An umbelliferone-derivated fluorescent sensor for selective detection of palladium(II) from palladium(0) in living cells

Dual channel chemosensor for successive detection of environmentally toxic Pd2+ and CN- ions and its application to cancer cell imaging

BACKGROUND

Detecting and neutralizing Pd2+ ions are a significant challenge due to their cytotoxicity, even at low concentrations. To address this issue, various chemosensors have been designed for advanced detection systems, offering simplicity and the potential to differentiate signals from different analytes. Nonetheless, these chemosensors often suffer from limited emission response and complex synthesis procedures. As a result, the tracking and quantification of residual palladium in biological systems and environments remain challenging tasks, with only a few chemosensing probes available for commercial use.

RESULTS

In this paper, a straightforward approach for the selective detection of Pd2+ ions is proposed, which involves the design, synthesis, and utilization of a propargylated naphthalene-derived probe (E)-N'-((2-(prop-2-yn-1-yloxy)naphthalen-1-yl)methylene)benzohydrazide (NHP). The NHP probe exhibits sensitive dual-channel colorimetry and fluorescence Pd2+ detection over other tested metal ions. The detection process is performed through a catalytic depropargylation reaction, followed by an excited state intramolecular proton transfer (ESIPT) process, the detection limit is as low as 11.58 × 10-7 M under mild conditions. Interestingly, the resultant chemodosimeter adduct (E)-N'-((2-hydroxynaphthalen-1-yl)methylene)benzohydrazide (NHH) was employed for the consecutive detection of CN- ions, exhibiting an impressive detection limit of 31.79 × 10-8 M. Validation of both detection processes was achieved through 1H nuclear magnetic resonance and density functional theory calculations. For real-time applications of the NHP and NHH probes, smartphone-assisted detection, and intracellular detection of Pd2+ and CN- ions within HeLa cells were studied.

SIGNIFICANCE

This research presents a novel naphthalene derivative for visually detecting environmentally toxic Pd2+ and CN- ions. The synthesized probe selectively binds to Pd2+, forming a chemodosimeter. It successfully detects CN- ions through colorimetry and fluorimetry, offering a low detection limit and quick response. Notably, it's the first naphthalene-based small molecule to serve as a dual probe for toxic analytes - palladium and cyanide. Moreover, it effectively detects Pd2+ and CN- intracellularly in cancer cells.

A Pd-labile fluoroquinolone prodrug efficiently prevents biofilm formation on coated surfaces

Surface-adhered bacteria on implants represent a major challenge for antibiotic treatment. We introduce hydrogel-coated surfaces loaded with tailored Pd-nanosheets which catalyze the release of antibiotics from inactive prodrugs. Masked and antibiotically inactive fluoroquinolone analogs were efficiently activated at the surface and prevented the formation of Staphylococcus aureus biofilms.

Aminoisophthalate Bridged Cd(II)-2D Coordination Polymer: Structure Description, Selective Detection of Pd2+ in Aqueous Medium, and Fabrication of Schottky Diode

Photoluminescence activity of coordination polymers (CPs) has evoked intricate applications in the field of materials science, especially sensing of ions/molecules. In the present study, 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) and 5-aminoisophthalate (HAIPA^-) coordinated to Cd(II) to architect a coordination polymer, {[Cd(HAIPA)(tppz)(OH)]·3H₂O}_n (CP1) which unveils blue emission in an aqueous acetonitrile (98% aqueous) suspension. The emission is selectively quenched by Pd²⁺ only without interference in the presence of as many as 16 other cations. The structure of CP1 shows the presence of a free -COOH group, and the interlayer (-CO)O(2)···O(7) (OC-) distance, 4.242 Å, along with the π···π interactions (3.990, 3.927 Å), may make a cavity which suitably accommodates only Pd²⁺ (van der Waal's radius, 1.7 Å) through the Pd(II)-carboxylato (-COO-Pd) coordination. The stability of the composite, [CP1 + Pd²⁺] may be assessed from the fluorescence quenching experiment, and the Stern-Volmer constant (K_SV) is 7.2 × 10⁴ M^-1. Therefore, the compound, CP1, is a promising sensor for Pd(II) in a selective manner with limit of detection (LOD), 0.08 μM. The XPS spectra of CP1 and [CP1 + Pd²⁺] have proven the presence of Pd²⁺ in the host and the existence of a coordinated -COO-Pd bond. Interestingly, inclusion of Pd²⁺ in CP1 decreases the band gap from 3.61 eV (CP1) to 3.05 eV ([CP1 + Pd²⁺]) which lies in the semiconducting region and has exhibited improved electrical conductivity from 7.42 × 10^-5 (CP1) to 1.20 × 10^-4 S m^-1 ([CP1 + Pd²⁺]). Upon light irradiation, the electrical conductivities are enhanced to 1.45 × 10^-4 S m^-1 (CP1) and 3.81 × 10^-4 S m^-1 ([CP1 + Pd²⁺]); which validates the highly desired photoresponsive device applications. Therefore, such type of materials may serve as SDG-army (sustainable development goal) to battle against the environmental issues and energy crisis.

A quinoline-based fluorescent chemosensor for palladium ion (Pd2+)-selective detection in aqueous solution

Quinoline-based fluorescent chemosensors have been extensively developed for various metal cations, but it was still rare for Pd²⁺-selective detection. In this work, a novel quinoline-benzimidazole conjugate containing one carboxylic acid group (QBM) was designed, and the QBM displayed highly selective fluorescence quenching response towards Pd²⁺ over other metal cations in aqueous solution. The fluorescence titration revealed a good linear relationship between the fluorescence intensity and the Pd²⁺ concentration in the range of 0.5-10 μmol L^-1, with the detection limit of 0.26 μmol L^-1 (S/N = 3). Fluorescence detection of Pd²⁺ in practical water sample was also successfully achieved.

Phytochemicals toward Green (Bio)sensing

Because of numerous inherent and unique characteristics of phytochemicals as bioactive compounds derived from plants, they have been widely used as one of the most interesting nature-based compounds in a myriad of fields. Moreover, a wide variety of phytochemicals offer a plethora of fascinating optical and electrochemical features that pave the way toward their development as optical and electrochemical (bio)sensors for clinical/health diagnostics, environmental monitoring, food quality control, and bioimaging. In the current review, we highlight how phytochemicals have been tailored and used for a wide variety of optical and electrochemical (bio)sensing and bioimaging applications, after classifying and introducing them according to their chemical structures. Finally, the current challenges and future directions/perspective on the optical and electrochemical (bio)sensing applications of phytochemicals are discussed with the goal of further expanding their potential applications in (bio)sensing technology. Regarding the advantageous features of phytochemicals as highly promising and potential biomaterials, we envisage that many of the existing chemical-based (bio)sensors will be replaced by phytochemical-based ones in the near future.