The steady state native fluorescence emission and excitation spectra of human normal and cancerous oral tissues are studied in the visible region. The fluorescence excitation spectrum is recorded for 600 nm emission by scanning the excitation. The excitation spectrum of normal tissues has peaks at 406, 524 and 552 nm, whereas the cancerous tissues have peaks at 406, 513 and 552 nm respectively. The fluorescence emission spectra were also recorded at 405 and 560 nm excitations. The emission spectrum of cancerous tissues has two distinct peaks at 604 and 660 nm. It is also observed that there is a distinct difference between normal and cancerous tissues at 560 nm excitation. The ratio parameter R<SUB>1$ equals (I(subscript 406</SUB>/I<SUB>550</SUB>) is introduced from the excitation spectrum for 600 nm emission and two ratio parameters R<SUB>2</SUB> equals (I<SUB>470</SUB>/I<SUB>600</SUB>) and R<SUB>3</SUB> equals (I<SUB>470</SUB>/I<SUB>660</SUB>) are introduced for the emission spectrum at 405 nm excitation. Among the three ratio parameters the R<SUB>1</SUB> classifies the normal and cancerous tissues at a specificity and sensitivity of 83 percent and 93 percent respectively. A critical value of 1.8 is suggested for classifying the normal from cancerous tissues.
Native fluorescence spectroscopy of biomolecules has emerged as an intrinsic parameter in the characterization of the physiological state and the discrimination of pathological from normal conditions of cells and tissues. The key fluorescing biomolecules inc ells and tissues ar tryptophan, tyrosine, phenylalanine, collagen, elastin, NADH, flavin and porphyrin. Extensive studies were made on tissues of various origin to discriminate the malignancy from normal. The differences in the fluorescence emission spectra have been shown to separate benign and malignant tissues. In the present work, a pilot study was carried out on the characterization of blood plasma of both normal and cancerous subjects. The blood plasma was separated by centrifuging the blood and it was diluted in PBS by adjusting the O.D. to 0.5 at 280 nm. This diluted sample as excited in the UV region between 250-340 nm. Among the various excitation wavelengths, emission spectrum at 300 nm excitation has considerable difference between blood plasma of normal subjects and cancer patients. To quantify these differences and to verify if there is any diagnostic potential exists, the ratio of fluorescence intensities at 340 and 440 nm was calculated. It is found that the ratio value of normal blood plasma is less than 11 and for tumor, it is greater than 11. Besides, it is found that the ratio value of blood plasma from patients with cancer varies from 11 to 28, depending upon the stage of malignancy.