Preparation And Characterisation Of Biomedical Porous Metals Based On Carbon Skeleton

Since biomedical porous metal has unique structure which could avoid stress shieldeffect and achieve biomedical fixation, it appears more attention in recent years. Owing toPalladium’s and Silver’s excellent corrosion resistance, low toxicity, good ductility andbiocompatibility, they appear wide applications in medical field. Moreover, silver, which hasparticular bacteriostatic properties, have been wide used as antibacterial agent for healthcareand diseases cure. However, there is no study about porous palladium and porous silver yet.In this paper, we designed a novel preparation process, which a porous carbon skeletonwith three-dimensional interconnected porous structure were introduced, after electrolessplating and electroplating process, the Pd or Ag metallic layer was deposited on the porouscarbon skeleton, resulting a novel porous Pd or Ag scaffolds with foam-like structure withadjustable porosities. The porous structure, phase composition, compression behavior andbiocompatibility evaluations of as-prepared porous Pd and Ag scaffolds were investigated. Inaddition, the antibacterial activity of porous Ag scaffolds was investigated.The open cell polyurethane foam solidified with phenolic resin, were pyrolyzed at1100oC in the vacuum, through which could successfully produce the porous carbon skeletonwith foam-like structure which average pore size287²020μm. The as-prepared porouscarbon skeleton was characterized with short-range ordered non-graphitizing glass-like carbonphase composition. The carbon skeleton prepared by the polyurethane foam with55ppipossessed95%porosity and602±93μm average pore size which was considered to be aappropriate porous structure as substrate of electroless plating and electroplating processafterwards. Moreover, the in vitro cytotoxicity evaluation showed that as-prepared carbonskeleton possessed a good biocompatibility.We successfully prepared porous Pd scaffolds exhibiting highly interconnected porousstructure with porosities82.9%⁶3.5%, apparent densities91.7³19.6g/cm³average pore size500⁶00μm by optimizing the parameters of electroless planting process （PdCl22g/L, N2H₄10ml/L, EDTA60g/L, NH₄OH340ml/L, pH11, Ce additive1.5g/L） and electroplatingprocess （current density1.5A/g, pH value9.0, temperature50oC, additive2.5g/L） on porouscarbon skeleton. The as-prepared porous Pd scaffolds were face-centered cubic palladium. The porous Pd scaffolds had the porosities, apparent densities and average pore size muchsimilar as nature cancellous bone. The porous Pd scaffolds possessed elasticity modulus11.5⁶7.6MPa which was similar as the compression behaviors of femur cancellous bone andspinal cancellous bone. Moreover, the porous Pd scaffolds showed low ion release rate andlow cell toxicity. Therefore, the porous Pd scaffolds may have a promising application forporous coating of dental implant or joint arthroplasty implant.As porous Pd scaffolds, we successfully prepared porous Ag scaffolds with highlyinterconnected porous structure which porosities68%⁸1%, apparent densities13.1⁹7g/cm³average pore size387⁵75μm by optimizing the parameters of electroless plantingprocess (AgNO316g/L, NH3H2O80ml/L, NaOH12g/L, C₆H₁₂O₆21g/L, C2H5OH75ml/L)and electroplating process （current density4A/g, pH value9.0, temperature25oC） on porouscarbon skeleton. The as-prepared porous Ag scaffolds were face-centered cubic silver. Theporous Ag scaffolds had the porosities, apparent densities and average pore size much similaras nature cancellous bone and possessed elasticity modulus1.94⁴9.3MPa which was similaras the compression behavior of femur cancellous bone. Moreover, the porous Ag scaffoldsshowed low ion release rate and acceptable cell toxicity. After heat treatment, the porous Agscaffolds showed a compact smooth metallic layer and a high compress property. However,heat treatment altered the ion release behavior and the treated porous Ag scaffolds showedlower long term biosafty. Consequently, the porous Ag scaffolds may have a promisingapplication for porous coating of dental implant or joint arthroplasty implant.