Surface Functionalized Barium Sulfate Nanoparticles: Controlled In Situ Synthesis And Application In Bone Cement

Bone cement plays an important role in orthopedic implantation. Acrylic bone cement ismostly used clinically. Radiopacifier is a vital component of bone cement, which is used to trackthe surgery and post-operation healing process of the artificial joint replacement. However, theintroduction of the radiopacifier (BaSO4) into bone cement causes series of detrimental effects onthe performance of bone cements. It reduces the mechanical properties, looses the orthopaedicimplant and shorts the service life of the implants. Therefore, it is essential to develop newradiopacifier materials which maintain the radiopacity and enhance the mechanical andperformance of bone cement. In this dissertation, new difunctional molecules were used as surfacemodification agents to control the morphology and surface properties of BaSO4. Furthermore, thedecomposition of K2S2O8, under mild conditions to generate SO42-in situ was realized to control thenucleation and growth of BaSO4nanoparticles. This work will establish a solid scientific basis fordeveloping new bone cement which maintains good radiopacity, mechanical properties andbiocompatibility. This dissertation includes the following three parts:(1)“one pot” method was used to synthesize surface functionalized BaSO4nanoparticles. Thein situ generation of SO42-via the thermal decomposition of K2S2O8was coupled with the use ofdifunctional surface modification to control the morphology and surface functionality of the BaSO4nanoparticles. It is found that by increasing the amount of surface modification agent of2-(methylpropylene acyl oxygen radicals) ethyl] dimethyl-(3-sulfonic acid propyl) ammonium hydroxide(MSAH), BaSO4nanoparticles with narrow size distribution were obtained. And the particle sizedecreased first, followed by gradual increase. The mechanism of the particle growth process andmorphology control of the MSAH-BaSO4nanoparticles was investigated.(2) By introducing the pre-decomposition process of K2S2O8, a “two-step” method wasapplied to control the morphology and surface functionality of the BaSO4nanoparticles. The in situgeneration of SO42-was decoupled with the use of difunctional surface modification agent. Bysystematically varying the pre-decomposition time, the type and amount of the surfacemodification agent, the morphology and surface functionality control of the BaSO4nanoparticleswere investigated. It is found that by controlling the pre-decomposition time, the type and the amount of the surface modification agent, the size of the BaSO4nanoparticles can be reduced to therange between10nm and50nm.(3) Based on the controlled synthesis of surface functionalized BaSO4nanoparticles, bonecement containing the synthesized BaSO4nanoparticles were fabricated. The impact of the amount,morphology, and surface functionality of the synthesized BaSO4nanoparticles on the mechanical,radiopacity, and biocompatibility of the bone cements were investigated. It is found that the BaSO4nanoparticles synthesized by “one-pot” method effectively improved the mechanical properties ofthe bone cements. Furthermore, the BaSO4nanoparticles synthesized with the “two-step” methodalso improved the bending modulus and compressive strength of the bone cements. Besides, theradiopacity of the bone cements was also improved. The biocompatibility of the bone cementscontaining the BaSO4nanoparticles was not deteriorated and even improved under certaincondition.