Preparation Of Hydroxyapatite Materials Based On Novel Amyloid-like Assemblies

Hydroxyapatite has a huge potential application prospect in the biomedical and tissue engineering,due to its good biocompatibility and mechanical properties.However,a key factor for successful design of such bioactive complex,organic-inorganic hybrid biomaterials is the facilitation and control of adhesion at the interfaces,as many current synthetic biomaterials are inert,lacking interfacial bioactivity.In this regard,the development of a simple,unified way to biofunctionalize diverse organic and inorganic materials towards biomineralization remains a critical challenge.In this report,a universal biomineralization route that can be applied to virtually any type and morphology of scaffold materials was provided to induce nucleation and growth of hydroxyapatite(HAp)crystals based on Phase-Transited Lysozyme(PTL)coating.This thesis developed a versatile route for biomineralization,which was inspired by the interface adhesion of the amyloid protein assemblies in native.The route offered easy applicability to be an extremely versatile strategy for diverse functional.This Bottom-up crystal construction is then successfully applied in hard bone repair of the rat model,underpinning the expectation for such material in future tissue engineering.The research outline is as follows:(1)Preparation of hydroxyapatite crystals via PTL(nanofilm/microcoating)as a template.It is well known that protein template is critically important for hydroxyapatite biomineralization.We report that natural biological macromolecule,lysozyme,could undergo a phase transition under a stimulus from a disulfide breaker,tris(2-carboxyethyl)phosphine(TCEP)in an ambient aqueous solution.By controlling the phase transition process of lysozyme,the tight PTL coating would be obtained.According to the amyloid-mediated adhesion,we can got the attachment of the PTL(nanofilm/macrocoating)onto various surfaces.Inspired by the adhesion mechanism of amyloid structure contained in PTL,such protein assembly could readily integrate HAp on ceramics,metals,semiconductors,and synthetic polymers irrespective of their size and morphology,with robust bonding stability and corresponding ultralow wear extent under normal bone pressure.Surface-anchored abundant functional groups in PTL enrich the interface with strongly bonded calcium ions,facilitating the formation of HAp crystals with the morphology and alignment being similar to that observed in natural HAp in mineralized tissues.The PTL-template is a powerful approach to create novel organic-inorganic hybrid biomaterials regardless of type,size,and shape of counterpart materials.(2)Biological evaluation of HAp@PTL biomaterial.Due to the direct contact of cell and HAp coating,the biocompatibility of HAp on the PTL nanofilm is unavoidable in tissue engineering.Based on the above,in vitro cytotoxicity assays have detected to indicate that the HAp on the PTL coating favors good biocompatibility and cytocompatibility towards rat bone marrow mesenchymal stem cells(BMSCs).And in vivo animal test on subcutaneous implantation also indicates that this biomaterial presents an excellent osteoconductivity in a rat model.We construct HAp by the PTL coating as a template with excellent mechanical properties that well matched human bone by template approach.And this structural biomimetic process via PTL coating template method might bring about another route for mimicking complex hierarchical designs of natural structures and helpful for fabricating new hard tissue engineering materials with improved properties.We further expect that a new avenue on the biomolecular assembly engineering may be opened up towards green and sustainable biomaterials.