Preparation, Characterization And Application Research Of Hydrogel With Amino Acid Functionation

Many inorganic minerals are produced by living organisms, such as teeth, bone, diatom, shell and so on. Biominerals with complex morphologies and structures have special functions and fascinating properties. Now the synthesis of hierachial composite using in vitro biomimetic mineralization has intrigued people.Mineralization in vivo is controlled by some extracellular proteins and polysaccharides. These extracellular proteins containing many anionic amino acids (aspartate, glutamate), along with structural and stereochemical interactions, are thought to lead to attraction of calcium-rich mineral nuclei and initiation of mineral growth. For this reason, hydrogels functionalized with anionic amino acids, can be used as model compounds to initiate mineral nucleation. Hydrogel materials was synthesized by silution polymerization using 2-hydroxyethylmethacrylate (HEMA) and functionalized 2-hydroxyethylmethacrylate as monomer, poly(ethylene glycol) dimethacrylate (PEGDMA) as cross-linking additive, ammonium persulfate solution(APS) and tetramethylenedimine (TEMED) as initiators. The experimental results showed the equilibrium water content (EWC) of HEMA, Asp-HEMA, Glu-HEMA and Glu-HEMA hydrogel was 50%-60% and all of hydrogel have porose structure.Calcium carbonate is one of the most important simulate objects in biomeralization field. It isn't only rich in existence on the earth's crust, but also play an important role in organisms. Calcium carbonate has three anhydrous crystalline patterns: calcite, aragonite, and vaterite. This paper describes the mineralization of calcium carbonate on the surfaces of different amino acids functionalized poly(2-Hydroxyethyl methacrylate) hydrogels using gas diffusion method. The reaction time was 12h, 24h and 36h. The design of the system was based upon examples from biomineralization in which hydrogels were coupled with functionalized, organic surfaces to control crystal morphology and orientation of biominerals. The morphology and polymorphism of these calcium carbonate crystals were characterized using scanning electron microscope (SEM), Fourier transform infrared spectroscope (FT-IR) and powder X-ray diffraction (XRD). The results showed that amino acids played an important role in the process of crystal growth of calcium carbonate at the early stage. The possible formation mechanisms of CaCO3 produced in different amino acid based hydrogels were also discussed. The results showed that all of four hydrogel could keep vaterite stable in 36h. Asp-HEMA hydrogel was propitious to form aragonite and Glu-HEMA hydrogel was propitious to form calcite.Natural bone tissue is a composite material that contains collagen fibrils and hydroxyapatite (HAP) crystals in a hierarchical organization. The unusual combination of a hard inorganic material and an underlying elastic hydrogel network endows native bone with unique mechanical properties, such as low stiffness, resistance to tensile and compressive forces, and high fracture toughness. Therefore, as a biomimetic strategy, using organic materials as templates for the growth of HAP, to mimic the structure and property of natural bone is very intriguing. To mimic the formation of hydroxyapatite as natural bone, an alternative immersion technique was used in this study to nucleate the hydroxyapatite crystals onto different amino acids functionalized poly(2-Hydroxyethyl methacrylate) hydrogels. The morphologies of the mineralized hydrogels analyzed by scanning electron microscope showed that amino acids functionalized hydrogels had stronger hydroxyapatite binding affinity than the control hydrogel, and the hydroxyapatite crystals were not only formed on the surface of the hydrogels, but also in pore channels and attached to the pore walls. HAP particles are the evenlist distributed on the surface of Asp-HEMA hydrogel. The HAP particles are the worst reunited on the surface of HEMA hydrogel. The X-ray diffraction and Fourier transformed infrared spectroscope confirmed the formation of apatite crystals. The in-vitro biocompatibility tests with embryonic kidney cells demonstrated that the mineralized hydrogels were suitable substrates for cell attachment and migration.