The polymer granules inside babies’ nappies are exceptionally absorbent, capable of holding up to 300 times their own weight in water (or pee). But, scientists have come up with a wholly different purpose for this remarkable swelling material: expanding tissue samples for microscopy. This ingenious concept – which involves fluorescently labelling the tissue, incorporating the polymer, chopping up the cell structures (so they don’t resist expansion) and then adding water – increases a sample’s size equally in all directions by up to five times. Shown is an expanded sample of mouse brain containing neurons (green) and synapses (red and blue). Importantly, the technique allows researchers to see greater detail than would normally be possible with a regular light microscope. Other methods to achieve such 'super-resolution' images exist, but they require specialised, expensive equipment. With the new tissue-swelling technique, on the other hand, it might cost the price of a box of Pampers.
Written by Ruth Williams
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.
BPoD is also available in Catalan at www.bpod.cat with translations by the University of Valencia.