Digital archive of theses discussed at the University of Pisa


Thesis etd-10142011-162221

Thesis type
Tesi di dottorato di ricerca
Thesis title
Engineering composite conductive scaffolds for locomotor tissue regeneration
Academic discipline
Course of study
relatore Dott. Domenici, Claudio
tutor Prof.ssa Ahluwalia, Arti Devi
relatore Prof. Vozzi, Giovanni
  • conductive scaffolds
  • bioactive
  • tissue engineering
Graduation session start date
The present study investigates the realisation of bioactive conductive scaffolds for application to locomotor tissue regeneration. Blend systems of synthetic materials with nanotubes or conducting polymer as fillers were characterised and used to realise 3D and tubular shaped scaffolds with bioactive properties.
The term bioactive has been widening with the expansion of research in biomaterials, however it can be defined as a biocompatible material with the ability of inducing a required response from the host. Thus, the interaction between scaffold and organism is more profound than merely acting as a mechanical support. Conductive scaffolds have emerged as substrates that used electrical stimulation to enhance cell growth. There is much evidence and many experimental results which show that numerous tissues including bone, cartilage, skin, spinal nerves, and peripheral nerves respond favourably to electric fields. These outcomes motivate the development of conductive and bioactive biomaterials.

Different synthetic polymers, such as poly(-caprolactone), poly(lactic acid) and poly(lactic-co-glycolide) have been investigated as potential candidate for scaffold materials. Here, the use of carbon nanotubes as reinforcement fillers and electrical conductors in synthetic polymer was investigated due to the remarkable properties of carbon nanotubes such as high tensile strength, Young’s modulus, and electrical conductivity. Biodegradable polymers/carbon nanotube composite films were prepared using a solution based processes. The presence of carbon nanotubes allowed high stresses to be applied to the composite scaffolds. The conducting performance of the composite is enhanced by the carbon nanotubes as fillers in polymers. These two properties have been characterised here and enabled us to identify the optimum concentration of CNT in the polymer composites. Additionally, analytical and numerical simulations were also proposed to model the mechanical and electrical characteristics.

A rapid prototyping method, PAM, was used to create a porous scaffold. This structure was aimed to provide appropriate diffusion of biochemical cues and elimination of cellular waste as well as to improve the mechanical properties. A simple 3D porous structure made of CNT/PLLA blend was realised and characterized. Additionally, tubular scaffolds were also fabricated and studied since there are still limited options available for scaffolds suitable for engineering tissues containing a luminal structure.
We also present a specific tailored material that can electroactively release and uptake a bioactive molecule for instance glutamate. Glutamate is an important neuromodulator and plays a major role in synaptic transmission. In this work we demonstrated that it was possible to use incorporate glutamate ions in to the conducting polymer through a simple adsorption. Our study has shown that these molecules can be effectively released upon electrical stimulation. Furthermore, we tried to explain the effect of various potentials on the release and uptake of glutamate ions. In parallel, studies were performed to improve the mechanical characteristics of this conducting polymer by blending with polycaprolactone. The optimum blend was then used to fabricate tubular scaffolds for application to peripheral nerve regeneration.
Finally, an application of CNT/polymer composites for bone tissue scaffolds was performed. The tailored conducting property enables us to study the attachment of cells on the scaffolds via impedance monitoring. Furthermore, these composites were shown to be highly biocompatible for human osteoblasts and hepatocytes.