The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Laura Marcu - One of the best experts on this subject based on the ideXlab platform.
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Time‐resolved Fluorescence Spectroscopy for the diagnosis of oral lichen planus
Clinical and Experimental Dermatology, 2018Co-Authors: Dimitris Gorpas, D. Gregory Farwell, Parastoo Davari, Laura Marcu, Maxwell A Fung, Nasim FazelAbstract:Lichen planus (LP) is a T-cell mediated autoimmune disorder of unknown aetiology that affects the skin, nails, oral and genital mucous membranes. Conventionally, oral LP (OLP) is diagnosed through clinical assessment and histopathological confirmation by oral biopsy. To explore the use of Time-Resolved Fluorescence Spectroscopy (TRFS) to detect Fluorescence lifetime changes between lesional OLP and perilesional normal mucosa. In this pilot study, measurements of lesional and perilesional buccal and mouth floor mucosa were conducted in vivo with a TRFS system. Histopathological findings were consistent with OLP in 8 out of 10 patients biopsied. Two patients with histopathological diagnoses of frictional hyperkeratosis and oral candidiasis, respectively, were excluded from the study. Our preliminary data show that lifetime values in the 360-560 nm spectral range indicate a significant differentiation between normal and diseased tissue. In contrast to the standard oral biopsy procedure, this technique is noninvasive, painless, time-efficient and safe. Future studies are needed to better elucidate the diagnostic capability of TRFS and to further explore the sources of Fluorescence contrast. This pilot study suggests that, based on Fluorescence lifetime parameters, TRFS is a very promising technology for the development of a novel OLP diagnostic technique. © 2018 British Association of Dermatologists.
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Detection of Pentosidine Cross-Links in Cell-Secreted Decellularized Matrices Using Time Resolved Fluorescence Spectroscopy
ACS biomaterials science & engineering, 2016Co-Authors: Debika Mitra, Laura Marcu, Hussain Fatakdawala, Michael Nguyen-truong, Amy Creecy, Jeffry S. Nyman, J. Kent LeachAbstract:Hyperglycemia-mediated, nonenzymatic collagen cross-links such as pentosidine (PENT) can have deleterious effects on cellular interactions with the extracellular matrix (ECM). Present techniques to quantify PENT are limited, motivating the need for improved methods to study the accumulation and contribution of PENT toward diabetic clinical challenges such as impaired bone healing. Current methods for studying PENT are destructive, laborious, and frequently employ oversimplified collagen films that lack the complexity of the native ECM. The primary goal of this study was to evaluate the capacity of Time-Resolved Fluorescence Spectroscopy (TRFS) to detect PENT in cell-secreted ECMs possessing enhanced compositional complexity. To demonstrate an application of this method, we assessed the response of human mesenchymal stem cells (MSCs) to cross-linked substrates to explore the role of detected PENT on osteogenic differentiation. We exposed MSC-secreted decellularized matrices (DMs) to 0.66 M ribose for 2 wee...
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Time-Resolved Fluorescence Spectroscopy and ultrasound backscatter microscopy for nondestructive evaluation of vascular grafts
Journal of biomedical optics, 2014Co-Authors: Hussain Fatakdawala, Leigh G. Griffiths, Sterling Humphrey, Laura MarcuAbstract:Quantitative and qualitative evaluations of structure and composition are important in monitoring development of engineered vascular tissue both in vitro and in vivo. Destructive techniques are an obstacle for performing time-lapse analyses from a single sample or animal. This study demonstrates the ability of Time-Resolved Fluorescence Spectroscopy (TRFS) and ultrasound backscatter microscopy (UBM), as nondestructive and synergistic techniques, for compositional and morphological analyses of tissue grafts, respectively. UBM images and integrated backscatter coefficients demonstrate the ability to visualize and quantify postimplantation changes in vascular graft biomaterials such as loss of the external elastic lamina and intimal/medial thickening over the grafted region as well as graft integration with the surrounding tissue. TRFS results show significant changes in spectra, average lifetime, and Fluorescence decay parameters owing to changes in collagen, elastin, and cellular content between normal and grafted tissue regions. These results lay the foundation for the application of a catheter-based technique for in vivo evaluation of vascular grafts using TRFS and UBM.
