Organic-inorganic Hybrid Materials Used In Subchondral Bone Repair

Osteoarthritis is a degenerative joint disease accompanied by joint stiffness and pain.Millions of people have been affected by osteoarthritis and morbidity has been growing with the rise of age.The purposes of osteoarthritis therapies focused on improving joint function and releasing symptom of pain due to complexity of the pathogenesis of osteoarthritis which matter cartilage and subchondral bone.At present clinical therapies of osteoarthritis can be divided as follows,application of NSAIDs to relief pain,injection of adrenal cortical hormone or sodium hyaluronate to intra articular and Arthroscopic treatment.It’s difficult to obtain radical cures for painkillers and injection medicine to intra articular can only relief pain.The emerging of tissue engineering in 1980 s which based on cell biology and material science bring hope for osteoarthritis therapy.Tissue engineering is a method that combine cells and scaffold to defect sites to achieve goals of tissue repair and regeneration.Scaffold is cruicial to tissue engineering. Osteoarthritis involves pathological changes of cartilage and subchondral bone,so repair of these tissues separately is neccesary.In this study,we focus on repair of subchondral bone.Bioglass is a potential bone repair material due to its excellent bioactivity and bone conduction among numerous biomaterials.The mechnical property of bioglass is unmatched with subchondral bone and hard to process into complex structure of subchondral bone due to its hard and brittle characteristics.Recently Organic-inorganic hybrid materials which possess excellent mechannical property and a certain content of bioacticity, have been developed through method of sol-gel method by mixing degradable polymers and bioglass.At present, biodegradable polyesters have been applied for synthesis of hybrid materials due to its excellent crystallinity and high modulus,wheras compatibility with subchondral bone in mechanical property is unsatisfied.Introducing PEG into backbone of PCL can inhibit crystallinity of PCL and improve flexibility of molecular chain of PCL and thus mechanical compatibility with sunchondral bone can be obtained.In this study,four groups of different PEE have been synthesized by adjusting moleclar weight of PEG and feed ratios though ring-opening polymerization of PEG and caprolactone. Organic-inorganic hybrid materials are synthesized as following steps,PEE and IPTS formed prepolymers and prepolymers reacted with Ethyl orthosilicate, three ethyl phosphate, calcium nitrate. Small angle scattering results shows low molecular weight PEEs achieved better conjunction with bioglass,which is beneficial to improvement of mechnical property of hybrid material but mineralization of materials are hindered.Though hybrid materials synthesized successfully,the highest modulus of materials can merely reach 49.83 MPa.The modulus of the material is insufficient to the repair of subchondral bone and enhancing mechnical property of material is ugently in need.In this study,4 groups of PEE of 3000 dalton with different content of polyester have been applied to synthesis of hybrid material. Mineralization and mechnical test shows that higher content of polyester in PEE is advantageous to the increasing of mechanical property and mineralization rate of material.We have synthesized polysuccinic acid- octylene glycol ester as organic segment to investigate function of polyether in hybrid material.XRD result of hybrid material present strong crystallization peak and macroeconomic performance of material is brittle.Results indicates polyether segment in PEE inhibit crystallinity of hybrid material effectively and thus improve flexibility of hybrid material.In this study, comprehensive performance of a group of hybrid material with molecular weight of 3000,1:4 of polyether and polyester ratio,70% content of organic segment behaves excellent mineralization and mechanical performance and the material will be a promising subchondral bone repair material.