Real-Time Analysis of Lipid Droplet Morpho-Chemical Dynamics in Living Human Hepatocytes via Phase-Guided Raman Sampling.

Lipid droplets (LDs) are highly dynamic organelles, undertaking many important functions such as maintaining lipid metabolism and cellular homeostasis. Traditional methods to analyze LD dynamics focus on morphological changes, while chemical dynamics cannot be easily probed with traditional analytical chemistry techniques. To overcome this challenge, we show here how our phase-guided Raman sampling method, where high-resolution phase microscopy images direct a Raman sampling beam, can perform label-free, multimodal characterization of LD dynamics in living cells at both the single-cell and single-LD levels with submicron accuracy and high temporal resolution. We demonstrate the study of the morphological-compositional dynamics of human hepatocellular carcinoma cells (PLC cells) under different environmental conditions and with and without fatty acid supplementation, providing insight into LD heterogeneity and heterogeneity of response. Finally, we introduce a measurement method for the dynamics of cell-average LD composition, which can quickly and accurately characterize the lipid dynamics at the single-cell level with <30 s temporal resolution. The results here show the promise of the phase-guided Raman sampling method for dynamic morpho-chemical profiling of organelle populations.