Title Page

Contents

1. INTRODUCTION 9

2. MATERIALS AND METHODS 14

2.1. Synthesis of prepolymers 14

2.1.1. Synthesis of GelGMA 14

2.1.2. Synthesis of GelMAGMA 14

2.1.3. Synthesis of GelMAGMA GO 14

2.2. Characterization of materials 15

2.2.1. ¹H NMR spectra of materials 15

2.2.2. Fourier Transform-Infrared Spectroscopy (FT-IR) analysis 16

2.2.3. Field Emission Scanning Electron Microscope (FE-SEM) 16

2.3. Fabrication of hydrogel 16

2.3.1. Preparation of photocurable bioink 16

2.3.2. 3D printing of bilayer hydrogel 16

2.4. Mechanical properties of materials 17

2.4.1. Compressive strength test 17

2.4.2. Swelling test 17

2.4.3. Degradation test 17

2.5. Biocompatibility of hydrogels 18

2.5.1. Preparation of TMSC 18

2.5.2. 3D bioprinting 18

2.5.3. Cell proliferation and viability assay 19

2.5.4. Cytocompatibility assay 19

2.6. In vitro analysis 19

2.6.1. Quantitative Polymerase Chain Reaction (qPCR) 19

2.6.2. Immunofluorescence staining of bilayer hydrogel 20

2.6.3. qPCR of bilayer hydrogel 20

2.7. In vivo repair of osteochondral defects 21

2.7.1. Animal experiments 21

2.7.2. Immunohistochemistry analysis 21

2.8. Statistical analysis 22

3. RESULTS 24

3.1. Characterization of materials 24

3.2. Mechanical properties of materials 28

3.3. 3D bioprinting of bilayer hydrogel 30

3.4. Biocompatibility of hydrogels 32

3.5. Quantitative Polymerase Chain Reaction (qPCR) 34

3.6. Immunofluorescence staining of bilayer hydrogel 36

3.7. qPCR of bilayer hydrogel 38

3.8. Osteochondral defect repair in the knee joint of a rabbit 40

3.9. Hematoxylin & Eosin (H&E) staining analysis 42

4. DISCUSSION 44

5. CONCLUSION 48

6. REFERENCE 49

DLP 3D 프린터를 이용한 골연골 결함 치료용 그래핀 옥사이드 복합 이중층 하이드로겔 54

Graphene oxide composite bilayer hydrogel using DLP 3D printer for osteochondral defect repair 56

Table 1. DNA sequences used for PCR primers 23

Table 2. EDS map sum spectrum 27

Figure 1. Fabrication of bilayer hydrogel. 13

Figure 2. Characterizations of materials. 25

Figure 3. A) SEM images of GelGMA, GelMAGMA, GelMAGMA GO samples. B) SEM EDS mapping reflect main elements in each material. 26

Figure 4. Mechanical properties of 3D printing hydrogels. 29

Figure 5. Printability of DLP 3D printing bilayer hydrogel. 31

Figure 6. Cell viability and proliferation test of 3D printing hydrogels. 33

Figure 7. Quantitative gene expression of differentiation in GelGMA, GelMAGMA, and GelMAGMA GO hydrogel. 35

Figure 8. Immunofluorescence staining of differentiation in bilayer hydrogel. 37

Figure 9. Quantitative gene expression of differentiation in bilayer hydrogel according to growth factor and time. 39

Figure 10. Animal experiments. 41

Figure 11. Histological analysis of repaired osteochondral defects. 43