Subcellular spectroscopic markers, topography and nanomechanics of human lung cancer and breast cancer cells examined by combined confocal Raman microspectroscopy and atomic force microscopy

The nanostructures and hydrophobic properties of cancer cell membranes are important for membrane fusion and cell adhesion. They are directly related to cancer cell biophysical properties, including aggressive growth and migration. Additionally, chemical component analysis of the cancer cell membrane could potentially be applied in clinical diagnosis of cancer by identification of specific biomarker receptors expressed on cancer cell surfaces. In the present work, a combined Raman microspectroscopy (RM) and atomic force microscopy (AFM) technique was applied to detect the difference in membrane chemical components and nanomechanics of three cancer cell lines: human lung adenocarcinoma epithelial cells (A549), and human breast cancer cells (MDA-MB-435 with and without BRMS1 metastasis suppressor). Raman spectral analysis indicated similar bands between the A549, 435 and 435/BRMS1 including ∼720 cm−1 (guanine band of DNA), 940 cm−1 (skeletal mode polysaccharide), 1006 cm−1 (symmetric ring breathing phenylalanine), and 1451 cm−1 (CH deformation). The membrane surface adhesion forces for these cancer cells were measured by AFM in culture medium: 0.478 ± 0.091 nN for A549 cells, 0.253 ± 0.070 nN for 435 cells, and 1.114 ± 0.281 nN for 435/BRMS1 cells, and the cell spring constant was measured at 2.62 ± 0.682 mN m−1 for A549 cells, 2.105 ± 0.691 mN m−1 for 435 cells, and 5.448 ± 1.081 mN m−1 for 435/BRMS1 cells.