Mechanobiology of soft tissues: FT-Raman spectroscopic studies (original) (raw)
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Structural alteration of collagen fibres--spectroscopic and mechanical studies
Acta of bioengineering and biomechanics / Wrocław University of Technology, 2010
Fourier Transform Near Infrared Raman Spectroscopy has been used to monitor the molecular changes of collagen in a tendon subjected to strain. In the Raman spectrum of the unstrained tendon, some protein bands, mainly assigned to collagen, can be observed: amide I (1666 cm-1) and III (1266 and 1248 cm-1) vibrational modes and skeletal (C-C) stretching vibrations (816 and 940 cm-1). The position of these bands is changing with the increasing strain values. It is concluded that elastin and non-helical domains of collagen are initially involved in the load transfer and triple helices of collagen are gradually joining this process.
Biomacromolecules, 2011
Collagen is a versatile structural molecule in nature and is used as a building block in many highly organized tissues, such as bone, skin, and cornea. The functionality and performance of these tissues are controlled by their hierarchical organization ranging from the molecular up to macroscopic length scales. In the present study, polarized Raman microspectroscopic and imaging analyses were used to elucidate collagen fibril orientation at various levels of structure in native rat tail tendon under mechanical load. In situ humidity-controlled uniaxial tensile tests have been performed concurrently with Raman confocal microscopy to evaluate strain-induced chemical and structural changes of collagen in tendon. The methodology is based on the sensitivity of specific Raman scattering bands (associated with distinct molecular vibrations, such as the amide I) to the orientation and the polarization direction of the incident laser light. Our results, based on the changing intensity of Raman lines as a function of orientation and polarization, support a model where the crimp and gap regions of collagen hierarchical structure are straightened at the tissue and molecular level, respectively. However, the lack of measurable changes in Raman peak positions throughout the whole range of strains investigated indicates that no significant changes of the collagen backbone occurs with tensing and suggests that deformation is rather redistributed through other levels of the hierarchical structure.
FT-Raman spectroscopic study of human skin subjected to uniaxial stress
Journal of the Mechanical Behavior of Biomedical Materials
Fourier Transform Raman Spectroscopy was used to investigate the molecular changes of structural proteins in human skin subjected to strain. In the Raman spectrum of unstrained skin, bands assigned mainly to collagen and elastin were observed at 1658cm(-1) (amide I), 1271 and 1255cm(-1) (amide III), and 935 and 817cm(-1) (CC stretching modes of the protein backbone). Moreover, bands characteristic for amino acids were observed at 1336cm(-1) (desmosine), 1004cm(-1) (phenylalanine), 919 and 856cm(-1) (proline), and 877cm(-1) (hydroxyproline). Positions and intensities of the listed Raman bands were analysed as a function of applied strain. A clear correlation between Raman wavenumbers and the level of mechanical stress was established. Wavenumbers of the analysed bands changed gradually with increasing strain. Distinct responses, depending on the sample cutting direction, i.e. longitudinal or perpendicular to the Langer's lines, were noticed. It was concluded that elastin and non...
Ultrastructural elastic deformation of cortical bone tissue probed by NIR Raman spectroscopy
SPIE Proceedings, 2004
Raman spectroscopy is used as a probe of ultrastructural (molecular) changes in both the mineral and matrix (protein and glycoprotein, predominantly type I collagen) components of murine cortical bone as it responds to loading in the elastic regime. At the ultrastructural level, crystal structure and protein secondary structure distort as the tissue is loaded. These structural changes are followed as perturbations to tissue spectra. We load tissue in a custom-made dynamic mechanical tester that fits on the stage of a Raman microprobe and can accept hydrated tissue specimens. As the specimen is loaded in tension and/or compression, the shifts in mineral P-O 4 ν 1 and relative band heights in the Amide III band envelope are followed with the microprobe. Average load is measured using a load cell while the tissue is loaded under displacement control. Changes occur in both the mineral and matrix components of bone as a response to elastic deformation. We propose that the mineral apatitic crystal lattice is deformed by movement of calcium and other ions. The matrix is proposed to respond by deformation of the collagen backbone. Raman microspectroscopy shows that bone mineral is not a passive contributor to tissue strength. The mineral active response to loading may function as a local energy storage and dissipation mechanism, thus helping to protect tissue from catastrophic damage.
Spectroscopy-an International Journal, 2012
The goal of this work was to evaluate the ability of Raman spectroscopy to identify molecular organization and chemical composition of extracellular matrix such as the collagen fibers arrangement, the level of mineralization, and the carbonate accumulation in mineral phase in spongy bone of the human head of the femur. Changes in composition and structure of the spongy bone tissue were illustrated using maps of polarized Raman spectra. In particular, the purpose of the present study was determination of arrangement of mineralized collagen on surface of trabecula by using transformations of Raman spectra maps. Transformations of Raman spectra maps were needed in order to remove impact of chemical composition on images of Raman spectra map, which display the collagen fibers orientation. These transformations allow to obtain simultaneously the distribution of constituents of bone and arrangement of collagen fibers on tissue surface. A method to indicate the collagen orientations is developed to understand the molecular organization in healthy and unhealthy bone at the microstructural level.
