Label-free assessment of carotid artery biochemical composition using fiber-based fluorescence lifetime imaging

Alfonso-García, Alba; Haudenschild, Anne K.; Marcu, Laura

doi:10.1364/boe.9.004064

Cited by 13 publications

(13 citation statements)

References 47 publications

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“…The absolute fluorescence lifetime value is not always a robust comparison parameter as it can be affected by the experimental situations as well as biological variability from patient‐to‐patient. Factors that can affect fluorescence lifetime include in tissue blood perfusion or metabolism (eg, in vivo vs ex vivo measurements [110]), processing (eg, fresh vs frozen/thawed resected tissue [238]) and specific biochemical, biophysical and biomechanical tissue parameters (ie, pH, temperature, viscosity) [61]. Additionally, inter‐patient variability due to inherent patient characteristics (ie, inflammatory response, co‐morbidities and clinical history, demographics) will lead to errors when working with small sample numbers.…”

Section: Discussionmentioning

confidence: 99%

Mesoscopic fluorescence lifetime imaging: Fundamental principles, clinical applications and future directions

Alfonso-García

Bec

Weyers

et al. 2021

Journal of Biophotonics

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Fluorescence lifetime imaging (FLIm) is an optical spectroscopic imaging technique capable of real‐time assessments of tissue properties in clinical settings. Label‐free FLIm is sensitive to changes in tissue structure and biochemistry resulting from pathological conditions, thus providing optical contrast to identify and monitor the progression of disease. Technical and methodological advances over the last two decades have enabled the development of FLIm instrumentation for real‐time, in situ, mesoscopic imaging compatible with standard clinical workflows. Herein, we review the fundamental working principles of mesoscopic FLIm, discuss the technical characteristics of current clinical FLIm instrumentation, highlight the most commonly used analytical methods to interpret fluorescence lifetime data and discuss the recent applications of FLIm in surgical oncology and cardiovascular diagnostics. Finally, we conclude with an outlook on the future directions of clinical FLIm.

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Section: Discussionmentioning

confidence: 99%

Mesoscopic fluorescence lifetime imaging: Fundamental principles, clinical applications and future directions

Alfonso-García

Bec

Weyers

et al. 2021

Journal of Biophotonics

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“…To evaluate the fluorescence decay characteristics, the FLIm data was processed based on a constraint least-squares deconvolution with Laguerre basis functions as described previously . Intensity ratios were calculated by dividing the fluorescence intensity of each spectral band by the sum of fluorescence intensities in all three spectral bands . Data are presented as the mean and standard deviation from pixels within selected ROIs from all N = 6 samples per group.…”

Section: Methodsmentioning

confidence: 99%

FLIm-Guided Raman Imaging to Study Cross-Linking and Calcification of Bovine Pericardium

et al. 2020

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Bovine pericardium (BP) is a vascular biomaterial used in cardiovascular surgery that is typically cross-linked for masking antigenicity and enhance stability. There is a need for biochemical evaluation of the tissue properties prior to implantation to ensure that quality and reliability standards are met. Here, engineered antigen removed BP (ARBP) that was cross-linked with 0.2% and 0.6% glutaraldehyde (GA), and further calcified in vitro to simulate graft calcifications upon implantation was characterized nondestructively using fluorescence lifetime imaging (FLIm) to identify regions of interest which were then assessed by Raman spectroscopy. We observed that the tissue fluorescence lifetime shortened, and that Raman bands at 856, 935, 1282, and 1682 cm–1 decreased, and at 1032 and 1627 cm–1 increased with increasing GA cross-linking. Independent classification analysis based on fluorescence lifetime and on Raman spectra discriminated between GA-ARBP and untreated ARBP with an accuracy of 91% and 66%, respectively. Pearson’s correlation analysis showed a strong correlation between pyridinium cross-links measured with high-performance liquid chromatography and fluorescence lifetime measured at 380–400 nm (R = −0.76, p = 0.00094), as well as Raman bands at 856 cm–1 for hydroxy-proline (R = −0.68, p = 0.0056) and at 1032 cm–1 for hydroxy-pyridinium (R = 0.74, p = 0.0016). Calcified areas of GA cross-linked tissue showed characteristic hydroxyapatite (959 and 1038 cm–1) bands in the Raman spectrum and fluorescence lifetime shortened by 0.4 ns compared to uncalcified regions. FLIm-guided Raman imaging could rapidly identify degrees of cross-linking and detected calcified regions with high chemical specificity, an ability that can be used to monitor tissue engineering processes for applications in regenerative medicine.

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“…Optical imaging technology, on the other hand, offers the possibility to assess tissue content and properties in a tissue-conservative approach that enables longitudinal monitoring. Time-resolved fluorescence imaging has been used to study collagen and elastin content [ 7 , 8 ], collagen cross-linking [ 9 ], recellularization processes [ 10 ], and mechanical properties [ 9 , 11 ] of tissues in a label-free and non-destructive manner. Time-resolved fluorescence is a versatile imaging technique that can be used in a microscope (FLIM) and through flexible optical fibers (FLIm).…”

Section: Introductionmentioning

confidence: 99%

FLIm and Raman Spectroscopy for Investigating Biochemical Changes of Bovine Pericardium upon Genipin Cross-Linking

et al. 2020

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Biomaterials used in tissue engineering and regenerative medicine applications benefit from longitudinal monitoring in a non-destructive manner. Label-free imaging based on fluorescence lifetime imaging (FLIm) and Raman spectroscopy were used to monitor the degree of genipin (GE) cross-linking of antigen-removed bovine pericardium (ARBP) at three incubation time points (0.5, 1.0, and 2.5 h). Fluorescence lifetime decreased and the emission spectrum redshifted compared to that of uncross-linked ARBP. The Raman signature of GE-ARBP was resonance-enhanced due to the GE cross-linker that generated new Raman bands at 1165, 1326, 1350, 1380, 1402, 1470, 1506, 1535, 1574, 1630, 1728, and 1741 cm−1. These were validated through density functional theory calculations as cross-linker-specific bands. A multivariate multiple regression model was developed to enhance the biochemical specificity of FLIm parameters fluorescence intensity ratio (R2 = 0.92) and lifetime (R2 = 0.94)) with Raman spectral results. FLIm and Raman spectroscopy detected biochemical changes occurring in the collagenous tissue during the cross-linking process that were characterized by the formation of a blue pigment which affected the tissue fluorescence and scattering properties. In conclusion, FLIm parameters and Raman spectroscopy were used to monitor the degree of cross-linking non-destructively.

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Label-free assessment of carotid artery biochemical composition using fiber-based fluorescence lifetime imaging

Cited by 13 publications

References 47 publications

Mesoscopic fluorescence lifetime imaging: Fundamental principles, clinical applications and future directions

Mesoscopic fluorescence lifetime imaging: Fundamental principles, clinical applications and future directions

FLIm-Guided Raman Imaging to Study Cross-Linking and Calcification of Bovine Pericardium

FLIm and Raman Spectroscopy for Investigating Biochemical Changes of Bovine Pericardium upon Genipin Cross-Linking

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