Issue 27, 2019, Issue in Progress

Rapid increase in transparency of biological organs by matching refractive index of medium to cell membrane using phosphoric acid

Abstract

Tissue clearing is a fundamental challenge in biology and medicine to achieve high-resolution optical imaging of tissues deep inside intact organs. The clearing methods reported up to now require long incubation times or physical/electrical pressure to achieve tissue clearing, which is done by matching the refractive indices of the whole sample and medium to that of the lipid layer. Here we show that phosphoric acid increases the refractive index of the medium and can increase the transparency of formalin-fixed tissue samples rapidly. While phosphoric acid (8.5–14.2 M) suppresses bright signals on the boundary of cells in their phase-contrast images, it does not damage the morphology of the phospholipid cell membrane. Immersion of fixed tissues of mice in phosphoric acid solutions (8.5–14.2 M) increased their transparency within 60 min in the case of 3 mm-thick fixed tissue specimens. Although further investigations are needed to apply this protocol to three-dimensional fluorescence imaging or immunohistochemistry, the protocol presented herein may contribute to developing better and faster soaking methods for tissue clearing than previously reported protocols.

Graphical abstract: Rapid increase in transparency of biological organs by matching refractive index of medium to cell membrane using phosphoric acid

Article information

Article type
Paper
Submitted
26 Feb 2019
Accepted
30 Apr 2019
First published
17 May 2019
This article is Open Access
Creative Commons BY license

RSC Adv., 2019,9, 15269-15276

Rapid increase in transparency of biological organs by matching refractive index of medium to cell membrane using phosphoric acid

M. Umezawa, S. Haruguchi, R. Fukushima, S. Sekiyama, M. Kamimura and K. Soga, RSC Adv., 2019, 9, 15269 DOI: 10.1039/C9RA01445D

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