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Title: Thermal and molecular investigation of laser tissue welding

Abstract

Despite the growing number of successful animal and human trials, the exact mechanisms of laser tissue welding remain unknown. Furthermore, the effects of laser heating on tissue on the molecular scale are not fully understood. To address these issues, a multi-front attack oil both extrinsic (solder/patch mediated) and intrinsic (laser only) tissue welding was launched using two-color infrared thermometry, computer modeling, weld strength assessment, biochemical assays, and vibrational spectroscopy. The coupling of experimentally measured surface temperatures with the predictive numerical simulations provided insight into the sub-surface dynamics of the laser tissue welding process. Quantification of the acute strength of the welds following the welding procedure enabled comparison among trials during an experiment, with previous experiments, and with other studies in the literature. The acute weld integrity also provided an indication of tile probability of long-term success. Molecular effects induced In the tissue by laser irradiation were investigated by measuring tile concentrations of specific collagen covalent crosslinks and characterizing the Fourier-Transform infrared (FTIR) spectra before and after the laser exposure.

Authors:
Publication Date:
Research Org.:
Lawrence Livermore National Lab., CA (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
665645
Report Number(s):
UCRL-LR-130533
ON: DE98057748; BR: YN0100000; CNN: W-7405-Eng-48
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1 Jun 1998
Country of Publication:
United States
Language:
English
Subject:
55 BIOLOGY AND MEDICINE, BASIC STUDIES; LASERS; WELDING; ANIMAL TISSUES; MATHEMATICAL MODELS; SPECTROSCOPY; IRRADIATION; MOLECULAR STRUCTURE

Citation Formats

Small, W., IV. Thermal and molecular investigation of laser tissue welding. United States: N. p., 1998. Web. doi:10.2172/665645.
Small, W., IV. Thermal and molecular investigation of laser tissue welding. United States. doi:10.2172/665645.
Small, W., IV. 1998. "Thermal and molecular investigation of laser tissue welding". United States. doi:10.2172/665645. https://www.osti.gov/servlets/purl/665645.
@article{osti_665645,
title = {Thermal and molecular investigation of laser tissue welding},
author = {Small, W., IV},
abstractNote = {Despite the growing number of successful animal and human trials, the exact mechanisms of laser tissue welding remain unknown. Furthermore, the effects of laser heating on tissue on the molecular scale are not fully understood. To address these issues, a multi-front attack oil both extrinsic (solder/patch mediated) and intrinsic (laser only) tissue welding was launched using two-color infrared thermometry, computer modeling, weld strength assessment, biochemical assays, and vibrational spectroscopy. The coupling of experimentally measured surface temperatures with the predictive numerical simulations provided insight into the sub-surface dynamics of the laser tissue welding process. Quantification of the acute strength of the welds following the welding procedure enabled comparison among trials during an experiment, with previous experiments, and with other studies in the literature. The acute weld integrity also provided an indication of tile probability of long-term success. Molecular effects induced In the tissue by laser irradiation were investigated by measuring tile concentrations of specific collagen covalent crosslinks and characterizing the Fourier-Transform infrared (FTIR) spectra before and after the laser exposure.},
doi = {10.2172/665645},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1998,
month = 6
}

Technical Report:

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  • The work was undertaken to establish whether polarized Raman spectra recorded through the Raman microprobe could reveal evidence of molecular orientation among cell wall constituents relative to the morphology of cell walls in woody tissue, and whether they are capable of detecting compositional variation within cell walls, both within individual cells and between adjacent cells. The findings were affirmative in both instances. That is, evidence of molecular orientation relative to the plane of the cell wall was found for both lignin and cellulose. Furthermore, compositional variations were detected between different locations within an individual cell wall, and to an evenmore » greater extent between cell walls of adjacent cells. Innovations were made with respect to procedures for optimizing performance of the microprobe, and in the preparation and mounting of the samples of native tissue for acquisition of the micro-Raman spectra. In the course of supporting work to obtain reference spectra from highly crystalline celluloses, a cellulose more highly ordered than any previously reported was isolated from the alga Rhizoclonium hieroglyphicum. 32 references, 14 figures, 5 tables.« less
  • Raman microprobe spectroscopy has been used to investigate molecular architecture in the cell walls of native woody tissue. At the outset it was demonstrated that spectra can be acquired from cell wall domains as small as 1 to 3 micrometers in diameter, and that polarized Raman spectra are sensitive to the orientation of the electric vector of the exciting laser beam relative to the plane of the cell wall. Spectra of adjacent points on cell wall sections have been examined and compared with spectra from points in the walls of adjacent cells. The spectra were interpreted in terms of themore » orientation of molecular species relative to the plane of the cell wall and the compositional variations within the cells and between cells. Both the aromatic components of lignin and the anhydroglucose rings of cellulose appear to be oriented with respect to the plane of the cell wall. The ratio of lignin to cellulose varies from point to point in the cell wall and over an even wider range between points on different cells. Some studies of native celluloses were carried out in order to characterize the spectral features associated with cellulose. 10 refs.« less
  • Although the primary emphasis of our program has remained with the application of Raman spectroscopy to the study of native tissue, the scope of the work has been expanded to include a number of complementary approaches. These have included Solid State 13C NMR, autoradiography of radiolabeled woody tissue sections, and the generation of biomimetic tertiary aggregates which simulate states of aggregation characteristic of cell walls. Our Raman spectroscopic studies have resulted in progress in the areas of interpretation of the spectral features, and confirmation of the variability of the patterns of orientation of lignin reported earlier. We have assembled andmore » made operational our new microprobe and spectrometer systems acquired under the DOE-URIP program. We have also demonstrated that, operating with gated detection and pulsed laser excitation, we can discriminate against the laser-excited fluorescence characteristic of most woody tissue. Our studies of celluloses, which combine Raman spectroscopy and 13C NMR have shown that all native celluloses are composites of two forms which have the same secondary structure but different tertiary structures.« less
  • Efforts have been directed at understanding the sources of the luminescence which is encountered when plant tissue is exposed to laser excitation. The luminescence is one of the major obstacles to rapid acquisition of Raman spectra from such tissue. We are, therefore, developing procedures for limiting the interference of luminescence with acquisition of the spectra. We have established that the species contributing to luminescence in lignin rich samples differ from those dominant in purely cellulosic samples, and that the dominant luminescent processes are phosphorescent rather than fluorescent. We have also carried out a preliminary assessment of the utility of molecularmore » oxygen as an alternative to water for quenching the luminescence during acquisition of the Raman spectra. 3 refs., 1 fig.« less
  • The program has focused on installation of the Raman microprobe system and making it operational, on demonstrating the feasibility of the experimental approach, and on exploratory studies of molecular organization and structural variability in selected samples of plant tissue. The key findings are: (1) it is possible to acquire significant Raman spectral information from domains that are 1 to 3 ..mu..m in diameter in sections of plant cell walls; (2) polarized spectra are sensitive to orientation of the electric vector relative to the plane of the cell wall, indicating anisotropy of molecular organization with respect to the geometry of themore » cell; (3) preliminary explorations of woody tissue from black spruce and loblolly pine suggest that, in most instances, the aromatic rings of lignin are preferentially oriented in the plane of the cell wall, as are the anhydroglucose rings of the cellulose chains; and (4) preliminary studies also suggest that there is significant variation in the ratio of lignin to polysaccharide in the cell wall. In related studies, evidence of transverse anisotropy in the structure of ramie fibers has been detected. A spectrum of lignin in situ has been recorded by difference spectroscopy.« less