Study On The Preparation And Properties Of Nano Apatite, Calcium Silicate And Their Composite Biomaterials And Environmental Materials

In this study,theβ-tricalcium phosphate(β-Ca₃(PO₄)₂,β-TCP)nanopowders, hydroxyapatite(Ca₁₀(PO₄)₆(OH)₂,HAp)nanopowders,tobermorite (Ca₅Si₆O₁₆(OH)₂·4H₂O)nanowires,xonotlite(Ca₆Si₆O₁₇(OH)₂)nanowires,calcium silicate(CaSiO₃,CS)ultrafine powders and nanowires,β-TCP/CS and HAp/CS composite nanopowders were prepared.The bioactivity and degradability of tobermorite nanowires in vitro were investigated.The sintering ability of the apatite nanopowders and calcium silicate nanopowders,and the properties of the sintered matrixes were performed.Theβ-TCP/CS and HAp/CS composite nanoceramics were developed,and the mechanical properties,bioactivity(bone-like apatite-formation ability in vitro)and in vitro dissolution behavior of the fabricated samples with different composite ratios were examined.The macroporousβ-TCP and CS ceramic scaffolds with high mechanical strength and the novel porous samples similar to the natural bone structures were explored,and the biocompatibility,bioactivity, degradability and in vivo bone-regenerative capacity of the scaffolds were investigated.Furthermore,the adsorption of phenolic pollutants on HAp nanopowders was studied.The obtained results are described as followings:1.(1)The HAp nanopowders with different morphologies,crystallinity,particle size and specific surface area could be obtained using chemical precipitation method, hydrothermal microemulison method,ultrasonic chemical method or homogeneous-precipitation method.(2)Theβ-TCP nanopowders with 80～100nm could be obtained in large-scale by chemical precipitation method.(3)The monodispersed tobermorite nanowires with diameter of 30～50nm and up to tens of micrometers in length were prepared via hydrothermal microemulsion method.(4) The monodispersed xonotlite nanowires with diameter of 10～30nm and up to tens of micrometers in length were prepared via a simple hydrothermal method.After calcining at 800℃for 2h,xonotlite nanowires completely transformed intoβ-wollastonite nanowires and the wire-like structure and sizes were also preserved.(5) Theβ-TCP/CS and HAp/CS composite nanopowders with different composite ratios and well dispersions were synthesized by two-step chemical precipitation method. The particle sizes ofβ-TCP/CS and HAp/CS composite nanopowders were 20～80nm and 10～30nm,respectively.2.In vitro bioactivity of the tobermorite nanofibers was evaluated by examing the bone-like HAp forming ability on the surface after soaking in simulated body fluid (SBF)for various periods.After soaking in SBF for 3d,the nanofibers were completely covered by bonelike hydroxycarbonate apatite(HCA)layers,and the nanofibers after soaking still kept stability in fibrous morphology.The dissolution of the nanofibers reached about 24.5%after soaking in SBF for 14d.The results suggested that the tobermorite nanofibers exhibited certain desirable characteristics including bioactivity,degradability and stability in morphology,and a potential candidate as reinforcement materials to develop novel bioactive and degradable composites for biomedical applications.On the other hand,the tobermorite nanofibers might be used as the alkaline biodegradability materials to fabricate the composite biomaterials,which might not only contribute to the improved bioactivity of those acid biodegradability polymer materials,but also be able to neutralize the acidic degradation products of the polymers.3.Using the nanopowders as raw materials,the apatite and calcium silicate bioceramics were fabricated by sintering green compacts at atmosphere after cold isostatic pressure respectively.The results showed that the nanopowders possessed excellent sintering ability,and the ceramic samples with ultrafine crystal size and high densities could be obtained.Therefore,the apatite and calcium silicate bioceramics with well mechanical strength could be fabricated using nano-sized powders.(1)β-TCP bioceramics with high mechanical strength of 200MPa were fabricated using the nano-size powders,which were more than two times higher as compared to those of samples fabricated from micro-size powders.(2)The transparentβ-TCP bioceramics were fabricated using nano-size powders and(Spark Plasma Sintering, SPS).The transparent bodies had an average grain size of 250nm.The transparency of the samples with 1.0mm thickness reached about 52%.The MTT method showed that the proliferation of bone mesenchymal stem cells on transparentβ-TCP bioceramics was much better than that on the polystyrene cell culture cluster,suggesting that the transparentβ-TCP may be used as cell carrier materials and window materials for biomedical applications.(3)The dense HAp nanoceramics with an average grain size of 193nm were obtained through two-step sintering method.The fracture toughness reached 1.18MPa·m^1/2,which was about 60%higher than that of the samples with an average grain size of 765nm and fabricated by normal sintering method.(4)The bending strength of the CaSiO₃ bioceramics sintered from nanowires reached about 146MPa,which was similar to the upper value of the human cortical bones and was 53%higher than that of the samples sintered from superfine powders.The elastic modul of the fabricated CaSiO₃ bioceramics was similar to the human cortical bone. The study showed that the CaSiO₃ bioceramics with well mechanical strength could be fabricated using nanowires as raw materials.