabolism, and dynamics.