Selective rhodamine–based probe for detecting Hg2+ and its application as test strips and cell staining

Dual-Responsive Hydrogels for Mercury Ion Detection and Removal from Wastewater

This study describes the development of a fast and cost-effective method for the detection and removal of Hg2+ ions from aqueous media, consisting of hydrogels incorporating chelating agents and a rhodamine derivative (to afford a qualitative evaluation of the heavy metal entrapment inside the 3D polymeric matrix). These hydrogels, designed for the simultaneous detection and entrapment of mercury, were obtained through the photopolymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA) and N-vinyl-2-pyrrolidone (NVP), utilizing N,N'-methylenebisacrylamide (MBA) as crosslinker, in the presence of polyvinyl alcohol (PVA), a rhodamine B derivative, and one of the following chelating agents: phytic acid, 1,3-diamino-2-hydroxypropane-tetraacetic acid, triethylenetetramine-hexaacetic acid, or ethylenediaminetetraacetic acid disodium salt. The rhodamine derivative had a dual purpose in this study: firstly, it was incorporated into the hydrogel to allow the qualitative evaluation of mercury entrapment through its fluorogenic switch-off abilities when sensing Hg2+ ions; secondly, it was used to quantitatively evaluate the level of residual mercury from the decontaminated aqueous solutions, via the UV-Vis technique. The ICP-MS analysis of the hydrogels also confirmed the successful entrapment of mercury inside the hydrogels and a good correlation with the UV-Vis method.

A Study of Small Molecule-Based Rhodamine-Derived Chemosensors and their Implications in Environmental and Biological Systems from 2012 to 2021: Latest Advancement and Future Prospects

Rhodamine-based chemosensors have sparked considerable interest in recent years due to their remarkable photophysical properties, which include high absorption coefficients, exceptional quantum yields, improved photostability, and significant red shifts. This article presents an overview of the diverse fluorometric, and colorimetric sensors produced from rhodamine, as well as their applications in a wide range of fields. The ability of rhodamine-based chemosensors to detect a wide range of metal ions, including Hg+2, Al3+, Cr3+, Cu2+, Fe3+, Fe2+, Cd2+, Sn4+, Zn2+, and Pb2+, is one of their major advantages. Other applications of these sensors include dual analytes, multianalytes, and relay recognition of dual analytes. Rhodamine-based probes can also detect noble metal ions such as Au3+, Ag+, and Pt2+. They have been used to detect pH, biological species, reactive oxygen and nitrogen species, anions, and nerve agents in addition to metal ions. The probes have been engineered to undergo colorimetric or fluorometric changes upon binding to specific analytes, rendering them highly selective and sensitive by ring-opening via different mechanisms such as Photoinduced Electron Transfer (PET), Chelation Enhanced Fluorescence (CHEF), Intramolecular Charge Transfer (ICT), and Fluorescence Resonance Energy Transfer (FRET). For improved sensing performance, light-harvesting dendritic systems based on rhodamine conjugates has also been explored for enhanced sensing performance. These dendritic arrangements permit the incorporation of numerous rhodamine units, resulting in an improvement in signal amplification and sensitivity. The probes have been utilised extensively for imaging biological samples, including imaging of living cells, and for environmental research. Moreover, they have been combined into logic gates for the construction of molecular computing systems. The usage of rhodamine-based chemosensors has created significant potential in a range of disciplines, including biological and environmental sensing as well as logic gate applications. This study focuses on the work published between 2012 and 2021 and emphasises the enormous research and development potential of these probes.

