Wear debris generated by total hip replacements (THRs) may cause mechanical instability, inflammation, osteolysis and ultimately implant loosening, thus limiting the lifetime of such devices [1]. This has led to the development of biocompatible coatings for prostheses. Silicon nitride (SiN) coatings are highly wear resistant and any resultant wear debris are soluble, reducing the possibility of a chronic inflammatory reaction [2]. SiN wear debris produced from coatings have not been characterized Commercial silicon nitride particles of <50nm (Sigma Aldrich) were incubated with formalin fixed sheep synovium at a volume of 0.01mm3 /g of tissue (n=3). The tissue was digested with papain (1.56mg/ml) for 6h and subsequently proteinase K (1mg/ml) overnight. Proteinase K digestion was repeated for 6h and again overnight, after which samples appeared visibly homogeneous [Figure 1]. Samples were then subjected to density gradient ultracentrifugation using sodium polytungstate (SPT) [3]. The resulting protein band was removed from the pellet of particles. Control tissue samples, to which no particles were added, were also subjected to the procedure. Particles were washed with filtered water to remove residual SPT using ultracentrifugation and filtered onto 15nm polycarbonate filters. The filtered particles were imaged by cold field emission scanning electron microscopy (CFE-SEM) and positively identified by elemental analysis before and after the isolation procedure. To validate whether the isolation method affected particle size or morphology, imaging software (imageJ) was used to determine size distributions and morphological parameters of the particles. A Kolmogorov-Smirnov test was used to statistically analyse the particle morphology.Introduction
Methods
Articular hyaline cartilage has a unique structural composition that allows it to endure high load, distribute load to bone and enables low friction movement in joints. A novel acellular xenogenic graft is proposed as a biological cartilage replacement, for repair of osteochondral defects. Acellular porcine cartilage has been produced using repeated freeze thaw cycles and washing using hypotonic buffers and sodium dodecyl sulphate solution (SDS; Keir, 2008). DNA content of the acellular matrix was reduced by 93.3% compared to native cartilage as measured by nanodrop spectrophotometry of extracted DNA, with a corresponding reduction in glycosaminoglycan (GAG) content. It was hypothesised that penetration of decellularisation solutions into the native tissue could be improved through deformation of the cartilage under confined compression and then allowing the osteochondral pin to recover in solution, allowing removal of cellular DNA and greater retention of the GAGs.Introduction
Hypothesis