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design and evaluation of a device for fast multispectral time resolved Fluorescence Spectroscopy and imaging
Review of Scientific Instruments, 2014Co-Authors: Diego R. Yankelevich, Yinghua Sun, Julien Bec, Daniel S Elson, Yang Sun, Jing Liu, Laura MarcuAbstract:The application of Time-Resolved Fluorescence Spectroscopy (TRFS) to in vivo tissue diagnosis requires a method for fast acquisition of Fluorescence decay profiles in multiple spectral bands. This study focusses on development of a clinically compatible fiber-optic based multispectral TRFS (ms-TRFS) system together with validation of its accuracy and precision for Fluorescence lifetime measurements. It also presents the expansion of this technique into an imaging Spectroscopy method. A tandem array of dichroic beamsplitters and filters was used to record TRFS decay profiles at four distinct spectral bands where biological tissue typically presents Fluorescence emission maxima, namely, 390, 452, 542, and 629 nm. Each emission channel was temporally separated by using transmission delays through 200 μm diameter multimode optical fibers of 1, 10, 19, and 28 m lengths. A Laguerre-expansion deconvolution algorithm was used to compensate for modal dispersion inherent to large diameter optical fibers and the finite bandwidth of detectors and digitizers. The system was found to be highly efficient and fast requiring a few nano-Joule of laser pulse energy and <1 ms per point measurement, respectively, for the detection of tissue autofluorescent components. Organic and biological chromophores with lifetimes that spanned a 0.8–7 ns range were used for system validation, and the measured lifetimes from the organic fluorophores deviated by less than 10% from values reported in the literature. Multi-spectral lifetime images of organic dye solutions contained in glass capillary tubes were recorded by raster scanning the single fiber probe in a 2D plane to validate the system as an imaging tool. The lifetime measurement variability was measured indicating that the system provides reproducible results with a standard deviation smaller than 50 ps. The ms-TRFS is a compact apparatus that makes possible the fast, accurate, and precise multispectral Time-Resolved Fluorescence lifetime measurements of low quantum efficiency sub-nanosecond fluorophores.
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Design and evaluation of a device for fast multispectral Time-Resolved Fluorescence Spectroscopy and imaging
Review of Scientific Instruments, 2014Co-Authors: Diego R. Yankelevich, Dinglong Ma, Yinghua Sun, Julien Bec, Daniel S Elson, Yang Sun, Jing Liu, Laura MarcuAbstract:The application of Time-Resolved Fluorescence Spectroscopy (TRFS) to in vivo tissue diagnosis requires a method for fast acquisition of Fluorescence decay profiles in multiple spectral bands. This study focusses on development of a clinically compatible fiber-optic based multispectral TRFS (ms-TRFS) system together with validation of its accuracy and precision for Fluorescence lifetime measurements. It also presents the expansion of this technique into an imaging Spectroscopy method. A tandem array of dichroic beamsplitters and filters was used to record TRFS decay profiles at four distinct spectral bands where biological tissue typically presents Fluorescence emission maxima, namely, 390, 452, 542, and 629 nm. Each emission channel was temporally separated by using transmission delays through 200 μm diameter multimode optical fibers of 1, 10, 19, and 28 m lengths. A Laguerre-expansion deconvolution algorithm was used to compensate for modal dispersion inherent to large diameter optical fibers and the finite bandwidth of detectors and digitizers. The system was found to be highly efficient and fast requiring a few nano-Joule of laser pulse energy and
Seiji Akimoto - One of the best experts on this subject based on the ideXlab platform.
