Toward Raman Spectroscopy of
Inclusive Dates: 10/01/02 - 02/01/03
Background - Current cancer detection often relies upon anatomical imaging techniques such as conventional endoscopy, computer tomography, and ultrasound, followed by a histopathological examination of a biopsied specimen taken from the patient. These conventional methods of cancer diagnosis often occur years after the onset and early stages of the cancer and, therefore, delay early treatment. Recently, the molecular information associated with specific disease processes has been acknowledged by the medical field to potentially improve the sensitivity and specificity of early disease detection. Raman spectroscopy is one of the optical spectroscopic methods that has the potential to detect molecular changes of tissue and therefore to determine whether the tissue is normal, benign, or cancerous.
Approach - The Institute, collaborating with the Institute for Drug Development in San Antonio, compared the Raman spectra of jejunum tissue from a normal C57 black mouse and from a tumor Apcmin mouse. The Apcmin mouse is a common colon cancer model. The Holoprobe Raman Spectrometer (Kaiser Optical System Inc.) was used to acquire the Raman spectrum from the tissues. A near-infrared laser at 785 nm with the power of 85 mW was used as the excitation source. The Raman spectrum from 700 to 1,800 cm-1 was recorded from a sample with 15 seconds (three 5-second accumulations) exposure time. Twenty-five spectra were obtained from normal and abnormal tissues, respectively.
Accomplishments - The following figure illustrates the averaged Raman spectra of jejunum tissue from normal and Apcmin mice. Differences in Raman intensities were found at the following Raman peaks: 718, 757, 783, 854, 902, 938, 959, 1004, 1086, 1126, 1209, 1263, 1302, 1321, 1336, and 1657 cm-1. From an analysis of variance, the Raman intensity at 1657 cm-1 for the Apcmin mouse tissue was shown to be significantly lower (p < 0.01) than that of the normal tissue. The Raman peak at 1,657 cm-1 is often assigned to the carbon-carbon double bond (C=C) lipid stretching mode and the intensity often varies with the degree of fatty acid saturation. This suggests that Apcmin mouse tissue has a lower lipid content than normal tissue. Future research will be performed to extend this study to human colon tissues.