title: A fractal nature for polymerized laminin.
abstract: Polylaminin (polyLM) is a non-covalent acid-induced nano- and micro-structured polymer of the protein laminin displaying distinguished biological properties. Polylaminin stimulates neuritogenesis beyond the levels achieved by ordinary laminin and has been shown to promote axonal regeneration in animal models of spinal cord injury. Here we used confocal fluorescence microscopy (CFM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) to characterize its three-dimensional structure. Renderization of confocal optical slices of immunostained polyLM revealed the aspect of a loose flocculated meshwork, which was homogeneously stained by the antibody. On the other hand, an ordinary matrix obtained upon adsorption of laminin in neutral pH (LM) was constituted of bulky protein aggregates whose interior was not accessible to the same anti-laminin antibody. SEM and AFM analyses revealed that the seed unit of polyLM was a flat polygon formed in solution whereas the seed structure of LM was highly heterogeneous, intercalating rod-like, spherical and thin spread lamellar deposits. As polyLM was visualized at progressively increasing magnifications, we observed that the morphology of the polymer was alike independently of the magnification used for the observation. A search for the Hausdorff dimension in images of the two matrices showed that polyLM, but not LM, presented fractal dimensions of 1.55, 1.62 and 1.70 after 1, 8 and 12 hours of adsorption, respectively. Data in the present work suggest that the intrinsic fractal nature of polymerized laminin can be the structural basis for the fractal-like organization of basement membranes in the neurogenic niches of the central nervous system.
authors.affiliation: Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Camila
authors.initials: C
authors.lastname: Hochman-Mendez
authors.affiliation: Division of Biomedical Engineering, School of Engineering, University of Glasgow, Glasgow, United Kingdom.
authors.forename: Marco
authors.initials: M
authors.lastname: Cantini
authors.affiliation: Center for Biomaterials and Tissue Engineering, Universitat Politècnica de València, València, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Moratal
authors.affiliation: Division of Biomedical Engineering, School of Engineering, University of Glasgow, Glasgow, United Kingdom.
authors.forename: Manuel
authors.initials: M
authors.lastname: Salmeron-Sanchez
authors.affiliation: Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Coelho-Sampaio
mesh_terms: D001485:Basement Membrane / Q000378:metabolism; D017709:Fractals; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007797:Laminin / Q000737:chemistry*; D008853:Microscopy; D055503:Protein Multimerization; D000644:Quaternary Ammonium Compounds
chemical_list: D007797:Laminin; D000644:Quaternary Ammonium Compounds