Rhodamine-Based Cu 2+ -Selective Fluorosensor: Synthesis, Mechanism, and Application in Living Cells

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ORIGINAL PAPER

Rhodamine-Based Cu2+ -Selective Fluorosensor: Synthesis, Mechanism, and Application in Living Cells Anindita Sikdar & Swapnadip Roy & Kakali Haldar & Soma Sarkar & Sujit S. Panja

Received: 4 October 2012 / Accepted: 31 January 2013 / Published online: 10 February 2013 # Springer Science+Business Media New York 2013

Abstract A rhodamine B-based fluorescence probe (1) for the sensitive and selective detection of Cu2+ ion has been designed and synthesized using pyridine moiety. The optical properties of this compound have been investigated in acetonitrile-water binary solution (7:3 v/v). Compound 1 is found to be an excellent sensor for a biologically/physiologically very important transition metal ion (Cu2+) using only the two very different modes of measurements (absorption and emission); one case displayed intensity enhancement whereas in other case showed intensity depletion (quenching). A mechanistic investigation has been performed to explore the static nature of quenching process. The sensor has been found to be very effective in sensing Cu2+ ion inside living cells also. Keywords Chemosensors . Rhodamine B . Cations . Static quenching . Living cells

Introduction The development of artificial chemosensors for selective and sensitive recognition of biologically and environmentally important ion species, especially transition-metal ions, has attracted wide-spread interests of chemists, biologists, Electronic supplementary material The online version of this article (doi:10.1007/s10895-013-1169-y) contains supplementary material, which is available to authorized users. A. Sikdar : S. Roy : S. Sarkar : S. S. Panja (*) Department of Chemistry, National Institute of Technology, Durgapur, W.B, India 713209 e-mail: [email protected] K. Haldar Department of Chemistry, MUC Women’s College, Burdwan, W.B, India 713104

clinical biochemists and environmentalists in recent years [1–4]. Because of their many advantages e.g. low cost, simple instrumentation, high sensitivity and easy analysis, many efficient colorimetric/fluorescent sensors for transition-metal ions have been developed during the last two decades [1–8]. Generally, a typical synthesized probe of this type is constructed by covalent linkage of three parts: a chelating unit, a spacer and a reporting group, though there are some examples of spacer-free probes. Upon the binding of metal ions, these sensor molecules display completely different absorption/fluorescence signals compared to free sensors in solution, enabling the qualitative/quantitative determination of metal ions [9]. On the other hand, among the transition-metal ions of interest, divalent copper, Cu2+, is particularly attractive, because it is not only an environmental pollutant at high concentrations [10, 11], but also an essential trace element for many biological processes and systems [12, 13]. Therefore, many excellent works of Cu2+ sensing colorimetric/ fluorescent probes have been reported and investigated [14–19]. However, there is still an intense demand for new efficient