Characterisation of Biomedical Materials, Cells & Interfaces using Environmental SEM (ESEM)
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Characterisation of Biomedical Materials, Cells & Interfaces using Environmental SEM (ESEM) D.J. Stokes,1 S.M. Rea,2 A. E. Porter,2 S. M. Best2 & W. Bonfield.2 1 Polymers & Colloids Group, University of Cambridge, Department of Physics, Cavendish Laboratory, Madingley Road, Cambridge, CB3 0HE, UK. 2 Department of Materials Science & Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ, UK.
ABSTRACT
The ability of Environmental Scanning Electron Microscopy (ESEM) to image insulating and/or moist specimens without the need for the removal of volatile components or the application of a conductive coating has significantly increased the potential range of experiments and observations that can be performed at the high resolution of electron microscopy. Such a technological advance has particularly important implications for the study of soft matter, complex fluids and biological specimens [1]. Thus an important field of research to which ESEM can be applied is the study of materials for biomedical applications such as tissue engineering. The bioactivity of these materials is dependent upon such factors as phase composition, chemical composition, surface activity, crystallinity and microstructure. Using ESEM it is possible to obtain surface-sensitive, specimen-dependent secondary electron images (in the absence of specimen coating), yielding potentially new perspectives on microstructure to complement information derived from other techniques. We have used ESEM to study the apposition of bone on hydroxyapatite-based biomedical materials, from both in vitro and in vivo investigations.
INTRODUCTION
Development of synthetic materials for bone tissue engineering is currently a very active area of research and includes the study of bioglasses, bioceramics and polymers, as well as composites thereof. One such material of interest is hydroxyapatite (HA), a hydrated calcium phosphate bioceramic, Ca10(PO4)6(OH)2, which resembles the mineral phase in natural bone and exhibits bioactive and osseoconductive properties in vivo. A major use of hydroxyapatite is as a bone graft material in many medical and dental applications, either in the form of dense granules or as porous scaffolds into which the host bone can regenerate and heal [2]. HA can also be used in conjunction with a polymer to form a bone-analogue composite such as the polyethylene/HA material known as HAPEXï››, used in clinical applications as a middle ear implant and in suborbital floor (eye socket) reconstructive surgery [3] [4]. Many questions regarding the mechanisms of bone apposition on HA-based biomaterials remain, and a complete understanding of overall bone bonding and growth processes requires a variety of analytical methods covering a range of length-scales, from molecular to macroscopic. It is well known that conventional (high vacuum) SEM is very useful for observing features with FF6.5.1
dimensions of nanometers to microns, although biological specimens may only be viewed following often complex preparative sequences such as chemical
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