Probe-assisted detection of Fe3+ ions in a multi-functionalized nanopore

Iron is an essential element that plays critical roles in many biological/metabolic processes, ranging from oxygen transport, mitochondrial respiration, to host defense and cell signaling. Maintaining an appropriate iron level in the body is vital to the human health. Iron deficiency or overload can cause life-threatening conditions. Thus, developing a new, rapid, cost-effective, and easy to use method for iron detection is significant not only for environmental monitoring but also for disease prevention. In this study, we report an innovative Fe3+ detection strategy by using both a ligand probe and an engineered nanopore with two binding sites. In our design, one binding site of the nanopore has a strong interaction with the ligand probe, while the other is more selective toward interfering species. Based on the difference in the number of ligand DTPMPA events in the absence and presence of ferric ions, micromolar concentrations of Fe3+ could be detected within minutes. Our method is selective: micromolar concentrations of Mg2+, Ca2+, Cd2+, Zn2+, Ni2+, Co2+, Mn2+, and Cu2+ would not interfere with the detection of ferric ions. Furthermore, Cu2+, Ni2+, Co2+, Zn2+, and Mn2+ produced current blockage events with quite different signatures from each other, enabling their simultaneous detection. In addition, simulated water and serum samples were successfully analyzed. The nanopore sensing strategy developed in this work should find useful application in the development of stochastic sensors for other substances, especially in situations where multi-analyte concurrent detection is desired.

A thiophene-linked terpyridine based phenanthridine chemoreceptor for Cd2+ and Cr3+ selective ratiometric fluorescence detection in environmental water and rice samples

BACKGROUND

The studied materials, Cadmium (Cd2+) and Chromium (Cr3+) are highly toxic, and it focuses on investigating various environmental sources, such as industrial processes and waste water. When quantities of Cr3+ and Cd2+ exceed the allowable limit, biological toxicity and hazardous environmental pollution are unavoidable. In order to address this problem, we introduce 5-(5-(4-([2,2':6',2″-terpyridin]-4'-yl) phenyl) thiophen-2-yl)-7,8,13,14-tetrahydrodibenzo [a,i] phenanthridine (TPTP), a dual-emission response chemosensor that employs a colorimetric and fluorescence turn-on approach for the rapid, sensitive, and discriminate detection of Cr3+ and Cd2+ ions.

RESULTS

We created a newly designed luminous TPTP sensor based on intramolecular charge transfer (ICT). TPTP sensor probe specifically determined Cr3+ and Cd2+ ions with an immediate colour shift from cyan to green and orange in CH3CN: H2O (6:4) solvent solution. The permissible level set by the Environmental Protection Agency (EPA) of the United States for the presence of Cr3+ and Cd2+ ions in drinking water was higher than the detection level of 3.5 and 9.7 nM, by this sensor respectively. NMR titrations, HRMS, and theoretical calculation methods were employed to examine the accurate sensing processes of TPTP and complexes.

SIGNIFICANCE

This is an effective method of detecting Cr3+ and Cd2+ ions in an environmental system using a ratiometric methodology. In addition, TPTP was used to determine the concentration of Cr3+ and Cd2+ ions in natural water and food samples. Fluorescent bio-imaging studies revealed that the present sensor TPTP could identify Cr3+ and Cd2+ ions inside living HeLa cells. A paper kit analysis has been done on TPTP, which has a time-to-result of less than 1 s and offers a cost-effective assay. As a result, the platform offers portability.

AIE active luminous dye with a triphenylamine attached benzothiazole core as a portable polymer film for sensitively detecting CN- ions in food samples

Aggregation-induced emission (AIE) active 3-(3-(benzo[d]thiazol-2-yl)-2-hydroxyphenyl)-2-(4'-(diphenylamino)-[1,1'-biphenyl]-4-yl)acrylonitrile (BTPA) has been designed and synthesized herein, with the goal of detecting CN^- ions at a low-level in semi-aqueous medium. The deliberate addition of the electron-deficient alkene BTPA increased its sensitivity and selectivity to CN^- ions, with a better detection limit of 6.4 nM, unveiling the next-generation approach to creating sophisticated CN^- ions selective chemosensors. The ESI-MS and NMR spectra analyses provided strong support for the structures of the chemosensors, while the UV-Vis, photoluminescence, and ¹H-NMR titration experiments provided support for the sensing efficiencies. Subsequently, PVDF/BTPA electrospun nanofibers have been effectively produced as functional films. These nanofiber films exhibit outstanding mechanical strength, photo/thermal stability, and optical responsiveness to CN^- ions, making them a potential choice for on-field emerging contaminant detection.

