Raman Spectroscopy of Circulating Single Red Blood Cells in Microvessels in vivo

Jingwei Shao, Huilu Yao, LingJing Meng, YongQing Li, ManMan Lin, Xue li, JunXian Liu, Jianpin Liang

Raman tweezers have been used to study single blood cells in vivo without requiring invasive procedures. In the present study, we use optical tweezers to capture single blood cells(RBCs) in the microvessel of a mouse ear. Without the use of any invasive procedures, we were able to obtain the Raman spectra of single red blood cells from a mouse ear. An analysis of these spectra indicated that RBCs in arterioles are oxygenated, while those in the capillaries of venules are deoxygenated, those in vitro are similar to that in venules. In addition, hemoglobin in vivo was observed to be more concentrated than that in vitro. By studying the change of the band at 1604 cm−1, we concluded that the pH in arterioles is higher than that in venules. The information gained from the single RBCs in vivo is important for the understanding of the reaction of RBCs to changes in their environment and may have many applications in the diagnosis and treatment of red blood cell disorders.

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Raman spectroscopic analysis of apoptosis of single human gastric cancer cells

Huilu Yao, Zhanhua Tao, Min Ai, Lixin Peng, Guiwen Wang, Bijuan He and Yong-qing Li

A drug (5-FU) was employed to treat the gastric carcinoma cells and induce apoptosis of the cancer cells. Raman spectra obtained from single gastric carcinoma cells and the induced apoptotic cells through scan-excitation mode were used to analyze the effectiveness of the treatment. The major difference of the apoptotic cells from the cancer cells are the reduction in intensities of vibration bands generated by cellular lipids, proteins and nucleic acids. In particular, large intensity reduction in nucleic vibrations at 782, 1092, 1320, 1340, and 1578 cm⁻¹ was observed upon apoptosis of the gastric carcinoma cells. Up to 45% reduction in the magnitude of the 782 cm⁻¹ peak in Raman spectra of the apoptotic cells was observed, which suggests the breakdown of phosphodiester bonds and DNA bases. We showed that the principal components analysis (PCA), a multivariate statistical tool, can be used to distinguish single apoptotic cells and gastric carcinoma cells based on their Raman spectra.

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