Study Of The Biocompatibility Of Natural Diatomite And Its Applications In Bone Cement And Anti-infection Material

Natural diatomite is the fossil remains of ancient diatoms and mainly composed of biogenic SiO₂ that structurally possesses the skeleton of single-celled alga with 3D structure.Natural diatomite has demonstrated to possess special physical properties such as high porosity,hydrophilic,high strength,high specific surface area and superior adsorption capacity.More importantly,mechanical property of diatomite is reportedly better than other biomineral material.However,the biocompatibility property of diatomite is still unknown to date,which limits its application in the field of biomedical engineering.Natural diatomite has been well known for its reinforcing effects on Portland cement or concrete,especially improving the compressive strengths of the cements.In clinical practice,calcium phosphate bone cement?CPC?is not applicable to kyphoplasty due to its low compressive strength.It is therefore hypothesized that adding diatomite into the CPC may also improve the compressive strengths of CPC.On the other hand,modifying diatomite to develop a material having both biocompatibility and anti-bacterial property is also of interest to orthopaedic research.The first part of this study is the investigation on the biocompatibility of diatomite.Natural diatomite was calcined,washed by acid and segregated into different shapes and sizes.To evaluate the biocompatibility of the diatomite,two types of cell?osteoblasts and fibroblasts?were both used for proliferation and cytotoxicity tests.The results showed that,the particles of 30DT-disk had the best biocompatibility,while the 3DT had the highest cytotoxicity among all diatomite samples.Also,the cytotoxicity of diatomite shows the size-,dose-and shape-dependent effects.In the second part of this study,the 30DT-disk was modified and assed to the CPC to improve the mechanical strength of CPC.In order to obtain a better dispersity and homogeneity of diatomite in CPC,30ST-disk particles were modified by two approaches,10-fold simulated body fluid?10×SBF?soaking and HA coating.According the SEM and XRD results,HA crystals formed and attached onto the diatomite surface by both modification approaches.Both the SBF-and HA-treated diatomite revealed significant reinforcing effects on improving the compressive strength and modulus compression of CPC or starch gel/CPC.The third part of the study focused on developing a biocompatible and anti-infective material based on diatomite.Porous architectures of diatomite could absorb the Ag ions,and the Ag⁺was later reduced by the glucose to form nanoparticles deposition on30DT-disk.According to the SEM and XRD results indicated that Ag nanoparticles were evenly attached onto the surface of diatomite particles.Cell experiment results showed that samples of 0.1 and 0.5 mg/ml of Ag-diatomite did not show cytotoxicity but better cell viability than the control group.When the concentration of Ag-diatomite increased to 1,2.5 and 5 mg/ml,obvious cytotoxicity was observed.Bacterial culture experiments indicated that 0.5mg/ml of Ag-diatomite could clearly decreased bacterial colonies and thus exhibit bacterial inhibition.Therefore,0.5 mg/ml of Ag-diatomite was found to have both good biocompatible and anti-infective properties.