A Chromo-Fluorogenic Naphthoquinolinedione-Based Probe for Dual Detection of Cu2+ and Its Use for Various Water Samples

Abstract

The presence of an abnormal amount of Cu2+ in the human body causes various health issues. In the current study, we synthesized a new naphthoquinolinedione-based probe (probe 1) to monitor Cu2+ in different water systems, such as tap water, lakes, and drain water. Two triazole units were introduced into the probe via a click reaction to increase the binding affinity to a metal ion. In day-light, probe 1 dissolved in a mixed solvent system (HEPES: EtOH = 1:4) showed a vivid color change from light greenish-yellow to pink in the presence of only Cu2+ among various metal ions. In addition, the green luminescence and fluorescence emission of the probe were effectively bleached out immediately after Cu2+ addition. The limit of detection (LOD) of the probe was 0.5 µM when a ratio-metric method was used for metal ion detection. The fluorescence titration data of the probe with Cu2+ showed a calculated LOD of 41.5 pM. Hence, probe 1 possesses the following dual response toward Cu2+ detection: color change and fluorescence quenching. Probe 1 was also useful for detecting Cu2+ spiked in tap/lake water as well as the cytoplasm of live HeLa cells. The current system was investigated using ultraviolet-visible and fluorescence spectroscopy as well as density functional theory calculations (DFT).

A Naphthoquinoline-Dione-Based Cu2+ Sensing Probe with Visible Color Change and Fluorescence Quenching in an Aqueous Organic Solution

“…Heavy metal ions, such as Hg 2+ /CH 3 Hg + and Pb 2+ , are toxic to humans [14,15]. Thus, selective detection of individual metal ions is indispensable, and monitoring the quantity/concentration of these metal ions in environmental sources is required and should be regulated, especially in drinking water (e.g., tap/lake water) [16][17][18][19]. Cu 2+ is the third most common heavy metal ion in the human body and functions to sustain bones, blood vessels, the immune system, nerves, and metabolism, and it serves a critical function in iron absorption in the human body [20].…”

Protein‐based metal bio‐cleaner for detoxification of wastewater

“…Frequently, two experimental approaches, namely reassignment of sense (residue-specific incorporation) and nonsense suppression (site-specific incorporation), are used for in vivo incorporation of NCAAs into recombinant proteins. [17][18][19][20][21][22][23][24][25] In the work reported here, we aimed to introduce donor-acceptor non-natural chemistry in the GFP chromophore, offering significant Stokes shifts to GFP. 11,26 We aimed to incorporate aminotyrosine as an electron-donating group (amine group) into the GFP chromophore for the development of an efficient red-shifted fluorescent protein-based biosensor that can also act as a bio-cleaner for the removal of Cu 2+ ions from environmental samples.…”

“…Synthetic NCAAs offer non‐natural potential with new functional chemistry for proteins with enhanced spectral properties. Frequently, two experimental approaches, namely reassignment of sense (residue‐specific incorporation) and nonsense suppression (site‐specific incorporation), are used for in vivo incorporation of NCAAs into recombinant proteins 17‐25 . In the work reported here, we aimed to introduce donor–acceptor non‐natural chemistry in the GFP chromophore, offering significant Stokes shifts to GFP 11,26 .…”