Pyrophosphate Complex Research Articles

Mechanism of β-MnO2 particle for the peroxymonosulfate activation under electric field: the promoting effect of carbamazepine on Mn(III) and reactive oxygen species production

In this study, β-MnO2 was introduced into electro-peroxymonosulfate process as particle electrodes (E/PMS/β-MnO2) to reveal the pathway of reactive manganese species (RMnS) and its promoting effect on reactive oxygen species (ROS) production. A significant synergistic was observed in the E/PMS/β-MnO2 process, the reaction constant was 3 times higher than that in the E/PMS process. The mechanism experiments revealed the generation pathway of Mn(III)aq during the E/PMS/β-MnO2 process. The pyrophosphate complex experiments and electrochemical analysis demonstrated that Mn(III)aq was dominantly generated through the electron transfer between carbamazepine (CBZ) and Mn(IV) under electric field conditions, rather than the reduction process in the cathode area. Furthermore, quenching experiments and competition kinetics method demonstrated the production of Mn(III)aq has the potential to enhance the formation of reactive oxygen species (ROS), especially •OH and SO4•−. In addition, Mn(V)aq and Mn(VI)aq was proved unable to be produced during the E/PMS/β-MnO2 process. Different from other similar electrochemical studies, 1O2 was mainly generated by the reaction betweenO2•− and •OH in this research. It was observed that the inclusion of Cl— facilitated the removal of CBZ, whereas the addition of humic acid (HA) had negligible impact on CBZ removal during the E/PMS/β-MnO2 process. At last, the results of various water matrices effects and toxicology analysis showed that the E/PMS/β-MnO2 process has satisfactory performance in practical application. This study could provide new insights for electro-persulfate treatment processes.

Oxidative dissolution of Cr(OH)3 and mixed Fe-Cr(III) phases by aqueous Mn(III)-pyrophosphate complex

The key role of manganese (Mn) in the biogeochemical cycle of trace elements has been of great interest in recent years. Nevertheless, the redox properties of aqueous Mn(III) have been studied to a lesser extent. Mn(III) is not stable in solution by itself. However, when complexed with inorganic ligands, it has shown potential to oxidize and reduce trace elements. In the present study, we are exploring the redox characteristics of the complex Mn(III)-Pyrophosphate (Mn(III)-PP). This complex is stable over a wide range of pH values but requires the ratio of Mn:PP to be less than 1:6. Specifically, the redox reaction of chromium (Cr(III)) and Mn(III)-PP is investigated. A solid, Cr(OH)3, is used as a source of Cr(III). For this reaction, environmentally relevant parameters, such as pH, ionic strength, ratio Mn(III)/Cr(III), and excess of ligand, were assessed. Results showed that Mn(III) can effectively oxidize Cr(III) to Cr(VI), taking about 15 days for the reaction to complete. This reaction occurs only under acidic conditions (pH 4), and with a low excess of Pyrophosphate. The initial Mn(III) concentration decreases as the Cr(VI) is produced, and Cr(VI) can be adsorbed back into the Cr(OH)3 surface, limiting the mobility of this toxic species. Despite this adsorption, significant amounts of Cr(VI) are release in the aqueous phase. This study shows the importance of a mobile species (Mn-PP complex) in the oxidation of Cr(III) and the release of Cr(VI) to the environment.

Methylmercury Degradation by Trivalent Manganese.

Methylmercury (MeHg) is a potent neurotoxin and has great adverse health impacts on humans. Organisms and sunlight-mediated demethylation are well-known detoxification pathways of MeHg, yet whether abiotic environmental components contribute to MeHg degradation remains poorly known. Here, we report that MeHg can be degraded by trivalent manganese (Mn(III)), a naturally occurring and widespread oxidant. We found that 28 ± 4% MeHg could be degraded by Mn(III) located on synthesized Mn dioxide (MnO2-x) surfaces during the reaction of 0.91 μg·L-1 MeHg and 5 g·L-1 mineral at an initial pH of 6.0 for 12 h in 10 mM NaNO3 at 25 °C. The presence of low-molecular-weight organic acids (e.g., oxalate and citrate) substantially enhances MeHg degradation by MnO2-x via the formation of soluble Mn(III)-ligand complexes, leading to the cleavage of the carbon-Hg bond. MeHg can also be degraded by reactions with Mn(III)-pyrophosphate complexes, with apparent degradation rate constants comparable to those by biotic and photolytic degradation. Thiol ligands (cysteine and glutathione) show negligible effects on MeHg demethylation by Mn(III). This research demonstrates potential roles of Mn(III) in degrading MeHg in natural environments, which may be further explored for remediating heavily polluted soils and engineered systems containing MeHg.

