title: Photobleaching as a tool to measure the local strain field in fibrous membranes of connective tissues.
abstract: Connective tissues are complex structures which contain collagen and elastin fibers. These fiber-based structures have a great influence on material mechanical properties and need to be studied at the microscopic scale. Several microscopy techniques have been developed in order to image such microstructures; among them are two-photon excited fluorescence microscopy and second harmonic generation. These observations have been coupled with mechanical characterization to link microstructural kinematics to macroscopic material parameter evolution. In this study, we present a new approach to measure local strain in soft biological tissues using a side-effect of fluorescence microscopy: photobleaching. Controlling the loss of fluorescence induced by photobleaching, we create a pattern on our sample that we can monitor during mechanical loading. The image analysis allows three-dimensional displacements of the patterns at various loading levels to be computed. Then, local strain distribution is derived using the finite element discretization on a four-node element mesh created from our photobleached pattern. Photobleaching tests on a human liver capsule have revealed that this technique is non-destructive and does not have any impact on mechanical properties. This method is likely to have other applications in biological material studies, considering that all collagen-elastin fiber-based biological tissues possess autofluorescence properties and thus can be photobleached.
authors.affiliation: Université de Lyon, F-69622 Lyon;IFSTTAR, LBMC, UMR-T9406; Université Lyon 1, France. Electronic address: charles.jayyosi@ifsttar.fr.
authors.forename: C
authors.initials: C
authors.lastname: Jayyosi
authors.affiliation: Plateforme IVTV, CNRS, 36 Avenue Guy de Collongue, Bâtiment G8, 69134 Ecully Cedex, France.
authors.forename: G
authors.initials: G
authors.lastname: Fargier
authors.affiliation: LUNAM Université, GEM, UMR CNRS 6183, Ecole Centrale de Nantes, Université de Nantes, France.
authors.forename: M
authors.initials: M
authors.lastname: Coret
authors.affiliation: Université de Lyon, F-69622 Lyon;IFSTTAR, LBMC, UMR-T9406; Université Lyon 1, France.
authors.forename: K
authors.initials: K
authors.lastname: Bruyère-Garnier
mesh_terms: D003238:Connective Tissue / Q000737:chemistry*; D006801:Humans; D008856:Microscopy, Fluorescence; D038761:Photobleaching; D013312:Stress, Physiological
keywords: Collagen; Elastin; Multiphoton microscopy; Photobleaching; Strain measurement