Nitrogen-doped carbon dots: Recent developments in its fluorescent sensor applications

Doped carbon dots have attracted great attention from researchers across disciplines because of their unique characteristics, such as their low toxicity, physiochemical stability, photostability, and outstanding biocompatibility. Nitrogen is one of the most commonly used elements for doping because of its sizeable atomic radius, strong electronegativity, abundance, and availability of electrons. This distinguishes them from other atoms and allows them to perform distinctive roles in various applications. Here, we have reviewed the most current breakthroughs in nitrogen-doped CDs (N-CDs) for fluorescent sensor applications in the last five years. The first section of the article addresses several synthetic and sustainable ways of making N-CDs. Next, we briefly reviewed the fluorescent features of N-CDs and their sensing mechanism. Furthermore, we have thoroughly reviewed their fluorescent sensor applications as sensors for cations, anions, small molecules, enzymes, antibiotics, pathogens, explosives, and pesticides. Finally, we have discussed the N-CDs' potential future as primary research and how that may be used. We hope that this study will contribute to a better understanding of the principles of N-CDs and the sensory applications that they can serve.

Benzothiazole appended 2,2'-(1,4-phenylene)diacetonitrile for the colorimetric and fluorescence detection of cyanide ions

A benzothiazole appended 2,2'-(1,4-phenylene)diacetonitrile derivative (2Z,2'Z)-2,2'-(1,4-phenylene)bis(3-(3-(benzo[d]thiazol-2-yl)-4-hydroxyphenyl)acrylonitrile) (PDBT) has been synthesized and investigated as a novel sensor, capable of showing high selectivity and sensitivity towards CN^- over a wide range of other interfering anions. After reaction with CN^-, PDBT shows a new absorption peak at 451 nm with a color transformation from colorless to reddish-brown. When yellow fluorescent PDBT is exposed to CN^-, it displays a significant increase in fluorescence at 445 nm, resulting in strong sky-blue fluorescence emission. The nucleophilic addition reaction of CN^- plays a role in the sensing mechanism of PDBT to CN^-. PDBT can distinguish between a broad variety of interfering anions and CN^- with remarkable selectivity and sensitivity. Furthermore, the detection limit of the PDBT probe for CN^- is 0.62 μM, which is significantly lower than the WHO standard of 1.9 μM for drinking water. Density functional theory simulations corroborated the observed fluorescence changes and the internal charge transfer process that occurs after cyanide ion addition. In addition, real-time applications of PDBT, such as cell imaging investigations and the detection of CN^- in water samples, were successfully carried out.

Zinc ion detection using a benzothiazole-based highly selective fluorescence "turn-on" chemosensor and its real-time application

A new photochromic fluorescence chemosensor was devised and effectively synthesized using benzothiazole and imidazopyridine derivatives. A "turn-on" fluorescence sensor BIPP for Zn²⁺ detection was developed and has a quick response, excellent sensitivity, and remarkable selectivity over other metal ions. When Zn²⁺ was added to the BIPP solution, a new strong fluorescence emission peak at 542 nm formed with a considerable increase in intensity. The fluorescence color of the BIPP solution changed from blue to bright green. The binding ratio 8 : 2 was found between BIPP and Zn²⁺ by the results of Job's plot, HRMS and ¹H-NMR. The detection limit (LOD) of BIPP towards Zn²⁺ was determined to be 2.36 × 10^-8, which is remarkably low. The ability to detect Zn²⁺ in real water samples demonstrates that BIPP may also be used in environmental systems. Additionally, BIPP can be used to measure Zn²⁺ levels in living cells.

