Achievement of cornea-like organizations in dense collagen I solutions: clues to the physico-chemistry of cornea morphogenesis

International audienceMultiphoton and electron microscopic analyses show that acido-soluble collagen I prepared in 5 mM acetic acid (pH 3.5) at concentration above 45 mg mL−1 spontaneously generates liquid crystal phases mimicking plywood organization found in cornea tissues. Those organizations extend for several hundred micrometers. Transmission electron microscopy reveals the presence of small nanofibrils organized in a complex phase, coupling overall smectic and cholesteric organizations together with local order. Those nanofibrils could be the mesogen elements giving rise to this plywood organization. These data provide clues to physico-chemical events that may take place in cornea morphogenesis in vivo. This result is invaluable for bioengineering fields, as this liquid crystal organization paves the way for the generation of collagen based bio-mimetic cornea matrices

Collagen-silica nanocomposites as dermal dressings preventing infection in vivo

The controlled delivery of multiple drugs from biomaterials is a timely challenge. In particular the nanocomposite approach offers a unique opportunity to combine the scaffold-forming ability and biocompatibility of hydrogels with the versatile and tunable drug release properties of micro- or nano-carriers. Here, we show that collagen-silica nanocomposites allowing for the prolonged release of two topical antibiotics are promising medicated dressings to prevent infection in wounds. For this purpose, core–shell silica particles loaded with gentamicin sulfate and sodium rifamycin were combined with concentrated collagen type I hydrogels. A dense fibrillar network of collagen exhibiting its typical periodic banding pattern and a homogenous particle distribution were observed by scanning electron microscopy. Antibiotics release from nanocomposites allowed a sustained antibacterial effect against Staphylococcus aureus over 10 days in vitro. The acute dermal irritation test performed on albino rabbit skin showed no sign of severe inflammation. The antibacterial efficiency of nanocomposites was evaluated in vivo in a model of cutaneous infection, showing a 2 log steps decrease in bacterial population when loaded systems were used. In parallel, the histological examination indicated the absence of M1 inflammatory macrophages in the wound bed after treatment. Taken together, these results illustrate the potentialities of the nanocomposite approach to develop collagen-based biomaterials with controlled dual drug delivery to prevent infection and promote cutaneous wound repair.Fil: Mebert, Andrea Mathilde. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Alvarez, Gisela Solange. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Peroni, Roxana Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Farmacológicas. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Investigaciones Farmacológicas; ArgentinaFil: Illoul, Corinne. Centre National de la Recherche Scientifique; FranciaFil: Hélary, Christophe. Centre National de la Recherche Scientifique; FranciaFil: Coradin, Thibaud. Centre National de la Recherche Scientifique; FranciaFil: Desimone, Martín Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; Argentin

Development of human corneal epithelium on organized fibrillated transparent collagen matrices synthesized at high concentration

International audienceSeveral diseases can lead to opacification of cornea requiring transplantation of donor tissue to restore vision. In this context, transparent collagen I fibrillated matrices have been synthesized at 15, 30, 60 and 90 mg/mL. The matrices were evaluated for fibril organizations, transparency, mechanical properties and ability to support corneal epithelial cell culture. The best results were obtained with 90 mg/mL scaffolds. At this concentration, the fibril organization presented some similarities to that found in corneal stroma. Matrices had a mean Young's modulus of 570 kPa and acellular scaffolds had a transparency of 87% in the 380-780 nm wavelength range. Human corneal epithelial cells successfully colonized the surface of the scaffolds and generated an epithelium with characteristics of corneal epithelial cells (i.e. expression of cytokeratin 3 and presence of desmosomes) and maintenance of stemness during culture (i.e. expression of Delta Np63 alpha and formation of holoclones in colony formation assay). Presence of cultured epithelium on the matrices was associated with increased transparency (89%). (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

USPIO–PEG nanoparticles functionalized with a highly specific collagen-binding peptide: a step towards MRI diagnosis of fibrosis

International audienceFibrosis is characterized by a pathologic deposition of collagen I, leading to impaired function of organs. Tissue biopsy is the gold standard method for the diagnosis of fibrosis but this is an invasive procedure, subject to sampling errors. Several non-invasive techniques such as magnetic resonance imaging (MRI) using non-specific probes have been developed but they are not fully satisfying as they allow diagnosis at a late stage. In this study, collagelin, a collagen-binding peptide has been covalently linked using click chemistry to pegylated Ultra Small Super Paramagnetic Iron Oxide Nanoparticles (USPIO–PO–PEG–collagelin NPs) with the aim of diagnosing fibrosis at an early stage by MRI. USPIO–PO–PEG–collagelin NPs showed a high affinity for collagen I, two times higher than that of free collagelin whereas not peptide labeled USPIO NPs (USPIO–PO–PEG-yne) did not present any affinity. NPs were not toxic for macrophages and fibroblasts. Diffusion through collagen hydrogels concentrated at 3 and 10 mg mL−1 revealed a large accumulation of USPIO–PO–PEG–collagelin NPs within the collagen network after 72 hours, ca. 3 times larger than that of unlabeled USPIO, thereby evidencing the specific targeting of collagen I. Moreover, the quantity of USPIO–PO–PEG–collagelin NPs accumulated within hydrogels was proportional to the collagen concentration. Subsequently, the NPs diffusion through collagen hydrogels was monitored by MRI. The MRI T2 time relaxation decreased much more significantly with depth for USPIO–PO–PEG–collagelin NPs compared to unlabeled ones. Taken together, these results show that USPIO–PEG–collagelin NPs are promising as effective MRI nanotracers for molecular imaging of fibrosis at an early stage

Synthesis of an Artificial Cornea Allowing In Vitro Colonization of the Host Cells

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