The Preparation And Osteogenic Performance Of Hydroxyapatite/Mollusk Shell-derived Organic Template Composites

Severe osteochondral defects can lead to osteoarthritis,an arthritis involving the entire joint tissue.The osteochondral is naturally avascular,non-neurological and lymphatic-free,which make it difficult for the defect in this region to repair by itself.Osteoarthritis receives little attention and will lead to disability in the body eventually because it does not affect the sustainability of life.In addition to the degradation of cartilage,the problem of cartilage defect extending to the subchondral bone is also receiving more and more attention and the successful reconstruction of subchondral bone is the key to osteochondral repair.There are lots of natural or synthetic polymers which have been used for the repair of the osteochondral defects,but clinical failure which due to insufficient bone support has continually motivated people to discover or create new subchondral bone constructs which can meet the increasing clinical requirements.In this work,we prepared biodegradable subchondral bone constructs with biomimetic structure successfully,which based on the organic template of mollusk shell(OTMS)and could meet the functional requirements of the subchondral bone construct,such as effective mechanical support,excellent bioactivity,cytocompatibility.and osseointegration properties.The specific contents of the study are as follows:(1)In this section,a hydroxyapatite/organic template composite construct,HA/pDA-OTMS,was obtained on an organic "superglue" polydopamine-modified organic template(pDA-OTMS)through a one-step biomineralization process.The characterization of each group of materials and the cell experiments using MC3T3-E1 cells as target cells in vitro found that the honeycomb-like OTMS had excellent mechanical properties,and the interconnected channel array could promote gas exchange and nutrient transport;it was a combination of sugar and protein,and the biosafety of OTMS was mainly attributed to the natural source;it was biocompatible and allowed the adhesion and proliferation of cells;the negative electrode surface after the modification of pDA was beneficial to the nucleation of calcium phosphate,which did not have obvious cytotoxicity and was conducive to the proliferation and growth of cells;the honeycomb-like structure of the organic substrate allowed the smallest material to create the largest and most stable geometric space,loading HA on the entire surface and inner wall could provide certain mechanical properties,promote the expression of osteogenesis-related genes and enhance the osteogenic properties of the construct.It was the first time that it had demonstrated the feasible for OTMS as the substrate for biomaterial,in this work,and a wide range of sources as well as the simple preparation could facilitate the widespread use of OTMS.(2)In this section,Hydroxyapatite doped with different amounts of cobalt ions,HA/Co X,was deposited on the pDA-modified organic template derived from mollusk shell(pDA-OTMS)by two-step biomimetic method,in which the X was the concentration of Co2+ incorporated in theory,respectively,0,0.1,1,5,10,15,20 ?M.The characterization of each group of materials and the cell experiments using MC3T3-E1 cells as target cells in vitro found that proper concentration of Co2+ could promote adhesion and proliferation of cells,the HA/Co 20 group with the highest concentration of Co2+ was adverse for cell adhesion and spreading,and the presence of Co2+ could promote the differentiation of osteoblasts and all doped groups that compared with the pure HA group showed significant difference.The ALP activity increased first and then decreased with the increase of the concentration of Co2+,among which the HA/Co 10 group had the best osteogenesis,indicating that the presence of Co2+ with a certain range could enhance the osteogenesis of the material.In summary,this experiment prepared three-dimensional organic/inorganic composite constructs which both based on the organic template derived from the mollusk shell,HA/pDA-OTMS construct by one-step biomimetic mineralization,and HA/Co X(X = 0,0.1,1,5,10,15,20)construct by two-step biomimetic method.The investigation showed that it was feasible for honeycomb-like OTMS as the base of the biomaterial:the natural space structure of OTMS gave the excellent mechanical properties,the composition of OTMS was safe and non-toxic,and it was cytocompatibility and biodegradation,the connected pore structure of that allowed cells to migrate and proliferate in the tissue deeply,facilitating the exchange of nutrients and wastes;the HA/pDA-OTMS and the HA/Co combined the advantages of organic template and inorganic crystal fully,which could promote the growth and differentiation of osteoblasts on the basis of providing sufficient mechanical support.The Co2+ doped HA could effectively enhance the osteogenesis of the material.The both could be applied to the reconstruction of subchondral bone.