Institute of Nuclear Physics Polish Academy of Sciences, PL-31342 Krakow, Poland.
Nanotechnology. 2019 Oct 18;30(42):425502. doi: 10.1088/1361-6528/ab31dd. Epub 2019 Jul 13.
The recent development of the AFM-IR technique, which combines nanoscale imaging with chemical contrast through infrared spectroscopy, opened up new fields for exploration, which were out of reach for other modalities, e.g. Raman spectroscopy. Lipid droplets (LDs) are key organelles, which are associated with stress response mechanisms in cells and their size falls into that niche. LDs composition is heterogeneous and varies depending on cancer cell type and the tumor microenvironment. Prostate cancer cells show a unique lipid metabolism manifested by an increased requirement for lipid accumulation in cytosolic LDs. In the current work, AFM-IR nanoimaging was undertaken to analyze lipids in untreated and x-ray irradiated PC-3 prostate cancer cells. Cells poor in LDs showed slightly increased lipid signal in cytoplasm close to the nucleus. On the other hand, high lipid signal coming from LDs accumulation could be found in any part of the cytoplasmic region. The observed behavior was found to be independent from irradiation and its dose. According to the band assignment of the collected AFM-IR spectra, the main components of LDs were assigned to cholesteryl esters. The size of LDs present in cells poor in lipids was found to be of less than 1 μm, whereas LDs aggregates spread out over a few microns. Analysis of AFM-IR spectra shows relative homogeneity of LDs composition in single cells and heterogeneity of LDs content within the PC-3 cell population.
AFM-IR 技术的最新发展将纳米成像与红外光谱的化学对比相结合，为探索开辟了新的领域，这是其他模式（如拉曼光谱）无法企及的。脂滴（LDs）是关键的细胞器，与细胞的应激反应机制有关，其大小也处于这一范围。LDs 的组成是不均匀的，并且根据癌细胞类型和肿瘤微环境而变化。前列腺癌细胞表现出独特的脂质代谢，表现为细胞质中 LD 的脂质积累需求增加。在目前的工作中，进行了 AFM-IR 纳米成像以分析未经处理和 X 射线照射的 PC-3 前列腺癌细胞中的脂质。LDs 含量低的细胞在靠近细胞核的细胞质中显示出略有增加的脂质信号。另一方面，在细胞质区域的任何部分都可以发现来自 LD 积累的高脂质信号。观察到的行为与照射及其剂量无关。根据收集的 AFM-IR 光谱的带分配，LDs 的主要成分被分配为胆固醇酯。发现脂质含量低的细胞中存在的 LD 的大小小于 1μm，而散布在几个微米上的 LD 聚集体。AFM-IR 光谱分析表明，单个细胞中 LD 组成相对均匀，而 PC-3 细胞群中 LD 含量存在异质性。
