Plasmonic slides for stain-free optical histology

Eugeniu Balaur and colleagues demonstrate a technique that can add striking colour contrast — without chemical staining — to normally translucent histological samples. Their key idea is to embed a thin metal layer just below the surface of a microscope sample slide, with that layer patterned in such a way that surface plasmon polaritons are excited when light shines on them. The wavelength of the excited modes is highly sensitive to the local dielectric constant, however, so that the colour of the transmitted light depends on the dielectric constant of whatever is on top of the slide. They use this platform to look at a range of histological tissue sections, and show that their technique allows different cell types and subcellular features to be distinguished by eye, without the need for any additional staining or labelling. Such slides should also find use in the study of other optically transparent materials.