Cancerous Tissue Diagnosis by LIF Spectroscopy Derived From Body-Compatible Fluorophores

Introduction: The laser-induced fluorescence (LIF) method as molecular emission spectroscopy is used to diagnose cancerous tissues. According to the previous reports, the red-shift in the fluorescence spectrum from Rhodamine 6G (Rd6G)-stained cancerous tissues compared to healthy ones impregnated with the same dye provides the feasibility for diagnosis. In this paper, we have employed the LIF emissions as a diagnostic method to distinguish between cancerous and healthy tissues infiltrated by a body-compatible fluorophore to avoid the toxicity and hazard of Rd6G dye. Methods: Biological tissue specimens are stained with sodium fluorescein (NaFl) dye and then irradiated by the blue CW diode laser (405 nm) to examine the spectral properties that are effective in detecting cancerous tissues. Results: The spectral shift and the intensity difference of fluorescence are keys to diagnosing in vitro cancerous breast, colon, and thyroid tissues for clinical applications. The notable tubular densities in the breast and colon tissues and the space between the papillae in the thyroid ones cause the cancerous tissues to be prominently heterogeneous, providing numerous micro-cavities and thus more room for dye molecules. Conclusion: Here, we have assessed the spectral shift and intensity difference of fluorescence as a diagnostic method to distinguish between cancerous and healthy tissues for clinical applications.

Fluorescence Spectroscopy for Studying Evaporating Droplets Using the Dye Eosin-Y

Laser-induced fluorescence (LIF) spectroscopy using dyes is frequently applied for characterization of liquids and two-phase flows. The technique is utilized e.g., for mixing studies, thermometry, or droplet sizing. One major application of the LIF technique combined with Mie-scattering is the planar measurement of droplet sizes in spray systems. However, its uncertainty is determined, among others, by varying dye concentration and temperature changes occurring during mixing and droplet evaporation. Systematic experimental investigations are necessary to determine the influence of dye enrichment effects on the LIF-signal of single droplets. For these investigations, the fluorescence dye Eosin-Y is dissolved in water and ethanol, which are typical solvents and working fluids in bio-medical applications and power engineering. A photo-physical characterization of the mixtures under various conditions was conducted using a spectrometric LIF setup and a micro cell. For ethanol, a small temperature dependency of the Eosin-Y LIF signal is observed up to 373 K. Photo-dissociation of Eosin-Y is negligible for solution in ethanol while it is distinct in water. The LIF signals of the single droplets are studied with an acoustic levitator. Effects of droplet evaporation, droplet deformation and varying dye concentration on the LIF-signal are studied. The single droplet measurements revealed a complex change of the fluorescence signal with reduced droplet size. This is due to droplet deformations leading to variations in the internal illumination field as well as dye enrichment during evaporation.

Diagnosis of Oral Squamous Cell Carcinoma (OSCC) Using Laser Induced Fluorescence

Cancer is a dreaded disease; a large number of deaths occur every year due to this disease. Oral squamous cell carcinoma (OSCC) is the most common cancer of the head and neck, which is approximately 16% to 40% of all malignancies. In this study, Laser induced fluorescence (LIF) spectroscopy has been utilized to discriminate OSCC against healthy (normal) tissues and to investigate whether the LIF could provide information from formalin-fixed paraffin-embedded (FFPE) tissue samples similar to that reported using fresh tissues. Samples were prepared after biopsy from ten patients using standard FFPE tissues methods. LIF system consists of a continuous wave (CW) He–Cd laser at 325 nm, a seven-core optical fiber cable coupled to the laser, a spectrometer with cooled charge coupled device (CCD) detector, and a computer for acquisition of the LIF spectra. Spectra were decomposed using second derivative and curve fitting analysis to reveal the changes in molecular composition of the samples. Moreover, samples spectra were discriminated by hierarchical cluster analysis (HCA) and principal components analysis (PCA). Spectral results showed differences in peak areas and positions between normal and OSCC tissues. LIF spectroscopy revealed significant decrease in the peak area of collagen and decrease in peak area of coenzymes of OSCC tissues. In addition, significant shift in the peak position of coenzymes was recorded. HCA and PCA of LIF indicated a very clear discrimination of the normal and FFPE-OSCC tissues. The achieved discrimination between elliptic polygons of normal and OSCC tissues was 96.3% by PCA. This study confirms that the LIF spectroscopy is a good diagnostic tool for OSCC and it could be used with samples that are prepared using FFPE tissues methods.

