Search Results (108)

The accurate monitoring of metal ions is essential for applications that include environmental protection, food safety, and biomedical diagnostics. These areas depend on highly sensitive and selective methods for detecting both toxic and biologically relevant ions. Electrochemical sensors have emerged as promising devices due to their excellent sensitivity, cost-effectiveness, and ease of use. Within these sensor systems, ionophores, either synthetic or natural ligands that exhibit selective ion binding, are fundamental in boosting analytical performance. This review outlines the current progress of ionophore-based electrochemical sensors for metal-ion analysis, emphasizing material selection, architectural strategies, and practical applications. Key classes of ionophores, such as crown ethers, calixarenes, Schiff bases, porphyrins, and oxime derivatives, are discussed with an emphasis on their recognition mechanisms. We also examine strategies for incorporating ionophores into diverse electrochemical sensor configurations and explore recent advances in technologies, such as all-solid-state sensor construction and the development of portable analytical devices. This review bridges the chemistry of ionophores with sensor engineering and serves as a resource for the rational development of advanced platforms for metal-ion sensing. Full article

Salinomycin and monensin represent a class of natural ionophore antibiotics with strong anticancer properties. In this paper we report on chemical modification of these compounds by conjugation with phosphonium cations for targeting conjugates to the mitochondria of cancer cells. Our findings indicate that this approach yields conjugates with enhanced anticancer activity and selectivity, outperforming not only the parent compounds but also the widely used chemotherapeutic agent, doxorubicin. Comprehensive biological and biophysical analyses proved that the conjugates target the mitochondria in cancer cells, with some of the derivatives additionally promoting generation of mitochondrial reactive oxygen species (mtROS). This targeted strategy holds significant promise for the development of effective mitochondrial-targeted novel anticancer agent. Full article

This study presents the design and application of an electrochemical sensor for selective detection of lead ions (Pb²⁺) based on ionophore-modified raspberry-like Fe₃O₄–Au nanostructures. The material was engineered with a magnetic Fe₃O₄ core, coated with polyethyleneimine (PEI) to facilitate nucleation, and subsequently decorated with Au nanoparticles, providing a raspberry-like (Fe₃O₄@PEI@AuNPs) nanostructure with high surface area and excellent electrochemical conductivity. Surface functionalization with Lead Ionophore IV (ionophore thiol) introduced Pb²⁺-selective binding sites, whose presence and structural evolution were verified by TEM and Raman spectroscopy. The Fe₃O₄ core endowed strong magnetic properties, enabling facile manipulation and immobilization onto screen-printed carbon electrodes (SPCEs) via physical adsorption, while the Au nanoparticles enhanced electron transfer, supplied thiol-binding sites for stable ionophore anchoring, and increased the effective electroactive surface area. Operational conditions were systematically optimized, with acetate buffer (HAc/NaAc, pH 5.7) and chronoamperometric preconcentration (CA) at −1.0 V for 175 s identified as optimal for differential pulse voltammetry (DPV) measurements. Under these conditions, the sensor exhibited a linear response toward Pb²⁺ from 0.025 mM to 2.00 mM with superior sensitivity and reproducibility compared to conventional AuNP-modified SPCEs. Furthermore, the ionophore-modified Fe₃O₄–Au nanostructure-based sensor demonstrated outstanding selectivity for Pb²⁺ over competing heavy metal ions (Cd²⁺, Hg²⁺, Cr³⁺), owing to the specific coordination interaction of Lead Ionophore IV with target ions. These findings highlight the potential of raspberry-like Fe₃O₄@PEI@AuNP nanostructures as a robust and efficient electrochemical platform for the sensitive and selective detection of toxic heavy metal ions. Full article

Fertilisation failure following intracytoplasmic sperm injection (ICSI) is a significant challenge in assisted reproductive technology (ART), particularly in the absence of an identifiable cause. Artificial oocyte activation (AOA), typically with calcium ionophores, has emerged as a potential solution in scenarios characterised by a deficiency of phospholipase C zeta (PLCζ). This narrative review consolidates the latest clinical and experimental data regarding the application of calcium ionophores for oocyte activation, the significance of PLCζ testing in instances of unexplained fertilisation failure, and the impact of AOA on the morphokinetics and developmental potential of embryos. AOA has demonstrated an enhancement in fertilisation, cleavage, and pregnancy outcomes in specific patient populations, including individuals with diminished ovarian reserve or those who have previously attempted conception unsuccessfully. Although AOA appears to have no impact on embryo morphokinetics, certain studies indicate slight alterations in early cleavage features. The available statistics indicate that there are no significant safety concerns about outcomes for babies. This finding underscores the significance of tailored ART methodologies that incorporate molecular diagnostics and targeted AOA therapies. It emphasises the necessity for additional prospective trials to enhance patient selection and long-term safety surveillance. Full article

