2D and 3D biomaterials produced from natural polymers with potential applications for bone regeneration in the treatment of periodontal lesions

Resumo

The thesis is concerned with the synthesis and characterization of cell-interacting biomaterials produced from natural polymers, in particular chitosan and DNA, for their potential use as scaffolds for bone regeneration in the treatment of periodontal lesions presenting advanced bone damage. The biomaterials were shaped to present 2D (membranes) and 3D configurations (pearls) in order to develop potentially complementary tools to be applied alone or simultaneously at different spatial locations of the periodontal system. On the one hand, 2D membranes were synthesized by solvent casting followed by surface-crosslinking and rationalized to be implanted between the damaged alveolar bone and the gingiva, in close contact with the gingival connective tissue. At this particular location and thanks to the implemented surface treatment, the membranes are envisaged to carry out two main functions important to bone regeneration. First, they were tailored to promote the adhesion and proliferation of osteoblast cells by one of their surfaces (that pointing to the alveolar region). Second, and by virtue of their selective surface modification, once implanted the membranes are also anticipated to act as a physical barrier between the alveolar bone and the gingiva so as to avoid the migration of gingival cells to the bone compartment, as typically practiced in Guided Tissue Regeneration (GTR) strategies. On the other hand, cell-laden 3D pearls were synthesized by UV-light mediated crosslinking on top of superhydrophobic surfaces and rationalized to be implanted directly to the damaged alveolar region, underneath the membranes, where voids characteristic of periodontitis take place as a result of bone destruction. At this deeper location (close to the root), the 3D pearls are expected to avoid membrane collapse inside the defect due to the soft tissue pressure during the healing process and promote the bone tissue regeneration upon release and proliferation of encapsulated cells. Important to both purposes, and thanks to their a core-shell architecture, the cell-laden pearls here produced proved to display (i) an outstanding structural stability for their practical handling and easy implantation and (ii) a necessary capability to release viable osteoblast cells once in contact with simulated body fluids (cell culture media). To prove their suitability for the tentative proposed applications, the biomaterials were characterized in terms of their chemical, mechanical, and biological properties by means of a battery of experimental techniques. Primary methods included Nuclear Magnetic Resonance spectroscopy (NMR), Fourier Transform Infrared spectroscopy (FT-IR), Atomic Force Microscopy (AFM), Mechanical Puncture Assays, Optical and Confocal Microscopy, Cell Culture, Water Contact Angle Measurements (WCA), and different Enzyme-Linked Immunosorbent Assays (ELISA). Basic synthetic procedures included Chemical Vapor Deposition and grafting polymerization mediated by a liquid-phase methacrylation reaction.