Raman and Laser Induced Fluorescence (LIF) spectroscopic techniques were used for studying Azotobacter vinelandii- a genus of free-living diazotrophic soil bacteria. Azotobacter has generated a great deal of interest owing to their unique mode of metabolism. It is a large, obligately aerobic soil bacterium, which has one of the highest respiratory rates known among living organisms and is able to grow on a wide variety of carbohydrates, alcohols and organic acids. The Raman Scattering of Azotobacter, incubated with gold nanoparticles, was examined with 532-nm as an excitation laser wavelength. The basic instrumentation for characterizing the bacteria by Raman spectroscopy employed a continuous wave (CW) frequency doubled Nd: YAG laser (532-nm) and a modified In-Photonics fiber optic state-of-art miniaturized Raman Probe. The surface enhancement effects allowed the observation of Raman spectra of such bacterial cells, and were excited in the visible region of wavelength at low incident power for minimum sample degradation. LIF spectra of Azotobacter were measured with a 410-nm CW diode laser as an excitation source, and a reflection probe to deliver laser beam on the sample and collect the LIF signal from the sample. Spectral contrast observed in gold particles conjugated bacteria, from nitrogen fixing and non-nitrogen fixing condition was analyzed for characterizing the bacteria cells, and the results are presented in the paper.
An optical fiber sensor is being developed for diagnosis of human breast cancer cell lines. The sensor exploits laser-induced fluorescence spectroscopy in conjugation with fiber optics. The main advantage of fluorescence detection compared to absorption measurements is the greater achievable sensitivity due to the fact that the fluorescence signal has a very low background. However, an accurate and sensitive method for the diagnosis of cancer cell lines is quit challenging. The sensitivity and accuracy of LIF technique can be improved by optimizing the sensor configuration. In this work, the spectral characteristics of the fluorescence, which was induced by frequency tripled Nd:YAG laser operating at 355nm are recorded from two different type of human breast cancer cell line. Effects of various influential experimental parameters and configuration were investigated in order to optimize the sensor performance. The sensor with optimum configuration enables to differentiate two types of cancerous cell lines with a maximum achievable fluorescence spectral contrast. A unique data processing technique has been developed to analyze the recorded data for cell lines identification and differentiation.
Laser-induced fluorescence (LIF) is an accurate, sensitive and rapid method for the diagnosis of a normal and malignant tissue. In this paper, an optical fiber sensor was developed to enhance spectral difference between the normal and malignant tissue with sensor optimization to improve the accuracy of cancer diagnosis. This instrument incorporated a pulsed laser operating at 355 nm (frequency triple Nd:YAG and Q-switched Nd:YAG pump dye laser) with bifurcated optical fiber to allow illumination of tissue and collection of fluorescence with a single fiber. Using the laser excitation, the detection of the fluorescence signal from the tissue was performed almost instantaneously. A sufficient fluorescence contrast (of the order of more than 22.22 times) for malignant versus normal tissue was obtained. The results of our approach were compared with histopathology results and indicated excellent agreement in the classification of normal and malignant tissue.
Auto fluorescence of tissue depends not only on the concentration of fluoro-phores present in tissues but also on the configuration of optical fiber sensor. In this paper, feasibility of using laser induced fluorescence spectroscopy as a diagnostic tool for distinguishing malignant animal tissue from its normal counterpart under various design configurations is explored. Three different design configurations are tested for the performance optimization. The optimized Y-shaped optical reflection fiber probe gives the best laser induced fluorescence signal comparing to other probes. This instrument incorporated a continuous wave (CW) Nd:YAG laser operating at 532 nm.