Rhodamine-Based Fluorescent Probe for Highly Selective Determination of Hg2

The determination of mercuric ions (Hg²⁺) in environmental and biological samples has attracted the attention of researchers lately. In the present work, a novel turn-on Hg²⁺ fluorescent probe utilizing a rhodamine derivative had been constructed and prepared. The probe could highly sensitively and selectively sense Hg²⁺. In the presence of excessive Hg²⁺, the probe displayed about 52-fold fluorescence enhancement in 50% H₂O/CH₃CH₂OH (pH, 7.24). In the meantime, the colorless solution of the probe turned pink upon adding Hg²⁺. Upon adding mercuric ions, the probe interacted with Hg²⁺ and formed a 1:1 coordination complex, which had been the basis for recognizing Hg²⁺. The probe displayed reversible dual colorimetric and fluorescence sensing of Hg²⁺ because rhodamine's spirolactam ring opened upon adding Hg²⁺. The analytical performances of the probe for sensing Hg²⁺ were also studied. When the Hg²⁺ concentration was altered in the range of 8.0 × 10^-8 to 1.0 × 10^-5 mol L^-1, the fluorescence intensity showed an excellent linear correlation with Hg²⁺ concentration. A detection limit of 3.0 × 10^-8 mol L^-1 had been achieved. Moreover, Hg²⁺ in the water environment and A549 cells could be successfully sensed by the proposed probe.

Rational design of a FRET-based ratiometric fluorescent probe with large Pseudo-Stokes shift for detecting Hg2+ in living cells based on rhodamine and anthracene fluorophores

The development of fluorescent dyes has been a continuing attractive research topic in the field of fluorescence sensing and bioimaging technologies, most of them were subject to a single signal change. In this work, a novel colorimetric and ratiometric fluorescent probe 1 based on rhodamine and anthracene groups was designed and synthesized via the fluorescence resonance energy transfer (FRET) mechanism. Probe 1 showed excellent selectivity, higher sensitivity and ratiometric response to Hg²⁺ in the CH₃CN/H₂O (1/1, v/v) system, with a fast response time (less than 30 s); The fluorescent color changed from purple to orange and the solution visible to the naked-eye changed from colorless to pink. The Pseudo-Stokes shift was 174 nm upon addition of Hg²⁺. The limit of detection (LOD) was calculated to be 0.81 μM and 0.38 μM according to fluorescence and UV/vis measurements, respectively. Furthermore, a possible mechanism for the detection of Hg²⁺ by probe 1 was verified by using ¹H NMR, ESI-MS, and HPLC spectra. Meanwhile, probe 1 was successfully used for cell imaging for the detection of Hg²⁺ in living cells.

Rapid and sensitive detection of Hg2+ with a SERS-enhanced lateral flow strip

A SERS-LFS strategy was designed and applied for the direct detection of target Hg2+ with greatly improved sensing performance by SERS measurements on the T line of the LFS, which did not change the intrinsic simplicity of the LFS.

Mercury Toxicity and Detection Using Chromo-Fluorogenic Chemosensors

Mercury (Hg), this non-essential heavy metal released from both industrial and natural sources entered into living bodies, and cause grievous detrimental effects to the human health and ecosystem. The monitoring of Hg2+ excessive accumulation can be beneficial to fight against the risk associated with mercury toxicity to living systems. Therefore, there is an emergent need of novel and facile analytical approaches for the monitoring of mercury levels in various environmental, industrial, and biological samples. The chromo-fluorogenic chemosensors possess the attractive analytical parameters of low-cost, enhanced detection ability with high sensitivity, simplicity, rapid on-site monitoring ability, etc. This review was narrated to summarize the mercuric ion selective chromo-fluorogenic chemosensors reported in the year 2020. The design of sensors, mechanisms, fluorophores used, analytical performance, etc. are summarized and discussed.

Novel integrated sensing system of calixarene and rhodamine molecules for selective colorimetric and fluorometric detection of Hg2+ ions in living cells

Three novel and facile calixarene derivatives (5, 6 and 7), which were appended with four rhodamine units at the upper rim of calixarene skeleton, were firstly prepared and evaluated for selective detection of metal ions in solution. Receptors (5) and (7) indicated immediate turn on fluorescence output toward Hg²⁺ ions over other most competitive metal ions with the ultralow detection limits, indicating their high efficiency and reliability. The binding response to Hg²⁺ ions in solution was also observed through a chromogenic change (from colorless to pale pink). Furthermore, in vitro and bio-imaging studies with MCF-7 or MIA PaCa-2 cell lines were also performed to investigate the use of receptors in biological systems in order to monitor of mercury ions. Results showed that new receptors (5) or (7) were cell permeable and suitable for real-time imaging of Hg²⁺ in living cells (MCF-7) or (MIA PaCa-2) without any damage to healthy cell lines (HEK 293).

