Title Page
Contents
Abstract 9
General introduction 11
Part 1. Synthesizing optimal material for use in esophageal tissue engineering 14
1.1. Introduction 15
1.2. Materials and Methods 18
1.2.1. Synthesis of gelatin-modified polyurethane 18
1.2.2. Material analysis and thermal properties characterization 20
1.2.3. Evaluation of hydrophilic properties 21
1.2.4. Evaluation of acid-base resistance 22
1.2.5. Mechanical analysis 23
1.2.6. In vitro evaluation for cytocompatibility 24
1.2.7. Scoring of the evaluated properties of samples 25
1.2.8. Statistical analysis 27
1.3. Results 28
1.3.1. Chemical structure characterization using FTIR 28
1.3.2. Thermal analysis (DSC, TGA) 30
1.3.3. Hydrophilicity evaluation 32
1.3.4. Evaluation of acid-base resistance 36
1.3.5. Mechanical properties 38
1.3.6. Biocompatibility evaluation with MTT assay 40
1.4. Discussion 42
Part 2. Scaffold fabrication with optimized material and evaluation for esophageal epithelial regeneration 47
2.1. Introduction 48
2.2. Materials and Methods 52
2.2.1. Preparation of the polymer solution 52
2.2.2. Scaffold fabrication using the ESN (electrospinning/netting) technique 53
2.2.3. Scanning electron microscopy (SEM) evaluation 55
2.2.4. Esophageal epithelial cell isolation 56
2.2.5. Cell seeding protocol 58
2.2.6. Histological analysis and immunohistochemistry (IHC) 59
2.2.7. Statistical analysis 60
2.3. Results 61
2.3.1. Morphologic analysis of scaffolds using the ESN technique 61
2.3.2. Histologic and immunohistochemical properties of esophageal epithelial cells on fabricated scaffolds 65
2.4. Discussion 70
General conclusion 75
References 76
Abstract (in korean) 91
Table 1. Thermal properties of polyurethane samples determined from differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) 31
Table 2. Mechanical properties of polyurethane samples 39
Table 3. Summary of unmodified and modified polyurethane properties for use in esophageal tissue engineering 46
Table 4. Details of electrospinning/netting conditions in the electrospinning machine 54
Table 5. Morphologic properties of scaffold samples fabricated using the electrospinning/netting technique 64
Figure 1. Schematic illustration of polyurethane synthesis. Utilizing polycaprolactone diol (PCL) as a polyol, hexamethylene diisocyanate (HDI) as... 19
Figure 2. FTIR spectra of polyurethane samples. The N-H stretching vibration (3318-3330 cm⁻¹), C-H symmetric and asymmetric stretching vibrations (2850... 29
Figure 3. Mean contact angle according to the gelatin content ratio in the R 0.9, R 1, and R 1.1 groups. The mean contact angle decreased as the gelatin content... 33
Figure 4. Images of the water drop contact angle test on (a) R 1.1 G 0 and (b) R 0.9 G 30 samples. The highest mean contact angle (lowest hydrophilicity) in all... 34
Figure 5. Water absorption rate over time for all polyurethane groups. The water absorption rate increased as gelatin content increased for all R ratios... 35
Figure 6. In vitro sample degradation rates (loss of mass) in (a) HCl and (b) NaOH. An increasing trend of degradation rate in HCl and NaOH solutions was... 37
Figure 7. Effect of polyurethane sample extracts on NIH3T3 mouse fibroblast growth based on the MTT assay after 24 h of incubation.... 41
Figure 8. Morphologies of electrospinning/netting scaffolds. (A) 4 wt% polymer concentration under 12 kV conditions; (B) 4 wt% polymer concentration under... 62
Figure 9. Pore size distribution of fabricated scaffolds. Nano pore sizes (〈1 μm²) were significantly observed in 6.5wt% polymer concentration group compared... 63
Figure 10. Comparison of epithelial growth and morphology on various fabricated scaffolds. The sample with 4 wt% polymer solution, compared to that... 66
Figure 11. Immunohistochemistry of cytokeratin marker (AE1/AE3). Sample D, compared to other samples and the control group, had a relatively low level of... 67
Figure 12. Immunohistochemistry of proliferation marker (Ki-67). (Esophagus) Normal esophageal epithelium as control; (A) 4 wt% polymer concentration... 68
Figure 13. Proliferation indices for 2-weeks samples. Sample B (38.82 ± 6.68%) had most closely resembled the proliferation index of the control group (42.10 ±... 69