Implant surface

Figure 1 shows the results of those experiments. It is important to recognize that in this experiment the polymer was present in a form affording high surface area when compared to other studies where rods, pellets, plates, fibers, and so forth were used. It is often quite difficult to compare exact degradation times from various independent studies due to differences in implant surface area and... 

Biodegradation times vary depending on implant surface area, porosity, and molecular weight. 

Slavik, J. and Smetana, K. (1997). Intracellular pH of macrophages and foreign body giant cells colonising an implant surface, J. Fluores., 7, 203S-205S. 

In an optical micrograph of a commercially available nitinol stent s surface examined prior to implantation, surface craters can readily be discerned. These large surface defects are on the order of 1 to 10 p.m and are probably formed secondary to surface heating during laser cutting. As mentioned above, these defects link the macro and micro scales because crevices promote electrochemical corrosion as well as mechanical instability, each of which is linked to the other. Once implanted, as the nitinol is stressed and bent, the region around the pits experiences tremendous, disproportionate strain. It is here that the titanium oxide layer can fracture and expose the underlying surface to corrosion (9). 

The transfer of glucose from the blood to an implanted biosensor is dictated by the proximity of the sensing surface to the host tissue, by the local tissue vascularity and perfusion, and by the response of the tissue to the implant surface.11 All of these parameters change with the length of time after implantation. The primary components of the foreign body reaction to an implant along with the potential to observe these in a tissue window chamber preparation are listed in Table 4.1. 

In addition, the ability to optimize biosensor design is of central importance and initially depends on the determination of what aspects of the foreign body reaction and biosensor surface properties are critical to the success of the implanted biosensor. To accomplish this efficiently, it would be very beneficial if active sensors could be imaged in situ. Thus, sensor performance could be quantified relative to the manipulation of local tissue and microvascular conditions in response to various implant properties. Some important implant features include surface texture, porosity, and surface material composition. Surface texture of the implant has been observed to affect the extent of collagen formation. Smooth implant surfaces, which the local... 

Bobyn J, Jacobs J, Tanzer M, Urban R, Aribini R, Sumner D, Turner T, Brooks C. The susceptibility of smooth implant surfaces to periimplant fibrosis and migration of polyethylene wear debris. Clinical Orthopaedics and Related Research 1995 311, 21-39. 

The FBR is increased in the presence of bacteria, a secondary challenge to sensor biocompatibility.3 6 7 Initial bacterial association with an implant surface is quickly followed by more permanent cell attachment through cell surface adhesion... 

Other applications use self-assembling fibers to coat materials. For example, preassembled peptide amphiphiles have been covalently immobilized on titanium implant surfaces via a silane layer (Sargeant et al., 2008). Primary bovine artery endothelial cells or mouse calvarial preosteoblastic cells spread on these coated surface and proliferated to a far greater extent than on samples where the peptide amphiphiles had been drop cast onto the metal surface. This study therefore suggests that covalent attachment is required in order to prevent fibers lifting from the coated surface and to encourage maximal cell growth. 

Mendonca G, Mendonca DBS, Aragao FJL, Cooper LF (2008) Advancing dental implant surface technology - from micron- to nanotopography. Biomaterials 29(28) 3822-3835... 

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