16 research outputs found
Développement de matériaux à base de protéines extraites du byssus de la moule bleue Mytilus edulis
Le byssus est un amas de fibres que les moules produisent afin de sâancrer aux surfaces immergĂ©es sous lâeau. Ces fibres sont pourvues de propriĂ©tĂ©s mĂ©caniques impressionnantes combinant rigiditĂ©, Ă©lasticitĂ© et tĂ©nacitĂ© Ă©levĂ©es. De plus, elles possĂšdent un comportement dâauto-guĂ©rison de leurs propriĂ©tĂ©s mĂ©caniques en fonction du temps lorsque la contrainte initialement appliquĂ©e est retirĂ©e. Les propriĂ©tĂ©s mĂ©caniques de ces fibres sont le rĂ©sultat de lâagencement hiĂ©rarchique de protĂ©ines de type copolymĂšre blocs riches en collagĂšne et de la prĂ©sence de mĂ©taux formant des liens sacrificiels rĂ©versibles avec certains acides aminĂ©s comme les DOPA et les histidines. Bien que cette fibre soit trĂšs intĂ©ressante pour la production de matĂ©riaux grĂące Ă son contenu Ă©levĂ© en collagĂšne potentiellement biocompatible, cette ressource naturelle est traitĂ©e comme un dĂ©chet par les mytiliculteurs. Lâobjectif de cette thĂšse Ă©tait de valoriser cette fibre en extrayant les protĂ©ines pour gĂ©nĂ©rer une nouvelle classe de matĂ©riaux biomimĂ©tiques.
Un hydrolysat de protĂ©ines de byssus (BPH) riche en acides aminĂ©s chargĂ©s, i.e. ~30 % mol, et permettant de former des films a pu ĂȘtre gĂ©nĂ©rĂ©. Lorsque solubilisĂ© Ă pH 10.5, le BPH forme un hydrogel contenant des structures en triple hĂ©lice de collagĂšne et des feuillets ÎČ anti-parallĂšles intra- et inter-molĂ©culaires. Suite Ă lâĂ©vaporation de lâeau, le film de BPH rĂ©sultant est insoluble en milieu aqueux Ă cause des structures secondaires trĂšs stables agissant comme points de rĂ©ticulation effectifs. Les propriĂ©tĂ©s mĂ©caniques des films de BPH sont modulables en fonction du pH. Au point isoĂ©lectrique (pI = 4.5), les interactions Ă©lectrostatiques entre les charges opposĂ©es agissent comme points de rĂ©ticulation et augmentent la rigiditĂ© des films et leur contrainte Ă la rupture sans affecter la dĂ©formation Ă la rupture. Ă pH plus Ă©levĂ© ou plus bas que le pI, les performances mĂ©caniques des films sont plus faibles Ă cause de la rĂ©pulsion entre les groupements fonctionnels de mĂȘme charge qui interagissent plutĂŽt avec les molĂ©cules dâeau et causent le gonflement de la matrice protĂ©ique des films. Le BPH contenant un nombre Ă©levĂ© dâacides aminĂ©s chargĂ©s et rĂ©actifs, nous avons pu rĂ©ticuler les films de maniĂšre covalente Ă lâaide dâEDC ou de glutaraldĂ©hyde. Les propriĂ©tĂ©s mĂ©caniques des films sont modulables en fonction de la concentration dâEDC utilisĂ©e lors de la rĂ©ticulation ou en employant du glutaraldĂ©hyde comme agent rĂ©ticulant. Les films sont Ă la fois plus rigides et plus forts avec un degrĂ© de rĂ©ticulation Ă©levĂ©, mais perdent leur extensibilitĂ© Ă mesure que les segments libres de sâĂ©tirer lors dâune traction deviennent entravĂ©s par les points de rĂ©ticulation. La rĂ©ticulation augmente Ă©galement la rĂ©sistance Ă la dĂ©gradation enzymatique par la collagĂ©nase, les films les plus fortement rĂ©ticulĂ©s lui Ă©tant pratiquement insensibles. La spectroscopie infrarouge montre enfin que la rĂ©ticulation entraĂźne une transition de feuillets ÎČ anti-parallĂšles inter-molĂ©culaires vers des structures de type hĂ©lices de collagĂšne/PPII hydratĂ©es. Des liens sacrificiels ont Ă©tĂ© formĂ©s dans les films de BPH par traitement au pI et/ou avec diffĂ©rents mĂ©taux, i.e. Na+, Ca2+, Fe3+, afin de moduler les propriĂ©tĂ©s mĂ©caniques statiques et dâĂ©valuer le rĂŽle de ces traitements sur le comportement dâauto-guĂ©rison lors de tests mĂ©caniques cycliques avec diffĂ©rents temps de repos. Plus la valence des ions mĂ©talliques ajoutĂ©s augmente, plus les propriĂ©tĂ©s mĂ©caniques statiques affichent un module, une contrainte Ă la rupture et une tĂ©nacitĂ© Ă©levĂ©s sans toutefois affecter la dĂ©formation Ă la rupture, confirmant la formation de liens sacrificiels. Les tests mĂ©caniques cycliques montrent que les traitements au pI ou avec Ca2+ crĂ©ent des liens sacrificiels ioniques rĂ©versibles qui mĂšnent Ă un processus dâauto-guĂ©rison des performances mĂ©caniques dĂ©pendant du pH. Lâajout de Fe3+ Ă diffĂ©rentes concentrations module les performances mĂ©caniques sur un plus large intervalle et la nature plus covalente de son interaction avec les acides aminĂ©s permet