A Versatile High Resolution Low Vacuum FEG SEM for the Biosciences and Interdisciplinary Research

Field emission gun scanning electron microscopy (FEG-SEM) is a type of microscopy capable of producing very high resolution images of the surface of a sample. It has a wide range of applications in biological and materials science in which researchers wish to visualise and analyse the surface of a sample over a wide range of magnifications. Field emmision gun scanning electron microscopy can be used to image over a large surface area, can be used to image bulk materials as well as thin films or spots and modern microscopes can image structures as small as one or two nanometres. Conventional FEG-SEM requires samples to be imaged under a high vacuum which means that specimens, for example biological materials which are wet, would produce a lot of vapour which interferes with the images. To visualise biological specimens by conventional FEG-SEM the specimens have to be dried and coated, which can distort images of structures. Another form of SEM, called environmental SEM (ESEM) allows samples to be visualised in low pressure gaseous environments and high humidity which means that biological samples can be imaged in their hydrated state either directly or in the frozen state. In this application we are seeking to replace a conventional SEM which is 27 years old, still requires film processing (does not acquire digital images) and frequently breaks down. We wish to purchase a versatile high resolution low-vacuum FEG-SEM and a cryo-workstation. The microscope is critically required for a large number of current and future projects in biological sciences, in particular research in tissue engineering, biomaterials, structural molecular and cellular biology. The microscope requested, is the most versatile high resolution feild emmision gun electron microscope available with extended low-vacuum capabilities. A major feature is that it does with a single tool, what used to require multiple systems. The scanning electron microscope has three modes of operation: high vacuum, low vacuum and environmental scanning (ESEM). The resolution achievable under different modes is 1-nanometres. The equipment will directly replace the old SEM in the current electron microscope unit in the Faculty of Biological Sciences. No refurbishment will be required. The use of the equipment will be supported by a Faculty funded full time technician. The microscope will be used to image a range of different specimens carried out by numerous researchers and postgraduate students. Examples of specimens that will be imaged include three dimensional collagenous scaffolds which are used in tissue engineering, cells adhering to and growing in tissue engineering scaffolds, nanoparticles produced by biomaterials used in hip and knee replacements, nanoparticles in body tissues and in environmental samples, virus particles, fibrils of proteins that cause disease such as amyloid and prion proteins and proteins that cause muscles to contract and bacteria to move.

We seek to replace a 27-year old conventional SEM in the Faculty of Biological Sciences with a versatile high resolution low-vacuum field emission gun scanning electron microcope (FEG-ESEM). The FEG-ESEM is critically required for a large number of current and future projects in biological and interdisciplinary programmes. The microscope requested, the Quanta 200 FEG-SEM is the most versatile high resolution FEG-SEM available with extended low-vacuum capabilities. The Quanta FEG-SEM has three modes of operation: high vacuum, low vacuum and environmental scanning (ESEM) with a resolution of 1-3 nanometres. In addition to directly replacing an outdated SEM for conventional imaging, the FEG-ESEM would provide a step-change in current research capability. Imaging surface and sub-surface features of specimens in fully hydrated environments is currently restricted to a resolution of around 10 microns with current instrumentation (ESEM with a thermionic source; in Engineering Faculty) owing to the substantial scattering of the electron beam by the hydrated environment. The FEG-ESEM would enhance ability to image nanofeatures of tissue engineering scaffolds and cell-seeded constructs in fully hydrated environments. The microscope would be used in a programme of work to characterise prosthetic nanoparticles for cell biology studies. Identification of 5-10 nm sized polyethylene particles by conventional FEG-SEM is problematic since coating materials are simultaneously imaged. FEG-ESEM, without the need to coat would overcome this problem. FEG-ESEM will provide a simple and rapid means of imaging amyloid and prion protein assembly and allowing characterisation of gross morphological features of the more heterogeneous structures that form from assembly of fibrils, and provide a rapid method for determining the hand of different fibrillar forms. Currently there is no FEG-ESEM capability in the University and without this equipment these studies would not be possible.