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Microscopie de second harmonique résolue en polarisations linéaire et circulaire pour caractériser l'organisation 3D du collagène

Abstract : Collagen is a major component of organ architecture in mammals where it forms various three-dimensional (3D) structures specific to each tissue. The visualization of this multi-scale 3D organization is crucial to decipher the structure of organs such as the cornea or the skin and to guide the engineering fully functional tissue substitutes. Moreover, the organization of collagen is also affected in many diseases, so that in situ quantitative characterization of such disorders is a major biomedical issue.SHG microscopy has been recognized for several years as the gold-standard technique for imaging fibrillar collagen in situ in unmarked tissues with excellent contrast. This thesis presents the development and the application of new polarization-based SHG microscopy modalities to obtain reliable and quantitative parameters in order to more accurately describe the three-dimensional structure of collagen.First, we present a modality using linear incident polarizations (P-SHG) to analyze the multi-scale organization of collagen in various tissues, healthy and pathological. These analyses were carried out on cultural heritage objects (parchments, made of collagen from animal skins) as well as on biological tissues (corneas). On one hand, taking advantage of the non-invasive nature of this modality, we characterize the degradation of collagen in ancient parchments, precious objects of art and history. This proves the interest of SHG microscopy in the field of cultural heritage, particularly to decipher the state of conservation of objects rich in collagen. On the other hand, quantitative imaging of healthy human corneas is presented, and compared to corneas with keratoconus, a common pathology today. Murine models of corneal keratoconus are also being studied to validate their relevance.Finally, a modality using circular incident polarizations to measure circular dichroism signals (CD-SHG) is exposed. First, we present the rigorous experimental implementation of this modality, by identifying and correcting typical artifacts of this technique. Secondly, we propose a new theoretical approach to describe CD-SHG signals. Numerical simulations of the obtained analytical expression are compared to experimental results in order to understand the evolution of CD-SHG signals with the 3D architecture of collagen.
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Margaux Schmeltz. Microscopie de second harmonique résolue en polarisations linéaire et circulaire pour caractériser l'organisation 3D du collagène. Optique [physics.optics]. Université Paris Saclay (COmUE), 2019. Français. ⟨NNT : 2019SACLX074⟩. ⟨tel-02955517⟩

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