Laser-induced fluorescence (LiF) spectroscopy for detecting REE cross-contaminations in the Smithsonian rare-earth element phosphate standards

<p>Spectroscopy based methods have proven great potential in efficient, non-invasive material characterization. Recording the material-specific optical properties delivers instant information on the composition of an investigated sample surface without chemical sample preparation and may be operated in spatially continuous mode. In minerals, laser-induced fluorescence (LiF) provides a promising method to address the challenges of robust and efficient rare-earth element (REE) detection. The method is based on the characteristic electronic transitions within the incompletely filled f-shell of REE. The corresponding emission shows distinct features (spectral fingerprints) in the visible and near-infrared (VNIR) range of the electromagnetic spectrum that allow to distinguish between individual REE and mineral matrix luminescence. Only REE with completely filled or empty f-orbitals miss characteristic luminescence (i.e. Y<sup>3+</sup>, Sc<sup>3+</sup>, La<sup>3+</sup>, Lu<sup>3+</sup>), while the emissions of Gd<sup>3+</sup> lie at lower wavelengths than the observed VNIR range.</p><p>We test the suitability of LiF in applications of REE identification by (1) building a spectral LiF library from a sample set of luminescent REE phosphates and (2) evaluating observed emissions in samples of non-luminescent REE, and (3) comparing indicated REE cross-contamination to results of neutron activation analysis (NAA). As samples, we use the Smithsonian REE phosphate standards for electron microprobe analysis. The synthetic material delivers a simple, well-defined host composition, is well investigated and NAA results are available on additional trace REE concentration resulting from the material production procedure. The trace REE concentrations are at the order of 10<sup>-4</sup> given in mass fraction. We employ laser-induced fluorescence at three commonly used laser wavelengths (325 nm, 442 nm, 532 nm) to acquire our REE sample spectra and record LiF signals in the visible to near-infrared spectral range (350 – 1080 nm).</p><p>The comparison of spectra from non-luminescent REE phosphates shows clear similarities in emission patterns that can be assigned to specific luminescent REE using the spectral LiF library. Our results demonstrate the suitability of LIF for REE detection along with the benefits of selective element excitation and highlight the high sensitivity of the LiF method. The detected emissions in the non-luminescent samples indicate a detection limit below mass fractions of 10<sup>-4</sup>, when compared to NAA results, but also show that not all REE are equally responsive. Here, the co-existence of REE with complex interactions such as charge transfer contributes to the observed emission pattern. Adding to the spectral LiF library data and expanding investigations to further mineral hosts will facilitate new applications of LIF for REE analysis in natural samples and its implementation in raw material exploration.</p>

Integrated Laser Sensor (ILS) for Remote Surface Analysis: Application for Detecting Explosives in Fingerprints

Here, we describe an innovative Integrated Laser Sensor (ILS) that combines four spectroscopic techniques and two vision systems into a unique, transportable device. The instrument performs Raman and Laser-Induced Fluorescence (LIF) spectroscopy excited at 355 nm and Laser-Induced Breakdown Spectroscopy (LIBS) excited at 1064 nm, and it also detects Laser Scattering (LS) from the target under illumination at 650 nm. The combination of these techniques supplies information about: material change from one scanning point to another, the presence of surface contaminants, and the molecular and elemental composition of top target layers. Switching between the spectroscopic techniques and the laser wavelengths is fully automatic. The instrument is equipped with an autofocus, and it performs scanning with a chosen grid density over an interactively-selected target area. Alternative to the spectroscopic measurements, it is possible to switch the instrument to a high magnification target viewing. The working distances tested until now are between 8.5 and 30 m. The instrument is self-powered and remotely controlled via wireless communication. The ILS has been fully developed at ENEA for security applications, and it was successfully tested in two outdoor campaigns where an automatic recognition of areas containing explosives in traces had been implemented. The strategies for the identification of nitro-compounds placed on various substrates as fingerprints and the results obtained at a working distance of 10 m are discussed in the following.

Rapid and Sensitive Analysis of Trace Leads in Medicinal Herbs Using Laser-Induced Breakdown Spectroscopy–Laser-Induced Fluorescence (LIBS-LIF)

Toxic metals in medicinal herbs are potentially harmful for people taking herbal medicines. In this work, laser-induced breakdown spectroscopy–laser-induced fluorescence (LIBS-LIF) spectroscopy was first applied to carry out rapid and sensitive trace lead analysis in medicinal herb samples. To overcome the problem of diversity on the sample size, shape, and density for different samples, original samples were pulverized to powder and then pressed into pellets for spectral analysis. A series of standard samples were self-made for building a calibration curve. As an exemplary study, lead in Rheum officinale was analyzed with LIBS-LIF spectroscopy with significantly improved analytical sensitivity. The R2 of the build linear calibration curve was 0.996 and the detection limit of lead in R. officinale was determined to be 0.13 ppm. The enhancement factor on the signal-to-background ratio was >100 under low lead concentrations if compared with LIBS analysis. The lead concentrations in several original R. officinale samples were quantitatively determined. This work demonstrated that LIBS-LIF can be successfully applied to carry out rapid, sensitive, and quantitative trace lead analysis for medicinal herbs.