Electrical simulation and synthesis of semi-conductive nanofibers for the stimulation of osteoblasts

This Master's Thesis project deals with the effects of electrical stimulation provided to pre-osteoblasts through nanofibers. While electric fields are known to influence a variety of cell activities, nanostructures can mimic the biological environment structurally. Therefore, one way to improve the functional outcome of bone tissue engineering may be electrical stimulation in combination with a biomimetic structure (e.g. nanofibers). The goal of this project is the analysis the properties of electrical stimuli delivered through a nanostructure (for example, the confinement of the field in a sub-cellular region), with a finite element method (FEM) approach, followed by the synthesis of the conductive nanofibers and cell culture experiments. A FEM analysis of the system was performed, with the goal of determining the profile of the electric field in the cytoplasm and in the cell membrane. Since the fibers are in contact with the cell media, an electric double layer is formed at the interface with the electrodes. An electrostatic (DC) study was conducted, modeling the double layer using the Stern model. An AC study was also carried out to analyze the effects of frequency; the double layer was modeled with the Helmholtz model to reduce the computational effort. The fibers were then synthesized; the goal of the synthesis was to obtain a stable material with a well-defined chemical structure, ideal for use in a variety of experiments. Moreover, the aim was to obtain nanofibers characterized by high conductivity, biodegradability, and solubility; ideally with the possibility to include additional chemical functionality if needed. An experimental set-up to electrically stimulate cells with nanofibers inside a common 12-well plate was then developed. Several solutions were tested, with the final goal of minimizing the material consumption while maximizing the reliability and the mechanical stability of the system. Once the optimal set-up was found, an electrical stimulus was delivered to cells using different materials, among which the synthesized nanofibers. The mineralization and the proliferation of pre-osteoblasts were assessed: they are among the properties influenced by electric fields. Those tests allowed to make comparisons between different materials and validate the idea of using nanofibers as a tool in tissue engineering for electrical stimulation.