Articles

Monitoring dynamic collagen reorganization during skin stretching with fast polarization‐resolved second harmonic generation imaging
- Ducourthial Guillaume
- Affagard Jean‐sébastien
- Schmeltz Margaux
- Solinas Xavier
- Lopez‐poncelas Maeva
- Bonod‐bidaud Christelle
- Rubio‐amador Ruth
- Ruggiero Florence
- Allain Jean-Marc
- Beaurepaire Emmanuel
- Schanne-Klein Marie-Claire
Journal of Biophotonics, Wiley , 2019, 12 (5), pp.e201800336 . The mechanical properties of biological tissues are strongly correlated to the specific distribution of their collagen fibers. Monitoring the dynamic reorganization of the collagen network during mechanical stretching is however a technical challenge because it requires mapping orientation of collagen fibers in a thick and deforming sample. In this work, a fast polarization-resolved SHG microscope is implemented to map collagen orientation during mechanical assays. This system is based on line-to-line switching of polarization using an electro-optical modulator and works in epidetection geometry. After proper calibration, it successfully highlights the collagen dynamic alignment along the traction direction in ex vivo murine skin dermis. This microstructure reorganization is quantified by the entropy of the collagen orientation distribution as a function of the stretch ratio. It exhibits a linear behavior, whose slope is measured with a good accuracy. This approach can be generalized to probe a variety of dynamic processes in thick tissues. (10.1002/jbio.201800336)
DOI : 10.1002/jbio.201800336
Generalized time delay, velocity, and absorption in dispersive and absorbing media
- Gallot Guilhem
Physical Review A, American Physical Society , 2019, 99 (1) . (10.1103/PhysRevA.99.013829)
DOI : 10.1103/PhysRevA.99.013829
Ces manuscrits que l’on croyait perdus – La renaissance des manuscrits de Chartres
- Robinet Laurianne
- Pottier Fabien
- Schmeltz Margaux
- Heu-Thao Sylvie
- Poirel Dominique
- Rabel Claudia
- Schanne-Klein Marie-Claire
- Latour Gaël
- Michelin Anne
Support Tracé, Association pour la Recherche Scientifique sur les Arts Graphiques (ARSAG) , 2019, 18, pp.12-21 .
Size-Exclusion Mechanism Driving Host-Guest Interactions between Octahedral Rhenium Clusters and Cyclodextrins
- Ivanov Anton A
- Falaise Clement
- Laouer Kevin
- Hache François
- Changenet Pascale
- Mironov Yuri V
- Landy David
- Molard Yann
- Cordier Stéphane
- Shestopalov Michael A
- Haouas Mohamed
- Cadot Emmanuel
Inorganic Chemistry, American Chemical Society , 2019, 58 (19), pp.13184-13194 . In aqueous solution, cyclodextrins (CDs) are able to bind strongly either hydrophobic species or also hydrophilic molecules such as octahedral hexametallic cluster. Systematic investigation of the reactivity between native CDs (α- or β-CD) and water-soluble rhenium clusters [ReQ(CN)] with Q = S, Se, and Te were performed, leading to six new crystal structures revealing different types of supramolecular arrangements. Encapsulation of [ReQ(CN)] (Q = S, Se, or Te) within two β-CDs is observed regardless of the cluster size. Interestingly, different assembling scenarios are pointed out depending on the host-guest matching featured by no, partial, or deep inclusion complexes that involved either primary or secondary rim of the CD tori. In the specific case of α-CD, only the smaller cluster [ReS(CN)] is able to form inclusion complex with the tori host. Solution investigations, using a set of complementary techniques including isothermal titration calorimetry, multinuclear NMR methods, cyclic voltammetry, and electrospray ionization mass spectrometry, corroborate nicely conclusions of the solid-state studies. It appears clearly that size-matching supported by solvent effects play key roles in the stability of the host-guest complexes. At last, circular dichroism studies underline that the chirality induction from cyclodextrins to the rhenium cluster depends strongly on the strength of host-guest interactions. (10.1021/acs.inorgchem.9b02048)
DOI : 10.1021/acs.inorgchem.9b02048