This study investigates the potential of transient potentiometric signals generated by an array of ion-selective electrodes (ISEs) as the basis for a potentiometric electronic tongue capable of identifying and quantifying a range of inorganic and organic cations. Six distinct polymeric membrane ISEs were fabricated, differing in plasticizer type (either NPOE or DEHS), and in the presence or absence of a lipophilic ion exchanger (KTClPB) and/or an ionophore (DB18C6). Transient potential responses were recorded following the exposure of the electrode array to various cations at different concentrations. A total of 810 transient signals were analyzed through visual inspection and principal component analysis (PCA), revealing characteristic dynamic patterns influenced by membrane composition, ion type, and ion concentration. PCA was conducted both on the transient signals from each individual electrode and on the aggregated dataset comprising signals from the full six-electrode array (electronic tongue). The electronic tongue exhibited a markedly enhanced capacity for discriminating and quantifying ion concentrations in comparison to any single electrode. Full article

Livestock farming is a vital component of global food security, yet it remains a major contributor to greenhouse gas (GHG) emissions, particularly methane (CH₄), which has a global warming potential 28 times greater than carbon dioxide (CO₂). This review provides a comprehensive synthesis of current knowledge surrounding the sources, biological mechanisms, and mitigation strategies related to CH₄ emissions from ruminant livestock. We first explore the process of methanogenesis within the rumen, detailing the role of methanogenic archaea and the environmental factors influencing CH₄ production. A thorough assessment of both direct and indirect methods used to quantify CH₄ emissions is presented, including in vitro techniques (e.g., syringe method, batch culture, RUSITEC), in vivo techniques (e.g., respiration chambers, Greenfeed, laser CH₄ detectors), and statistical modeling approaches. The advantages and limitations of each method are critically analyzed in terms of accuracy, cost, feasibility, and applicability to different farming systems. We then examine a wide range of mitigation strategies, organized into four core pillars: (1) animal and feed management (e.g., genetic selection, pasture quality improvement), (2) diet formulation (e.g., feed additives such as oils, tannins, saponins, and seaweed), (3) rumen manipulation (e.g., probiotics, ionophores, defaunation, vaccination), and (4) manure management practices and policy-level interventions. These strategies are evaluated not only for their environmental impact but also for their economic and practical viability in diverse livestock systems. By integrating technological innovations with sustainable agricultural practices, this review highlights pathways to reduce CH₄ emissions while maintaining animal productivity. It aims to support decision-makers, researchers, and livestock producers in the global effort to transition toward climate-smart, low-emission livestock farming. Full article

A new Na⁺ ionophore with two 12-crown-4 moieties on silicon atoms and hydrophobic hydrocarbon groups on silicon atoms has been synthesized. The silicon-bridged bis(12-crown-4)s were easily obtained in high yield by simply mixing dichlorodiorganosilane and 2-hydroxymethyl-12-crown-4 under room temperature and nitrogen atmosphere. Seven compounds with different hydrocarbon substituents were synthesized. To investigate their properties as ionophores, PVC membrane-type ion-selective electrodes incorporating them were prepared, and the ion selectivity coefficients were determined. The typical selectivity sequence is Na⁺ > K⁺ > Rb⁺ > Cs⁺ > NH₄⁺ > Li⁺ > Ca²⁺ > Mg²⁺ > H⁺. The magnitude of selectivity depends on the structures of hydrocarbon substituents on the silicon atoms. The compound with two 2-ethylhexyl groups has particularly good Na⁺ selectivity, and the performance of the electrode is equal to or better than that of an electrode using a commercially available Na⁺ ionophore, malonate-bridged bis(12-crown-4). The electrode also showed better-aging stability than that of another known Na⁺ ionophore, tetraethyl 4-tert-butylcalix[4]arene-O,O′,O″,O‴-tetraacetate, indicating high utility. Full article

