Contents lists available at ScienceDirect Sensors and Actuators B: Chemical journal homepage: www.elsevier.com/locate/snb In vivo bio-imaging studies of highly selective, sensitive rhodamine based fluorescent chemosensor for the detection of Cu 2+ /Fe 3+ ions A. Senthil Murugan a , N. Vidhyalakshmi b , U. Ramesh b , J. Annaraj a, ⁎ a Department of Materials Science, School of Chemistry, Madurai Kamaraj University, Madurai, 21, India b Department of Molecular Biology, School of Biological Sciences, Madurai Kamaraj University, Madurai, 21, India ARTICLE INFO Keywords: Rhodamine dye Paramagnetic metal ions Different detection style Zebrafish embryos Molecular logic gate ABSTRACT A Rhodamine based quinoline conjugated fluorescence chemosensor (RhQA) was delineated for the detection of two paramagnetic metal ions (Fe 3+ /Cu 2+ ) through various analytical techniques. The addition of Fe 3+ and Cu 2+ ions induced a great enhancement in the absorption of RhQA; moreover, Fe 3+ also induced a strong fluorescence enhancement. Hence, this is an admirable example for the selective detection of the biologically/ environmentally significant transition metal ions as dual chemosensor. The obtained results reveal that the chemosensor (RhQA) has remarkable selectivity towards Fe 3+ /Cu 2+ ions even in the presence of higher con- centration of various interference metal ions such as Pb 2+ , Cd 2+ , Hg 2+ , Zn 2+ , Ni 2+ , Co 2+ , Mn 2+ , Fe 2+ , Cr 3+ , Ca 2+ , Ba 2+ , Mg 2+ , Na + ,K + , and Ag + . Its excellency in sensitivity was confirmed by the obtained linear re- lationship with Fe 2+ /Cu 3+ ions, and the calculated detection limit values are, 1.8 × 10 -8 and 3.3 × 10 -8 M for Cu 2+ and Fe 3+ ions respectively. More interestingly, this chemosensor, RhQA was successfully employed to trace out the intra cellular Fe 3+ ions in Zebrafish embryos. 1. Introduction Human body consists of various metal ions, which play important roles in many physiological activities. For example, Zn 2+ ion plays a vital role in protein synthesis and important biochemical processes, inducing apoptosis, enzyme regulation, and gene expression. Also, iron plays very significant role in many fundamental physiological processes such as growth and development in living systems [1,2]. Specifically, Fe 3+ is widely observed in various proteins and enzymes either for structural purposes or as part of a catalytic active site. Correspondingly, copper is also one of the vital trace elements used to maintain normal life activities, plays major role in catalytic process and electron transfer from DNA, RNA, etc., [3–7]. However, the higher concentrations of Cu 2+ /Fe 3+ ions leads toxin to human health and causes many serious diseases, such as Alzheimer’s, Parkinson’s, Wilson disease, Huntington, and Menke’s disease. Hence, it is highly essential to detect these ions in human body and also in the environment [8–14]. However, the earlier reports of fluorescent chemosensors for Fe 3+ in aqueous medium are very rare, also their paramagnetic nature leads them signalled by fluorescence quenching [15–19]. In general, Hg 2+ , Pb 2+ and Cr 3+ ions are the leading obstacles for the sensitive and selective detection of Fe 3+ ions, consequently, fluorescent chemosensors for the distinct re- cognition of Fe 3+ is still scantly. Hence, people are much interested to design a rapid and highly selective fluorescent chemosensor to detect Cu 2+ and Fe 3+ ions simultaneously as it is of great importance and is highly desirable [20–23]. Though, several fluorophores have been reported as fluorescent chemosensors, such as coumarin, pyrene, 1,8-naphthalimide, rhoda- mine, squaraine, cyanine, boron dipyrromethenedifluoride (BODIPY), and nitrobenzofurazan. Rhodamine-based dyes are the excellent can- didate to construct an off/on-type fluorescent probe due to its peculiar photo-physical and biological properties [24–28]. In the year 1997, Czarnik et al have reported a novel fluorescence chemosensor protocol based on the spirolactam ring opening of rhodamine dyes [29]. This report ignites the related research community on developing novel chemosensors for the recognition of metal ions with rhodamine dyes. In general, rhodamine derivatives are non-fluorescent and colourless, however it undergoes an apparent colour changes, consequently sig- nificant fluorescent enhancement due to their coordination with spe- cific metal ions and may show their respective bands in the higher wavelength (> 500 nm) region [30]. Mostly, these types of chemo- sensors may utilized as labelling agent for the heavy metal ions such as Cu 2+ , Hg 2+ , Pb 2+ and Fe 3+ [31–34]. However, earlier reports for the simultaneous detection of two paramagnetic metal ions by a multi- functional chemosensor are quiet rare [35–37]. In this connection, we have designed and successfully synthesised a quinoline conjugated https://doi.org/10.1016/j.snb.2018.07.104 Received 1 March 2018; Received in revised form 10 July 2018; Accepted 22 July 2018 ⁎ Corresponding author. E-mail address: annaraj.chem@mkuniversity.org (J. Annaraj). Sensors & Actuators: B. Chemical 274 (2018) 22–29 Available online 23 July 2018 0925-4005/ © 2018 Elsevier B.V. All rights reserved. T