Reprint of: Purification and Characterization of an Extracellular Mn(ll)-Dependent Peroxidase from the Lignin-Degrading Basidiomycete, Phanerochaete chrysosporium

A Mn(II)-dependent peroxidase found in the extracellular medium of ligninolytic cultures of the white rot fungus, Phanerochaete chrysosporium, was purified by DEAE-Sepharose ion-exchange chromatography, Blue Agarose chromatography, and gel filtration on Sephadex G-100. Sodium dodecyl sulfate-gel electrophoresis indicated that the homogeneous protein has an Mr of 46,000. The absorption spectrum of the enzyme indicates the presence of a heme prosthetic group. The pyridine hemochrome absorption spectrum indicates that the enzyme contained one molecule of heme as iron protoporphyrin IX. The absorption maximum of the native enzyme (406 nm) shifted to 433 nm in the reduced enzyme and to 423 nm in the reduced-CO complex. Both CN- and N3− readily bind to the native enzyme, indicating an available coordination site and that the heme iron is high spin. The absorption spectrum of the H2O2 enzyme complex, maximum at 420 nm, is similar to that of horseradish peroxidase compound II. P. chrysosporium peroxidase activity is dependent on Mn(II), with maximal activity attained above 100 μM. The enzyme is also stimulated to varying degrees by α-hydroxy acids (e.g., malic, lactic) and protein (e.g., gelatin, albumin). The peroxidase is capable of oxidizing NADH and a wide variety of dyes, including Poly B-411 and Poly R-481. Several of the substrates (indigo trisulfonate, NADH, Poly B-411, variamine blue RT salt, and Poly R-481) are oxidized by this Mn(II)-dependent peroxidase at considerably faster rates than those catalyzed by horseradish peroxidase. The enzyme rapidly oxidizes Mn(II) to Mn(III); the latter was detected by the characteristic absorption spectrum of its pyrophosphate complex. Inhibition of the oxidation of the substrate diammonium 2,2-azino-bis(3-ethyl- 6-benzothiazolinesulfonate) (ABTS) by Na-pyrophosphate suggests that Mn(III) plays a role in the enzyme mechanism.© 1985 Academic Press, Inc.

DETERMINATION OF POLYLIGAND COMPLEXES OF COBALT (II) WITH CITRATE AND PYROPHOSPHATE IONS

In the work it is shown by the spectrophotometry method that depending on the concentration ratio of ligands [PPi4–]/[Cit3–] in the pyrophosphate-citrate electrolyte, cobalt (II) ions form not only citrate [Co(Cit)2]4– and pyrophosphate [Co(PPi)2]6–, but also polyligand complexes [Co(PPi)m(Cit)n]+2–(4m+3n). The composition of polyligand complexes [Co(PPi)Cit]5– was determined, and the equilibrium constant of the reaction of their formation and the constant of their stability were calculated (pβ=8.47). The dependence of the degree of formation of citrate, polyligand, and pyrophosphate complexes of cobalt (II) in the pyrophosphate-citrate electrolyte on the logarithm of the ratio of equilibrium concentrations of ligands is calculated.

Structural, Spectroscopic, Antiferromagnetic and in vitro antiproliferative studies of copper (II) pyrophosphate complex against Human breast cancer cell lines

In purpose to search for compounds of biological interest, we have succeeded in synthesizing a copper complex with polypyridine ligands. The architecture of the compound consists of O, N-donor entities, the pyrophosphate anion HP2O73− and the two heterocyclic molecules, 1,10-phenanthroline and 2,2′-bipyridine. X-ray diffraction study proves that our compound crystallizes in a monoclinic cell of space group P21/n. The atomic arrangement can be described by the aggregation of [(C10H8N2)(C12H10N2)Cu2(H2O)2(HP2O7)]+ cation, which contributes to the macrocyclic compound-complex. The second sphere of the cationic complex is localized the anion ClO4− to complete the neutrality. Magnetic studies show an antiferromagnetic coupling exchange between metal copper ions which mediated throw neighboring oxygen atom belonging from the pyrophosphate anion. The biological antiproliferative activity of the sample shows a relatively high cytotoxicity IC50 respectively toward MCF-7 breast cancer cell lines.

