Auto-assemblage de polyélectrolytes : formation de nanoring, adhésion de protéines et de cellules
Langue Anglais
Ce document est protégé en vertu du Code de la Propriété Intellectuelle.
Auteur : Flores, Hector
Date de soutenance : 01-01-2005
Directeur(s) de thèse : Cuisinier, Frédéric
Établissement de soutenance : Université Louis Pasteur (Strasbourg)
École doctorale : École doctorale Sciences de la vie et de la santé (Strasbourg ; 2000-....)
Discipline : Odontologie
Classification : Sciences de la vie, biologie, biochimie
Mots-clés libres : Polyélectrolytes , autoassemblage , protéines , cellules
Mots-clés :
- Polyélectrolytes
- Thèses et écrits académiques
- Électrolytes
- Thèses et écrits académiques
Résumé : Frequently, the dental surgery one faces serious problems of defects osseous and loss of teeth; this means that those must be replaced by prostheses or implants to reconstitute the function and static. These materials were called biomaterials, since they interact with the systems made up of cells and fabrics. It is currently difficult to give a definition of "biomaterial" since the concepts changed in the last few years. We can however define a biomaterial as "a nonbiological material which interacts with biological systems" (Williams 1987). Since it interacts with biological systems, this material must be biologically accepted or at least no cause tissue injure; consequently we must also give a definition of "biocompatibility" which is "the capacity of a material to induce a suitable answer of the host for a specific application" (Williams 1987). These terms are appropriate in the majority of materials currently used like biomaterials, however the "nonbiological" term is not completely exact, since many materials used like biomaterials or medical devices are of biological origin, such is the case of bone grafts. One already used a large variety of materials like biomaterials, metals, ceramics, polymers, glasses, carbon, and composite materials. There are many examples of applications of the biomaterials: cardiac valves, articulations of knee, implants dental, intraocular lenses, etc. Now, many medical fields use the biomaterials. Each year in the United States more than 30.000 prostheses of the knee and hip also 100.000 to 300.000 dental implants are placed (D.A. Puleo, 1999). In the European Community more than 50.000 prostheses of hip and approximately 100.000 dental implants are placed (SIMI Project). These statistics increase each year as the materials used get a greater safety with their patients, which also tend to lower the costs, by facilitating their good use gradually. One of most significant advanced in this field, was "the material bioactive" design. i.e. works with the design and the development of biomaterials to which biologically activated molecules were built-in, in order to control the cellular answer. One conceived a series of process to this end by stressing polymer adhesion at surface of materials. The method suggested by Decher is of a great interest for self-assembly polyelectrolytes thin films made on the surface of materials. The alternate absorption of polyelectrolytes anion and cation on solid surfaces gives us the possibility of forming the multi-layer ones of very thin polyelectrolytes, which constitutes a versatile technique to modify surfaces. This possibility is of a great attraction for industry and medicine. The most significant characteristic of the polyelectrolytes is their capacities to be charged electrically in solution, which gives us the possibility of forming self-assembly polyelectrolytes films, with the possibility of intercalating and of immobilizing a large variety of made up on treated surface, such with inorganic particles or organics like proteins, the enzymes, etc, by providing to the surface of material really active characteristics, which constitute new strategies to control the answer of the host. This can be the key for the design and manufacture of biomaterials bioactives able to control the answer of the host at the molecular level by creating an adequate, fast and directed answer.Our work consisted in : the study of the formation of nanoring, the study of the adsorption of proteines on films in a field of precise pH, the study of the adhesion of cells on films of polyelectrolytes for micro aspiration.We studied the adsorption of the HSA on films made of polypeptides, the poly(L-lysine) (PLL), and the acid poly(glutamique) (PGA) in a field of pH 3.0-10.5. We showed that adsorption depends enormously on the last layer of the film. For the PLL, to low pH, an electrostatic repulsion limits adsorption. With the pH superiors one on adsorption of HSA on the PGA is observed. This is with the conformation of the rich PGA helical alpha which increases the roughness of film. Finally, we studied the adhesion of cells of films of polyelectrolytes. All the biological processes are achieved thanks to weak specific molecular interactions which generate connections of short duration; too strong interactions would remove all dynamics essential to the life.We thus evaluated by the technique of micromanipulation by micropipette the short-term interactions of cells with multi-layer films. By grafting hundreds of cells on a substrate, one will be able to distinguish the mechanical answers from the healthy cells. The goal of this work was the modulation of the multi-layer film properties with respect to the cellular adhesion.We observed also at the time of the deposit of PSS on a layer of PEI, the formation of circular structures. We named these structures of the nanorings. These structures are variable sizes of 300 Nm diameters to 2 m diameter between the various experiments but by experiment, are of very homogeneous size. Such structures had never been observed. We thus sought to include/understand the mechanisms of controls and formation of these structures. These observations were realizes in AFM by using a liquid cell which prevents the appearance of artefacts due to dehydration. We determined that the two parameters which control the size of the nanoring are the size of the pores of the filters used for the preparation of the solution of PSS and the time of contact of the solutions with the air. Indeed, divalent ions CO3 -- play a dominating role in the formation of this nanoring. It is about a mechanism of car-assembly of hydrophobic complexes of PSS on the surface of film of PEI. The size being controlled by a balance enters the electrostatic repulsions and hydrophobic attractions and under the dependence of the electrostatic interactions between the PEI and the PSS.
Entrepôt d'origine : 
Identifiant : ecrin-ori-288433
Type de ressource : Thèse
