A new six-membered spiro-rhodamine probe for Cu2+ and its imaging in mitochondria and lysosomes of Hela cells

Abstract

Different from five-membered rhodamine spirolactam (Rh-OH), a new six-membered spiro-rhodamine probe (SRh-OH) bearing urea structure has been developed in this paper. Compared with five-membered Rh-OH, six-membered SRh-OH exhibited higher selectivity and sensitivity to Cu2+ in aqueous solution. Upon addition of 10 equiv. Cu2+, the molar extinction coefficient of SRh-OH at 563 nm can be up to 4.73 × 104 Lmol−1cm−1. In the range of Cu2+ from 0 to 28 μM, there was an excellent linear relationship between the absorption or emission intensity and Cu2+ concentration. The detection limit of SRh-OH was as low as 26 nM (S/N = 3). The reversible binding mode of SRh-OH with Cu2+ was further confirmed by S2− and EDTA addition. Bio-imaging showed SRh-OH can map the distribution of Cu2+ not only in mitochondria but also in lysosomes of Hela cells.