Osmium Plasma Coater Model OPC-60

Human astrocytoma cells, gold tagged, BSE imaging


Direct original magnification: 100,000 X Coating Device: OPC-60 Osmium Plasma Coater Coating Material: Osmium Coating Thickness: 2 nm Accelerating Voltage: 5.0 kV	Direct original magnification: 100,000 X Coating Device: OPC-60 Osmium Plasma Coater Coating Material: Osmium Coating Thickness: 2 nm Accelerating Voltage: 5.0 kV
Human astrocytoma cells derived from a surgically resectioned tumor, BSE imaging on JEOL FESEM. Double labelling was done with both 5 and 10 nm gold . Samples were conventionally prepared and critical point dried except they were coated with 2 nm amorphous osmium metal using the OPC-60 Osmium Plasma Coater. Courtesy of Dr. Cameron Ackerley, and Hospital for Sick Children, University of Toronto, Toronto, Ontario CANADA.

Discussion:
The gold tagging of cells has been reported by a number of workers for some number of years, many of whom have demonstrated the tagging using backscattered electron (BSE) imaging techniques. These samples are of course all non-conductive and some form of conductive coating has to be applied. If carbon is selected, while the sample is rendered sufficiently conductive to do the work, the image in general suffers from the lack of topographical information that is generated and what normally becomes a part of the information in the final image.

Ideally one would like a high atomic number element for the metallization, however in the case of the more commonly used high Z elements, which tend to be precious metals, such as Au, Ag, Pd, or even Pt, the grain size becomes a serious problem in the image, especially using a current state of the art FESEM. But with the OPC-60 osmium coater, and with the osmium metal coating being amorphous and without grain size, one can capture not only the images of the gold particles but also, good topographical information as well.

Further details about these results:
There are relatively few 10 nm gold particles present in the micrographs because of the expression level. The two proteins labeled in these (what we consider rather remarkable) micrographs are hyaluronate binding receptors. One is resident (the small particles) and the other transient (the large particles).

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