Anion binding properties for pyrophosphate derived from a 2,6-diamidopyridinedipyrromethane macrocycle

A 2,6-diamidopyridinedipyrromethane macrocyclic receptor was prepared by a Schiff base condensation reaction. The structures of the free macrocycle and its complex with H2P2O72− were analyzed by single crystal X-ray diffraction (SC-XRD). The stability constants for the binding of the receptor with tetrabutylammonium salts of HP2O73− were determined by isothermal titration calorimetry using acetonitrile solutions. According to the titration data, the receptor exhibited high affinity with HP2O73−. The crystal structure analysis demonstrated that the neutral sandwich-type pyrophosphate complex was formed via the protonation of the macrocyclic receptor.

焦磷酸钠络合Fe2+活化过硫酸盐降解四环素的效应研究

焦磷酸钠络合Fe²⁺活化过硫酸盐降解四环素的效应研究

Enhanced transformation of phenolic compounds by manganese(IV) oxide, manganese(II) and permanganate in the presence of ligands: The determination and role of Mn(III)

In this study, colorimetric methods using diethyl phenylene diamine (DPD), 2,2′-azino-bis(3-ethylbenzothiazoline)-6-sulfonate (ABTS), and potassium iodide (KI) were adopted to determine manganese(III)-pyrophosphate complex (Mn(III)-PP) in trace levels (10 µM). An ozonation method was developed to measure the concentration of dissolved Mn including Mn(II) and Mn(III) via quantifying permanganate (Mn(VII)) generation during ozonation of dissolved Mn with PP. The ozonation method combined with DPD method were applied to determine MnO2 dissolution kinetics in the presence of oxalic acid through monitoring MnO2 decay and Mn(III)/Mn(II) formation. PP and oxalic acid could enhance the oxidation of bisphenol A (BPA) by MnO2 at acidic pH, while no promoting effects were found at neutral pH. EDTA had enhancing effect on the oxidation of BPA by MnO2 at neutral pH but inhibiting effect at acidic pH. This result indicated high activities of Mn(III)-PP at acidic pH, Mn(III)-oxalic acid at acidic pH, and Mn(III)-EDTA at neutral pH, respectively. Enhancing effect of low concentration of humic acid (HA) on the oxidation of BPA by MnO2 at acidic pH, however inhibiting effect was found with high dosage of HA due to the occupation of HA on the active sites of MnO2. Furthermore, desferrioxamine B (DFO) was observed to accelerate the transformation of hydroquinone (HQ) with Mn(II) at alkaline pH, ascribed to the formation of Mn(III)-DFO from the reaction of oxygen with Mn(II) rapidly. Finally, a Mn(VII)-reducer-PP system for the transformation of phenolic compounds was evaluated. Two effective reducers (i.e., Mn(III) inducers), Mn(II) and bisulfite, could accelerate Mn(III)-PP formation in the initial step, and then promote the oxidation of phenolic compounds by Mn(VII). Transformation of phenolic compounds were enhanced by MnO2(IV), Mn(II) and Mn(VII) in the presence of ligands due to the generation of Mn(III), which reflected the potential application value of Mn(III) in micro-polluted water treatment.

Deciphering the levelling mechanism of sorbitol for copper electrodeposition via electrochemical and computational chemistry study

A combined method using electrochemical analysis, molecular dynamic simulation and quantum chemical calculation was employed to reveal the effects of sorbitol on copper electrodeposition from the pyrophosphate bath. It was demonstrated that sorbitol is a desirable leveler. A possible mechanism responsible for the levelling improvement was that sorbitol displayed lower adsorption energy on the electrode surface than pyrophosphate, due to its smaller energy gap. Therefore, adding sorbitol into the pyrophosphate bath could significantly elevate the adsorption capacity of copper pyrophosphate complex ions {[Cu(P2O7)2]6−} on cathode, thereby increasing the diffusion coefficient (D) of [Cu(P2O7)2]6− and the number density (N) of copper nuclei. And the increased D and N are beneficial to improve the bath's levelling power. It should also be pointed out that sorbitol did not influence the purity and electrical conductivity of copper deposit as well as its nucleation mechanism, i.e., an irreversible and instantaneous nucleation process with three-dimensional growth of nuclei controlled by the diffusion of [Cu(P2O7)2]6−.

