Effect of functionalized PHEMA micro- and nano-particles on the viscoelastic properties of fibrin-agarose biomaterials

Two types of PHEMA-based particles, exhibiting either carboxyl or tertiary ammine functional groups, were incorporated to fibrin-agarose (FA) hydrogels, and the effect of the addition of these synthetic particles on the viscoelastic and microstructural properties of the biomaterials was evaluated. Experimental results indicated that the incorporation of both types of polymeric particles to FA scaffolds was able to improve the biomechanical properties of the biomaterials under steady state and oscillatory shear stresses, resulting in scaffolds characterized by higher values of the storage, loss, and shear moduli. In addition, the microstructural evaluation of the scaffolds showed that the nanoparticles exhibiting carboxyl functional groups were homogeneously distributed across the fibrous network of the hydrogels. The addition of both types of artificial polymeric particles was able to enhance the viscoelastic properties of the FA hydrogels, allowing the biomaterials to reach levels of mechanical consistency under shear stresses in the same range of some human native soft tissues, which could allow these biomaterials to be used as scaffolds for new tissue engineering applications.Peer ReviewedPostprint (author's final draft

Etude des O-carboxyméthylcelluloses à degré de substitution variable. I : Préparation et caractérisation des produits

International audienc

Étude des O-carboxyméthylcelluloses à degré de substitution variable. I. — Préparation et caractérisation des produits

Une nouvelle méthode de préparation des O-carboxyméthylcelluloses à DS variable est décrite, conduisant à des produits bien définis de DS compris entre 0,4 et 2,84.Une étude morphologique par viscosité de ces produits permet d'attribuer aux CMC de DS > 0,7 en solution aqueuse, une forme de bâtonnet rigide de 10 à 12 Å de diamètre

Fibrinogen and fibrin in strong magnetic fields. Complementary results and discussion.

International audienceWhen fibrin polymerizes in a strong magnetic field, it can be highly oriented. The structural diffraction study of the oriented polymer becomes thus possible. The magnetic birefringence can also be used to study the development of the polymer Fibrinogen in solution is weakly oriented in high magnetic fields. In this work we present complementary results and discussion. The validity of the comparison of the orientation parameters of fibrinogen and fibrin with those of other orientable known biological structures is discussed. The orientation of fibrin formed from fibrin monomer solution is compared to that of fibrin formed by the action of thrombin on fibrinogen. The conditions to obtain highly oriented fibrin gels suitable for three dimensional structure studies are also briefly discussed.When fibrin polymerizes in a strong magnetic field, it can be highly oriented. The structural diffraction study of the oriented polymer becomes thus possible. The magnetic birefringence can also be used to study the development of the polymer Fibrinogen in solution is weakly oriented in high magnetic fields. In this work we present complementary results and discussion. The validity of the comparison of the orientation parameters of fibrinogen and fibrin with those of other orientable known biological structures is discussed. The orientation of fibrin formed from fibrin monomer solution is compared to that of fibrin formed by the action of thrombin on fibrinogen. The conditions to obtain highly oriented fibrin gels suitable for three dimensional structure studies are also briefly discussed

Fibrinogen and fibrin structure and fibrin formation measured by using magnetic orientation.

International audienceAccurate birefringence measurements show that fibrinogen orients to a small degree in high magnetic fields. This effect can be explained as due to the molecule having about 30% (by weight) alpha-helix oriented relatively parallel to the long axis. Birefringence measurements on fully oriented fibrin suggest that aligned alpha-helical content is less than that estimated for fibrinogen. But because of limitations in the analysis this difference must be viewed with caution. Highly oriented fibrin results when polymerization takes place slowly in a strong magnetic field. Low-angle neutron diffraction patterns from oriented fibrin made in the presence of EDTA, made in the presence of calcium, or stabilized with factor XIIIa are very similar, showing that the packing of the molecules within the fibers is the same or very similar in these different preparations. The induced magnetic birefringence was used to follow fibrin formation under conditions in which thrombin was rate limiting. The fiber network formed by approximately the gelation point constitutes a kind of matrix or frame that is largely built upon during the remaining approximately 85% of the reaction. After gelation the reaction is pseudo-first order.Accurate birefringence measurements show that fibrinogen orients to a small degree in high magnetic fields. This effect can be explained as due to the molecule having about 30% (by weight) alpha-helix oriented relatively parallel to the long axis. Birefringence measurements on fully oriented fibrin suggest that aligned alpha-helical content is less than that estimated for fibrinogen. But because of limitations in the analysis this difference must be viewed with caution. Highly oriented fibrin results when polymerization takes place slowly in a strong magnetic field. Low-angle neutron diffraction patterns from oriented fibrin made in the presence of EDTA, made in the presence of calcium, or stabilized with factor XIIIa are very similar, showing that the packing of the molecules within the fibers is the same or very similar in these different preparations. The induced magnetic birefringence was used to follow fibrin formation under conditions in which thrombin was rate limiting. The fiber network formed by approximately the gelation point constitutes a kind of matrix or frame that is largely built upon during the remaining approximately 85% of the reaction. After gelation the reaction is pseudo-first order

Orientation of fibrin in strong magnetic fields.

International audienceMagnetic field orientation can be considered as a new valuable technique for the study of fibrin. Birefringence measurements during polymerization in the magnetic field enables a new approach to study the mode of association of fibrin monomers. Stable fully oriented clots can be obtained for investigation of the three-dimensional and the secondary structures of the fibrin fiber. Such experiments could be useful to assess the structure of other biopolymers diamagnetically anisotropic.Magnetic field orientation can be considered as a new valuable technique for the study of fibrin. Birefringence measurements during polymerization in the magnetic field enables a new approach to study the mode of association of fibrin monomers. Stable fully oriented clots can be obtained for investigation of the three-dimensional and the secondary structures of the fibrin fiber. Such experiments could be useful to assess the structure of other biopolymers diamagnetically anisotropic