An actin-based viscoplastic lock ensures progressive body-axis elongation
- Lardennois Alicia
- Ferraro Teresa
- Llense Flora
- Labouesse Michel
- Pásti Gabriella
- Pontabry Julien
- Rodriguez David
- Kim Samantha
- Gally Christelle
- Mahou Pierre
- Beaurepaire Emmanuel
- Ono Shoichiro
Nature, Nature Publishing Group , 2019, 573 (7773), pp.266-270 . Body-axis elongation constitutes a key step in animal development, laying out the final form of the entire animal. It relies on the interplay between intrinsic forces generated by molecular motors1,2,3, extrinsic forces exerted by adjacent cells4,5,6,7 and mechanical resistance forces due to tissue elasticity or friction8,9,10. Understanding how mechanical forces influence morphogenesis at the cellular and molecular level remains a challenge1. Recent work has outlined how small incremental steps power cell-autonomous epithelial shape changes1,2,3, which suggests the existence of specific mechanisms that stabilize cell shapes and counteract cell elasticity. Beyond the twofold stage, embryonic elongation in Caenorhabditis elegans is dependent on both muscle activity7 and the epidermis; the tension generated by muscle activity triggers a mechanotransduction pathway in the epidermis that promotes axis elongation7. Here we identify a network that stabilizes cell shapes in C. elegans embryos at a stage that involves non-autonomous mechanical interactions between epithelia and contractile cells. We searched for factors genetically or molecularly interacting with the p21-activating kinase homologue PAK-1 and acting in this pathway, thereby identifying the α-spectrin SPC-1. Combined absence of PAK-1 and SPC-1 induced complete axis retraction, owing to defective epidermal actin stress fibre. Modelling predicts that a mechanical viscoplastic deformation process can account for embryo shape stabilization. Molecular analysis suggests that the cellular basis for viscoplasticity originates from progressive shortening of epidermal microfilaments that are induced by muscle contractions relayed by actin-severing proteins and from formin homology 2 domain-containing protein 1 (FHOD-1) formin bundling. Our work thus identifies an essential molecular lock acting in a developmental ratchet-like process. (10.1038/s41586-019-1509-4)
DOI : 10.1038/s41586-019-1509-4
A Molecular Mechanics Model for Flavins
- Aleksandrov Alexey
Journal of Computational Chemistry, Wiley , 2019, 40 (32), pp.2834-2842 . Flavin containing molecules form a group of important cofactors that assist a wide range of enzymatic reactions. Flavins use the redox‐active isoalloxazine system, which is capable of one‐ and two‐electron transfer reactions and can exist in several protonation states. In this work, molecular mechanics force field parameters compatible with the CHARMM36 all‐atom additive force field were derived for biologically important flavins, including riboflavin, flavin mononucleotide, and flavin adenine dinucleotide. The model was developed for important protonation and redox states of the isoalloxazine group. The partial charges were derived using the CHARMM force field parametrization strategy, where quantum mechanics water–solute interactions are used to target optimization. In addition to monohydrate energies and geometries, electrostatic potential around the compound was used to provide additional restraints during the charge optimization. Taking into account the importance of flavin‐containing molecules special attention was given to the quality of bonded terms. All bonded terms, including stiff terms and torsion angle parameters, were parametrized using exhaustive potential energy surface scans. In particular, the model reproduces well the butterfly motion of isoalloxazine in the oxidized and reduced forms as predicted by quantum mechanics in gas phase. The model quality is illustrated by simulations of four flavoproteins. Overall, the presented molecular mechanics model will be of utility to model flavin cofactors in different redox states. (10.1002/jcc.26061)
DOI : 10.1002/jcc.26061