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How Light-Harvesting and Energy-Transfer Processes Are Modified Under Different Light Conditions: STUDIES by Time-Resolved Fluorescence Spectroscopy
Photosynthesis: Structures Mechanisms and Applications, 2017Co-Authors: Seiji Akimoto, Makio YokonoAbstract:Photosynthetic organisms contain specific pigment-protein complexes that absorb light energy and subsequently transfer excitation energy to the photosynthetic reaction centers. Changing the quality and/or quantity of the complexes is how light-harvesting and energy-transfer processes adapt to environments. Cyanobacteria and red algae form a unique peripheral membrane complex, phycobilisome, whereas integral membrane complexes containing specific carotenoids are found in green algae and higher plants. We examine light-harvesting and energy-transfer processes in different types of complexes by Time-Resolved Fluorescence Spectroscopy. Changes in these processes in response to different environments are also discussed.
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energy transfer processes in chlorophyll f containing cyanobacteria using time resolved Fluorescence Spectroscopy on intact cells
Biochimica et Biophysica Acta, 2014Co-Authors: Tatsuya Tomo, Toshiyuki Shinoda, Min Chen, Suleyman I Allakhverdiev, Seiji AkimotoAbstract:We examined energy transfer dynamics in the unique chlorophyll (Chl) f-containing cyanobacterium Halomicronema hongdechloris. The absorption band of Chl f appeared during cultivation of this organism under far-red light. The absorption maximum of Chl f in organic solvents occurs at a wavelength of approximately 40 nm longer than that of Chl a. In vivo, the cells display a new absorption band at approximately 730 nm at 298 K, which is at a significantly longer wavelength than that of Chl a. We primarily assigned this band to a long wavelength form of Chl a. The function of Chl f is currently unknown. We measured the Fluorescence of cells using Time-Resolved Fluorescence Spectroscopy in the picosecond-to-nanosecond time range and found clear differences in Fluorescence properties between the cells that contained Chl f and the cells that did not. After excitation, the Fluorescence peaks of photosystem I and photosystem II appeared quickly but diminished immediately. A unique Fluorescence peak located at 748 nm subsequently appeared in cells containing Chl f. This finding strongly suggests that the Chl f in this alga exists in photosystem I and II complexes and is located close to each molecule of Chl a. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy.
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Time-Resolved Fluorescence Spectroscopy study of excited state dynamics of alkyl- and benzo-substituted triphyrin(2.1.1)
Physical Chemistry Chemical Physics, 2014Co-Authors: Yusuke Iima, Daiki Kuzuhara, Hiroko Yamada, Seiji Akimoto, Keisuke TominagaAbstract:We have investigated the photophysical properties of alkyl-substituted triphyrin(2.1.1) (ATp) and benzotriphyrin(2.1.1) (BTp) by steady-state and Time-Resolved Fluorescence Spectroscopy. We focused on the effect of NH proton tautomerization, planarity of the macrocycles, and substituents on these properties. The Fluorescence quantum yields (Φy) of ATp did not depend on solvent viscosity, whereas those of BTp increased with solvent viscosity, reaching a maximum value of 0.17 in paraffin. Interestingly, analyzing Φy showed that the non-radiative rate constant of BTp decreased sharply as the solvent viscosity increased. These results suggest that the substituted phenyl groups play a crucial role in suppressing molecular distortion, thus leading to decreased non-radiative relaxation in triphyrin(2.1.1). The hydrogen bond formed in the inner cavity potentially contributes to the suppression of the structural distortion, whereas the pyrrole rings in the macrocycle are close, as in porphycene.
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Short-term light adaptation of a cyanobacterium, Synechocystis sp. PCC 6803, probed by Time-Resolved Fluorescence Spectroscopy
Plant physiology and biochemistry : PPB, 2014Co-Authors: Seiji Akimoto, Makio Yokono, Shimpei Aikawa, Erina Yokono, Akihiko KondoAbstract:In photosynthetic organisms, the interactions among pigment–protein complexes change in response to light conditions. In the present study, we analyzed the transfer of excitation energy from the phycobilisome (PBS) and photosystem (PS) II to PSI in the cyanobacterium Synechocystis sp. PCC 6803. After 20 min of dark adaptation, Synechocystis cells were illuminated for 5 min with strong light with different spectral profiles, blue, green, two kinds of red, and white light. After illumination, the energy-transfer characteristics were evaluated using steady-state Fluorescence and picosecond Time-Resolved Fluorescence Spectroscopy techniques. The Fluorescence rise and decay curves were analyzed by global analysis to obtain Fluorescence decay-associated spectra, followed by spectral component analysis. Under illumination with strong light, the contribution of the energy transfer from the PSII to PSI (spillover) became greater, and that of the energy transfer from the PBS to PSI decreased; the former change was larger than the latter. The energy transfer pathway to PSI was sensitive to red light. We discuss the short-term adaptation of energy-transfer processes in Synechocystis under strong-light conditions.
