Design of biodegradable tissue scaffold assisted cell sheet for pneumothorax treatment

The aim of the presented thesis is to develop an alternative, cell sheet-based therapeutic approach for pneumothorax treatment that does not restrict the dynamic movements of the lung, is resistant to intrathoracic pressure and motion, and does not require suturing or gluing for application. To achieve this goal, cell sheet technology was utilized. A cell sheet was generated from human umbilical cord-derived mesenchymal stem cells (hUC MSCs) in the presence of ascorbic acid (vitamin C, VC). For this purpose, cell culture was conducted at a high seeding density (5 × 10⁴ cells/cm²) with the addition of 20 µg/mL VC to the culture medium. Since the mechanical strength of the obtained cell sheet alone was not sufficient, nanofibrous surfaces were used to reinforce the cell sheets. iii In the first part of the study, a nanofibrous tissue scaffold was produced via electrospinning of a polycaprolactone (PCL)/gelatin (GEL) solution. To endow the scaffold with antimicrobial properties, broad-spectrum amoxicillin (AMX) was incorporated. The electrospinning/netting (ESN) technique was employed to obtain nanofiber-net (NFN) matrices. Characterization of the synthesized NFN matrices was carried out using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) to examine fiber morphology and structure. The chemical structure and properties of the NFN matrices were further confirmed using X-ray Photoelectron Spectroscopy (XPS) and Fourier-Transform Infrared Spectroscopy (FTIR). Tensile tests and hydrolytic degradation assays were performed to evaluate the mechanical strength of the produced scaffolds. The encapsulation efficiency of AMX and its release profile from the NFN matrices were assessed. The antibacterial efficacy of AMX within the matrices was evaluated through antibacterial activity assays, while cytotoxicity assays were conducted to determine the potential toxic effects of the NFN matrices on cells. The findings demonstrated the potential of the NFN matrices as a scaffold material for pneumothorax treatment. In the second part of the study, the NFN matrices were combined with the hUC-MSC cell sheets. To assess the compatibility of the cell sheets supported by NFN matrices with the target tissue, material–cell interactions and mechanical strength were investigated. For this purpose, viability assays, SEM, confocal imaging, tensile testing, and Hematoxylin & Eosin (H&E) staining for histological evaluation were performed on the NFN matrix supported cell sheets. The analysis results revealed excellent compatibility between the hUC-MSC-derived cell sheets and the NFN matrices. In conclusion, biodegradable tissue scaffold-supported cell sheets intended for pneumothorax treatment were successfully developed. With their biocompatibility, high mechanical strength, and applicability, this composite structure can be considered a promising alternative therapeutic approach for the treatment of pneumothorax and pleural injuries.