Implementation of artifact-free circular dichroism SHG imaging of collagen
- Schmeltz Margaux
- Teulon Claire
- Latour Gaël
- Ghoubay Djida
- Borderie Vincent
- Aimé Carole
- Schanne-Klein Marie-Claire
Optics Express, Optical Society of America - OSA Publishing , 2019, 27 (16), pp.22685 . Second harmonic generation (SHG) enables in situ imaging of fibrillar collagen architecture in connective tissues. Recently, Circular Dichroism SHG (CD-SHG) microscopy has been implemented to take advantage of collagen chirality to improve 3D visualization. It measures the normalized difference in the SHG signal obtained upon excitation by left versus right circular polarizations. However, CD-SHG signal is not well characterized yet, and quite different CD-SHG values are reported in the literature. Here, we identify two major artifacts that may occur in CD-SHG experiments and we demonstrate that thorough optimization and calibration of the experimental setup are required for CD-SHG imaging. Notably it requires a careful calibration of the incident circular polarizations and a perfect mechanical stabilization of the microscope stage. Finally, we successfully record CD-SHG images in human cornea sections and confirm that this technique efficiently reveals collagen fibrils oriented out of the focal plane. (10.1364/OE.27.022685)
DOI : 10.1364/OE.27.022685
Structural and functional insight into serine hydroxymethyltransferase from Helicobacter pylori
- Sodolescu Andreea
- Dian Cyril
- Terradot Laurent
- Bouzhir-Sima Latifa
- Lestini Roxane
- Myllykallio Hannu
- Skouloubris Stéphane
- Liebl Ursula
PLoS ONE, Public Library of Science , 2018, 13 (12), pp.e0208850 . Serine hydroxymethyltransferase (SHMT), encoded by the glyA gene, is a ubiquitous pyridoxal 5’-phosphate (PLP)-dependent enzyme that catalyzes the formation of glycine from serine. The thereby generated 5,10-methylene tetrahydrofolate (MTHF) is a major source of cellular one-carbon units and a key intermediate in thymidylate biosynthesis. While in virtually all eukaryotic and many bacterial systems thymidylate synthase ThyA, SHMT and dihydrofolate reductase (DHFR) are part of the thymidylate/folate cycle, the situation is different in organisms using flavin-dependent thymidylate synthase ThyX. Here the distinct catalytic reaction directly produces tetrahydrofolate (THF) and consequently in most ThyX-containing organisms, DHFR is absent. While the resulting influence on the folate metabolism of ThyX-containing bacteria is not fully understood, the presence of ThyX may provide growth benefits under conditions where the level of reduced folate derivatives is compromised. Interestingly, the third key enzyme implicated in generation of MTHF, serine hydroxymethyltransferase (SHMT), has a universal phylogenetic distribution, but remains understudied in ThyX-containg bacteria. To obtain functional insight into these ThyX-dependent thymidylate/folate cycles, we characterized the predicted SHMT from the ThyX-containing bacterium Helicobacter pylori. Serine hydroxymethyltransferase activity was confirmed by functional genetic complementation of a glyA-inactivated E. coli strain. A H. pylori ΔglyA strain was obtained, but exhibited markedly slowed growth and had lost the virulence factor CagA. Biochemical and spectroscopic evidence indicated formation of a characteristic enzyme-PLP-glycine-folate complex and revealed unexpectedly weak binding affinity of PLP. The three-dimensional structure of the H. pylori SHMT apoprotein was determined at 2.8Ǻ resolution, suggesting a structural basis for the low affinity of the enzyme for its cofactor. Stabilization of the proposed inactive configuration using small molecules has potential to provide a specific way for inhibiting HpSHMT. (10.1371/journal.pone.0208850)
DOI : 10.1371/journal.pone.0208850
Author Correction: A mechanism for CO regulation of ion channels
- Kapetanaki Sofia
- Burton Mark
- Basran Jaswir
- Uragami Chiasa
- Moody Peter
- Mitcheson John
- Schmid Ralf
- Davies Noel
- Dorlet Pierre
- Vos Marten H.
