Biocompatibility of orthopaedic metal implants: The influence of surface chemistry and topography

Meredith, David Osian (2005) Biocompatibility of orthopaedic metal implants: The influence of surface chemistry and topography. PhD thesis, University of Glasgow.

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The initial aim of this work was to investigate in vitro fibroblastic response to the orthopaedic grade materials stainless steel (SS), titanium and Ti-6Al-7Nb (TAN), with the primary aim of assessing and comparing the soft tissue response towards TAN. The industrial 'standard' surface finish of orthopaedic implant materials varies considerably between smooth and rough, despite their use in similar applications. For this investigation, electropolished variants of titanium and TAN were specially produced to help distinguish between the effects of the material and those of the topography, no roughened SS was included due to being an industrially non-viable surface. Thermanox was included as a control substrate. All materials were characterised using atomic force microscopy (AFM), profilometry, scanning electron microscopy (SEM) and contact angle measurements. Profilometry and AFM provided strictly topographical assessments while the SEM's various modes helped establish not only topography, but elucidate the elemental distribution on the surface. SS had a very smooth topography and its alloyed composition was visible with the SEM. Both electropolished titanium (TE) and TAN (NE) were not as smooth as (standard) electropolished SS. Both 'standard' preparations of titanium (TS) and TAN (NS) were rough and had similar roughness measurements, however, their topographies varied considerably. TS had characteristic 'basket weave' topography, while NS had an undulating topography punctuated with protruding particles - these particles are the (3-phase of TAN and an element of its microstructure. The in vitro investigation of cell growth, morphology and adhesion provided a basis upon which to establish a material or topography's cytocompatibility. The smooth metal topographies of SS, TE and NE, in addition to control Th, were demonstrated to both qualitatively and quantitatively allow for favourable cell growth. For TS, the roughened topography was not inhibitory to cell growth on the surface, however, NS demonstrated considerable growth impairment. Cell morphology was observed to be spread on all the smooth metal topographies. The roughened microtopography of NS visibly and quantitatively changed the morphology, with adherent cells being less spread and more elongated. Surface roughness also reduced the number and length of focal adhesions, which were lower in both number and size on TS and lowest on NS. Four features of NS were identified to possibly influence cells; surface chemistry, surface topography, P-phase particle endocytosis and ion leeching. Endocytosis of (3-phase particles was investigated by cell recovery from the surface of NS - these were demonstrated to have internalised P-phase particles. Clathrin staining of cells on NS failed to demonstrate any visible signs of endocytosis. Cells cultured in the presence of NS displayed endocytosed particles but their growth was not significantly inhibited, suggesting that particle endocytosis was not a contributory factor. This also ruled out ion leeching affecting the cells, and reduced NS cell influence to topography and/or chemistry. Gene expression analysis was conducted to further elucidate cell reactivity on the surfaces. All sample types were compared to cells cultured on Thermanox. Of the smooth samples, only SS demonstrated some low expression changes while TE and NE demonstrated no significant differences compared to Th. These results confirmed that the surface chemistry and minimal topography did not affect cell behaviour. (Abstract shortened by ProQuest.).

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Biomedical engineering, medicine.
Colleges/Schools: College of Medical Veterinary and Life Sciences
Supervisor's Name: Supervisor, not known
Date of Award: 2005
Depositing User: Enlighten Team
Unique ID: glathesis:2005-71156
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 10 May 2019 10:49
Last Modified: 17 Aug 2021 11:06
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