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In Situ Forming Chitosan/PEG Hybrid Hydrogels with Tunable Physicochemical Properties

초록/요약

Chitosan-based hydrogels have been widely used as biomedical applications due to versatile properties such as biocompatibility, biodegradability, muco-adhesiveness, hemostatic effect and so on. However, the inherent rigidness and brittleness of pure chitosan hydrogels are still uncontrollable which has limited their applications in various fields. To overcome these limitations poly(ethylene glycol) (PEG), a synthetic polymer, has been used for improving mechanical properties by flexibility. By varying the contents, chain lengths, and geometries of PEG the properties of hydrogels would be readily changed for a wide range of applications. Previously, Park and colleagues developed the HRP/H¬2O2 mediated in situ chitosan-PEG-tyramine (CPT) hydrogels, which have tunable elastic modulus (0.5-17 kPa) and adhesive strength (8-97 kPa) depending on H¬2O2 concentrations. However, the effect of versatile PEG parameters on physicochemical properties of chitosan-based hydrogels has not been well studied in the literature. In this study, we prepared the in situ forming chitosan/PEG hybrid hydrogels using HRP/H2O2 mediated cross-linking. And then, we investigated the physicochemical properties of hydrogels by varying the parameters of PEGs content (0-100%), molecular weight (4, 10 and 20 kDa) and geometry (linear, 4-arm). Chitosan and PEG were grafted with phenol moieties and characterized by 1H NMR and UV-spectrometer. Hydrogels were formed by simply mixing chitosan and PEG derivatives in the presence of HRP and H2O2. Physicochemical properties of hydrogels such as gelation time, water uptake, compressive test and adhesive test were fully characterized. It was found that the hydrogels formed by 70% contents of linear PEG10 K showed the highest failure stress (4.9 ± 1.3 MPa) and toughness (45 ± 19 J/m3), leading to enhanced adhesive strength to 192 ± 8 kPa. In addition, in vitro degradation behavior was evaluated during 42 days. The chitosan/liner PEG10 K=3/7 hydrogels showed the good hemostatic effect (60 ± 17 mg) compared to commercial fibrin glue (123 ± 26 mg). From the obtained results, we suggest that chitosan/PEG hybrid hydrogels with tunable physicochemical properties could be promising biomaterial for various applications.

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ABSTRACT ⅰ
CONTENTS ⅲ
LIST OF FIGURES ⅵ
LIST OF TABLES ⅷ
ABBREVIATIONS ⅸ
Ⅰ. INTRODUCTION 1
1. Tissue engineering 1
1.1. Hydrogels 2
1.2. In situ forming hydrogels 3
1.2.1. Cross-linking strategies for in situ forming hydrogels 4
1.2.1.1. Enzyme-mediated cross-linking 5
1.2.1.2. Horseradish peroxidase (HPR)/H2O2 ¬mediated cross-linking 6
1.3. Natural and synthetic hydrogels 8
1.3.1. Chitosan 9
1.3.1.1. Chitosan-based hydrogels 10
1.3.2. Poly(ethylene glycol) (PEG) 12
2. Objectives 14
Ⅱ. EXPERIMENTS 16
1. Materials 16
2. Synthesis procedure of chitosan derivative 17
3. Synthesis procedure of PEG derivative 17
4. Characterization of chitosan and PEG derivatives 19
4.1. 1H NMR for chemical structure of polymers 19
4.2. UV-vis spectroscopy for phenol contents of polymers 19
5. Preparation and gelation time of in situ forming chitosan/PEG hybrid hydrogels 20
6. Characterization of in situ forming chitosan/PEG hybrid hydrogels 21
6.1. Water uptake 21
6.2. Compressive test 21
6.3. Tissue adhesive test 23
7. In vitro enzymatic degradation behavior 24
8. In vivo hemostatic effect test 25
Ⅲ. RESULT AND DISSCUSSION 26
1. Synthesis and characterization of chitosan and PEG derivatives 26
2. Preparation and gelation time of in situ forming chitosan/PEG hybrid hydrogels 28
3. Characterization of in situ forming chitosan/PEG hybrid hydrogels 30
3.1. Water uptake 30
3.2. Compressive test 32
3.4. Tissue adhesive test 37
4. In vitro enzymatic degradation behavior 39
5. In vivo hemostatic effect test 40
Ⅳ. CONCLUSION 42
Ⅴ. REFERENCES 43

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