dâatteindre des valeurs nettement plus Ă©levĂ©es que les autres traitements Ă©tudiĂ©s. Le Fe3+ permet aussi la formation de liens sacrificiels rĂ©versibles menant Ă lâauto-guĂ©rison des propriĂ©tĂ©s mĂ©caniques. Les spectroscopies Raman et infrarouge confirment que le fer crĂ©e des liaisons avec plusieurs acides aminĂ©s, dont les histidines et les DOPA. Les rĂ©sultats dans leur ensemble dĂ©montrent que les films de BPH sont des hydrogels biomimĂ©tiques du byssus qui peuvent ĂȘtre traitĂ©s ou rĂ©ticulĂ©s de diffĂ©rentes façons afin de moduler leurs performances mĂ©caniques. Ils pourraient ainsi servir de matrices pour des applications potentielles dans le domaine pharmaceutique ou en ingĂ©nierie tissulaire.The byssus is a set of protein-based anchoring threads produced by marine mussels to tether to water immersed surfaces. These fibers have impressive mechanical properties combining stiffness, elasticity and toughness, as well as a self-healing behavior of their mechanical performance upon rest following removal of stress. These properties are the result of collagen-rich block copolymer-like proteins hierarchically assembled and of the presence of organo-metallic reversible sacrificial bonds. Even though these fibers have outstanding mechanical properties and a high content of potentially biocompatible collagen, the mussel farming industry still treats them as a waste. The main objective of this thesis was to use byssus as a sustainable biological feedstock to produce a new family of biomimetic protein-based materials. We developed a method to produce a byssus protein hydrolyzate (BPH) rich in charged amino acids (~30 % mol) and with good film-forming capabilities. A hydrogel rich in inter- and intra-molecular anti-parallel ÎČ-sheets and in collagen triple helical structures forms following the BPH solubilization at pH 10.5. After evaporation of water, the resulting film is insoluble in aqueous media as a result of the BPH self-assembly into stable secondary structures. The mechanical properties of the films are pH-responsive owing to their high electrostatic charges content that act like effective crosslinking points at the isoelectric point (pI = 4.5), but causes swelling of the protein matrix and loss of mechanical performance at pH higher or lower than the pI. The strain at fracture remains constant, which increases the toughness of the materials when moving toward the pI. The high content in charged and reactive amino acids was used to covalently crosslink the BPH films using either EDC or glutaraldehyde. Increasing the crosslinking degree gives rise to stiffer and stronger films but leads to a loss of extensibility as a consequence of protein chains being trapped by the crosslinking points. The crosslinked films become resistant to collagenase degradation even though infrared spectroscopy shows the conversion of aggregated strands to hydrated collagen/PPII related structures following the crosslinking reaction. Thus, the crosslinked collagen-related structural elements hinder the collagenase action on the BPH films. Sacrificial bonds were formed in the BPH films by treatments at their pI and/or with various metallic ions, i.e. Na+, Ca2+, Fe3+, in order to tune the mechanical properties and to evaluate the role of sacrificial bonds on the self-healing behavior during cyclic mechanical testing. Using metallic ions of higher valence to treat the films results in an increase of the modulus, strength and toughness without reducing the strain at fracture, confirming the formation of organo-metallic sacrificial bonds. Cyclic mechanical testing shows that pI and Ca2+ treatments create reversible ionic sacrificial bonds that induce a pH-dependent self-healing behavior. Fe3+ addition at various concentrations enables tuning the mechanical performances over a larger interval and to reach higher values than other treatments. This behavior is attributed to the more covalent nature of the iron-amino acids bonding and to the affinity of iron with numerous amino acids, including histidines and DOPA, as detected using Raman and infrared spectroscopy. Iron addition also leads to the formation of reversible sacrificial bonds that procure a self-healing behavior of the mechanical properties to BPH films. Altogether, our results show that the BPH films are byssus biomimetic hydrogels whose mechanical properties can be tuned by using various treatments or crosslinking reactions. The materials could thus find a niche as protein matrix in domains such as the pharmaceutical industry or soft tissue engineering
