Label-Free Monitoring 5-FU Induced SW 620 Cells Apoptosis Using FTIR Microspectroscopy

The aim of the present study was to evaluate Fourier transform infrared spectroscopy (FTIR) monitoring of biochemical changes in apoptosis cells. Different concentrations of 5-fluorouracil (5-FU) treated colon cancer cell lines SW620 were used to determine the optimum concentration of 5-FU IC50 by means of MTT assay. Cell starvation and 5-Fu synergistic cell cycle arrest was in G1 and S phase. FTIR combined with flow cytometry was applied to analysis of SW 620 cells and SW620 cells treated with 5-FU for 12h, 24h (early apoptosis) and 48 h (late apoptosis) respectively. The peak position and the intensity of all bands were measured and comparison was made between the 5W620 and apoptotic SW620 cells. Apoptosis cells have following characteristics compared with SW620 cells (1) The band at 1 740 cm(-1) is an C=O stretching vibration. Changes in these bands can reflect lipid changes, and relative peak intensity ratio I-1740/I-1 (460) significantly increased (p<0. 05), indicating that the relative contents of lipid in apoptosis cells increased. (2) The band at the 1 410 cm(-1) peak represents that C-H stretching related was increased to amino acid residues and shifted to higher wave numbers compared to other groups. I-1 410/I-1 (460) at early and late death phase was significantly increased, which suggests that the relative contents of amino acid residues in apoptosis cells increased (p < 0. 05). New vibrational bands at 1 120 cm(-1) appeared at 24 h and increased at 48 h compared with other groups. The 1 120 cm(-1) absorption band is mainly due to ser, serine and threonine C-O(H) stretching vibration, and I-1 120/I-1 460 significantly increased (p<0. 05), indicating that the relative quantity of amino acid residues in apoptosis cells increased due to that DNA unwinds the double helix. (3) 1 240 cm(-1) is mainly due to the asymmetric stretching modes of phosphodiester groups shifting to higher wave number, illustrating that nucleic acid conformation was changed in apoptosis cells. (4) The band 1 040 cm(-1) associated with polysaccharide appeared at 24 and 48 h, meanwhile shifted to higher wave number, suggesting that polysaccharide decreased in late apoptotic cells, and I-1 040/I-1 460 increased at late stage apoptosis, indicating that the relative content of polysaccharide in apoptosis cells increased. The authors' results suggest that FTIR applied to monitoring 5W620 cells apoptosis may be as a potential diagnostic tool for cancer chemotherapy monitoring.