title: Correlative nonlinear optical microscopy and infrared nanoscopy reveals collagen degradation in altered parchments.
abstract: This paper presents the correlative imaging of collagen denaturation by nonlinear optical microscopy (NLO) and nanoscale infrared (IR) spectroscopy to obtain morphological and chemical information at different length scales. Such multiscale correlated measurements are applied to the investigation of ancient parchments, which are mainly composed of dermal fibrillar collagen. The main issue is to characterize gelatinization, the ultimate and irreversible alteration corresponding to collagen denaturation to gelatin, which may also occur in biological tissues. Key information about collagen and gelatin signatures is obtained in parchments and assessed by characterizing the denaturation of pure collagen reference samples. A new absorbing band is observed near the amide I band in the IR spectra, correlated to the onset of fluorescence signals in NLO images. Meanwhile, a strong decrease is observed in Second Harmonic signals, which are a structural probe of the fibrillar organization of the collagen at the micrometer scale. NLO microscopy therefore appears as a powerful tool to reveal collagen degradation in a non-invasive way. It should provide a relevant method to assess or monitor the condition of collagen-based materials in museum and archival collections and opens avenues for a broad range of applications regarding this widespread biological material.
authors.affiliation: Laboratoire Imagerie et Modélisation en Neurobiologie et Cancérologie, Univ. Paris-Sud, Univ. Paris-Diderot, CNRS, Université Paris-Saclay, 91405 Orsay cedex, France.
authors.forename: Gaël
authors.initials: G
authors.lastname: Latour
authors.affiliation: Centre de Recherche sur la Conservation, Sorbonne Universités, Muséum national d'Histoire naturelle, Ministère de la Culture et de la Communication, CNRS, 75005 Paris, France.
authors.forename: Laurianne
authors.initials: L
authors.lastname: Robinet
authors.affiliation: Laboratoire de Chimie Physique, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405 Orsay cedex, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Dazzi
authors.affiliation: Laboratoire de Chimie de la Matière Condensée de Paris, Sorbonne Universités, UPMC Univ Paris 06, CNRS, Collège de France, 75005 Paris, France.
authors.forename: François
authors.initials: F
authors.lastname: Portier
authors.affiliation: Laboratoire de Chimie Physique, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405 Orsay cedex, France.
authors.forename: Ariane
authors.initials: A
authors.lastname: Deniset-Besseau
authors.affiliation: Laboratoire d'Optique et Biosciences, Ecole Polytechnique, CNRS, INSERM, Université Paris-Saclay, 91128 Palaiseau cedex, France.
authors.forename: Marie-Claire
authors.initials: MC
authors.lastname: Schanne-Klein
mesh_terms: D003094:Collagen / Q000737:chemistry*; D000073758:Nonlinear Optical Microscopy / Q000379:methods*; D011489:Protein Denaturation; D059748:Proteolysis; D013055:Spectrophotometry, Infrared
chemical_list: D003094:Collagen