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Fluorescence properties of chlorophyll d-dominating prokaryotic alga, acaryochloris marina: studies using Time-Resolved Fluorescence Spectroscopy on intact cells
Biochimica et biophysica acta, 1999Co-Authors: Mamoru Mimuro, Seiji Akimoto, Iwao Yamazaki, Hideaki Miyashita, Shigetoh MiyachiAbstract:Antenna components and the primary electron donor of the photosystem (PS) II in the Chlorophyll (Chl) d-dominating prokaryote, Acaryochloris marina, were studied using Time-Resolved Fluorescence Spectroscopy in the ps time range. By selective excitation of Chl a or Chl d, differences in Fluorescence properties were clearly resolved. At physiological temperature, energy transfer was confirmed by a red shift of emission maximum among PS II antenna components, and the equilibrium of energy distribution among Chl a and Chl d was established within 30 ps. A Fluorescence component that can be assigned to delayed Fluorescence (DF) was observed at 10 ns after the excitation; however, it was not necessarily resolved by the decay kinetics. At -196 degrees C, a red shift of emission maximum was reproduced but the equilibrium of energy distribution was not detected. DF was resolved in the wavelength region corresponding to Chl a by spectra and by decay kinetics. The lifetime of the DF was estimated to be approx. 15 ns, and the peaks were located at 681 and 695 nm, significantly shorter wavelengths than those of Chl d. These findings strongly suggest that an origin of DF is Chl a, and Chl a is most probably the primary electron donor in the PS II reaction center (RC). These results indicate that the constitution of PS II RC in this alga is essentially identical to that of other oxygenic photosynthetic organisms.
Wiesław Wiczk - One of the best experts on this subject based on the ideXlab platform.
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Photophysical Properties of Tyrosine and Its Simple Derivatives in Organic Solvents Studied by Time-Resolved Fluorescence Spectroscopy and Global Analysis {
Photochemistry and photobiology, 2005Co-Authors: Katarzyna Guzow, Alicja Rzeska, Justyna Mrozek, Mariusz Szabelski, Jerzy Karolczak, Radosław Majewski, Tadeusz Ossowski, Wiesław WiczkAbstract:Photophysical properties of tyrosine and its derivatives with free and blocked functional groups were studied by steady state and Time-Resolved Fluorescence Spectroscopy and global analysis in organic solvents, such as methanol, 2-propanol, tetrahydrofuran (THF), and dimethylsulfoxide (DMSO). The mono-exponential Fluorescence intensity decays were observed for all tyrosine derivatives in THF and DMSO solutions, whereas in alcohols some derivatives have bi-exponential decays. The rotamer population calculated from 1H nuclear magnetic resonance Spectroscopy in DMSO does not correspond to the pre-exponential factors obtained from Fluorescence Spectroscopy. Moreover in the case of DMSO, the strong interaction of this solvent with the hydroxyl group of the fluorophore's phenol ring causes substantial changes in the Fluorescence and nonradiative rate constants of tyrosine derivatives compared with those of tyrosine with a blocked hydroxyl group, Tyr(Me). The steady state and Time-Resolved Fluorescence measurements in pure organic solvents and water-organic solvent mixtures indicate that the Fluorescence quenching of the phenol chromophore of tyrosine by an acetyl or amide group or both depends on the polarity of the solvent used as well as the ability of the solvent to form hydrogen bonds with functional groups of tyrosine.
