Synthesis of a water soluble red fluorescent dye and its application to living cells imaging

•A water soluble fluorescent dye based on PEGylated dicyanoisophorone derivative is prepared.•The fluorescent dye shows deep red emission (λem = 669 nm) and a very large Stoke's shift (Δλ = 140 nm) in water.•The fluorescent dye can be clearly expressed in mitochondria of HeLa cells with high contrast.

A water soluble red fluorescent dye (TD-mPEG750) has been prepared by treatment of 2-(3,5,5-trimethylcyclohex-2-en-1-ylidene)malononitrile with 4-(diethylamino)-2-mPEG benzaldehyde (mPEG-OH, average MW = 750). TD-mPEG750 exhibits red emission at λem = 664 nm in water, a small fluorescence quantum yield (ϕf = 0.01) and a large Stoke's shift (Δλ = 145 nm) are obtained. Using HeLa cells as prototype, the application of TD-mPEG750 to living cells imaging has been investigated. It is found that TD-mPEG750 can be clearly expressed in mitochondria with high contrast in HeLa cells imaging.

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