Monitoring fungicide residues in orange fruits is vital, as fungicides for orange cultivation are increasingly used to prevent yield loss. At the same time, increasing restrictions are added by regulatory organizations. For facile on-site monitoring of the fungicide carbendazim (MBC), five ion-selective potentiometric sensors are proposed and compared. The first two sensors were prepared with a precipitation-based technique using molybdate (sensor 1) and tetraphenylborate (TPB) (sensor 2), respectively. Furthermore, two ionophore-based sensors were prepared using β-cyclodextrin as ionophore together with TPB (sensor 3) and tetrakis(4-chlorophenyl)borate (TpClPB) (sensor 4) as ion-exchanger. Further incorporation of multi-walled carbon nanotubes (MWCNTs) between the graphite rod and the sensing membrane of sensor 4 (sensor 5) further improved the stability and significantly lowered the limit of detection (LOD). Their performance was evaluated according to IUPAC recommendations, revealing linear response in the concentration range 1 × 10⁻⁴–1 × 10⁻² M, 1 × 10⁻⁵–1 × 10⁻² M, 1 × 10⁻⁵–1 × 10⁻³ M, 1 × 10⁻⁶–1 × 10⁻³ M, and 1 × 10⁻⁷–1 × 10⁻³ M with a Nernstian slope of 54.56, 55.48, 56.00, 56.85, and 57.34 mV/decade, respectively. The LOD values for the five sensors were found to be 7.92 × 10⁻⁵, 9.98 × 10⁻⁶, 9.72 × 10⁻⁶, 9.61 × 10⁻⁷, and 9.57 × 10⁻⁸ M, respectively. The developed potentiometric sensors were successfully applied to determine the residue and degradation rate of MBC in orange samples. After the researched fungicide was applied to the orange trees, the preharvest interval (PHI) could be calculated based on the MBC degradation kinetics determined in the tested orange samples. Full article

Plectasin, a novel antimicrobial peptide, has the potential to disrupt bacterial cell walls and alter the rumen fermentation mode, making it a superior alternative to antibiotics. However, there is limited research on the effects of plectasin on rumen microbiota. This study aimed to evaluate the effects of plectasin (0.057 μmol/L) on in vitro rumen fermentation characteristics and select groups of rumen bacterial communities in comparison with monensin (5 μmol/L), one of the most commonly used ionophores in ruminants, and as a control treatment with the basal substrate. Unlike monensin, plectasin was found to increase the molar proportions of butyrate and acetate/propionate ratio (p < 0.001) while decreasing pH and the molar proportions of propionate (p < 0.05). Principal component analysis of bacterial 16S rRNA gene amplicons clearly showed a separation between the bacteria shaped by plectasin and monensin. Comparative analysis also revealed differences in the relative abundance of certain bacteria in different taxa between plectasin and monensin. The divergent effects of plectasin and monensin on bacterial communities are likely responsible for the differences in their ability to alter rumen fermentation. Plectasin may have advantages over monensin in modulating ruminal bacterial communities and increasing the butyrate and the acetate/propionate ratio. Therefore, it may be considered as a potential additive for ruminant feed. Full article

A low level of Neurotrophins (NTs), their Tyrosine Kinase Receptors (Trks), Vascular Endothelial Growth Factors (VEGFs) and their receptors, mainly VEGFR1 and VEGFR2, characterizes AD brains. The use of NTs and VEGFs as drugs presents different issues due to their low permeability of the blood−brain barrier, the poor pharmacokinetic profile, and the relevant side effects. To overcome these issues, different functional and structural NT mimics have been employed. Being aware that the N-terminus domain as the key domain of NTs for the binding selectivity and activation of Trks and the need to avoid or delay proteolysis, we herein report on the mimicking ability of two cyclic peptide encompassing the N-terminus of Brain Derived Growth Factor (BDNF), (c-[HSDPARRGELSV-]), cBDNF(1-12) and of Neurotrophin3 (NT3), (c-[YAEHKSHRGEYSV-]), cNT3(1-13). The two cyclic peptide features were characterized by a combined thermodynamic and spectroscopic approach (potentiometry, NMR, UV-vis and CD) that was extended to their copper(II) ion complexes. SH-SY5Y cell assays show that the Cu²⁺ present at the sub-micromolar level in the complete culture media affects the treatments with the two peptides. cBDNF(1-12) and cNT3(1-13) act as ionophores, induce neuronal differentiation and promote Trks and CREB phosphorylation in a copper dependent manner. Consistently, both peptide and Cu²⁺ stimulate BDNF and VEGF expression as well as VEGF release; cBDNF(1-12) and cNT3(1-13) induce the expression of Trks and VEGFRs. Full article

An all-integrated on-chip electrochemical microcell (10 × 11 mm²) is developed using silicon technology. The potentiometric nitrate ion detection is based on the functionalization of the working microelectrode array with a polymer membrane in fluoropolysiloxane (FPSX) containing ionophore tetradodecylammoniumnitrate (TDDAN) and ionic additive potassium tetrakis[3,5-bis(trifuoromethyl)phenyl]borate (KTFPB) to form an all-solid-state ion selective electrode (ISE). The addition of an ion-to-electron transducing layer between the platinum working electrode and the polymer membrane helped to improve the sensor performances, especially the response time, the sensitivity, and the stability. Composites formed with two conductive polymers were compared: Polyethylenedioxythiophène (PEDOT) and Polypyrrole (PPy), doped with Poly(styrene sulfonate) or double-walled carbon nanotubes (DWCNTs). Full article

