Deciphering overlapping signals of phospholipids carbohydrates and nucleic acids in mid ir using colonic tissues as a model system

FTIR spectroscopy of cells and tissues has gained considerable importance in cancer diagnosis in the last few decades. Among the various components that are observed to contribute to the diagnostic capabilities of FTIR, the carbohydrates and nucleic acids are prominent. However there is a significant overlap of absorbance of nucleic acids, carbohydrates and phospholipids in the mid-IR region which pose a major obstacle in previous studies. In the present work, the colonic tissues are used as a model system to study the overlap of absorbance from these three groups of macromolecules. The results indicate that in case of tissues where there is a nuclear absorbance considered during diagnosis, the signals from nucleic acids especially DNA could be significant and relevant though interfered by absorbance due to carbohydrates and phosphates (phospholipids). This is especially true in case of formalin fixed colonic tissues which are routinely used in laboratory to diagnose malignancies. Among the diagnostic parameters that are affected by the absorbance from nucleic acids are the RNA/DNA ratio, the Amide I / Amide II ratio and the glucose /phosphate ratio which were reported to classify the normal and cancerous tissues with a high efficiency. The present work thus, underlines the specific contribution of the nucleus and in particular nucleic acids using colonic tissues which provide an ideal condition due to the unique anatomical structure of the colonic crypt.