- Storey Nina
- Raven Emma
Nature Communications, Nature Publishing Group , 2018, 9, pp.3354 . The originally published version of this article contained an error in the subheading ‘Heme is required for CO-dependent channel activation’, which was incorrectly given as ‘Hame is required for CO-dependent channel activation’. This has now been corrected in both the PDF and HTML versions of the Article (10.1038/s41467-018-05622-6)
DOI : 10.1038/s41467-018-05622-6
Color Imaging with Multimodal Three-Photon Microscopy
- Abdeladim Lamiae
- Mahou Pierre
- Supatto Willy
- Beaurepaire Emmanuel
- Guesmi Khmaies
- Jurkus Karolis
- Rigaud Philippe
- Georges Patrick
- Hanna Marc
- Druon Frédéric
- Tozer Samuel
- Kumamoto Takuma
- Loulier Karine
- Livet Jean
- Dray Nicolas
Optics and photonics news, Optical Society of America - OSA Publishing , 2018 .
Advances and challenges in drug design against tuberculosis: application of in silico approaches
- Aleksandrov Alexey
- Myllykallio Hannu
Expert Opinion on Drug Discovery, Informa Healthcare , 2018, pp.1 - 12 . (10.1080/17460441.2019.1550482)
DOI : 10.1080/17460441.2019.1550482
Chiral Cilia Orientation in the Left-Right Organizer
- Ferreira Rita
- Pakula Guillaume
- Klaeyle Lhéanna
- Fukui Hajime
- Vilfan Andrej
- Supatto Willy
- Vermot Julien
Cell Reports, Elsevier Inc , 2018, 25 (8), pp.2008-2016.e4 . (10.1016/j.celrep.2018.10.069)
DOI : 10.1016/j.celrep.2018.10.069
Snapshots of archaeal DNA replication and repair in living cells using super-resolution imaging
- Delpech Floriane
- Collien Yoann
- Mahou Pierre
- Beaurepaire Emmanuel
- Myllykallio Hannu
- Lestini Roxane
Nucleic Acids Research, Oxford University Press , 2018 . (10.1093/nar/gky829)
DOI : 10.1093/nar/gky829
Combining the polarizable Drude force field with a continuum electrostatic Poisson-Boltzmann implicit solvation model
- Aleksandrov Alexey
- Lin Fang-Yu
- Roux Benoît
- Mackerell Alexander
Journal of Computational Chemistry, Wiley , 2018, 39 (22), pp.1707-1719 . (10.1002/jcc.25345)
DOI : 10.1002/jcc.25345
Resonant broadband stimulated Raman scattering in myoglobin
- Ferrante C.
- Batignani G.
- Fumero G.
- Pontecorvo E.
- Virga A.
- Montemiglio L.
- Cerullo G.
- Vos Marten H.
- Scopigno T.
Journal of Raman Spectroscopy, Wiley , 2018, 49 (6), pp.913-920 . (10.1002/jrs.5323)
DOI : 10.1002/jrs.5323
Activation of the mismatch-specific endonuclease EndoMS/NucS by the replication clamp is required for high fidelity DNA replication
- Ishino Sonoko
- Skouloubris Stéphane
- Kudo Hanae
- L’hermitte-Stead Caroline
- Es-Sadik Asmae
- Lambry Jean-Christophe
- Ishino Yoshizumi
- Myllykallio Hannu
Nucleic Acids Research, Oxford University Press , 2018 . The mismatch repair (MMR) system, exemplified by the MutS/MutL proteins, is widespread in Bacteria and Eukarya. However, molecular mechanisms how numerous archaea and bacteria lacking the mutS/mutL genes maintain high replication fidelity and genome stability have remained elusive. EndoMS is a recently discovered hyperthermophilic mismatch-specific endonuclease encoded by nucS in Thermococcales. We deleted the nucS from the actinobacterium Corynebacterium glutamicum and demonstrated a drastic increase of spontaneous transition mutations in the nucS deletion strain. The observed spectra of these mutations were consistent with the enzymatic properties of EndoMS in vitro. The robust mismatch-specific endonuclease activity was detected with the purified C. glutamicum EndoMS protein but only in the presence of the β-clamp (DnaN). Our biochemical and genetic data suggest that the frequently occurring G/T mismatch is efficiently repaired by the bacterial EndoMS-β−clamp complex formed via a carboxy-terminal sequence motif of EndoMS proteins. Our study thus has great implications for understanding how the activity of the novel MMR system is coordinated with the replisome and provides new mechanistic insight into genetic diversity and mutational patterns in industrially and clinically (e.g. Mycobacteria) important archaeal and bacterial phyla previously thought to be devoid of the MMR system. (10.1093/nar/gky460)
