In situ and ex situ surface‐enhanced Raman spectroscopy (SERS) analysis of cell mitochondria

As the "powerhouse" of cells, mitochondrion is the main site of cellular aerobic respiration and plays a vital role in performing many important cellular functions. The consequence of mitochondrial dysfunction could lead to a wide range of disorders and diseases. Traditional mitochondria-related cytobiology methods always require the isolation of organelles for biological components, followed by structural analysis and quantitative analysis. In this study, we tried to assess the feasibility and reliability of the isolation-based method and the in situ approach from the spectral fingerprint characters. Surface-enhanced Raman scattering spectroscopy (SERS) was employed to investigate the molecular information of mitochondria from cancer cells (HepG2 and MCF-7 cells) in situ with the assistant of mitochondrion-targeting nanoprobes, which was compared with the isolation-based ex situ method. The results display two methods, which show high consistency in the spectral profiles of mitochondrion, proving the feasibility of both in bioanalysis. Abundant molecular information such as protein and DNA is disclosed, and protein is one of the main components. From spectral comparison between two cancer cells, differences in protein content are observed. We believe that this comparative study will provide a valuable and recommended reference for the selection of analytical methods for different study purposes.