| dc.description.abstract | The mechanisms that regulate the tissue response to artificial organs and implants are not well understood. An increased knowledge of these processes is necessary in order to develop new materials with optimized properties in a biological environment. The aim with this thesis was to study inflammation and tissue repair after implantation of materials with different surface chemical characteristics.The model implant materials were made of c.p. titanium (Ti) or silicon (Si) plates with ~200 nm physically vapor deposited gold (Au). The Au surfaces were functionalized by self assembly of SH(CH2)16OH (-OH) and SH(CH2)15CH3 (-CH3) alkane thiols, adsorption of mercaptoglycerol (MG) and glutathione (GSH), and spontaneous adsorption of immunoglobulin G (IgG) and albumin (Alb). The initial surface deposition pattern of selected plasma proteins was studied in vitro by ellipsometry and antibody techniques and a combination of sodium dodecyl sulfate polyacryl amide gel electrophoresis (SDS-PAGE), Western blot and densitometry. An animal experimental model was developed for systematic studies on inflammatory cell recruitment, distribution, activity and fibrous tissue formation around the implants. The implants were placed subcutaneously for 3 hours to 28 days in the back of the rat. Light microscopy (LM), fluorescent activated cell sorter (FACS) and DNA quantitations (luminescence spectrometry) were used for the analysis and quantification of the cells. Hydrogen peroxide (H2O2), luminol-enhanced chemiluminescence (CL) and cytokines (Il-1a, IL-1b, TNFa) were analyzed by luminescence, 125I assaying and ELISA. Light microscopy (LM) and transmission electron microscopy (TEM) were used for the analysis of the tissue-implant morphology. The differently prepared surfaces induced different human and rat plasma protein deposition patterns in vitro. The kinetics of rat and human complement activation on IgG precoated Au surfaces were different. The inflammatory cell recruitment and distribution as well as the ex vivo oxidative metabolism differed on -OH and -CH3 surfaces (with pure Au as reference). More DNA was found on the -OH surface than on the -CH3 at all time periods. On the contrary, the -CH3 surfaces gave rise to accumulation of more DNA in the exudate in the vicinity of the implants at short implantation times (1-3 d). The spontaneous H2O2 production and CL ex vivo was low, but could be augmented by phorbol ester. Cells on -OH surfaces responded with a greater CL in comparison with cells on the Au and -CH3 surfaces. The levels of the cytokines Il-1a, IL-1b and TNFa in the exudates decreased between 3 and 24 h. The cytokine levels were not influenced by material surface functionalization. Despite a larger accumulation of cells around implants, cytokine levels were lower around implanted materials than in sham sites. The thickness of the fibrous capsule, the location of vessels and the width of the fluid space were similar for the Au, -OH and -CH3 surfaces. During the early (3h-1 d) inflammatory response, a mixed population of His48+, ED1+ and ED2+ cells were detected in the exudate. After 24 h, monocytes and macrophages predominated in the implant-tissue interface.In summary, the different chemically functionalized gold surfaces induced different plasma protein adsorption, cell recruitment, distribution and phorbol ester-induced respiratory bursts, but did not influence the cytokine concentrations and the fibrous capsule parameters. Thus, differently functionalized gold surfaces induced different plasma protein adsorption patterns and influenced different events during the inflammatory response around implants. However, the studies indicate that other factors than implant surface chemical properties may be important for the wound healing and development of the fibrous capsule around implants in soft tissues. | en |