DOI : 10.1093/nar/gky460
Unique Features and Anti-microbial Targeting of Folate- and Flavin-Dependent Methyltransferases Required for Accurate Maintenance of Genetic Information
- Myllykallio Hannu
- Sournia Pierre
- Héliou Alice
- Liebl Ursula
Frontiers in Microbiology, Frontiers Media , 2018, 9, pp.918 . Comparative genome analyses have led to the discovery and characterization of novel flavin- and folate-dependent methyltransferases that mainly function in DNA precursor synthesis and post-transcriptional RNA modification by forming (ribo) thymidylate and its derivatives. Here we discuss the recent literature on the novel mechanistic features of these enzymes sometimes referred to as “uracil methyltransferases,” albeit we prefer to refer to them as (ribo) thymidylate synthases. These enzyme families attest to the convergent evolution of nucleic acid methylation. Special focus is given to describing the unique characteristics of these flavin- and folate-dependent enzymes that have emerged as new models for studying the non-canonical roles of reduced flavin cofactors (FADH2) in relaying carbon atoms between enzyme substrates. This ancient enzymatic methylation mechanism with a very wide phylogenetic distribution may be more commonly used for biological methylation reactions than previously anticipated. This notion is exemplified by the recent discovery of additional substrates for these enzymes. Moreover, similar reaction mechanisms can be reversed by demethylases, which remove methyl groups e.g., from human histones. Future work is now required to address whether the use of different methyl donors facilitates the regulation of distinct methylation reactions in the cell. It will also be of great interest to address whether the low activity flavin-dependent thymidylate synthases ThyX represent ancestral enzymes that were eventually replaced by the more active thymidylate synthases of the ThyA family to facilitate the maintenance of larger genomes in fast-growing microbes. Moreover, we discuss the recent efforts from several laboratories to identify selective anti-microbial compounds that target flavin-dependent thymidylate synthase ThyX. Altogether we underline how the discovery of the alternative flavoproteins required for methylation of DNA and/or RNA nucleotides, in addition to providing novel targets for antibiotics, has provided new insight into microbial physiology and virulence. (10.3389/fmicb.2018.00918)
DOI : 10.3389/fmicb.2018.00918
Use of MPA-capped CdS quantum dots for sensitive detection and quantification of Co2+ ions in aqueous solution
- Bel Haj Mohamed Naim
- Ben Brahim Nassim
- Mrad Randa
- Haouari Mohamed
- Ben Chaâbane Rafik
- Négrerie Michel
Analytica Chimica Acta, Elsevier Masson , 2018, 1028, pp.50 - 58 . Water soluble CdS quantum dots (QDs) were synthesized by a simple aqueous chemical route using mercaptopropionic acid (MPA) as a stabilizer. These QDs had a fluorescence emission band maximum at 540 nm with a FWHM ∼130 nm and a quantum yield of ∼12%. Transmission electronic microscopy images were used to determine the QD diameter of 8.9 ± 0.4 nm. From this value we calculated the molecular mass M(QD) = 1.17 × 106 g mol-1 and the extinction coefficient at the band edge (450 nm) ε450 = 4.7 × 106 cm-1 M-1, which allowed to determine the true molar concentration of 17 nM for spectroscopic measurements in solution. The fluorescence intensity of MPA-CdS QDs was quenched only in the presence of Co2+ ions, but not in the presence of thirteen other metal cations. The fluorescence quenching of MPA-CdS QDs appeared proportional to the Co2+ concentration in the range 0.04-2 μM. Based on a fluorescence peak position and a lifetime both independent from Co2+ concentration, the quenching mechanism of MPA-CdS QDs appeared static. Because the strong electronic absorption of Co2+ overlaps the emission of QDs, our results can be explained by Förster energy transfer from QD to the bound Co2+ cations. (10.1016/j.aca.2018.04.041)
