Short-term Cytotoxic and Inflammatory Responses of Human Monocytes to Stainless Steel Fibre Networks
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Short-term Cytotoxic and Inflammatory Responses of Human Monocytes to Stainless Steel Fibre Networks Rose L. Spear1, Roger A. Brooks2 and Athina E. Markaki1 1
Department of Engineering, University of Cambridge, Trumpington Street, Cambridge, CB2 1PZ, UK 2 Orthopaedic Research Unit, Addenbrooke’s Hospital, Hills Road, Cambridge, CB2 2QQ, UK ABSTRACT The aim of the current work was to examine the human monocyte response to 444 ferritic stainless steel fibre networks. 316L austenitic fibre networks, of the same fibre volume fraction, were used as control surfaces. Fluorescence and scanning electron microscopies suggest that the cells exhibited a good degree of attachment and penetration throughout both networks. Lactate Dehydrogenase (LDH) and TNF-α releases were used as indicators of cytotoxicity and inflammatory responses respectively. LDH release indicated similar levels of monocyte viability when in contact with the 444 and 316L fibre networks. Both networks elicited a low level secretion of TNF-α, which was significantly lower than that of the positive control wells containing zymosan. Collectively, the results suggest that 444 ferritic and 316L austenitic networks induced similar cytotoxic and inflammatory responses from human monocytes. INTRODUCTION Since many natural and biological materials are cellular and can have relatively high porosity levels, various types of porous materials are of interest for biological applications. A key feature for such applications is the space afforded for cellular, vascular and tissue in-growth. Provided that the surfaces are compatible with their biological surroundings, such materials could be used to anchor prosthetic implants, alleviating some of the stability problems affecting conventional ones (e.g. stress shielding, micromotion). In addition, further benefits may accrue by designing a porous implant device with the ability to induce therapeutic strains in vivo directly into in-growing bone tissue, drawing on concepts of strain-regulated bone modeling. This can be achieved by introducing a highly porous layer, composed of bonded ferromagnetic fibres, onto the surface of a conventional prosthesis [1]. By applying a magnetic field, a fibrous network of this type will deform elastically, squeezing or stretching the bone tissue. The primary requirement for such a device is that the material is ferromagnetic and that the device evokes no inflammatory and cytotoxic reactions. Recent work [2] demonstrated the compatibility of human osteoblasts and monocytes with fully dense 444 ferritic stainless steel surfaces. The aim of the current work was to examine the inflammatory and cytotoxic responses of human monocytes to 444 stainless steel fibre networks. Inflammatory and cytotoxicity potentials were investigated as a function of TNF-α and Lactate Dehydrogenase (LDH) releases, respectively. For comparative purposes, 316L fibre networks, of the same fibre volume fraction, were used as the control surfaces. While some work has been done on 316L fibre networks [3-5], there are no stud
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