Biomimetic Mineralization Of Silk Fibroin Hydrogels

It is well known that the biominerals have been formed in the hydrogel environment.Biomineralization is a complex process, which always influenced by the organic components inthe body. The insoluble organic macromolecules and the soluble acidic proteins work together toregulate the crystal nucleation and growth, to modulate the crystal size and shape, assemble thecrystals into complex structures through molecular recognition in mild environments. Theunusual structure endows biominerals with excellent performance far better than syntheticmaterials, including unique optical properties, high strength and fracture toughness. Inspired bybiomineralization process,3D silk fibroin hydrogel is designed as a model to modulate thenucleation and growth of hydroxyapatite crystals. The mineralization process of fibroinhydrogels containing different Ca ion contents and the influence of the mineralization time areinvestigated in phosphate solution via a simple ion diffusion methodï¼›On the other hand, bothcritic acid and sericin are chose as functional molecules. We examined the effect of3D silkfibroin hydrogel in the absence/presence of functional molecules on the mineralization process.XRD, FTIR, FE-SEM, TEM, TGA and mechanical test investigated the structure and propertycharacteristics of biomineralizated silk fibroin hydrogel. The biocompatibility of thebiomineralized hydrogel was evaluated using FE-SEM, MTT, Alamar blue and ALP examinedthe morphology, proliferation and differentiation of osteoblast MG-63cells in vitro.The results of the study are as follows: Ca2+existed in the hydrogel played an important rolein the biomineralization process. Ca ion inserted fibroin hydrogel provides the nucleation sitesfor crystals and subsequently regulates their oriented growth. Crystal formation ability is Caconcentration-dependent. The mineralization process is under precise control, when appropriatecontent of Ca ion exist in the fibroin hydrogel. XRD and FTIR analysis shown the obtainedminerals are hydroxyapatite. Crystal contents in the composites were33.8,36.6,37.4,37.8and38.8%corresponding to mineralization time of0.5,2,12,24and72h respectively, according tothe TG results. All mineralized samples exhibited better mechanical properties than blank fibroinhydrogel. Both the amount and the crystallinity of minerals and the compressive modulus of thesamples were enhanced with prolongation of the mineralization time. The presence of criticacid/sericin in the3D fibroin hydrogel inhibited the growth of hydroxyapatite crystals. Thecrystal contents were37.1and34.9%corresponding to the critic acid and sericin system respectively, which are less than38.7%of crystal quantity formed in the pure fibroin hydrogel.The cell culture experiment shown the MG-63cells can normally adhere, proliferation,differentiation in all of biomineralized hydrogels. The biomineralized hydrogels exhibited goodbiocompatibility and bioactivity. Meanwhile, the osteo-conductive ability of the composite wasimproved with enhanced mineral content and the regulation of acid protein.Our objective was to further understand the growth process of biomineral via a biomimeticmethod for subsequent preparation of biomedical materials. The SF/CaP composite has goodmechanical properties and biocompatibility, envisions the extensive applicability for preparing of3D bonelike biomaterials via an efficient and biomimetic process and achieving desired efficacyto repair bone defects.