(5)The CaSiO₃ bioceramics possessed excellent bioactivity,degradability and cell compatibility.After soaking in SBF for 1d,the samples were completely covered by bonelike HAp layers.The dissolution ratio of the ceramics reached about 27.85%after soaking in Tris-HCl buffer solution for 28d,which was much higher than that ofβ-TCP bioceramics.The adhesion and proliferation of bone marrow mesenchymal stem cells on the CaSiO₃ ceramics was examined and the results showed that the ceramics supported cell adhesion and proliferation,which indicated good biocompatibility.Our results suggested that CaSiO₃ ceramics might be a potential bioactive and degradable material as bone implant.4.Using the nano-composite powders as raw materials,theβ-TCP/CS composite nanoceramics have been fabricated by sintering green compacts at atmosphere after cold isostatic pressure.The mechanical strength,bioactivity and degradability of the composite ceramics could be regulated by the composite ratios.The bending strength of the samples withβ-TCP component higher than 50wt.%was similar to the bending strength of human cortical bone.The mechanical strength increased with the increase of theβ-TCP component amount.The composite ceramics showed excellent bioactivity when the CS component ratio was higher than 30wt.%.After soaking in SBF for 1d,the samples were completely covered by bonelike HAp layers.The bioactivity and degradability increased with the increase of the CS component amount.5.Using the nano-composite powders as raw materials,the HAp/CS composite nanoceramics have been fabricated by sintering green compacts at atmosphere after cold isostatic pressure.The mechanical strength,bioactivity and degradability of the composite ceramics could be regulated by the composite ratios.The bending strength of the samples was in the range of 98.06 and 221.30MPa,and the elastic modul of the fabricated nanocomposite bioceramics was similar to the human cortical bone.The bending strength of the samples with CS component over 50wt.%was higher than the bending strength of human cortical bone.The mechanical strength,bioactivity and degradability increased with the increase of the CS component amount.6.The macroporousβ-TCP and CS scaffolds were successfully fabricated by porogen burning-out method,casting method and polymer sponge method.The results showed that the scaffolds with well mechanical strength could be obtained by the porogen burning-out method and the casting method.And the structure of the scaffolds fabricated by the polymer sponge method was open and interconnected pores,which showed that the structure of the scaffolds was similar to that of natural cancellous bones.Furthermore,theβ-TCP scaffolds with high mechanical strength could be fabricated from the nano-size powders.After soaking in SBF for 1d,the CS scaffolds were completely covered by HCA layers.The degradability of the CS samples with porosity of 63.1%reached 7.14%after soaking in SBF for 7d.The results suggested excellent in vitro bioactivity and degradability of the macroporous CS scaffolds.Therefore,the CS scaffolds may be potential candidates as bioactive and degradable scaffolds for hard tissue repair and bone tissue engineering applications.7.Theβ-TCP and CS scaffolds were implanted in rabbit subcutaneous sites and the rabbit calvarial defect sites,respectively to investigate the biological characteristics,in vivo bone-regenerative capacity and resorption of the materials. Compared withβ-TCP,the results showed that the CS scaffolds possessed superiority in vascularization,ingrowth of new tissue,degradation and bone-regenerative ability in early stage.The TRAP-positive multinucleated cells were observed on the surface ofβ-CS,suggested a cell-mediated process involved in the degradation ofβ-CS in vivo.Histological observation demonstrated that newly formed bone tissue grew into the porousβ-CS,and a bone-like HAp layer was identified between the bone tissue and CS materials.The studies showed that the CS scaffolds could stimulate bone regeneration and may be used as bioactive and biodegradable materials for hard tissue repair and bone tissue engineering applications.8.The HAp nanopowders were used as the adsorbent,and the potential of HAp nanopowders for phenolic pollutant adsorption from aqueous solution was studied. The effect of contact time,initial phenol concentration,pH,adsorbent dosage, solution temperature and adsorbent calcining temperature on the phenol adsorption, and the adsorption kinetic,equilibrium and thermodynamic parameters of phenolic pollutants were investigated.The results showed that the HAp nanopowders possessed good adsorption ability to phenolic pollutants.The results suggested that the HAp nanopowders might be a new potential,biocompatible and good adsorbent for the removal of phenol pollutants from aqueous solutions.In conclusion,the apatite,calcium silicate and their composite bioceramics could be fabricated using the nano-size powders as the raw materials.The mechanical strength,bioactivity and degradability of theβ-TCP/CS and HAp/CS composite nanoceramics could be regulated by the composite ratios.The CS scaffolds possessed excellent biocompatibility,bioactivity,biodegradability and bone-regenerative ability, and may be used as bioactive and biodegradable materials for hard tissue repair and bone tissue engineering applications.The HAp nanopowders possessed good adsorption ability to phenolic pollutants,and may be a new potential,biocompatible and good adsorbent for the removal of phenol pollutants from aqueous solutions.