Antibacterial Properties of Ag-modified Ca-Phosphate Scaffolds for Bone Implant Applications

在我们的研究计划的前一阶段，气相传输烧结成功地应用于磷酸钙（CaP）陶瓷，建立了一种创新的方法，用于制造具有互连孔隙的生物活性植入材料。最重要的结果之一是在一个加工步骤中将陶瓷支架的几乎无收缩烧结和用银颗粒进行表面改性相结合，从而潜在地为材料提供抗菌性能。然而，气相输送有其局限性，因为它产生太小的孔径，骨组织向内生长。因此，为了完成这项研究，我们建议（i）在氯化银气氛中的气相传输烧结应用于具有足够大孔径的大孔CaP支架，以及（ii）体外测试以评估这些新型复合材料的抗菌性能。(i)通过气相传输烧结对生物源磷酸钙支架进行银改性水热转化的生物源碳酸盐将用作支架材料（HA：羟基磷灰石，BCP：双相磷酸钙），用银颗粒进行改性，因为它们提供了骨移植应用所需的孔体积和互连孔几何形状。而珊瑚文石HA的转换是一个商业上建立的过程中，我们以前的实验与海胆刺显示出巨大的潜力，BCP复合材料的制造，提供上级生物可吸收性，相比纯HA。用精细分散的金属银颗粒加载支架表面是一种新的工艺，有望为陶瓷植入物提供抗菌性能。(ii)抗菌性能的体外评估关于银改性陶瓷支架作为骨植入材料的潜在应用，如果银离子以适当的速率溶解以展现其抗菌性能，则特别令人感兴趣。因此，将在模拟生理条件下进行溶解度试验。如果获得了阳性结果，我们将使用通常在皮肤和慢性感染伤口中发现的细菌菌株进行细胞培养实验。

In a previous phase of our research program, vapor transport sintering was successfully applied to calcium phosphate (CaP) ceramics, establishing an innovative method for the fabrication of bioactive implant materials with interconnected porosity. Among the most important results was the combination of nearly shrinkage-free sintering of the ceramic scaffolds and a surface modification with silver particles in one processing step, potentially lending antibacterial properties to the material. However, vapor phase transport has its limitations, since it produces too small pore diameters for bone tissue ingrowth. Therefore, in order to complete this study, we propose (i) the application of vapor transport sintering in AgCl atmosphere to macroporous CaP scaffolds with sufficiently large pore diameters and (ii) in-vitro testing to assess the antibacterial properties of these novel composite materials.(i) Ag-modification of biogenic calcium phosphate scaffolds via vapor transport sinteringHydrothermally converted biogenic carbonates will be used as scaffold materials (HA: hydroxyapatite, and BCP: biphasic calcium phosphate) to be modified with Ag particles, as they provide the pore volume and interconnected pore geometry required for bone graft applications. Whereas the conversion of coralline aragonite to HA is a commercially established process, our previous experiments with sea urchin spines have shown great potential for the fabrication of BCP composites that offer superior bioresorbability, as compared to pure HA. Loading the scaffold's surface with finely dispersed metallic Ag particles is a novel process that is expected to lend antibacterial properties to the ceramic implant.(ii) In-vitro assessment of antibacterial propertiesConcerning the potential application of Ag-modified ceramic scaffolds as a bone implant material, it is of particular interest if silver ions are dissolved at an appropriate rate to unfold their antibacterial properties. Therefore, solubility tests under simulated physiological conditions will be performed. Positive results provided, we will proceed with cell culture experiments using bacterial strains typically found on the skin and in chronically infected wounds.