Abstract :
[en] The functionalization of biomaterial surfaces for the design and exploration of novel properties has attracted increasing attention in research. In the field of dentistry, fighting bacterial colonisation is largely associated to the use of antibiotics. More recently, the deposition of coatings on dental implants by wet chemical processes has been studied and it involves complicated protocols and leads to a high amount of produced wastes. Surface modification and coating of the implants through a plasma polymerization can offer a new, greener perspective for surface treatments with good control over surface morphology and chemistry. Atmospheric pressure plasma technique would undoubtedly be a good alternative for the deposition of fully organic thin films designed for the immobilization of biomolecules. Operating at low temperature and atmospheric pressure, such processes are easily up-scalable. This thesis aims at the development of a novel surface treatment to confer antibacterial and antibiofouling properties while maintaining osseointegration on Ti dental implants. To achieve this, different mild treatments in dry and aqueous media were combined (Fig.1.). The dry technique of Atmospheric Pressure Dielectric Barrier Discharge (AP-DBD) plasma deposition was used to deposit a coating containing highly chemical-reactive groups (catechol/quinone moieties), which can further serve for bioconjugate reactions. The AP-DBD was used to perform a liquid assisted, plasma-initiated polymerization setup including monomer spraying zone and subsequent plasma zone generated between two electrodes. Based on the good stability, chemical passiveness, mechanical resistance and reports of bio and cytocompatibility for polymethacrylates, the PhD research focused on the preparation of fully organic methacrylic-based coatings. The challenge was then to develop a coating that presents a sufficient number of reactive chemical groups for bioconjugation and, at the same time, a resistance to aqueous media at different pH.
During the project, the liquid-assisted AP-DBD approach allowed for the design and successful production of three different methacrylate-based coatings, stable in liquid media and bioactive after bioconjugation. As proof of concept, plasma copolymerization of ethylene glycol dimethacrylate (EGDMA) polymer layers with methyl 3-(3,4-dihydroxyphenyl)-2-(2-methylprop-2-enamido) propanoate (DOMAm) was then performed with the possibility to tune the number of functional catechol and quinone moieties.
All the plasma-deposited films have later served as versatile platforms for efficient immobilization of virtually any kind of biomolecules containing in its structure: thiol, amine or imidazole groups. Indeed, these nucleophilic groups promote the quinone-nucleophilic reactions. Here, Dispersin B1, Ranaspumin-2 derivative and Lysozyme were tested in order to create multifunctional biomaterial surfaces.
Primarily, to prove the concept of functional biomaterial in the field of dental implants, an antibiofilm activity was obtained by immobilization of Dispersin B1 derivative on EGDMA-DOMAm coating. After, the bioconjugation of bioengineered of Ranaspumin-2, another antifouling protein, was tested onto the robust EGDMA-MMA-DOMAm plasma coating. Lastly, to obtain multifunctional biomaterial surface, a controlled co-immobilization of two different biomolecules onto quinone-enriched EGDMAMMA-DOMAm surface was performed. Wherein Lysozyme, a natural bactericidal enzyme, and Ranaspumin-2 were both successfully immobilised on the polymer surface. Depending on the used biomolecule, biomaterials were tested against microorganisms’ adhesion, mortality as well as cytocompatibility in in vitro studies.