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Photophysical Properties of Tyrosine and Its Simple Derivatives Studied by Time-Resolved Fluorescence Spectroscopy, Global Analysis, and Theoretical Calculations
The Journal of Physical Chemistry B, 2004Co-Authors: Katarzyna Guzow, Robert Ganzynkowicz, Alicja Rzeska, Justyna Mrozek, Mariusz Szabelski, Jerzy Karolczak, And Adam Liwo, Wiesław WiczkAbstract:The photophysical properties of tyrosine and its derivatives with free and blocked functional groups in water were studied by steady-state and Time-Resolved Fluorescence Spectroscopy and global analysis. Tyrosine Fluorescence intensity decays in water at pH = 5.5 in the short-wavelength region (290−320 nm) are monoexponential, whereas, at longer wavelengths, they are biexponential. The monoexponential Fluorescence intensity decay of O-methyl tyrosine across the Fluorescence band is observed. The Fluorescence lifetimes of Tyr calculated using a global analysis are equal to 3.37 ± 0.04 ns at the short-wavelength region and 0.98 ± 0.12 ns at the longer-wavelength region. This observation, together with the decay-associated spectra, indicate that the short-lifetime component can be attributed to tyrosine with phenol hydroxyl groups hydrogen-bonded with water molecules. The rotamer populations calculated from potentials of mean forces, as well as those obtained from 1H NMR Spectroscopy, do not correspond to th...
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Determination of stoichiometry and equilibrium constants of complexes of tyrosine with cyclodextrins by Time-Resolved Fluorescence Spectroscopy and global analysis of Fluorescence decays
Chemical Physics Letters, 2001Co-Authors: Wiesław Wiczk, Katarzyna Guzow, Justyna Mrozek, Mariusz Szabelski, Jerzy Karolczak, Joanna MalickaAbstract:Abstract Time-Resolved Fluorescence Spectroscopy and global analysis of Fluorescence decay times were applied to determine stoichiometry and equilibrium constants of complexes of tyrosine with α-, β- and γ-cyclodextrins (CDs). This study reveals from Global analysis of Fluorescence decay curves of tyrosine with CDs in water the presence of only two Fluorescence life-times of tyrosine: 3.35±0.10 ns for free tyrosine and 4.3±0.3 ns for the tyrosine–CD complex. The formation constants of tyrosine–CD complexes were determined from the pre-exponential factors as well as the fractional intensities and average Fluorescence life-times. The cavity size of CD influenced the equilibrium constant but had no influence on the Fluorescence life-time of the tyrosine–CD complex.
Pierrette Dayhaw Barker - One of the best experts on this subject based on the ideXlab platform.
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Age-related changes in the Fluorescence of melanin and lipofuscin granules of the retinal pigment epithelium: a Time-Resolved Fluorescence Spectroscopy study.
Photochemistry and photobiology, 1991Co-Authors: F. Docchio, Rinaldo Cubeddu, Roberta Ramponi, Michael E. Boulton, Pierrette Dayhaw BarkerAbstract:The photophysical properties of purified populations of melanin and lipofuscin granules from human retinal pigment epithelium, and their changes with donor age, have been investigated using high-sensitivity Time-Resolved Fluorescence Spectroscopy techniques with picosecond gating capabilities. The overall Fluorescence intensity of both melanin and lipofuscin granules clearly increased with increasing donor age, the increase being most marked for melanin. In all granule populations the Fluorescence decays were multiexponential with subnanosecond and nanosecond decay components. The resultant time-integrated and time-gated spectra also exhibited marked age-variations for each type of granule. Young melanin showed spectral patterns similar to those of bovine melanin, while a yellow-orange Fluorescence band appeared in melanin samples from older age groups. Lipofuscin granules exhibited a blue, a yellow and an orange band whose relative amounts were age-related. The results demonstrate the potential of Time-Resolved techniques for discriminating fluorophores in vitro and in situ, and have confirmed results previously obtained using extraction techniques. Furthermore, the ability of this technique to identify and quantify individual fluorophores within granules may provide an important insight into the origin and development of lipofuscin within the retinal pigment epithelium and ultimately into the mechanisms of age-related retinal diseases.
