- Göransson, Anna, 1970-, et al.
Inflammatory response to oxidised surface with Mg 2+ -ions incorporated in vitro
Ingår i: 7th World Biomaterials Congress, Sidney, 17 -21 May 2004.
- Introduction Oxide films that grow spontaneously on titanium surfaces in contact with air may explain the bio-passivity of the material. Various procedures have been carried out to modify the properties of titanium oxide films to further improve the biocompatibility. Anodic oxidation is one technique to increase the thickness of the oxide layer that demonstrates significant stronger bone response in vivo. The concomitant increase in surface roughness and size and presence of pores of the thicker oxide layer seems to work as a potential contributor to the results (1). Attempts to implant ion in the oxide layers to overcome the drawbacks of calcium phosphate coatings (hydroxylapatite) such as i.e. delaminating and biodegradation during function seem promising (2). However the reasons why a thicker oxide layer with and without incorporated ions is favourable compared to conventionally turned and blasted surfaces are not fully understood. The aim of this study was to compare the early inflammatory response to the turned, blasted and electrochemically oxidised surface with Mg 2+ ions incorporated. Materials and Methods A total of 108 pure titanium discs were prepared with a turned surface. Thirty-six were kept as turned controls while 36 were blasted with 75 μm Al2O3 particles and 36 underwent electrochemically oxidation and Mg 2+ ion incorporation. MicroXam™, (Phase-Shift, Tucson, Arizona, USA) was used to for topographical characterisation. The disks were incubated with human mononuclear cells isolated from buffy coats of healthy blood donors (C-lab, Blood Supply Unit Sahlgrenska University hospital, Sweden) and cultured at a concentration of 106 cells/ml in 24 well cell culture plates. Half of the discs with the different treated surfaces were immediately treated with LPS while half were left without any stimuli. The incubation times were 24 and 72h. After each incubation period the incubation medium was collected and centrifuged. The supernatant was analysed with respect to cell viability and cytokine levels. Cell viability was estimated by analysing the content of lactatdehydrogenas (LDH)(Sahlgrenska University hospital, C-lab) and a commercially available ELISA assay (Biotrak system™, Amersham Bioscience, UK) was used to quantify TNF-α and IL -10 levels. The cells adherent to the material was stained with 2,6- diamidino-2-phenyindole (DAPI) (Sigma, USA) to evaluate the total cell number. In order to characterize differentiation of the adherent cells expression of 27E10 and RM3/1 (Biogenisis, UK) was used. The marker 27E10 and RM3/1 define acute and chronic inflammatory phenotypes respectively. Differentiated cells were evaluated as the percentage of positively stained cells from the total cell numbers. Results Surface evaluation revealed similar roughness for the turned control and the anodised surface with Mg 2+ ions incorporated while the blasted surface demonstrated a rougher surface profile (fig 1, 2). Fig 1 Fig 2 Sa-average height deviation (ym) SURFACE CTR Blasted Anodised+Mg Mean SA 1,2 1,0 ,8 ,6 ,4 ,2 0,0 Sdr-developed surface area (%) SURFACE CTR Blasted Anodised+Mg Mean SDR 40 30 20 10 0 LDH values were generally low for all surfaces (within the range of 0.8-1.6 μkat/l) but were slightly increased after LPS stimulation and after 72h. TNF-α was transient higher day one and after LPS stimulation especially on the turned control surface (fig 3, 4) Fig 3 Fig 4 TNF-a 24h (pg/ml) SURFACE CTR Blasted Anodised+Mg Mean C 3000 2000 1000 0 LPS LPSLPS+ TNF-a 72h (pg/ml) SURFACE CTR Blasted Anodised+Mg Mean C 400 300 200 100 0 LPS LPSLPS+ IL-10 levels were generally low irrespective of time. Increased IL-10 amounts after LPS stimulation and after 24 h were observed for all surfaces. The total cell numbers decreased on all surfaces from 24h to 72h but there were no major difference between stimulated and un-stimulated wells. Acute monocytic phenotype 27E10 marker dominated on all surfaces while the expression of the chronic RM3/1 marker was almost absent on all surfaces both at 24 and 72h. Conclusion The present study indicates a surface topography- and chemistry related difference in the acute inflammatory response with a stronger acute inflammatory response to the turned control compared to the blasted and anodised surface with Mg 2+ ions incorporated. References 1.Göransson, A, Jansson, E, Tengvall, P, Wennerberg, A. Bone formation after 4 weeks …topography : an in vivo study. Biomaterials 2002; 24: 197-205 2.Sul YT. PhD Thesis 2002, Göteborg University, Sweden