Visualisation of methacrylate-embedded human bone sections by infrared nanoscopy.

A recently developed ultra-resolving near-field infrared nanoscope is applied to investigate methyl methacrylate embedded, un-decalcified human bone sections. Results show detail at a resolution of 30 nm. Specific contrasting of mineral components is enabled by choosing an appropriate infrared wavelength, here 9.47 mu m, in the phosphate vibrational band. The method is surface-sensitive, probing to a depth of about 30 nm into the surface. The obtained infrared images are presented in direct comparison with optical and electron micrographs of the identical specimen. Lamellar bone organization, pericellular mineral deposition, and regional differences in mineral content are clearly detectable. Individual fibrils are resolved. - Infrared nanoscopy requires just standard hard tissue preparation techniques combined with section surface polishing. It can be integrated into existing laboratory environments without impeding subsequent routine staining and evaluation methods. Mid-infrared illumination of a scanning probe tip enables to highlight phosphate mineral in ultra-resolved (30 nm) images, here of a standardly polished human [GRAPHICS] bone section, featuring individual fibrils, and a canaliculus surrounded by enhanced mineral density material.