Photon avalanche is one of the anti-Stokes upconversion processes characterized by highly nonlinear response of the emission intensity to excitation power density changes. By exceeding the critical pumping power threshold, even minute increase of this power results in a steep increase (by 2-3 orders of magnitude) of the emission intensity. While photon avalanche has been observed in bulk materials since 80-ties, it was reported in thulium-doped nanocrystals only recently, enabling to use them for single excitation beam super-resolution imaging. In current work we explore new perspectives for nanoscale avalanche phenomenon by combining the avalanching materials with plasmonically active metallic nanostructures.
Nanovectors technology is a comprehensive solution, which comprises unique luminescent nanolabels, dedicated equipment for reading of the same and verification algorithms – all devoted for anti-forgery protection of valuable objects. Nanovectors themselves have a complex and unique luminescence spectrum fingerprint resulting from the selection of their composition, type and substrates, which make any attempt to fake the spectral information practically impossible. Nanovectors constitute a special code enabling correct identification only for specified measurement conditions. Moreover, nanovectors may be used for marking of a wide range of products such as documents, ID cards, access cards and employee cards, spare parts, elements of packaging, liquids, greases etc. Either entire volume of objects during their production process, pressing in a specified location of an object after production or unique printing on the object’s surface may be conveniently employed. Nanovectors are most often manufactured as invisible security features and, therefore, special tools are necessary to detect their presence. This work was focused on experimental verification of reproducibility of Nanovectors reading and theoretical estimation of maximal number of distinguishable optical codes, which confirmed the ability to unequivocally design thousands of such spectral fingerprints.
The human hepatoma HepaRG cell line is an in vitro cell model that is becoming an important tool in drug metabolism, hepatotoxicity, genotoxicity, and enzyme induction studies. The cells are highly proliferative during their undifferentiated state but once committed, they differentiate into two distinctly different cell types, namely, hepatocyte-like and biliary epithelial-like cells. The presence of the latter in the cell culture is considered to be a drawback of the cell model. Since the proliferating undifferentiated HepaRG cells have a bipotent character, the only way to improve the content ratio of hepatic versus biliary cells of differentiated HepaRG cells is to eradicate biliary cells in situ, in a way that free surface space does not become available and thus no transdifferentiation can occur. Spatially selective photodynamic therapy has proven to be effective for that purpose. First, all the cells were administered aminolevulinic acid (δ-ALA) to stimulate the synthesis of protoporphyrin IX (PpIX), a naturally occurring photosensitizer. Then, the biliary cells were automatically identified and outlined by bright-field image processing. Last, UV light patterns were projected onto the epithelial cells alone by a spatial light modulation device connected to an optical microscope; therefore, only these cells were destroyed by photodynamic therapy.
KEYWORDS: Image segmentation, Luminescence, Fluorescence lifetime imaging, Digital micromirror devices, Biological research, Data analysis, Image processing algorithms and systems, Statistical analysis, Fiber optic illuminators, Signal to noise ratio
Fluorescence lifetime imaging (FLIM) is very demanding from a technical and computational perspective, and the output is usually a compromise between acquisition/processing time and data accuracy and precision. We present a new approach to acquisition, analysis, and reconstruction of microscopic FLIM images by employing a digital micromirror device (DMD) as a spatial illuminator. In the first step, the whole field fluorescence image is collected by a color charge-coupled device (CCD) camera. Further qualitative spectral analysis and sample segmentation are performed to spatially distinguish between spectrally different regions on the sample. Next, the fluorescence of the sample is excited segment by segment, and fluorescence lifetimes are acquired with a photon counting technique. FLIM image reconstruction is performed by either raster scanning the sample or by directly accessing specific regions of interest. The unique features of the DMD illuminator allow the rapid on-line measurement of global good initial parameters (GIP), which are supplied to the first iteration of the fitting algorithm. As a consequence, a decrease of the computation time required to obtain a satisfactory quality-of-fit is achieved without compromising the accuracy and precision of the lifetime measurements.
