Nanowrap for better bioimaging
Image: Hydrogels wrapped with nanosheets with different thicknesses after 0, 6 and 24 hours.
Researchers at Tokai University, Japan, have developed a method of wrapping biological tissue in a polymer nanosheet to give high-quality microscopy images.
The wrap prevents samples from drying out and shrinking, enabling larger image-recording times.
Inspired by the use of plastic food wrap, Professor Yosuke Okamura and colleagues developed water-repellent nanosheets - composed of the amorphous fluoropolymer CYTOP - to fix tissue samples.
According to the researchers, the nanosheets are stiff yet stretchable, optically transparent and free of cracks or wrinkles.
A 133 nm thick CYTOP nanosheet, floating on water, used for wrapping biological tissue for better microscopy imaging.
As a first test of CYTOP, researchers coated a cylindrically shaped alginate-hydrogel sample in the nanosheet, and monitored the evolution of its water content.
After 24 hours, 60% of the original water content was still present while a similar sample left unwrapped in air became dehydrated after about 10 hours.
Through experimenting with various thicknesses, the scientists discovered that the nanosheet's water-retention capability increased proportionally with its thickness, and concluded that a 133 nm thick nanosheet offered the necessary surface adhesion and water retention for fixing a sample.
They then went onto wrap cleared mouse brain slices with a 133 nm thick nanosheet, achieving high spatial resolution neuron images while scanning over a large area - more than 750 µm x 750 µm - for around two hours.
"No visible artifacts arising from sample shrinkage were detected," highlights Okamura. "[We] expect that nanosheet wrapping could be effective over a longer time span by combining it with conventional agarose embedding."
Research is published in Advanced Materials.