DOI : 10.1016/j.aca.2018.04.041
Density of Grafted Chains in Thioglycerol-Capped CdS Quantum Dots Determines Their Interaction with Aluminum(III) in Water
- Ben Brahim Nassim
- Poggi Mélanie
- Lambry Jean-Christophe
- Bel Haj Mohamed Naim
- Ben Chaâbane Rafik
- Négrerie Michel
Inorganic Chemistry, American Chemical Society , 2018, 57, pp.4979 - 4988 . We aimed to quantify the interaction of watersoluble-functionalized CdS quantum dots (QDs) with metal cations from their composition and physical properties. From the diameter of thioglycerol-capped nanoparticles (TG-CdS QDs) measured by electronic microscopy (D = 12.3 ± 0.3 nm), we calculated the molecular mass of the individual particle MA QD = (3 ± 0.5) × 10 6 g•mol-1 and its molar absorption coefficient ε 450 = 21 × 10 6 M-1 •cm-1. We built a three-dimensional model of the TG-CdS QDs in agreement with the structural data, which allowed us to quantify the number of thioglycerol grafted chains to ∼2000 per QD. This value fully matches the saturation binding curve of Al 3+ cations interacting with TG-CdS QDs. The reaction occurred with a slow association rate (k on = 2.1 × 10 3 M-1 •s-1), as expected for heavy QDs. The photophysical properties of the functionalized QDs were studied using an absolute QD concentration of 7 nM, which allowed us to investigate the interaction with 14 metallic cations in water. The fluorescence intensity of TG-CdS QDs could be quenched only in the presence of Al 3+ ions in the range 0.2-10 μM but not with other cations and was not observed with other kinds of grafting chains. (10.1021/acs.inorgchem.7b03254)
DOI : 10.1021/acs.inorgchem.7b03254
Isolation and identification of two extremely halophilic archaea from sebkhas in the Algerian Sahara
- Khallef Sakina
- Lestini Roxane
- Myllykallio Hannu
- Houali Karim
Cellular and Molecular Biology, CMB Association , 2018, 64 (4), pp.83–91 . (10.14715/cmb/2018.64.4.14)
DOI : 10.14715/cmb/2018.64.4.14
Evolutionary insights into Trm112-methyltransferase holoenzymes involved in translation between archaea and eukaryotes
- Van tran Nhan
- Muller Leslie
- Ross Robert L
- Lestini Roxane
- Létoquart Juliette
- Ulryck Nathalie
- Limbach Patrick A
- De crécy-Lagard Valérie
- Cianférani Sarah
- Graille Marc
Nucleic Acids Research, Oxford University Press , 2018, 46 (16), pp.8483 - 8499 . Protein synthesis is a complex and highly coordinated process requiring many different protein factors as well as various types of nucleic acids. All translation machinery components require multiple maturation events to be functional. These include post-transcriptional and post-translational modification steps and methylations are the most frequent among these events. In eukaryotes, Trm112, a small protein (COG2835) conserved in all three domains of life, interacts and activates four methyltransferases (Bud23, Trm9, Trm11 and Mtq2) that target different components of the translation machinery (rRNA, tRNAs, release factors). To clarify the function of Trm112 in archaea, we have characterized functionally and structurally its interaction network using Haloferax volcanii as model system. This led us to unravel that methyltransferases are also privileged Trm112 partners in archaea and that this Trm112 network is much more complex than anticipated from eukaryotic studies. Interestingly, among the identified enzymes, some are functionally orthologous to eukaryotic Trm112 partners, emphasizing again the similarity between eukaryotic and archaeal translation machineries. Other partners display some similarities with bacterial methyltransferases, suggesting that Trm112 is a general partner for methyltransferases in all living organisms. (10.1093/nar/gky638)
