Secondary-electron SEM bioimaging of human erythrocytes in bloodstains on high-carbon steel substrate without specimen preparation

Abstract

The imaging of most biological samples via conventional scanning electron microscope (SEM) in secondary-electron mode involves routinely some kind of specimen preparation. Conventional SEMs are still used when a low-vacuum or variable-pressure SEM (usually known as ‘environmental’, or ESEM) is not available. But that preparatory approach may be undesirable in certain cases, for instance in museum specimens, forensic evidences or clinical samples. This report details a simple, low-cost, and sample-saving bioimaging protocol without specimen preparation, by using removable plastic conducting carbon cement, and then working under ex-profeso SEM conditions, i.e., by using an SEM in secondary-electron mode just like an ESEM. The successful use to image up to high magnifications human erythrocytes in bloodstains on an extensively bloodsmeared, high-carbon steel surgical blade is reported as an example of the potential of this procedure.