Fabrication and characterization of nanoparticles-containing melt electrowritten scaffolds for bone cancer treatment

This thesis aims to develop a PCL scaffold with magnetic (M) nanoparticles (NPs) or core-shell magnetic-silica nanoparticles (Si-MNPs) coating for bone cancer applications. Scaffolds were produced with Bioscaffolder 3.0 (Gesim) melt electro-writing (MEW), a high-resolution additive manufacturing (AM) method for printing highly porous scaffolds composed of synthetic biodegradable polymers. In the beginning, PCL from the printer was used, later it was replaced by PCL from Sigma Aldrich (45kDa). Then, after an alkaline treatment on the scaffold surface (for 1h, 2h and 3h), MNPs and Si-MNPs coatings were synthesized. Afterward, the scaffold’s physical, mechanical, and biological properties were investigated. In particular, Scanning Electron Microscopy (SEM) images illustrated the morphology of the scaffold’s fibers. For Gesim PCL the average fiber size was 44 ± 1 µm, while for PCL (45kDa) the average fiber size was 31 ± 3 µm. With the alkaline treatment, in both cases, fiber size decreases. SEM images showed also the presence of MNPs and Si-MNPs coating. The chemical structure of the fiber and the MNPs and Si-MNPs' presence was determined by Attenuated Total Reflection – Fourier transform infrared spectroscopy (ATR-FTIR). The mechanical test showed that there is no relevant difference in Young’s Modulus of PCL, PCL with alkaline treatment, and with MNPs or Si-MNPs scaffolds. Subsequently, the NPs stability in the DMEM medium was analyzed after 1 day and 7 days, by measuring the pH of the medium and by ATR-FTIR of the samples evidencing a probable release of both MNPs and Si-MNPs. The wettability analysis and the antioxidant activity, performed using DPPH assay, displayed successful surface modification after 3 hours of alkaline treatment: the wettability increased, and the colour of DPPH solution changed, as proof of alkaline treatment. The antibacterial study was carried out by direct turbidity assay with E. coli and S. aureus bacteria for 3h, 6h and 24h. The results showed that the incorporation of MNPs has a slightly antibacterial effect for S. aureus and E. coli strains at 6h. Finally, biological activity was studied: cytotoxicity was analyzed using osteoblast-like osteosarcoma MG63 cells, which showed that the samples were non-toxic. Subsequently, cell proliferation of osteoblastic M3T3 cells was analyzed after 1 and 7 days and by fluorescence staining, it was observed that the cells proliferated in the presence of MNPs and Si-MNPs - PCL scaffolds. In conclusion, the results show that the PCL scaffold with MNPs or Si-MNPs has good physical, mechanical and biological properties and is a potential candidate for bone cancer applications.