Preparation Of N-HA/CPP Composite Hydrogel And Its Application In Bone Cement

Calcium polyphosphate(CPP)is a calcium phosphate bioceramic with linear chain structure.The amorphous CPP has unique gelling properties,and CPP hydrogel can be formed by physical crosslinking in aqueous solution.At present,the gelling properties of CPP has attracted much attention in fields of drug loading and bone repair.In this article,CPP hydrogel was prepared by controlling the mixing ratio of amorphous CPP to distilled water,and then the CPP hydrogel was combined with nano-hydroxyapatite(n-HA)to prepare n-HA/CPP composite hydrogel by blending method.Finally,modified calcium phosphate cement(CPC)was prepared by mixing CPP hydrogel and n-HA/CPP composite hydrogel with CPC powder,respectively.To compare the influences of different mixing ratios of CPP to distilled water,and different amounts of n-HA addition on the structure,morphology,thermal stability,swelling properties,degradation properties and mechanical properties of CPP hydrogel.In addition,the influences of different mixing ratios of hydrogel to CPC powder and hydrogel type on the setting time,injectability,mechanical properties,cross-sectional morphology,anti-washout property and hydration process of the prepared cement were also investigated,and the hydration process mechanism was analyzed.The results obtained were as follows:The reduction of chain length of CPP hydrogel promoted the formation of crystallization.During the aging process,long-chain hydrogel tended to be shorter,sample with the mixing ratio of 1:20 had the highest degree of crystallization and best the thermal stability.With the increasing mixing ratio of CPP to distilled water,the phosphate chain length of CPP hydrogel increased,the swelling properties,degradation properties and compressive strength of CPP hydrogel increased gradually.After swelling,the internal pore morphology of the samples changed from stripe to honeycomb.With the increasing amount of n-HA addition,the phosphate chain length of n-HA/CPP composite hydrogel increased first and then decreased,and the thermal stability of n-HA/CPP composite hydrogel at 700? gradually increased,both of the swelling and degradation properties decreased first,then increased and then decrease,as well as the size of internal pores after swelling varied following a similar way.When the amount of n-HA addition was 1wt%,the compressive strength of the n-HA/CPP composite hydrogel reached a maximum value,5.06±0.60 MPa,22% higher than that of the pure CPP hydrogel.The CPC was prepared by modification of hydrogel matrix could be hydrated to formpoly-dicalcium phosphate dihydrate(DCPD),which improved the setting time,injectability,compressive strength and anti-washout property of traditional calcium phosphate cement.The properties of the hydrogel modified calcium phosphate cement were affected by the mixing ratio of the hydrogel to CPC powder and the type of hydrogel.With the increasing CPC powder,the setting time and injectability decreased,the compressive strength increased first and then decreased and the anti-washout properties increased.The compressive strength of calcium phosphate cement modified with CPP hydrogel as the matrix reached a maximum at the mixing ratio of 1:0.45,22.51±0.72 MPa.Compared with the calcium phosphate cement modified with CPP hydrogel as the matrix,the calcium phosphate cement modified with n-HA/CPP composite hydrogel as the matrix prolonged setting time,reduced injectability,increased compressive strength and improved anti-washout property and generated more DCPD in the same hydration time.