Characterisation of structural changes in collagen with Raman spectroscopy
Applied Spectroscopy Reviews, 2019
Raman spectroscopy can detect conformational changes in collagen structures and these findings are reviewed in this article. More specifically, some progressive diseases are mainly caused by alterations of collagen molecules but what is occurring at the biochemical level of this complex molecule usually remains unclear. While it may be true that a number of analytical techniques can analyze collagen, most of them have a series of limitations that limit their applicability to a wide range of samples. To understand in more detail the progression of a disease due to changes in the collagen structure, a technique that can detect subtle alterations at the biochemical level is needed. Raman spectroscopy is a label-free and noninvasive technique that can easily pick up on any conformational changes reflected primarily at the lipids, amides and proline and hydroxyproline regions. This review is the first compilation of studies of conformational changes in collagen molecules, providing help to understand changes in collagen biochemistry that can be of relevance to the human wound healing, ageing and pathologies.
FT-Raman spectroscopic study of thoracic aortic wall subjected to uniaxial stress
Journal of Raman Spectroscopy, 2010
The combination of Fourier transform-Raman spectroscopy and uniaxial tensile tests (in MTS Synergie 100 testing machine) was used to investigate microstructural changes in the secondary protein structure of the aortic wall under different levels of stress. The spectroscopic analysis clearly shows differing tension thresholds for material excised in two directions: circumferential and longitudinal. This is confirmed by the results of macroscopic mechanical analyses. The application of strain does not lead to any noticeable change in the bandwidths of the Raman bands. The stress-controlled Raman band analysis shows that the modes at 938 cm −1 assigned as C α -C of the α-helix, 1660 cm −1 amide I (the unordered structure of elastin) and 1668 cm −1 amide I (the collagen triple helix) undergo wavenumber shifting, but the bands at 1004 cm −1 assigned to the phenyl ring breathing mode and 2940 cm −1 to the ν (CH 3 ) and ν (CH 2 ) modes are not affected during the elastic behaviour. A clear correlation between Raman band shifting and the level of mechanical stress has been established. Elastin alone participates in the transmission of low stresses in the circumferential direction, whereas both elastin and collagen take part in the transmission of physiological and higher stresses.
Raman Spectroscopy in Skeletal Tissue Disorders and Tissue Engineering: Present and Prospective
Tissue Engineering Part B: Reviews, 2021
Musculoskeletal disorders are the most common reason of chronic pain and disability, representing an enormous socioeconomic burden worldwide. In this review, new biomedical application fields for Raman spectroscopy (RS) technique related to skeletal tissues are discussed, showing that it can provide a comprehensive profile of tissue composition in situ, in a rapid, label-free, and nondestructive manner. RS can be used as a tool to study tissue alterations associated to aging, pathologies, and disease treatments. The main advantage with respect to currently applied methods in clinics is its ability to provide specific information on molecular composition, which goes beyond other diagnostic tools. Being compatible with water, RS can be performed without pretreatment on unfixed, hydrated tissue samples, without any labeling and chemical fixation used in histochemical methods. This review first provides the description of the basic principles of RS as a biotechnology tool and is introduced into the field of currently available RS-based techniques, developed to enhance Raman signals. The main spectral processing, statistical tools, fingerprint identification, and available databases are mentioned. The recent literature has been analyzed for such applications of RS as tendon and ligaments, cartilage, bone, and tissue engineered constructs for regenerative medicine. Several cases of proof-of-concept preclinical studies have been described. Finally, advantages, limitations, future perspectives, and challenges for the translation of RS into clinical practice have been also discussed.
Application of Raman scattering to the measurement of ligament tension
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2008
More marginal results and complications occur as a result of knee ligament surgery than of other common surgical procedure. Long-term success rates of anterior cruciate ligament reconstruction range between 75 and 90%. The goal of knee surgery is to restore the normal kinematics of the knee. If the tension is too high, the range of motion of the joint is restricted, resulting in abnormal stresses on the articular cartilage and the meniscuses, and interfering with the revascularization of the graft. The use of Raman spectroscopy for the measurement of tension in ligaments and tendons is described. Measurements of the Raman spectrum demonstrate that the Raman frequencies shift with applied tension.
Stress mapping of undamaged, strained, and failed regions of bone using Raman spectroscopy
Journal of Biomedical Optics, 2009
Stress differences via spectral shifts that arise among failed, strained, and undamaged regions of bone can be determined using Raman spectroscopy and double-notch specimens. A double-notch specimen is a model in which the early stages of fracture can be examined. Upon four-point bending, fracture occurs at one of the notches. Tissue near each notch is representative of bone in a state either directly before or after bone failure. Raman images were acquired among three regions: control, strained (root of unbroken notch), and failed (root of fractured notch). The center of gravities (CGs), a way to monitor wavenumber shifts, of the phosphate ν 1 band were calculated. A PO 4 −3 ν 1 band shift most likely corresponded to a change in spacing between phosphate cations and anions. This spectral shift was converted into stress values using the dν/dP coefficient, determined by applying known pressures/stresses and measuring the change in position of the PO 4 −3 ν 1 band. In comparison to control regions, the residual stress in strained and failed regions was significantly higher (p=0.0425 and p=0.0169, respectively). In strained regions, residual stress was concentrated near the corners of the unbroken notch, whereas in failed regions the high stresses were confined near the edge of the fracture.