Abstract
Surface roughness on implant materials has been shown to be highly influential on the behavior of osteogenic cells. Four surface topographies were engineered on cobalt chromium molybdenum (CoCrMo) in order to examine this influence on human mesenchymal stem cells (MSC). These treatments were smooth polished (SMO), acid etched (AE) using HCl 7.4% and H2SO4 76% followed by HNO3 30%, sand blasted, and acid etched using either 50 μm Al2O3 (SLA50) or 250 μm Al2O3 grit (SLA250). Characterization of the surfaces included energy dispersive X‐ray analysis (EDX), contact angle, and surface roughness analysis. Human MSCs were cultured onto the four CoCrMo substrates and markers of cell attachment, retention, proliferation, cytotoxicity, and osteogenic differentiation were studied. Residual aluminum was observed on both SLA surfaces although this appeared to be more widely spread on SLA50, whilst SLA250 was shown to have the roughest topography with an R a value greater than 1 μm. All substrates were shown to be largely non‐cytotoxic although both SLA surfaces were shown to reduce cell attachment, whilst SLA50 also delayed cell proliferation. In contrast, SLA250 stimulated a good rate of proliferation resulting in the largest cell population by day 21. In addition, SLA250 stimulated enhanced cell retention, calcium deposition, and hydroxyapatite formation compared to SMO (p < 0.05). The enhanced response stimulated by SLA250 surface modification may prove advantageous for increasing the bioactivity of implants formed of CoCrMo. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 3747–3756, 2015.
Highlights
IntroductionThe average life expectancy in the UK has risen 4.2 years between 1990 and 2010.1 One of the many consequences of this situation is an increasing demand for arthroplasty procedures.[2]
The average life expectancy in the UK has risen 4.2 years between 1990 and 2010.1 One of the many consequences of this situation is an increasing demand for arthroplasty procedures.[2]. This growing demand for total hip replacements (THR) and total knee replacements (TKR) is not restricted solely to the UK, but is an international trend,[3] with the USA predicted to see a drastic increase in arthroplasty procedures by the year 2030.4,5 As a result of this, what was once deemed to be acceptable as sufficient implant performance in orthopedic devices is no longer so, as patients require devices that promote reduced recovery times, alongside increased longevity
Both SLA50 (0.82 6 0.03) and SLA250 (1.02 6 0.03) were significantly rougher than smooth polished (SMO) and acid etched (AE), whilst SLA250 was found to have a significantly greater Ra value compared to SLA50 (p < 0.05)
Summary
The average life expectancy in the UK has risen 4.2 years between 1990 and 2010.1 One of the many consequences of this situation is an increasing demand for arthroplasty procedures.[2]. To increase the performance of a biomaterial, the biological response at the bone implant interface can be influenced by surface modification of the implant.[6] In modifying the implant surface, cell behavior can be controlled and manipulated to promote a desired response.[7] Methods of surface modification are highly varied, ranging from micron scale machining and etching,[8] to the formation of grooves,[9] tubes,[10] pores,[11] and pillars[12,13] on the nanoscale. One such method of topographical surface modification used widely on titanium is sand blasting followed by acid etching (SLA), which has been shown to be capable of promoting a desirable response in vitro and in vivo.[14,15] The dual step procedure is thought to form a microscale topography through the blasting process, which is followed by the addition of a nanoscale topography via acid etching.[15]
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