W. B. Wang

Near infrared spectroscopy and imaging to probe differences in water content in normal and cancer human prostate tissues.

The content of water in cancerous and normal human prostate in vitro tissues was shown to be different using near infrared (NIR) spectroscopy. The water absorption peaks at 1444 nm and 1944 nm are observed in both types of prostate tissues. The measurements show that less water is contained in cancerous tissues than in normal tissues. The OH stretching vibrational overtone mode at 1444 nm and other water overtone modes provide key spectroscopic fingerprints to detect cancer in prostate tissue. Transmission and backscattered spectral imaging were measured in cancer and normal prostate tissues. The degree of polarization for 700nm, 800nm, 1200nm, and 1450nm is larger for normal than for cancer tissues. The knowledge about water content offers a potential as a diagnostic tool to better determine and image cancer in prostate and in other tissues types such as breast and cervix using the absorption from vibrational overtones of H2O molecules in the NIR.

Backilluminated GaN/AlGaN heterojunction ultraviolet photodetector with high internal gain

We report on a backilluminated GaN/Al0.18Ga0.82N heterojunction ultraviolet (UV) photodetector with high internal gain based on metal-semiconductor-metal structures. A narrow band pass spectral response between 365 and 343 nm was achieved. When operating in dc mode, the responsivity reaches up to the order of 102 A/W under weak UV illumination, which is due to enormous internal gain up to 103. The linear dependence of photocurrent on bias and its square root dependence on optical power are found and explained by a trapping and recombination model. The high photocurrent gain is attributed to trapping and recombination centers with an acceptor character induced by dislocations in GaN.

Spectral polarization imaging of human prostate cancer tissue using a near-infrared receptor-targeted contrast agent.

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.

Changes of collagen and nicotinamide adenine dinucleotide in human cancerous and normal prostate tissues studied using native fluorescence spectroscopy with selective excitation wavelength

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.

Native fluorescence spectra of human cancerous and normal breast tissues analyzed with non-negative constraint methods

The native fluorescence spectra of human cancerous and normal breast tissues were investigated using the selected excitation wavelength of 340 nm to excite key building block molecules, such as reduced nicotinamide adenine dinucleotide (NADH), collagen, and flavin. The measured emission spectra were analyzed using a non-negative constraint method, namely multivariate curve resolution with alternating least-squares (MCR-ALS). The results indicate that the biochemical changes of tissue can be exposed by native fluorescence spectra analysis. The MCR-ALS-extracted components corresponding to the key fluorophores in breast tissue, such as collagen, NADH, and flavin, show differences of relative contents of fluorophores in cancerous and normal breast tissues. This research demonstrates that the native fluorescence spectroscopy measurements are effective for detecting changes of fluorophores composition in tissues due to the development of cancer. Native fluorescence spectroscopy analyzed by MCR-ALS may have the potential to be a new armamentarium.

Native Fluorescence Spectroscopic Evaluation of Chemotherapeutic Effects on Malignant Cells using Nonnegative Matrix Factorization Analysis

The native fluorescence spectra of retinoic acid (RA)-treated and untreated human breast cancerous cells excited with the selective wavelengths of 300 nm and 340 nm were measured and analyzed using a blind source separation method namely Nonnegative Matrix Factorization (NMF). The results show that the fluorophores of human malignant breast cells change their compositions when they are treated with RA. The reduced contribution from tryptophan, NADH and flavin to the fluorescence of the treated breast cancerous cells was observed in comparison with that of the untreated cells. The results indicate that the decrease of adenosine triphosphate (ATP) in the RA-treated cells. The possible clinical applications of this native fluorescence study are discussed.

Stokes shift spectroscopic analysis of multifluorophores for human cancer detection in breast and prostate tissues

Abstract. Stokes shift spectroscopy (S3) offers a novel and simpler way to rapidly recognize spectral fingerprints of multiple fluorophores in complex media such as in tissue. This spectroscopic technique can be used as an effective approach to detect cancer in tissue. The alterations of the measured S3 spectra between cancerous and normal tissues were observed in human breast and prostate samples. In order to obtain the optimal Stokes shift interval, Δλi, for the purpose of breast/prostate cancer detection using S3, the S3 spectra of a mixed aqueous solution of tryptophan, nicotinamide adenine dinucleotide, and flavin were measured with different Δλi values. The experimental results analyzed using nonnegative least square method show that there is a reduced contribution from collagen and an increased contribution from tryptophan to the S3 signal of the cancerous tissue as compared with those of the normal tissue. This study indicates that the changes of relative contents of tryptophan and collagen in tissue shown by the S3 spectra may present potential native biomarkers for breast and prostate cancer detection. S3 has the potential to be a new armamentarium.

Investigation of photoluminescence and photocurrent in InGaAsP/InP strained multiple quantum well heterostructures

Multiple quantum well InGaAsP/InP p-i-n laser heterostructures with different barrier thicknesses have been investigated using photoluminescence (PL) and photocurrent (PC) measurements. The observed PL spectrum and peak positions are in good agreement with those obtained from transfer matrix calculations. Comparing the measured quantum well PC with calculated carrier escape rates, the photocurrent changes are found to be governed by the temperature dependence of the electron escape time.

Optical Detection of Meat Spoilage Using Fluorescence Spectroscopy with Selective Excitation Wavelength

The native fluorescence (FL) spectra of muscle foods (meat) stored at 4 °C (refrigerated) and 25 °C (at room temperature) were measured with the selected excitation wavelength of 340 nm as a function of storage time to detect the meat spoilage status. The contributions of the principal biochemical components to the FL spectra were extracted using Multivariate Curve Resolution with Alternating Least-Squares (MCR-ALS). The change of the reduced nicotinamide adenine dinucleotide (NADH) content was found from the measured FL spectra and the MCR-ALS analysis, which reflects the microbial spoilage of muscle foods involved in the metabolic processes. This study presents the possibility that the change of relative content of NADH determined by native FL spectroscopy may be used as a “fingerprint” or criterion for monitoring the spoilage status of muscle foods.

Near infrared photonic finger imager for prostate cancer screening.

A portable rectal near infrared (NIR) scanning polarization imaging unit with an optical fiber-based rectal probe, designated as a Photonic Finger (PF), was designed, developed, built and tested. PF was used to image and locate the three dimensional (3D) positions of abnormal prostate tissue embedded inside normal prostate tissue. An inverse image reconstruction algorithm, namely Optical Tomography using Independent Component Analysis (OPTICA) was developed to unmix the signal from targets (cancerous tissue) embedded in a turbid media (normal tissue) in the backscattering imaging geometry. The Photonic Finger combined with OPTICA was ex vivo tested to characterize different target(s) inside different tissue medium, including cancerous prostate tissue embedded inside large pieces of normal tissue. This new developed instrument, Photonic Finger, may provide an alternative imaging technique, which is accurate, of high spatial resolution and non-or-less invasive for prostate cancers screening.