# Raman Spectroscopy–Based Quantitative Analysis of Fatty Acid Compositions of Lipid Droplets in Live Cells

## TL;DR

This paper introduces a new method using Raman spectroscopy to analyze fatty acid compositions in live cells without destroying them.

## Contribution

A novel technique using simulated calibration data with Raman spectroscopy for nondestructive fatty acid analysis in live cells.

## Key findings

- PLSR models with simulated calibration data provided accurate predictions of fatty acyl group compositions.
- The method was successfully applied to estimate fatty acyl groups in live adipocytes.
- The technique offers a nondestructive alternative to traditional methods like gas chromatography.

## Abstract

The quantitative analysis of fatty acids (FAs) and their
acyl group
compositions in triacylglycerols (TAGs) has become one of the main
areas of interest for understanding the metabolism and function of
fats in the body. Although Raman spectroscopy and chemometric-based
analytical methods have previously been applied for directly and nondestructively
analyzing fats, fat samples are difficult to quantitatively analyze
because an appropriate analytical model must be constructed based
on a known calibration data set before applying the model to unknown
samples. Therefore, we developed a technique to construct calibration
models for fatty acyl groups using simulated TAG spectra generated
from fatty acid methyl esters (FAMEs) spectra. Because of the vast
diversity of TAGs and high prices of commercial pure reagents, the
preparation of accurate concentrations of TAGs for training models
would be very difficult and costly. Classical and nonnegative least-squares
regressions (CLSR and NNLSR, respectively), which do not require calibration
modeling, were compared with analyses using partial least-squares
regression (PLSR). A comparative analysis revealed that the combination
of PLSR modeling with simulated calibration data sets produced the
most accurate predictions. The PLSR models were evaluated using edible
oils and, compared to the results obtained using gas chromatography,
the models reasonably approximated the fatty acyl group compositions
in the fat samples. Then, the models were applied to estimate fatty
acyl group compositions in live, single adipocytes. Although the models’
accuracies were limited, they nondestructively estimated the fatty
acyl group compositions of LDs in live cells.