Raman spectroscopic characterization of urine of normal and oral cancer subjects Brindha Elumalai, a Aruna Prakasarao, a * Bharanidharan Ganesan, a Koteeswaran Dornadula b and Singaravelu Ganesan a Urine is considered as one of the diagnostically important bio fluids, as it has many metabolites. The distribution and the physiochemical properties of the metabolites may vary during any altered metabolic and pathological conditions. Raman spectroscopy was employed in the characterization of the metabolites of human urine of normal subjects and oral cancer patients in the finger print region (500–1800 cm À1 ). Principal component analysis-based linear discriminant analysis was performed to discriminate cancer patients from normal subjects. The discriminant analysis classifies the cancer patients from normal subjects with a sensitivity and specificity of 98.6% and 87.1%, respectively, with an overall accuracy of 93.7%. Copyright © 2014 John Wiley & Sons, Ltd. Additional supporting information may be found in the online version of this article at the publisher’s website Keywords: Raman spectroscopy; urine; oral cancer; pteridines; flavins; indoxyl sulfate Introduction Cancer becomes a major health problem in India next to car- diovascular diseases. It has been estimated that about 800 000 new cancer cases arise in India every year. [1] Data reported that mortality rate from various types of cancers viz. lungs, mouth, throat, esophagus, stomach, large intestine, and breast owing to the use of tobacco products, various dietary habits, and exposure to the environmental tobacco smoke – will con- tinue to increase significantly in the forthcoming years. [1–3] In this perspective, oral cancer is considered to be one of the prominent malignancies in India, due to the intake of tobacco in various forms. Oral cavity examination using conventional white light, followed by histopathological examination of the biopsy specimen is the golden standard for oral cancer diag- nosis. However, the few pitfalls of the conventional tech- niques adopted for the diagnosis of cancer are subjective, false negative results, time consuming, and painful to the pa- tients. Further, it may not be possible to predict the different grades of dysplasia and the exact treatment outcome of the premalignant conditions using aforementioned methods. [4–7] It is a well-known fact that early-stage disease diagnosis may lead to better treatment prognosis, which may increase the 5-year survival rate up to 90%. [6] Because the patients may not have any symptoms at the early stages of cancer, it may not be possible to detect the disease by conventional diagnostic procedures. Therefore, there is a need for the new diagnostic technique, which provides real-time, effec- tive, and non-invasive diagnosis of suspicious lesions and to treat at the early stage to reduce patient’s morbidity and mortality rate. During the progression of carcinogenesis, structural and bio- chemical variations takes place in cells and tissues with varying physico-chemical properties and such alterations may be considered to discriminate cancerous from normal conditions. In this regard, optical methods such as fluorescence spectros- copy (FS), Raman spectroscopy (RS), and infrared spectroscopy (IR) have been explored to probe and understand the changes that takes place at molecular level during the transformation of normal cells into neoplasm. [5–20] Many reported on the use of FS in the characterization of tissue and body fluids for disease diagnosis. [9,18–20] Alfano et al. had successfully demonstrated the ability of FS in discriminating the cancerous breast tissues from normal subjects. [18] Subsequently, Liu et al. reported on the combination of Raman, fluorescence and time-resolved light scattering techniques to separate the diseased tissues from nor- mal gynecological tissues. [10] Although FS has several advantages for disease diagnosis, some of the known hindrances associated with this technique are limited spectral information, longer time lag due to the use of multiple excitation wavelengths to probe various endogenous fluorophores present in tissue and biofluids. [6] In this context, RS has been emerged as more vibrant tech- nique, as it provides unique spectral signature, non-invasive diagnosis, minimal or no sample preparation is required and the spectra can be acquired within shorter time duration. Since RS provides both spatial and structurally sensitive infor- mation from various pathological conditions of cells and tissues, and the spectrum obtained elucidates the different * Correspondence to: Aruna Prakasarao, Department of Medical Physics, Anna University, Chennai, India. E-mail: aruna@annauniv.edu a Department of Medical Physics, Anna University, Chennai, India b Department of Oral Medicine and Radiology, Meenakshi Ammal Dental College and Hospital, Chennai, India J. Raman Spectrosc. (2014) Copyright © 2014 John Wiley & Sons, Ltd. Research article Received: 26 April 2014 Revised: 24 August 2014 Accepted: 12 September 2014 Published online in Wiley Online Library (wileyonlinelibrary.com) DOI 10.1002/jrs.4601