Effect of Controlled Humidity and Tissue Hydration on Colon Cancer Diagnostic via FTIR Spectroscopic Imaging

The effects of hydration on the DNA conformation in the colon biopsy tissues at different disease stages, hyperplasia, dysplasia, and cancer, and their subsequent classifications were investigated in this study. FTIR spectroscopic imaging was used to study the tissues while controlling the humidity from 16% RH to 88% RH using saturated salt solutions. A nonuniform uptake of water into the tissue at its maximum hydrated state was observed in the chemical images showing the distribution of the absorbance of the ν_as OH spectral band. The regions of high absorbance of this band in the tissues overlap with the regions of high absorbance of predominantly the phosphate (1143-1100 cm^-1) and lipid (2879-2844 cm^-1) bands. Analysis of the second derivative spectra of the hydrated and dehydrated colon tissues further revealed significant peak shifts and changes in absorbance of the spectral bands that correspond to the vibrations of the phosphate group of DNA. These findings showed some disparities when compared to the effect of hydration on the infrared spectra of live cells and pure isolated DNA, possibly due to the presence of DNA mostly in its A-form in the formalin fixed tissues. Coupled with principal component analysis, the spectral biomarkers that differentiate the healthy colon tissues from the diseased tissues were identified to be in the phosphodiester spectral region (1300-1000 cm^-1). This differentiation varied under different humidity conditions, with the highest sensitivity of ∼98% found at the dehydrated state of the tissues with random forest supervised classification.