Slipchenko Mikhail N, Le Thuc T, Chen Hongtao, Cheng Ji-Xin
Weldon School of Biomedical Engineering and Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA.
J Phys Chem B. 2009 May 28;113(21):7681-6. doi: 10.1021/jp902231y.
Cells store excess energy in the form of cytoplasmic lipid droplets. At present, it is unclear how different types of fatty acids contribute to the formation of lipid droplets. We describe a compound Raman microscope capable of both high-speed chemical imaging and quantitative spectral analysis on the same platform. We used a picosecond laser source to perform coherent Raman scattering imaging of a biological sample and confocal Raman spectral analysis at points of interest. The potential of the compound Raman microscope was evaluated on lipid bodies of cultured cells and live animals. Our data indicate that the in vivo fat contains much more unsaturated fatty acids (FAs) than the fat formed via de novo synthesis in 3T3-L1 cells. Furthermore, in vivo analysis of subcutaneous adipocytes and glands revealed a dramatic difference not only in the unsaturation level but also in the thermodynamic state of FAs inside their lipid bodies. Additionally, the compound Raman microscope allows tracking of the cellular uptake of a specific fatty acid and its abundance in nascent cytoplasmic lipid droplets. The high-speed vibrational imaging and spectral analysis capability renders compound Raman microscopy an indispensible analytical tool for the study of lipid-droplet biology.
细胞以细胞质脂滴的形式储存多余的能量。目前，尚不清楚不同类型的脂肪酸如何促进脂滴的形成。我们描述了一种能够在同一平台上进行高速化学成像和定量光谱分析的复合拉曼显微镜。我们使用皮秒激光源对生物样品进行相干拉曼散射成像，并在感兴趣的点进行共聚焦拉曼光谱分析。在培养细胞和活体动物的脂质体上评估了复合拉曼显微镜的潜力。我们的数据表明，体内脂肪比3T3-L1细胞中通过从头合成形成的脂肪含有更多的不饱和脂肪酸（FAs）。此外，对皮下脂肪细胞和腺体的体内分析表明，不仅在不饱和水平上，而且在其脂质体内脂肪酸的热力学状态上都存在显著差异。此外，复合拉曼显微镜允许追踪特定脂肪酸的细胞摄取及其在新生细胞质脂滴中的丰度。高速振动成像和光谱分析能力使复合拉曼显微镜成为研究脂滴生物学不可或缺的分析工具。
