Retrospective Study
Copyright ©The Author(s) 2017. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jan 14, 2017; 23(2): 286-296
Published online Jan 14, 2017. doi: 10.3748/wjg.v23.i2.286
Tracing overlapping biological signals in mid-infrared using colonic tissues as a model system
Ranjit Kumar Sahu, Ahmad Salman, Shaul Mordechai
Ranjit Kumar Sahu, Shaul Mordechai, Department of Physics, Ben Gurion University, Beer-Sheva 84105, Israel
Ranjit Kumar Sahu, Department of Medicine, University of Virginia, Charlottesville, VA 22901, United States
Ahmad Salman, Department of Physics, SCE-Shamoon College of Engineering, Beer-Sheva 84100, Israel
Author contributions: Sahu RK and Mordechai S designed the experiments; Sahu RK did the measurements and data collection; Salman A analyzed the data using advanced computational methods; and all authors contributed to drafting of the manuscript.
Institutional review board statement: The samples obtained were approved by the IRB of SUMC and BGU under the protocol approved for the project “Early detection of colon cancer and inflammatory bowel diseases using FTIR- microspectroscopy”; SUMC Helsinki Committee Approval No. 3827.
Informed consent statement: Approval from patients for obtaining the biopsies for research purposes was obtained as per the norms of the IRB and exist with the concerned authority.
Conflict-of-interest statement: The authors do not claim any conflict of interest.
Data sharing statement: The authors agree to share the data as per the international conventions on publication of scientific reports.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Shaul Mordechai, PhD, Professor, Head, Department of Physics, Ben Gurion University, Shderot Ben Gurion, Beer-Sheva 84105, Israel. shaulm@bgu.ac.il
Telephone: +972-8-6461749 Fax: +972-8-6472924
Received: August 28, 2016
Peer-review started: September 1, 2016
First decision: September 20, 2016
Revised: October 19, 2016
Accepted: November 16, 2016
Article in press: November 16, 2016
Published online: January 14, 2017
Processing time: 136 Days and 16.6 Hours
Abstract
AIM

To understand the interference of carbohydrates absorbance in nucleic acids signals during diagnosis of malignancy using Fourier transform infrared (FTIR) spectroscopy.

METHODS

We used formalin fixed paraffin embedded colonic tissues to obtain infrared (IR) spectra in the mid IR region using a bruker II IR microscope with a facility for varying the measurement area by varying the aperture available. Following this procedure we could measure different regions of the crypt circles containing different biochemicals. Crypts from 18 patients were measured. Circular crypts with a maximum diameter of 120 μm and a lumen of about 30 μm were selected for uniformity. The spectral data was analyzed using conventional and advanced computational methods.

RESULTS

Among the various components that are observed to contribute to the diagnostic capabilities of FTIR, the carbohydrates and nucleic acids are prominent. However there are intrinsic difficulties in the diagnostic capabilities due to the overlap of major absorbance bands of nucleic acids, carbohydrates and phospholipids in the mid-IR region. The result demonstrates colonic tissues as a biological system suitable for studying interference of carbohydrates and nucleic acids under ex vivo conditions. Among the diagnostic parameters that are affected by the absorbance from nucleic acids is the RNA/DNA ratio, dependent on absorbance at 1121 cm-1 and 1020 cm-1 that is used to classify the normal and cancerous tissues especially during FTIR based diagnosis of colonic malignancies. The signals of the nucleic acids and the ratio (RNA/DNA) are likely increased due to disappearance of interfering components like carbohydrates and phosphates along with an increase in amount of RNA.

CONCLUSION

The present work, proposes one mechanism for the observed changes in the nucleic acid absorbance in mid-IR during disease progression (carcinogenesis).

Keywords: Spectral interference; Fourier transform infrared diagnosis; Nucleic acids; Malignancy; Colonic tissue

Core tip: Techniques like infrared (IR) spectroscopy have been used in different research areas and their potential has been established in the field of biomedicine. However studies connecting the basic spectral data to histological features are very few. The connection between diagnosis of the disease pathology and spectral features often needs a correlation. This study address one such issue pertaining to the varying histology and the spectral signatures in mid IR region by trying to understand the contribution of one type of bio molecules in presence and absence of another using biopsies rather than synthetically created combinations.