Rapid optical tissue clearing using poly(acrylamide‐co‐styrenesulfonate) hydrogels for three‐dimensional imaging

Abstract

Optical tissue clearing methods are attractive for three‐dimensional imaging of intact tissues and organs. A CLARITY (clear lipid‐exchanged acrylamide‐hybridized rigid imaging/immunostaining/in situ‐hybridization‐compatible tissue‐hydrogel) method using polyacrylamide gels was recently developed. In the current study, we used poly(acrylamide‐co‐styrenesulfonate) gels as a polyelectrolyte gel for a passive CLARITY method. First, radical copolymerization of acrylamide (AAm) and sodium p‐styrenesulfonate (SS) at different ratios was performed. The composition of the copolymer could be controlled by changing the monomer ratio. With increased SS content, the molecular weight decreased and the refractive index slightly increased. The poly(AAm‐co‐SS) hydrogels with a higher SS content were more swollen and looser. The clearing time could be reduced using the poly(AAm‐co‐SS) hydrogel with a higher SS content. Three‐dimensional fluorescence imaging of the poly(AAm‐co‐SS) hydrogel‐cleared tissues was successfully performed after treatment using a blue fluorescent DNA stain. Therefore, the use of the poly(AAm‐co‐SS) hydrogel improved the clearing process in the passive CLARITY method, and the technique is useful for fluorescence imaging of DNA. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2297–2304, 2019.

Magnetic methacrylated gelatin-g-polyelectrolyte for methylene blue sorption

“…[24][25][26] Similarly, poly(sodium 4vinylbenzenesulfonate) (PSSNa) is characterized as being a strong anionic electrolyte with a sulfonate group (-SO 3 À ) that is widely used in the adsorption of contaminating cationic molecules. 27 Unlike PAMPS, PSSNa has an aromatic ring in its structure, which could be an advantage in removing pollutants that have aromatic rings. The use of hydrogels with a strong ion exchange capacity has been reported in the manufacture of metals within the three-dimensional hydrogel network, which can give the hydrogel magnetic properties, conductivity, and good adsorption capacities.…”

One-Shot Preparation of Polyacrylamide/Poly(sodium styrenesulfonate) Double-Network Hydrogels for Rapid Optical Tissue Clearing

“…Ono et al recently reported the application of polyelectrolyte hydrogels, which were synthesized by the radical copolymerization of acrylamide (AAm) and sodium 4styrenesulfonate (SS) in the presence of N , N ′-methylenebisacrylamide (bisAA), to the optical tissue clearing method. 42 The SS unit included in the hydrogel contributed to shortening an optical tissue clearing process because of an electrostatic repulsion and/or an increased osmotic pressure in the hydrogels. The tissues became transparent more rapidly when they were embedded in the SS-containing hydrogels.…”

“…It was possible that the network of SS as the first monomer was insufficiently grown because of the lower reactivity of bisAA to the SS radical under the polymerization conditions conducted in our previous study. 42 The structure control of the network consisting of SS repeating units as the electrolyte with an anionic charge is important for the tissue clearing. Previously, Aranas et al reported a simple one-step radical polymerization procedure using potassium 3-sulfo-1-propyl methacrylate and N -vinylpyrrolidone as the conjugating and nonconjugating monomers, respectively, in the presence of the two kind of corresponding cross-linkers for the synthesis of hydrogels.…”

Advances in Ex Situ Tissue Optical Clearing

“…The first proof of concept CLARITY protocol was challenging to perform due to utilization of electrophoretic tissue clearing (ETC) for lipid extraction, resulting in a variable clearing quality and frequent heat‐induced tissue damage. Since then, plenty of modifications appeared, for example, the passive clarity technique (PACT) and perfusion‐assisted agent release in situ (PARS), stochastic electrotransport including optimization of acrylamide, bisacrylamide and/or reaction initiator concentration, investigation of new types of polymers to reduce relatively long passive clearing times, resigning from using ETC or even skipping the step of hydrogel formation and establishing inexpensive mounting media solutions, which now allow to obtain robust and scalable results…”