New approach to acquisition, analysis and reconstruction of Microscopic Fluorescence Lifetime Images (FLIM) and
Hyper Spectral Images (HSI) is presented. Spatial selectivity is obtained with a Digital micro-Mirror Device Illuminator
(DMDI) combined with a fluorescence microscope. More specifically spatially selective illumination is achieved by
tilting the relevant group of micro-mirrors to reflect the excitation light from a UV picosecond laser diode towards
chosen regions on the sample. In the first step, the whole field fluorescence image is collected by a color CCD camera
for further qualitative spectral analysis and sample segmentation. In the next step fluorescence of the sample is excited
segment by segment and acquired with a single detector (e.g. photomultiplier in photon counting mode for FLIM, CCD
spectrophotometer for HSI) from the whole field of view. The acquired fluorescence is analyzed in following step for
further FLIM or HSI image reconstruction. This can be facilitated by either raster scanning over the sample or by directly
accessing specific regions of interest. The unique features of the DMD illuminator allow to Globally Analyze (GA) the
sample and supply on-line good initial values for fitting algorithms associated with the subsequent raster-scanning,
which in turn decreases the computation time needed to obtain a satisfactory quality-of-fit. FLIM/HIS images acquired
on phantoms and on biological samples demonstrate the possibilities for temporal and spectral "unmixing".
Theoretical considerations concerning new method for interstitial photodynamic therapy light dosimetry and distribution at different depths, by means of single-fiber multi-decay-probes is presented, basing on decomposition of multi-exponential decay. Successful decomposition of up to 25 and up to 7 components of the modelled fiber probe was achieved with noiseless and noise containing decay curves respectively. The impact of noise and distribution of excitation intensity were examined and optimisation algorithm was briefly described.
Photodynamic inactivation (PDI) may be a very promising alternative method for antimicrobial treatment of many localised infections. In the present study we report the activity of three lanthanides (Eu(III), Pr(III), Yb(III)) complexes of Fotolon sensitizer, composed of chlorin e6 and polyvinylpyrrolidone (PVP), against standard E.coli P. aeruginosa, K. pneumoniae and S. aureus ATCC strains. The 160±10mW/cm2 of 651 nm laser light was applied for 600 seconds after photosensitiser administration (50μg/ml) and 30 minutes incubation time. Impact of pure Fotolon and pure lanthanides solution was examined as control groups.
The goal of practical photodynamic therapy (PDT) dosimetry is to optimize the distribution of a light dose delivered to tissue by selecting the irradiation time and geometry to match the geometry and optical properties of the tumor and surrounding tissue. Homogeneous irradiation is among one of the sources of correct PDT dosimetry. The goal of this study is to model and predict the influence of the shape of a treated organ in need of light dose correction. Thus efficiency of light delivery to the tissue volume is defined and calculated with shape factors of the uterine cervix as parameters. Two cases (parallel and divergent beam) of enlightening configuration are investigated. The calculations presented extend PDT dosimetry with the influence of the shape of the uterine cervix on PDT necrosis depth. This allows for photodynamic excitation light dose correction for more reliable treatments.
The luminescence properties of the Nd3+:LaAlO3 nanocrystalline powders characterized by different sizes of grains in the range of 25-50 nm were investigated. The effect of the nanocrystallites sizes on the luminescence behavior of Nd3+ was observed. In particular decreasing the grain sizes was found to increase emission from the thermally populated 4F5/2 state. It's intensity increased with the increase of excitation power density. The spectroscopic parameters of Nd3+ doped LaAlO3 nanocrystallites were determined from luminescence spectra by using the Judd-Ofelt method and compared to those obtained for a single crystal of Nd3+:LaAlO3.
Laser action of two, identical in size and concentration Yb doped KYW and KGdW crystals was demonstrated and investigated in CW and Q-switch regime under laser diode pumping.
Comparison of characteristics of three laser materials doped with Yb3+ ions pumped with high power laser diodes in the end-pumped configuration is presented. The investigated materials are 10%Yb:KY(WO4)2, 10%Yb:KGd(WO4)2, 10%Yb:YAG disk and 10%Yb:YAG rod in semi-spherical configuration.
KEYWORDS: Luminescence, Arteries, Tissues, In vitro testing, Photodynamic therapy, Spectroscopy, Collagen, In vivo imaging, Detection and tracking algorithms, Picosecond phenomena
The main aim of the presented experiments was to assess in vitro capabilities of Photosensitizer Assisted Light Induced Fluorescence (PALIF) to recognise different stages of atherosclerosis. Mono-L-asparyl-chlorin e-6 was used as a photosensitising agent and ultraviolet light (440 nm) as an excitation source to obtain spectra map of artery wall. The luminescence spectra were collected and analised. The specimans were histologically examined and classified into three groups: normal artery wall, atherosclerotic noncalcified plaque and calcified plaque. The ratio of green fluorescence (coming from collagen) to red fluorescence (coming from chlorin e6 bonded with lipid reach, noncalcified tissue) gies a chance to distinguish between normal artery or calcified plaque and noncalcified, lipid reach plaque. Further trials must be performed to evaluate in vitro athermoa detection algorithm as a feedback system for photoangioplasty.
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