Fourier Transform Infrared spectroscopy discloses different types of cell death in flow cytometrically sorted cells

Abstract

Fourier Transform Infrared (FTIR) spectroscopy is a label free methodology showing promise in characterizing different types of cell death. Cervical adenocarcinoma (HeLa) and African monkey kidney (Vero) cells were treated with a necrosis inducer (methanol), novel apoptotic inducers (diphenylphosphino gold (I) complexes) and positive control, auranofin. Following treatment, cells stained with annexin-V and propidium iodide were sorted using a Fluorescence Activated Cell Sorter (FACS Aria) to obtain populations consisting of either viable, necrotic or apoptotic cells. Transmission Electron Microscopy confirmed successful sorting of all three populations. Four bands were identified which could discriminate between viable and necrotic cells namely 989cm−1, 2852cm−1, 2875cm−1 and 2923cm−1. In HeLa cells viable and induced apoptosis could be distinguished by 1294cm−1, while four bands were different in Vero cells namely; 1626cm−1, 1741cm−1, 2852cm−1 2923cm−1. Principal Component Analysis showed separation between the different types of cell death and the loadings plots indicated an increase in an additional band at 1623cm−1 in dead cells. FTIR spectroscopy can be developed into an invaluable tool for the assessment of specific types of chemically induced cell death with notably different molecular signatures depending on whether the cells are cancerous and mechanism of cell death.