Hydrogels is hydrophilic polymeric three-dimensional (3D) networks structures that can absorb surrounding water or biological fluids. It is cross-linked via covalent bond or physical (intramolecular or intermolecular) interactions, Due to the extracellular matrix (ECM) mimicking structure of the hydrogel that considered as a promising artificial scaffold for many biomedical applications. Their 3D microstructure provides delivery of bioactive molecules such as drugs, cells, growth factors and release as sustained manner. The hydrogel matrix should provide proper spaces for the cells to migrate and proliferate, finally, replaced by ECM components that naturally secreted as the tissue regeneration process. Therefore, designing criteria by the application specific condition of hydrogels as tissue engineering scaffolds should be considered with the physical/chemical (mechanical strength, material-tissue interaction and degradation rate) and biological (cellular responses, modulate cellular behavior) requirements. Among these hydrogel systems, an enzyme-catalyzed cross-linking mechanism has been widely studied to alter currently used cross-linking systems. Horseradish peroxidase (HRP)-catalyzed reaction system enable to control of physical and chemical properties. The porphyrin HRP structure containing iron that inducing the coupling of phenol or aniline derivatives in the presence H2O2 as the oxidant. It was demonstrated that HRP-catalyzed cross-linking system could control of cross-linking rate and degree, both of which affect key hydrogel properties, such as gelation time, mechanical stiffness, swelling properties and degradation rate.
In Chapter 2, injectable tissue adhesive hydrogels have been widely utilized to replace the use of surgical sutures and staples because of their ability to fill irregular defect and to interact with surrounding tissues during hydrogel formation. However, the insufficient tissue adhesive strength of these
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hydrogels still remaining as a challenge for achieving a stable wound closure. In this study, we developed enzyme-mediated crosslinking gelatin-hydroxyphenyl propionic acid (GH)/graphene oxide (GO) composite hydrogels to improve mechanical properties that can serve as an injectable tissue adhesive. The effect of different concentration of GO on the physico-chemical properties of GH hydrogels were investigated, particularly tissue adhesion strength. In vitro proteolytic degradation behavior and cyto-toxicity study confirmed the hydrogels were biodegradable and have an excellent cytocompatibility.
In chapter 3, gelatin-hydroxyphenyl propionic acid (GH)/fucoidan-tyramine (FTA) hybrid with ROS consuming behavior and electroconductive was developed. The he physicochemical properties of GH/FTA hydrogels were investigated, particularly the ROS consumption behavior and electroconductivity of the hydrogels. We demonstrate that injectable GH/FTA hydrogels have potential to be used as a cardiac tissue regeneration platform
