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The fluorescence spectra of human cancerous and normal prostate tissues obtained by the selective excitation wavelength of 340 nm were measured. The contributions of principle biochemical components to tissue fluorescence spectra were investigated using the method of multivariate curve resolution with alternating least squares. The results show that there is a reduced contribution from the emission of collagen and increased contribution from nicotinamide adenine dinucleotide (NADH) in cancerous tissues as compared with normal tissue. This difference is attributed to the changes of relative contents of NADH and collagen during cancer development. This research may present a potential native biomarker for prostate cancer detection.

The angular and temporal distributions of light scattered around the backward direction from biological tissues are measured. An enhancement of scattered light intensity around the backward direction, which is associated with the weak photon localization, is observed. The transport mean free path l(t) and the absorption length l(a) of the light in biological tissue can be obtained from the angular line shape of the coherent peak. The values l(t) and l(a) can also be obtained from the temporal profile of the scattered pulse.

Steady-state spectra, time-resolved spectroscopic, and excitation spectra from human cancer and normal tissues have been measured. Spectroscopic differences between normal and cancerous tissues have been found that could be used as a basis for an instrument for the early detection of cancer.

The Cypate-Bombesin Peptide Analogue Conjugate (Cybesin) was used as a prostate tumor receptor-targeted contrast agent. The absorption and fluorescence spectra of Cybesin were measured and shown to exist in the NIR tissue "optical window". The spectral polarization imaging of Cybesin-stained prostate cancerous and normal tissues shows that prostate cancerous tissue takes-up more Cybesin than that of prostate normal tissue, making Cybesin a potential marker of prostate cancer.Keywords: Prostate cancer; Receptor-targeted; Peptide analogue conjugate; Contrast agent; Spectral polarization imaging; Near-infrared; Absorption; and Fluorescence. IntroductionThe increasing incidence and mortality rate of prostate cancers in men makes early tumor detection research a challenge for oncological specialists. The region of the highest incidence is in the western world, where there are 10-11% chances for a man to develop prostate cancer, and 3-4% chances of dying from the disease (1). Conventional oncology imaging methods for prostate cancer diagnosis, still depend on bulk physical properties of cancer tissue and are not effective for earlystage primary tumors (2). It is well known that diagnosis of a small premalignant lesion is critical for the success of cancer therapy and a key to increase survival rates. Scientists have been looking for methods that emphasize gene-specific or receptor-specific, minimally invasive diagnosis for early-stage tumors (2).Near-infrared (NIR) optical imaging is a powerful tool in cancer research that relies on activating endogenous chromophores or applying contrast agents that can target cancer cells. The use of intrinsic chromophores to differentiate the optical properties of diseased and healthy human tissues has been reported in some studies using fluorescence and absorption (3, 4). The most attractive advantage of optical imaging is the high sensitivity, which can be superior to other in vivo imaging techniques (2). Over the past decade, cyanine dyes have been investigated by several groups (5, 6) as contrast agents for optical detection of tumors. In order to observe fluorescence from a substantial distance within the body, the emission wavelength must be in the NIR wavelength window in which light passing through tissue is less likely to be absorbed or scattered (7). Researchers are interested in cyanine dyes because their emission range of 700 nm to 900 nm is in the tissue "optical window" (8 absorption bands at 950nm and 1195nm due to water which is the main chromophore component in human tissue (4, 9).The investigations of receptor expression in normal and cancer tissue suggest that small peptide-dye conjugates can be used to target over-expressed receptors on tumors contrary to the traditional approach of dyes conjugated to large proteins and antibodies (5, 10, 11). As a small ICG-derivative dyepeptide, Cypate-Bombesin Peptide Analogue Conjugate (Cybesin) was synthesized and used as a contrast agent to detect pancreas tumors in an animal model a few years ago (5). The prior experimenta...

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