Hussain Fatakdawala - One of the best experts on this subject based on the ideXlab platform.
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Detection of Pentosidine Cross-Links in Cell-Secreted Decellularized Matrices Using Time Resolved Fluorescence Spectroscopy
ACS biomaterials science & engineering, 2016Co-Authors: Debika Mitra, Laura Marcu, Hussain Fatakdawala, Michael Nguyen-truong, Amy Creecy, Jeffry S. Nyman, J. Kent LeachAbstract:Hyperglycemia-mediated, nonenzymatic collagen cross-links such as pentosidine (PENT) can have deleterious effects on cellular interactions with the extracellular matrix (ECM). Present techniques to quantify PENT are limited, motivating the need for improved methods to study the accumulation and contribution of PENT toward diabetic clinical challenges such as impaired bone healing. Current methods for studying PENT are destructive, laborious, and frequently employ oversimplified collagen films that lack the complexity of the native ECM. The primary goal of this study was to evaluate the capacity of Time-Resolved Fluorescence Spectroscopy (TRFS) to detect PENT in cell-secreted ECMs possessing enhanced compositional complexity. To demonstrate an application of this method, we assessed the response of human mesenchymal stem cells (MSCs) to cross-linked substrates to explore the role of detected PENT on osteogenic differentiation. We exposed MSC-secreted decellularized matrices (DMs) to 0.66 M ribose for 2 wee...
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Time-Resolved Fluorescence Spectroscopy and ultrasound backscatter microscopy for nondestructive evaluation of vascular grafts
Journal of biomedical optics, 2014Co-Authors: Hussain Fatakdawala, Leigh G. Griffiths, Sterling Humphrey, Laura MarcuAbstract:Quantitative and qualitative evaluations of structure and composition are important in monitoring development of engineered vascular tissue both in vitro and in vivo. Destructive techniques are an obstacle for performing time-lapse analyses from a single sample or animal. This study demonstrates the ability of Time-Resolved Fluorescence Spectroscopy (TRFS) and ultrasound backscatter microscopy (UBM), as nondestructive and synergistic techniques, for compositional and morphological analyses of tissue grafts, respectively. UBM images and integrated backscatter coefficients demonstrate the ability to visualize and quantify postimplantation changes in vascular graft biomaterials such as loss of the external elastic lamina and intimal/medial thickening over the grafted region as well as graft integration with the surrounding tissue. TRFS results show significant changes in spectra, average lifetime, and Fluorescence decay parameters owing to changes in collagen, elastin, and cellular content between normal and grafted tissue regions. These results lay the foundation for the application of a catheter-based technique for in vivo evaluation of vascular grafts using TRFS and UBM.
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Nondestructive evaluation of tissue engineered articular cartilage using Time-Resolved Fluorescence Spectroscopy and ultrasound backscatter microscopy.
Tissue engineering. Part C Methods, 2012Co-Authors: Yang Sun, Jing Liu, Hongtao Xie, Hussain Fatakdawala, Donald J. Responte, Kyriacos A. Athanasiou, Laura MarcuAbstract:The goal of this study is to evaluate the ability of a bimodal technique integrating Time-Resolved Fluorescence Spectroscopy (TRFS) and ultrasound backscatter microscopy (UBM) for nondestructive detection of changes in the biochemical, structural, and mechanical properties of self-assembled engineered articular cartilage constructs. The cartilage constructs were treated with three chemical agents (collagenase, chondroitinase-ABC, and ribose) to induce changes in biochemical content (collagen and glycosaminoglycan [GAG]) of matured constructs (4 weeks); and to subsequently alter the mechanical properties of the construct. The biochemical changes were evaluated using TRFS. The microstructure and the thickness of the engineered cartilage samples were characterized by UBM. The optical and ultrasound results were validated against those acquired via conventional techniques including collagen and GAG quantification and measurement of construct stiffness. Current results demonstrated that a set of optical parameters (e.g., average Fluorescence lifetime and decay constants) showed significant correlation (p