Electrochemical impedance and chronopotentiometric measurements with Na⁺-selective solvent polymeric (PVC) membranes containing a neutral ionophore and a cation exchanger revealed low-frequency resistance, which is ascribed to Na⁺ ion transfer across the interface between the membrane and aqueous solution. The attribution is based on the observed regular dependence of this resistance on the concentration of Na⁺ in solutions. The respective values of the exchange current densities were found to be significantly larger than the currents flowing through ion-selective electrodes (ISEs) during an analysis in non-zero-current mode. This fact suggests that the interfacial electrochemical equilibrium is not violated by the current flow and implies that the Nernst equation can be applied to interpret the data obtained in non-zero-current mode, e.g., constant potential coulometry. Full article

Gemcitabine is a chemotherapeutic agent used to treat various malignancies, including breast and bladder cancer. In the current study, three innovative selective gemcitabine hydrochloride sensors are developed using 4-tert-butylcalix-[8]-arene (sensor 1), β-cyclodextrin (sensor 2), and γ-cyclodextrin (sensor 3) as ionophores. The three sensors were prepared by incorporating the ionophores with o-nitrophenyl octyl ether as plasticizer and potassium tetrakis(4-chlorophenyl) borate as ionic additive into a polyvinyl chloride polymer matrix. These sensors are considered environmentally friendly systems in the analytical research. The linear responses of gemcitabine hydrochloride were in the concentration range of 6.0 × 10⁻⁶ to 1.0 × 10⁻² mol L⁻¹ and 9.0 × 10⁻⁶ to 1.0 × 10⁻² mol L⁻¹ and 8.0 × 10⁻⁶ to 1.0 × 10⁻² mol L⁻¹ for sensors 1, 2, and 3, respectively. Over the pH range of 6–9, fast-Nernst slopes of 52 ± 0.6, 56 ± 0.3, and 55 ± 0.8 mV/decade were found in the same order with correlation regressions of 0.998, 0.999, and 0.998, respectively. The lower limits of detection for the prepared sensors were 2.5 × 10⁻⁶, 2.2 × 10⁻⁶, and 2.7 × 10⁻⁶ mol L⁻¹. The sensors showed high selectivity and sensitivity for gemcitabine. Validation of the sensors was carried out in accordance with the requirements established by the IUPAC, while being inexpensive and easy to use in drug formulation. A statistical analysis of the methods in comparison with the official method showed that there was no significant difference in accuracy or precision between them. It was shown that the new sensors could selectively and accurately find gemcitabine hydrochloride in bulk powder, pharmaceutical formulations, and quality control tests. The ionophore-based sensor shows several advantages over conventional PVC membrane sensor sensors regrading the lower limit of detection, and higher selectivity towards the target ion. Full article

Sodium has many vital and diverse roles in the human body, including maintaining the cellular pH, generating action potential, and regulating osmotic pressure. In cancer, sodium dysregulation has been correlated with tumor growth, metastasis, and immune cell inhibition. However, most in vivo sodium measurements are performed via Na²³ NMR, which is handicapped by slow acquisition times, a low spatial resolution (in mm), and low signal-to-noise ratios. We present here a plasticizer-free, ionophore-based sodium-sensing nanoparticle that utilizes a solvatochromic dye transducer to circumvent the pH cross-sensitivity of most previously reported sodium nano-sensors. We demonstrate that this nano-sensor is non-toxic, boasts a 200 μM detection limit, and is over 1000 times more selective for sodium than potassium. Further, the in vitro photoacoustic calibration curve presented demonstrates the potential of this nano-sensor for performing the in vivo chemical imaging of sodium over the entire physiologically relevant concentration range. Full article

A heterocyclic compound of S and N with cyclic structures, like Furans, thiophenes and related azole analogs, is important as a ligand because of it is readily available, stable and easily functionalized. Various types of heterocyclic molecules quinazolines and their derivatives contain important chromophores with desirable electrochemical properties to be applied in the sensor field. Metal complexes of these compounds have demonstrated significant electrochemical properties as ionophore or electroactive materials for the fabrication of ISEs with different polymeric membranes. R. Selva Kumar et al. 2019 reported the use of dibutyl(8-hydroxyquinolin-2-yl)methylphosphonate as ionophore in a PVC matrix for the fabrication of a potentiometric thorium(IV) ion-selective electrode These quinazoline-based membranes with other additives and plasticizers are very useful for the development of a potential difference across the membrane at membrane-solution interface in the required proportions . Analytes, such as Butralin, Hydroxylamine, and Nitrite, and heavy metal ions, like Fe³⁺ and Th⁴⁺, have also been determined using quinazoline-based membrane sensors. ISE-based electrochemical sensors are very useful in the analysis of food products, drinking water, beverages, fertilizers, soil industrial effluents, etc. They also are applied in potentiometric titration as indicator electrodes. Full article