New Platinum (II) Ternary Complexes of Formamidine and Pyrophosphate: Synthesis, Characterization and DFT Calculations and In vitro Cytotoxicity.

Platinum (II) and platinum (IV) of pyrophosphate complexes have been prepared and characterized to discover their potential as antitumor drugs. This study was conducted to prepare and characterize new ternary platinum (II) complexes with formamidine and pyrophosphate as an antitumor candidate. The complexes have been characterized by mass, infrared, UV-Vis. spectroscopy, elemental analysis, magnetic susceptibility, thermal analyses, and theoretical calculations. They have been tested for their cytotoxicity, which was carried out using the fastcolorimetric assay for cellular growth and survival against MCF-7 (breast cancer cell line), HCT- 116 (colon carcinoma cell line), and HepG-2 (hepatocellular cancer cell line). All complexes are diamagnetic, and the electronic spectral data displayed the bands due to square planar Pt(II) complexes. The optimized complexes structures (1-4) indicated a distorted square planar geometry where O-Pt-O and N-Pt-N bond angles were 82.04°-96.44°, respectively. Results also show that all complexes are neutral, stable and non-hygroscopic and have noticeable cytotoxicity with IC50 (μM): 0.035-0.144 MCF-7(breast cancer cell line), 0.042-0.187 HCT-116 (colon carcinoma cell line), and 0.063-0.168 HepG-2 (hepatocellular cancer cell line). Moreover, the results show that the complex (4) has the best IC50 value. The complexes showed noticeable cytotoxicity and are considered as promising antitumor candidates for further applications.

Discrete and Polymeric Cobalt Pyrophosphates Derived from Pyrophosphoric Acid Diester Ar2H2P2O7

While the structural elucidation and coordination chemistry of organo‐monophosphates have been well investigated, research on the simplest member of organo‐oligophosphates, viz. diorganopyrophosphates, is relatively rare due to the inherent hydrolytic instability of the ligand. Water elimination from the 2,6‐diisopropyl phenyl phosphate (dippH2) by the action of dicyclohexylcarbodiimide (DCC) results in the isolation of a diorganopyrophosphates ligand formulated as [O{P(OAr)(OH)(O)}2] (1 or pyrodippH2) (Ar = 2,6‐diisopropylphenyl). Due to the instability of 1, it has been transformed into its sodium salt [O{P(OAr)(ONa)(O)}2] (2), which has been used for further reactions to prepare cobalt pyrophosphate complexes 3–7. Reaction of 2 with anhydrous cobalt(II) chloride in the presence of N‐heterocyclic ligands results in the formation of [Co(pyrodipp)(imz)3] (3), [Co(pyrodipp)(bpy)2](CH3OH) (4) and [Co(pyrodipp)(phen)2] (5) (imz = imidazole; bpy = 2,2'‐bipyridine; phen = 1,10‐phenanthroline). Use of multidentate ancillary ligand such as 4‐pyridyl‐2,2':6',2''‐terpyridine (pyterpy) under similar reaction conditions leads to the formation of a one‐dimensional zig‐zag cobalt pyrophosphate coordination polymer [Co(pyrodipp)(pyterpy)(CH3OH)]n (6). In the absence of any ancillary ligand, the reaction between cobalt(II) chloride and 2 in acetonitrile results in the isolation of an interesting inorganic polymer [Co(pyrodipp)(CH3CN)2]n (7), whose backbone consists of a chain of spirocycles of CoP2O3 rings, joined at the cobalt centers. The newly synthesized cobalt pyrophosphates 3–7 have been characterized by both analytical and spectroscopic techniques, magnetic studies apart from single‐crystal X‐ray diffraction studies in each case. A striking and persistent structural feature in 3–7 is the presence of the cobalt pyrophosphate six‐membered metallacycle Co(OPOPO). While cobalt metal exists in trigonal bipyramidal geometry in complex 3, distorted octahedral coordination geometry is observed for cobalt centers in complexes 4–7.

Platinum-loaded, selenium-doped hydroxyapatite nanoparticles selectively reduce proliferation of prostate and breast cancer cells co-cultured in the presence of stem cells.