Red-emitting GSH-Cu NCs as a triplet induced quenched fluorescent probe for fast detection of thiol pollutants

Thiol compounds exist widely on the Earth and have certain significance in the fields of the circulation of the sulfur element and industrial production. However, the odor and biological toxicity of thiol compounds make them pollutants that seriously threaten the environmental safety and the living quality of human. In this study, a novel triplet induced fluorescence "turn-off" strategy was designed for the detection of thiol pollutants via a glutathione-stabilized copper nanocluster (GSH-Cu NC) probe. The as-prepared GSH-Cu NCs not only have small size and good water-solubility, but also exhibit strong red-emitting fluorescence at 630 nm, which could be quenched quantitatively with the increase of the concentration of thiol pollutants. So they were employed to detect thioglycolic acid (TGA), 3-mercaptopropionic acid (MPA), 2-mercaptoethanol (ME) and 2-(diethylamino)ethanethiol (2-AT) in a wide linear range of 1-100 μM with detection limits of 0.73 μM, 0.43 μM, 0.37 μM, and 0.69 μM, respectively. This method was successfully applied to detect the above thiol pollutants in lake water with good recoveries. Moreover, their further application was also expanded as luminous test strips based on the excellent fluorescence characteristics of GSH-Cu NCs for fast real-time detection of thiol pollutants.

A Highly Selective Fluorescent Probe for Hg2+ Based on a 1,8-Naphthalimide Derivative

Hg2+ has a significant hazardous impact on the environment and ecosystem. There is a great demand for new methods with high selectivity and sensitivity to determine mercury in life systems and environments. In this paper, a novel turn-on Hg2+ fluorescent probe has been reported with a naphthalimide group. The Hg2+ fluorescent probe was designed by the inspiration of the well-known specific Hg2+-triggered thioacetal deprotection reaction. A 1,2-dithioalkyl group was chosen as the specific recognition site of Hg2+. The probe showed weak fluorescence without Hg2+, and the color of the solution was light yellow. In the presence of Hg2+, the probe reacted specifically with the mercury ion to produce an aldehyde and emitted strong fluorescence, and the color of the solution also turned light green, thus realizing the monitoring of the mercury ion. The Hg2+ fluorescent probe showed outstanding sensitivity and selectivity toward Hg2+. Furthermore, the Hg2+ fluorescent probe could work in a wide pH range. The linear relationship between the fluorescence intensity at 510 nm and the concentration of Hg2+ was obtained in a range of Hg2+ concentration from 2.5 × 10-7 to 1.0 × 10-5 M. The detection limit was found to be 4.0 × 10-8 M for Hg2+. Furthermore, with little cell toxicity, the probe was successfully applied to the confocal image of Hg2+ in PC-12 cells.

New Pyridine-Bridged Ferrocene-Rhodamine Receptor for the Multifeature Detection of Hg2+ in Water and Living Cells

A challenge in the design of optical and redox-active receptors is how to combine a specific recognition center with an efficient responsive system to facilely achieve multifeature detection in biological and environmental analyses. Herein, a novel ferrocene-rhodamine receptor conjugated with a pyridine bridge was designed and synthesized. This receptor can sensitively sense Hg²⁺ in aqueous media via chromogenic, fluorogenic, and electrochemical multisignal outputs with a low detection limit and fast response time. Moreover, it can be qualified as a fluorescent probe for effectively monitoring Hg²⁺ in living cells. A plausible recognition mode was proposed and rationalized with theoretical calculations.