DOI : 10.1093/nar/gky638
The Future of Multiplexed Eukaryotic Genome Engineering
- Thompson David
- Aboulhouda Soufiane
- Hysolli Eriona
- Smith Cory
- Wang Stan
- Castanon Oscar
- Church George
ACS Chemical Biology, American Chemical Society , 2018, 13 (2), pp.313 - 325 . Multiplex genome editing is the simultaneous introduction of multiple distinct modifications to a given genome. Though in its infancy, maturation of this field will facilitate powerful new biomedical research approaches and will enable a host of far-reaching biological engineering applications, including new therapeutic modalities and industrial applications, as well as “genome writing” and de-extinction efforts. In this Perspective, we focus on multiplex editing of large eukaryotic genomes. We describe the current state of multiplexed genome editing, the current limits of our ability to multiplex edits, and provide perspective on the many applications that fully realized multiplex editing technologies would enable in higher eukaryotic genomes. We offer a broad look at future directions, covering emergent CRISPR-based technologies, advances in intracellular delivery, and new DNA assembly approaches that may enable future genome editing on a massively multiplexed scale. (10.1021/acschembio.7b00842)
DOI : 10.1021/acschembio.7b00842
Analyse d’une carte du monde du VIIIe siècle : la Mappa mundi d’Albi
- Robinet Laurianne
- Deschaux Jocelyne
- Tournié Aurélie
- Stéphane Vaidelich
- Latour Gael
- Michelin Anne
- Thao Sylvie
- Andraud Christine
- Schanne-Klein Marie-Claire
- Lavédrine Bertrand
Support Tracé, Association pour la Recherche Scientifique sur les Arts Graphiques (ARSAG) , 2018, 17, pp.5-13 .
Highly concentrated collagen solutions leading to transparent scaffolds of controlled three-dimensional organizations for corneal epithelial cell colonization
- Tidu Aurelien
- Ghoubay-Benallaoua Djida
- Teulon Claire
- Asnacios Sophie
- Grieve Kate
- Portier François
- Schanne-Klein Marie-Claire
- Borderie Vincent M.
- Mosser Gervaise
Biomaterials Science, Royal Society of Chemistry (RSC) , 2018, 6 (6), pp.1492-1502 . This study aimed at controlling both the organization and the transparency of dense collagen scaffolds making use of the lyotropic mesogen properties of collagen. Cholesteric or plywood-like liquid crystal phases were achieved using mixtures of acetic and hydrochloric acids as solvents. The critical pH at which the switch between the two phases occurred was around pH = 3. The use of the two acids led to fibril-lated collagen I scaffolds, whose visual aspect ranged from opaque to transparent. Rheological investigations showed that viscoelastic properties of the plywood-like solutions were optimized for molding due to faster recovery. They also confirmed the correlation between the elastic modulus and the diameter of collagen fibrils obtained after fibrillogenesis under ammonia vapor. Human corneal epithelial cells, grown from donor limbal explants, were cultured both on transparent plywood-like matrices and on human amniotic membranes for 14 days. The development of corneal epithelium and the preservation of epi-thelial stem cells were checked by optical microscopy, colony formation assay, immuno-fluorescence and quantitative polymerase chain reaction. A higher level of amplification of limbal stem cells was obtained with collagen matrices compared with amniotic membranes, showing the high biocompatibility of our scaffolds. We therefore suggest that collagen solutions presenting both plywood-like organization and transparency might be of interest for biomedical applications in ophthalmology. (10.1039/c7bm01163f)
DOI : 10.1039/c7bm01163f
Multiscale conformational dynamics probed by time-resolved circular dichroism.
- Schmid Marco
- Changenet Pascale
- Hache François
Proceedings of SPIE, the International Society for Optical Engineering, SPIE, The International Society for Optical Engineering , 2018 .