A combinação entre FTIR e XRD como uma ferramenta para estudo de neoplasias mamárias caninas

Abstract

Dogs are the most abundant companion animals worldwide. Breast cancer is the most recurrent disease that affects these animals, and has a multifactorial origin, especially hormonal. Studies indicate that neoplastic tissues undergo structural and molecular changes that can be identified by analytical techniques. X-ray diffraction (XRD) identifies the molecular structural components of a sample. In addition, Fourier-transform Infrared Spectrophotometry (FTIR) identifies the vibration of molecules in a sample through infrared absorption. These two techniques complement each other, allowing the identification of molecular and supramolecular components in a given sample. XRD and FTIR were used to investigate the changes in tissue structure in different length scale associated with breast cancer in canine mammary tissues. A total of 83 samples were evaluated, being 58 neoplastic (malignant and non-malignant) and 25 normal or non-neoplastic, according to the histological classification by a veterinarian pathologist. X-ray scattering profiles were determined using the commercial diffractometer Shimadzu XRD-7000 with a copper anode at the momentum transfer range of 4.27 < q (nm-1) < 50.18. FTIR spectral profiles were acquired using a Varian spectrometer 640-IR with a Pike Miracle ATR (attenuated total reflection) and a ZnSe crystal. Absorption bands corresponding to lipids and fatty acids (adipose tissue) between 1750 and 3050 cm-1, collagen fibers (1180-1300 cm-1) and amides I and II (1500-1650 cm-1), which compose the fibroglandular tissue, were determined from the FTIR data. These results corroborate the findings in XRD, in which the peaks found (13.9 nm-1 and 20.1 nm-1) correspond to the fatty acids and water present in adipose and fibroglandular tissues, respectively. Therefore, the complementarity between XRD and FTIR is crucial to identify and characterize the morphological changes in canine mammary tissues structures related to the tumor growth in different length scale.