Highly Sensitive and Fast Responsive Fluorescence Turn‐On Chemodosimeter for Cu²⁺ and Its Application in Live Cell Imaging

Abstract

A rhodamine B derivative 4 containing a highly electron-rich S atom has been synthesized as a fluorescence turn-on chemodosimeter for Cu(2+). Following Cu(2+)-promoted ring-opening, redox and hydrolysis reactions, comparable amplifications of absorption and fluorescence signals were observed upon addition of Cu(2+); this suggests that chemodosimeter 4 effectively avoided the fluorescence quenching caused by the paramagnetic nature of Cu(2+). Importantly, 4 can selectively recognize Cu(2+) in aqueous media in the presence of other trace metal ions in organisms (such as Fe(3+), Fe(2+), Cu(+), Zn(2+), Cr(3+), Mn(2+), Co(2+), and Ni(2+)), abundant cellular cations (such as Na(+), K(+), Mg(2+), and Ca(2+)), and the prevalent toxic metal ions in the environment (such as Pb(2+) and Cd(2+)) with high sensitivity (detection limit < or =10 ppb) and a rapid response time (< or =1 min). Moreover, by virtue of the chemodosimeter as fluorescent probe for Cu(2+), confocal and two-photon microscopy experiments revealed a significant increase of intracellular Cu(2+) concentration and the subcellular distribution of Cu(2+), which was internalized into the living HeLa cells upon incubation in growth medium supplemented with 50 muM CuCl(2) for 20 h.

A new rhodamine B based fluorometric chemodosimeter for Cu2+ ion in aqueous and cellular media

“…Due to the presence of reactive phenyl hydrazide group the probe exhibits above said silent features like specific irreversible "turn-on" absorbance/fluorescence changes with Cu 2 þ ions in the pH range 1-6 and the absorbance/emission wave lengths (550/580 nm) are longer compared to some of the reported probes [34][35][36]. The probe also has higher quantum yields compare to the reported rhodamine probes [30][31][32][33][34][35][36][37][38][39]. Due to its less cell toxicity, water solubility and cell permeability it has been utilized for the fluorescence imaging of Cu 2 þ ions in cellular media and for determination of copper in biological various biological fluids.…”

“…Especially while applying for monitoring heavy metal ions in cellular media the irreversible chemodosimeters shows higher quantum yields compared to reversible chemosensors because metal bound dyes has less quantum yields in cellular environment [32]. One of the chemodosimeter based on rhodamine derivative have been reported for imaging Cu 2 þ in living HeLa cells with high sensitivity and fast response time but this probe cannot distinctly recognize Cu 2 þ from Hg 2 þ , and thereby, is not suitable for monitoring the concentration of copper ions in complicated cellular environment [33]. Recently two fluorescent rhodamine derivatives were reported for Cu 2 þ ions but they posse's comparatively short emission wavelengths [34][35][36].…”

Fluorescent probe for copper(II) ion based on a rhodamine spirolactame derivative, and its application to fluorescent imaging in living cells

“…The fluorescence quenching methods using luminol derivative [4] and spiropyran derivative [7], respectively, exhibit wide linear range and good reversibility, even down to 0.27 nM LOD [4], but they both give big background fluorescence and aren't applicable for living cells. Most of the fluorescence enhancement methods possess wide quantitation span [11,[22][23][24][25], but some of them have more or less disadvantages, such as irreversibility [11,25], complicated purification [22,23], and long analysis time [11]. As for the two types of enhancement probes based on rhodamine derivative, dual-function detection for Cu 2+ and ClO -are realized [28] and reversible response in living cells are exhibited [29], however, low yields still restrict their further applications [28,29].…”

“…Even though considerable efforts have been undertaken to develop fluorescent probes for Cu 2+ , many reported fluorescent probes generally undergo fluorescence quenching upon binding with its inherent paramagnetic nature [4][5][6][7][8][9][10], which is not as sensitive as a fluorescence enhancement response. Recently there are still a few examples reported wherein enhancement in the fluorescence intensity has been observed upon complexation with Cu 2+ ions [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. In addition, the fluorescence enhancement in most cases is small and usually suffers from a high background.…”

Evolution of Rhodamine B into Near‐Infrared Dye by Phototriggered Radical Reaction and Its Application for Lysosome‐Specific Live‐Cell Imaging

“…The ring-opened intermediate (named R-b) facilitated the radical addition reaction. [37] R-b, with its highly reactive free radical, was rapidly converted into the final structure R-0 (Video S1 in the Supporting Information). R-0 has a larger conjugated system than the traditional ring-opened state …”