In vitro bioactivity of micro metal injection moulded stainless steel with defined surface features

Abstract

Micrometre-and nanometre-scale surface structuring with ordered topography features may dramatically enhance orthopaedic implant integration. In this study we utilised a previously optimised micron metal injection moulding (µ-MIM) process to produce medical grade stainless steel surfaces bearing micrometre scale, protruding, hemispheres of controlled dimensions and spatial distribution. Additionally, the structured surfaces were characterised by the presence of submicrometre surface roughness resulting from metal grain boundary formation. Following cytocompatibility (cytotoxicity) evaluation using 3T3 mouse fibroblast cell line, the effect on primary human cell functionality was assessed focusing on cell attachment, shape and cytoskeleton conformation. In this respect, and by day 7 in culture, significant increase in focal adhesion size was associated with the microstructured surfaces compared to the planar control. The morphological conformation of the seeded cells, as revealed by fluorescence cytoskeleton labelling, also appeared to be guided in the vertical dimension between the hemisphere bodies. Quantitative evaluation of this guidance took place using live cytoplasm fluorescence labelling and image morphometry analysis utilising both, compactness and elongation shape descriptors. Significant increase in cell compactness was associated with the hemisphere arrays indicating collective increase in focused cell attachment to the hemisphere bodies across the entire cell population. Micrometre-scale hemisphere array patterns have therefore influenced cell attachment and conformation. Such influence may potentially aid in enhancing key cellular events such as, for example, neo-osteogenesis on implanted orthopaedic surfaces.

MC3T3-E1 cell response to stainless steel 316L with different surface treatments

“…It has been generally accepted that cell response to an artificial implant is determined by its surface properties including surface morphology, physicochemical composition, surface free energy, etc., which can be modified through a series of surface treatment techniques such as polishing, sandblasting, plasma spraying, and acid-etching [24,25]. It is considered that recent research in this area has been intensified to investigate pure Ti or Ti-based alloy, and the cell response to stainless steel with different surface treatments has been lacking [26,27].…”

Addition of nanoscaledbioinspiredsurface features: A revolution for bone related implants and scaffolds?

“…Enhanced initial attachment of mouse stromal cells took place on the functionalized surfaces using all nanometer roughness variations indicating noticeable surface bioactivity. Sintering techniques . A new approach to obtain defined surface roughness in one step with implant production has recently been described, is micrometal injection moulding (microMIM) . The sintering of a compacted mixture of micro and nanoparticles resulted not only in a nanostructured bulk material with outstanding positive mechanical characteristics but, in addition led to submicrometer scale surface roughness.…”

“…The sintering of a compacted mixture of micro and nanoparticles resulted not only in a nanostructured bulk material with outstanding positive mechanical characteristics but, in addition led to submicrometer scale surface roughness. This roughness is the result of the grain boundary grooves at the material surface which dimensions can be steered by particle size and sintering temperature . In vitro these surfaces exhibited a good bioacceptance .…”

“…This roughness is the result of the grain boundary grooves at the material surface which dimensions can be steered by particle size and sintering temperature . In vitro these surfaces exhibited a good bioacceptance . The biological effects in vivo still have to be evaluated.…”

Effects of Sodium Hydroxide, Sodium Hypochlorite, and Gaseous Hydrogen Peroxide on the Natural Properties of Cancellous Bone

“…Subsequently, the biomechanical property was analyzed by a materials testing machine. Finally, the cytocompatibility was evaluated by using a mouse fibroblast cell line .…”