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Digital archive of theses discussed at the University of Pisa


Thesis etd-11112015-120733

Thesis type
Tesi di dottorato di ricerca
Thesis title
Preparation and characterization of micro/nanostructured three-dimensional scaffolds based on renewable polymers for tissue engineering applications
Academic discipline
Course of study
relatore Prof.ssa Chiellini, Federica
tutor Dott. Puppi, Dario
  • additive manufacturing
  • biodegradable stents
  • bone tissue engineering
  • osteochondral tissue engineering
  • renewable polymers
  • scaffolds
  • wet-spinning
Graduation session start date
Tissue Engineering (TE) applications range from the treatment of hard tissues like bone, cartilage, teeth, and soft tissues such as muscles and epithelia, thus leading to an increasing need to develop new materials with tailorable properties and new processing technologies to customize the support’s characteristics based on the specific application. At present, there is also an upsurge of interest in polymeric materials for biomedical applications obtained from natural and sustainable resources, to limit the depletion of fossil resources.
Aim of the present PhD work was the design and the development of micro/nanostructured threedimensional supports, based on renewable polymers and bioactive molecules, to use as scaffolds in TE applications and Regenerative Medicine. For this objective, biodegradable polymers from renewable sources, including polysaccharides, proteins and microbial polyesters, were investigated to assess their potential use as matrices for the production of three-dimensional scaffolds. The research activity was performed under a multidisciplinary approach and it was structured in three main topics:
• Additive manufacturing of wet-spun poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyexanoate] (PHBHHx) scaffolds tailored on a critical size long bone defect: Predefined three-dimensional PHBHHx scaffolds were produced layer upon layer by a computer controlled wet-spinning technique. The scaffolds were designed with anatomical geometry and dimensions modeled on a critical size defect in the radius of New Zealand White rabbits. Scaffolds with a longitudinal central channel to facilitate cell penetration in the inner parts of the constructs were also
designed and produced. Optical Microscopy analysis showed a good reproducibility of the internal architecture and high pores interconnection. FTIR spectroscopy and thermal analysis showed that the employed technique did not affect the material’s chemical-physical properties. The compressive and tensile mechanical properties of the structure were shown to be correlated to the direction of the stress relative to the fibers and scaffold axis.
• Development of poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyexanoate] (PHBHHx) and poly (ε-caprolactone) (PCL) biodegradable stents by computer-aided wet-spinning: PHBHHx and PCL biodegradable stents were developed for the treatment of injured small caliber (< 3 mm) blood vessels. A novel computer-aided wet-spinning apparatus for the production of threedimensional microstructured polymeric constructs with a tubular geometry was designed and
assembled. The produced stents exhibited a well defined tubular microfibrous structure. By tuning the fabrication parameters, it was possible to produce stents with different morphological characteristics (length, porosity and wall thickness), underlining the versatility of the developed technique in customizing stent structural and dimensional features. By axial and radial mechanical compression tests, PHBHHx stents demonstrated great elasticity, in particular a full elastic recovery up to radial deformation of 70 % of the diameter, thus showing potential compliance with the treated artery. PCL stents showed mechanical strength comparable with PCL stents produced by different techniques and the ability to expand through a coronary stent
system balloon, maintaining the expanded state after deployment.
• Wet-spun poly(ε-caprolactone) and poly(ε-caprolactone)/hydroxyapatite scaffolds for the development of an osteochondral interface tissue and vascularized bone construct: A model of an osteochondral tissue interface and a vascularized bone construct were developed using PCL and PCL/HA scaffolds in combination with methacrylated gelatin. Both scaffold components were seeded with human bone marrow derived mesenchymal stem cells (hMSCs) and supplied with chondrogenic and osteogenic media through a dual chamber bioreactor that allows the simultaneous, separate flow of each medium, for the simultaneous differentiation of each compartment towards a cartilaginous or osseous lineage to recreate the osteochondral complex. Human umbilical veins endothelial cells (HUVECs) have been used to create a capillary-like network in an engineered bone construct, produced by the combination of PCL-PCL/HA-gelMA construct seeded with hMSCs.