Covalently crosslinked mussel byssus protein-based materials with tunable properties
Musselsâ anchoring threads, named byssus, are collagen-rich fibers with outstanding mechanical properties. Our previous work has shown the possibility of producing a byssus protein hydrolyzate with good film-forming ability, providing a promising new avenue for the preparation of biomaterials. Materials prepared from regenerated fibrous proteins often need additional treatments to reach the performance required for targeted applications. Here, we studied the effect of covalent crosslinking, using a carbodiimide or glutaraldehyde, on the mechanical properties and enzymatic resistance of byssus-based materials. The results show that the mechanical properties of the films can be tuned, and that a higher crosslinking degree leads to increases in modulus and strength accompanied by a loss of extensibility. Structural analysis performed by infrared spectroscopy revealed that crosslinking induces an unexpected transition from aggregated strands to hydrated collagen/PPII-related helical structures. The materials were nevertheless more resistant to collagenase degradation as a result of higher crosslinking density. This new set of materials prepared in aqueous environment could find a niche in tissue engineering
Metalâligand interactions and salt bridges as sacrificial bonds in mussel byssus-derived materials
The byssus that anchors mussels to solid surfaces is a protein-based material combining strength and toughness as well as a self-healing ability. These exceptional mechanical properties are explained in part by the presence of metal ions forming sacrificial bonds with amino acids. In this study, we show that the properties of hydrogel films prepared from a byssus protein hydrolyzate (BPH) can also be improved following the biomimetic formation of sacrificial bonds. Strengthening and toughening of the materials are both observed when treating films with multivalent ions (Ca2+ or Fe3+) or at the BPH isoelectric point (pI) as a result of the formation of metalâligand bonds and salt bridges, respectively. These treatments also provide a self-healing behavior to the films during recovery time following a deformation. While pI and Ca2+ treatments have a similar but limited pH-dependent effect, the modulus, strength, and toughness of the films increase largely with Fe3+ concentration and reach much higher values. The affinity of Fe3+ with multiple amino acid ligands, as shown by vibrational spectroscopy, and the more covalent nature of this interaction can explain these observations. Thus, a judicious choice of treatments on polyampholyte protein-based materials enables control of their mechanical performance and self-healing behavior through the strategic exploitation of reversible sacrificial bonds
Solid-State NMR Structure Determination of Whole Anchoring Threads from the Blue Mussel Mytilus edulis
The molecular structure of the blue mussel Mytilus
edulis whole anchoring threads was studied by two-dimensional <sup>13</sup>C solid-state NMR on fully labeled fibers. This unique material
proves to be well ordered at a molecular level despite its heterogeneous
composition as evidenced by the narrow measured linewidths below 1.5
ppm. The spectra are dominated by residues in collagen environments,
as determined from chemical shift analysis, and a complete two-dimensional
assignment (including minor amino acids) was possible. The best agreement
between predicted and experimental backbone chemical shifts was obtained
for collagen helices with torsion angles (â75°, +150°).
The abundant glycine and alanine residues can be resolved in up to
five different structural environments. Alanine peaks could be assigned
to collagen triple-helices, ÎČ-sheets (parallel and antiparallel),
ÎČ-turns, and unordered structures. The use of ATR-FTIR microscopy
confirmed the presence of these structural environments and enabled
their location in the core of the thread (collagen helices and antiparallel
ÎČ-sheets) or its cuticle (unordered structures). The approach
should enable characterization at the molecular level of a wide range
of byssus macroscopic properties