A facile route to synthesize n-SnO2/p-CuFe2O4 to rapidly degrade toxic methylene blue dye under natural sunlight

In the present study, the n-SnO₂/p-CuFe₂O₄ (p-CFO) complex was prepared by a two-step process. p-CFO synthesized by the molten salt method was coated with SnO₂ synthesized by a facile in situ chemical precipitation method. The formation of n-SnO₂/p-CFO was confirmed by powder X-ray diffraction (PXRD). Scanning electron microscopy (SEM) images showed that the sharp edges of uncoated pyramid-like p-CFO particles were covered by a thick layer of n-SnO₂ on coated p-CFO particles. The complete absence of Cu and only 3 wt% Fe on the surface of the n–p complex observed in the elemental analysis using energy-dispersive X-ray spectroscopy (EDX) on the n–p complex confirmed the presence of a thick layer of SnO₂ on the p-CFO surface. Diffuse reflectance spectroscopy (DRS) was employed to elucidate the bandgap engineering. The n-SnO₂/p-CFO complex and p-CFO showed 87% and 58.7% methylene blue (MB) degradation in 120 min under sunlight, respectively. The efficiency of the n–p complex recovered after 5 cycles (73.5%) and was found to be higher than that of the uncoated p-CFO (58.7%). The magnetically separable property of the n–p complex was evaluated by using vibration sample magnetometry (VSM) measurements and it was confirmed that the prepared photocatalyst can be easily recovered using an external magnet. The study reveals that the prepared complex could be a potential candidate for efficient photodegradation of organic dyes under sunlight due to its efficient recovery and reusability owing to its magnetic properties.

The synthesis of n-SnO₂/p-CuFe₂O₄ to degrade toxic methylene blue dye under natural sunlight and its mechanism.

A benzothiazole-based new fluorogenic chemosensor for the detection of CN− and its real-time application in environmental water samples and living cells

Since the cyanide ion is used in a wide range of industries and is harmful to both human health and the environment, a number of research efforts are dedicated to creating fluorescence sensors for the detection of cyanide (CN⁻). Herein, for the fluorescence detection of CN⁻, a new highly selective and sensitive sensor 2-(3-(benzo[d]thiazol-2-yl)-4-hydroxybenzylidene)-1H-indene-1,3(2H)-dione (BID) was created by conjugating a benzothiazole moiety with 1H-indene-1,3(2H)-dione. The donor and acceptor components of this hybrid receptor were covalently connected through a double bond. The nucleophilic addition of a cyanide anion to the BID inhibits the intramolecular charge transfer (ICT) transition, resulting in spectral and colour alterations in the receptor. When the solvent polarity was increased from n-hexane to methanol, this molecule exhibited a bathochromic shift in the emission wavelength (610 to 632 nm), suggesting the presence of a solvatochromic action. The sensor BID has shown strong specificity towards CN⁻ by interrupting its internal charge transfer (ICT), resulting in a significant change in the UV-vis spectrum and a notable blue shift in the fluorescence emission spectrum. The cyanide anion (CN⁻) is responsible for the optical alterations observed by BID, as opposed to the other anions examined. The detection limit was 5.97 nM, significantly less than the WHO's permitted amount of CN⁻ in drinking water. The experimental findings indicate that BID's fluorescence response to CN⁻ is pH insensitive throughout a wide pH range of 6.0 to 12.0. The interaction mechanism between the BID and CN⁻ ions has been studied by HRMS, ¹H-NMR titration experiments, FT-IR, and DFT, which confirmed the nucleophilic addition of CN⁻ on vinylidene and subsequent disturbance of ICT. Additionally, we demonstrated the real-time detection application of CN⁻ in environmental water samples and live-cell imaging.

Since the cyanide ion is used in a wide range of industries and is harmful to both human health and the environment, a number of research efforts are dedicated to creating fluorescence sensors for the detection of cyanide (CN⁻).

A phenanthridine-based probe for selective detection of hypochlorite ions

A novel oxime-based fluorescent chemosensor (E)-2-(4′-(7,8,13,14-tetrahydrodibenzo[a,i]phenanthridin-5-yl)-[1,1′-biphenyl]-4-yl)ethen-1-ol (PBO) has been developed for the fluorimetric detection of hypochlorite ion (OCl−).

A Highly Selective and Sensitive Colorimetric Chemosensor for the Detection of Hydrogen Sulfide: Real-time Applications in Multiple Platforms

Calorimetric chemosensors are found to be advantageous sensing systems due to their simplicity and favorable responsive properties. Although some colorimetric probes have been reported to detect hydrogen sulfide (H₂ S), the creation of rapid, highly selective, and sensitive probes for the detection of H₂ S remains a challenging target. In this work, we established dinitrosulphonamide decorated phenanthridine, 2,4-dinitro-N-(4-(7,8,13,14-tetrahydrodibenzo[a, i]phenanthridin-5-yl)phenyl)benzenesulfonamide (PHSH), for the calorimetric detection of H₂ S. H₂ S triggered thiolysis of PHSH resulted in a marked absorption enhancement alongside a visual color change from colorless to dark yellow. The result indicated that the chemosensor showed high sensitivity and selectivity with a fast response of less than 10 s with a detection limit as low as 6.5 nM. The chemosensor reaction mechanism with H₂ S was studied by UV-vis, ¹ H NMR, mass and HPLC analysis. In addition, the chemosensor has been used for the determination of H₂ S in many real-time samples.

