International Journal of Research and Scientific Innovation (IJRSI) | Volume IV Issue XI, November 2017 | ISSN 2321–2705
Coumarin-Based Receptor for Recognition of Zn2+ Ion: Spectroscopic Evidence and Imaging Application in Living Cells
Dr. Subarna Guha
Faculty of Chemistry, Central Institute of Plastic Engineering and Technology, Haldia, West Bengal, India
Abstract: – A fluorescent Zn2+ sensor 4-Methyl-2, 6-bis (((2Hchromen-2-one) imino) methyl) – phenol (MCP) based on the 6- aminocoumarin platform has been synthesized. This sensor acts as a highly sensitive and selective fluorescent ON-OFF probe and strong binding ability towards Zn2+ in DMSO/water 9:1, v/v (100 mM HEPES buffer; pH 7.4) at room temperature. Other common alkali, alkaline earth and transition metal ions have negligible interference. MCP used for bio-medical applications like living cell imaging at physiological pH using a confocal microscope.
Keywords: Fluorescent ON-OFF sensor, Zn2+, coumarin, living cells, Theoretical calculations
I. INTRODUCTION
As the second most abundant transition-metal ion in the human body, Zn2+ is actively involved in various biological processes [1]. Such as gene transcription, regulation of metalloenzymes, and neural signal transmission [2]. Chelatable Zn2+ is present at especially high concentrations in brain,[3] pancreas,[4] and spermatozoa[5]. Chelatable Zn2+ regulates neuronal transmission in excitatory nerve terminals, suppresses apoptosis,[6] contributes to neuronal injury in certain acute conditions,[7] epilepsy,[8] and transient global ischemia,[9] seizures,[10] and brain injury [11]. In addition to acute toxicity, disruption of Zn2+ homeostasis may play a role in the pathology of several neurodegenerative disorders, [12] like the formation of β- amyloid plaques in Alzheimer’s disease [13-14] ischemic stroke, and infantile diarrhea [15]. In particular, compared to other tissues, pancreatic islets contain relatively high concentrations of Zn2+, which play a critical role in insulin biosynthesis, storage and secretion [16]. Hence, the development of Zn2+ -probes is a promising field. Rapid progress has been made in the development of fluorescent Zn2+ -probes in solution, due to their simplicity, high sensitivity and instantaneous response and based on ioninduced fluorescence changes [17]. However, reports of their intracellular Zn2+ imaging are rare [18]. It is desired to develop new fluorescent indicators with improved properties, especially with high efficiency in the spectral visible region and study of Zn 2+ -probes in cell. Most of the currently reported Zn2+ fluorescent sensors have the nature of metal chelation enhanced fluorescence (MCHEF), [19-20] which functions via Zn2+ binding-induced emission enhancement. Therefore, there is a huge scope and potential for exploring novel fluorophores for Zn2+ sensing.