• Manufattura additiva
• poli(idrossialcanoati)
• Scaffold
• Tissue engineering

Tissue engineering is a multidisciplinary research field that aims to develop scaffolds, i.e., three-dimensional (3D), porous, biodegradable structures that can be used as temporary supports for the regeneration of biological tissues. The use of additive manufacturing (AM), often also referred to as 3D Printing, for the fabrication of such structures allows a better control of the scaffold external geometry and macro/microporosity, in comparison to conventional manufacturing techniques. Scaffolds fabricated with this approach can be customized to specific tissue defects and optimized to better integrate with the physiological environment. For this reason, a fast growing interest of the scientific community is dedicated to emerging biodegradable and biocompatible polymers in AM, such as polyhydroxyalkanoates obtained through bacterial fermentation, that can be employed to fabricate scaffolds with a reproducible process.
This thesis work is part of a research trend concerning the study and application in the biomedical field of polymeric materials obtainable from renewable and sustainable sources. In particular, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), an aliphatic copolyester of microbial origin produced on an industrial scale by biotechnological fermentation processes, was investigated. PHBV was used as scaffolding material, possibly in combination with hydroxyapatite nanoparticles (nHAps), a commercial osteoconductive nanoceramic with composition similar to the main constituent of the bone tissue. Computer-Aided Wet-Spinning (CAWS) was employed for scaffold fabrication. CAWS is an AM technique which, starting from a polymeric solution or suspension, allows the fabrication of structures with a multiscale porosity characterized by a macroporous network, determined by the deposition path of the material, and by a micro/nanoporosity, determined by a non-solvent-induced phase separation process governing material solidification. PHBV blending with poly(D,L-lactide-co-glycolide) (PLGA), an aliphatic polyester approved by the Food and Drug Administration (FDA) for clinical use in humans, was investigated as an effective means to enhance the processing beahvior of the starting polymeric suspension as well as the final properties of the resulting scaffold. Scaffolds made of PHBV, PHBV/nHAps or PHBV/PLGA/nHAps were fabricated by keeping constant the concentration of the polymeric phase and investigating the influence of a variation of nHAps concentration in the starting suspension. The morphology of the manufactured scaffolds was studied through SEM analysis, which showed how the polymeric structures are characterized by a diffuse and interconnected porosity with a pore size of the order of hundreds of micrometers. Their chemical-physical properties were characterized by means of FT-IR analysis to evaluate the characteristic signals of corresponding chemical groups in PHBV, PLGA, and nHAps. Scaffold thermal properties were evaluated with thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), thus determining the degradation temperature, the glass transition temperature (Tg) and other thermal parameters. Scaffold mechanical properties were also studied by means of a compression test, to compare the modulus in compression of the scaffold PHBV-nHAps, PHBV-PLGA-nHAps at different concentrations of nHAps and after incubation at 37° in PBS. The wettability of the scaffolds was evaluated through contact angle measurements. These measurements were carried out first on PHBV and PLGA films, to evaluate the wettability of the starting materials, then on porous structures to evaluate any effect due to chemical composition.Ongoing in vitro cell culture experiments are aimed at investigating qualitatively and quantitatively scaffold biocompatibility through adhesion and proliferation test by employing MC3T3-E1 murine preosteoblast cell line. Overall, the experimental investigations carried out during the thesis highlighted that CAWS is a suitable AM techinue for the fabrication of microbial PHBV scaffolds with predefined shape and porous architecture, as well as that PHBV blending with PLGA and nHAps is an effective means to tune the properties of the resulting bone scaffolds.