Chemotherapeutic treatment of patients with bone tumors or bone metastases often leads to severe side effects such as high drug toxicity, lack of tumor specificity and induced drug resistance. A novel strategy to treat early stages of bone metastases involves local co-delivery of multiple chemotherapeutic agents to synergistically improve the curative effect and overcome shortcomings of traditional chemotherapy. Herein we show that selenite-doped hydroxyapatite nanoparticles loaded with a hydroxyapatite-binding anti-tumor platinum complex (PtPP-HASe) selectively reduce proliferation of cancer cells without reducing proliferation of bone marrow stem cells. These PtPP-HASe particles were nanocrystalline with selenium (Se) and platinum (Pt) contents ranging between 0-10 and 1.5-3 wt%, respectively. Release kinetics of Se and Pt from PtPP-HASe nanoparticles resulted in a cumulative release of ∼10 and ∼66 wt% after 7 days, respectively. At a Pt/Se ratio of 8, released Pt and Se species selectively reduced cell number of human prostate (PC3) and human breast cancer cells (MDA-MB-231) by a factor of >10 with limited effects on co-cultured human bone marrow stem cells (hBMSc). These novel nanoparticles demonstrate high anti-cancer selectivity, which offers ample opportunities for the design of novel biomaterials with potent and selective chemotherapeutic efficacy against cancer cells.

Synthesis and structural and magnetic characterization of an Iron(III) pyrophosphate complex with 1,10′-phenanthroline

The reaction of 1,10′-phenanthroline (phen), tetrasodium pyrophosphate (Na4PPi) and FeCl2·6H2O in deionized water yielded the iron(III)-PPi chelate complex, {[Hphen][Fe(phen)(H2P2O7)2]·2H2O} (1). Although ferric pyrophosphate is used in applications from food to pharmaceuticals, where PPi, acting as an iron chelator, can inhibit growth, be a source of iron, or facilitate iron transfer, there is little structural information on coordination complexes. Herein, the structure of 1 is described, as well as that of the magnetic properties, which confirm the iron in 1 is present as high spin (S = 5/2) Fe(III).

Insights into the Recognition of Phosphate Groups by Peptidic Arginine from Action Spectroscopy and Quantum Chemical Computations.

The side group of the amino acid arginine is typically in its guanidinium protonated form under physiological conditions and participates in a broad range of ligand binding and charge transfer processes of proteins. The recognition of phosphate moieties by guanidinium plays a particularly key role in the interactions of proteins with ATP and nucleic acids. Moreover, it has been recently identified as the driving force for the inhibition of kinase phosphorilation activity by guanidinium derivatives devised as potential anticancer agents. We report on a fundamental investigation of the interactions and coordination arrangements formed by guanidinium with phosphoric, phosphate, and pyrophosphate groups. Action vibrational spectroscopy and ab initio quantum chemical computations are employed to characterize the conformations of benchmark positively charged complexes isolated in an ion trap. The multidentate structure of guanidinium and of the phosphate groups gives rise to a rich conformational landscape with a particular relevance of tweezer-like configurations, where phosphate is effectively trapped by two guanidinium cations. The pyrophosphate complex incorporates a Na+ cation, which serves to compare the interactions associated with the localized versus diffuse charge distributions of the alkali cation and guanidinium, respectively, within a common supramolecular framework.

Insights into the Recognition of Phosphate Groups by Peptidic Arginine from Action Spectroscopy and Quantum Chemical Computations.

The side group of the amino acid arginine is typically in its guanidinium protonated form under physiological conditions, and participates in a broad range of ligand binding and charge transfer processes of proteins. The recognition of phosphate moieties by guanidinium plays a particularly key role in the interactions of proteins with ATP and nucleic acids. Moreover, it has been recently identified as the driving force for the inhibition of kinase phosphorilation activity by guanidinium derivatives devised as potential anticancer agents. We report on a fundamental investigation of the interactions and coordination arrangements formed by guanidinium with phosphoric, phosphate and pyrophosphate groups. Action vibrational spectroscopy and $ab$ $initio$ quantum chemical computations are employed to characterize the conformations of benchmark positively-charged complexes isolated in an ion trap. The multidentate structure of guanidinium and of the phosphate groups gives rise to a rich conformational landscape with a particular relevance of tweezer-like configurations, where phosphate is effectively trapped by two guanidinium cations. The pyrophosphate complex incorporates a Na+ cation, which serves to compare the interactions associated with the localized versus diffuse charge distributions of the alkali cation and guanidinium, respectively, within a common supramolecular framework.

METAL-ORGANIC COMPLEXES IN ENVIRONMENTAL SOLID SAMPLES: ON THE SELECTIVITY OF PYROPHOSPHATE EXTRACTION

Sequential extraction procedures (SEP) have been widely used for the fractionation of trace elements in soils according to their physicochemical mobility and bioaccessibility. Potassium/sodium pyrophosphate in alkaline medium may be considered as the most appropriate extracting reagent for the recovery of amorphous metal-organic complexes, which play a very important role in biological, physical, and chemical processes in soil. However, the selectivity of pyrophosphate has been poorly studied. In the present work the ability of pyrophosphate to attack mineral inorganic phases of environmental solids was assessed using dynamic extraction, which allows one to minimize artifacts and mimic natural conditions. Samples of gabbro and granite containing nearly no organic compounds were taken as example. The eluents applied addressed exchangeable, specifically sorbed, bound to Mn oxides, and bound to metal-organic complexes fractions extractable by 0.05 M Ca(NO3)2, 0.43 M CH3COOH, 0.1 M NH2OH · HCl, and 0.1 M K4P2O7 at pH 11, respectively. As expected, pyrophosphate extraction leads to a partial dissolution of elements bound to inorganic compounds. The recovery of aluminum, iron, manganese, and rare earth elements by pyrophosphate is up to 4% of their total concentrations in samples. The results were discussed on the basis of coordination chemistry of pyrophosphate complexes. In general, pyrophosphate extraction could be further regarded to be sufficiently selective for the dissolution of metal-organic complexes while using SEP in environmental analysis, soil science, and biogeochemistry. Nevertheless, in the interpretation of the fractionation results, a partial dissolution of mineral inorganic phases should be taken into consideration, especially for soils with low content of organic compounds.

Synthesis, structure and magnetic properties of a binuclear Co(II)-pyrophosphate complex, [Co2(phenanthroline-dione)4(P2O7)

A series of Co(II)-1,10-phenanthroline-5,6-dione (phendione) complexes were prepared as scaffolds for the incorporation of pyrophosphate or methylenediphosphonate bridging ligands. Minor modifications in reaction conditions yielded the mononuclear complexes [Co(phendione)(H2O)4](SO4)·2H2O (1) and methylenediphosphonate complex [Co(phendione)(H2O3PCH2PO3H)(H2O)2]Cl·3H2O (2). A bridged binuclear complex, [Co2(phendione)4(P2O7)]·nH2O (3) was also prepared and structurally characterized. The magnetic properties of 3 were investigated.

Regioselective 5'-position phosphorylation of ribose and ribonucleosides: phosphate transfer in the activated pyrophosphate complex in the gas phase.

Herein, we present a rapid, efficient and regioselective phosphorylation method at the 5'-position of unprotected ribose and ribonucleosides with pyrophosphate in the gas phase, which involves the formation of anionic complexes via electrospray ionization and collisional activation to induce phosphorylation within the complexes.

Potentiometric Characterization of Telomerase Activity Using a Copper(ii)-pyrophosphate Complex with a Copper ion-selective Electrode

A novel potentiometric sensing platform was designed for real-time electronic monitoring of telomerase activity using a copper(II) ion-selective electrode (Cu-ISE). The target-induced coordination of pyrophosphate ion with copper ion (Cu2+) was utilized for the detection of the enzyme activity. Upon telomerase introduction, a DNA primer was elongated in the presence of deoxyribonucleoside triphosphates, accompanying formation of the by-product (pyrophosphate ion; P2O74-). The generated pyrophosphate ions chemically coordinated with free copper ions to form the copper(II)-pyrophosphate complex, thereby resulting in a decrease in the number of free copper ions present in solution. With the addition of telomerase, the electrode potential on the Cu-ISE increased relative to the background signal. The results indicated that the copper(II)-pyrophosphate system exhibited good potentiometric response for the detection of telomerase activity, and allowed the determination of the analyte in HeLa cell extract at concentrations as low as 36 cells mL−1. Moreover, the Cu-ISE-based sensing platform afforded good reproducibility, thus representing a useful approach for practical use in quantitative telomerase activity assays.