A sensitive and selective BINOL based ratiometric fluorescence sensor for the detection of cyanide ions

A highly selective, novel BINOL based sensor BBCN has been developed for the fluorescent ratiometric detection of cyanide ions (CN⁻). The optical study revealed that BBCN exhibited unique spectral changes only with cyanide ions in the presence of other competing ions. Besides, an apparent fluorescent colour change from green to blue was observed. A clear linear relationship was observed between the fluorescence ratiometric ratio of BBCN and the concentration of CN⁻ with a reasonably low detection limit (LOD) of 189 nM (507 ppb). The optical response was due to the nucleophilic addition of CN⁻ to the dicyanovinyl group of the sensor, which compromises the probe's intramolecular charge transfer. This mechanism was well confirmed by Job's plot, ¹H-NMR and ESI-MS studies. BBCN showed immediate spectral response towards (1 second) CN⁻ and detection could be realized in a broad pH window. Furthermore, the practical utility of BBCN was studied by test paper-based analysis and the detection of CN⁻ in various water resources.

A highly selective, novel BINOL based sensor BBCN has been developed for the fluorescent ratiometric detection of cyanide ions (CN⁻).

Highly sensitive naphthalimide based Schiff base for the fluorimetric detection of Fe3

A simple 1,8-naphthalimide based Schiff base probe (E)-6-((4-(diethylamino)-2-hydroxybenzylidene)amino)-2-(2-morpholinoethyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (NDSM) has been designed and synthesized for the specific detection of Fe3+ based on a fluorimetric mode. The absorbance of NDSM at 360 nm increased significantly in acetonitrile : water (7 : 3, v/v) medium only in the presence of Fe3+ ions with a visible colour change from yellow to golden yellow. Likewise, fluorescence emission intensity at 531 nm was almost wholly quenched in the presence of Fe3+. However, other competitive ions influenced insignificantly or did not affect the optical properties of NDSM. Lysosome targetability was expected from NDSM due to the installation of a basic morpholine unit. The LOD was found to be 0.8 μM with a response time of seconds. The fluorescence reversibility of NDSM + Fe3+ was established with complexing agent EDTA. Fe3+ influences the optical properties of NDSM by complexing with it, which blocks C[double bond, length as m-dash]N isomerization in addition to the ICT mechanism. The real-time application of Fe3+ was demonstrated in test paper-based detection, by the construction of a molecular logic gate, quantification of Fe3+ in water samples and fluorescence imaging of Fe3+.

Biophysical approaches for exploring lipopeptide-lipid interactions

In recent years, lipopeptides (LPs) have attracted a lot of attention in the pharmaceutical industry due to their broad-spectrum of antimicrobial activity against a variety of pathogens and their unique mode of action. This class of compounds has enormous potential for application as an alternative to conventional antibiotics and for pest control. Understanding how LPs work from a structural and biophysical standpoint through investigating their interaction with cell membranes is crucial for the rational design of these biomolecules. Various analytical techniques have been developed for studying intramolecular interactions with high resolution. However, these tools have been barely exploited in lipopeptide-lipid interactions studies. These biophysical approaches would give precise insight on these interactions. Here, we reviewed these state-of-the-art analytical techniques. Knowledge at this level is indispensable for understanding LPs activity and particularly their potential specificity, which is relevant information for safe application. Additionally, the principle of each analytical technique is presented and the information acquired is discussed. The key challenges, such as the selection of the membrane model are also been briefly reviewed.

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A brief overview of topics to understand the generalities of lipopeptide (LP) science.

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Main analytical techniques used to reveal the interaction and the distorting effect of LP on artificial membranes.

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Guidelines for selecting of the most adequate membrane models for the given analytical technique.

Fused pyrazole-phenanthridine based dyads: synthesis, photo-physical and theoretical studies, and live cell pH imaging

The arrangement of small sized molecules with a scaffold structure plays an active role in the fields of sensors and health care. An efficient molecular design strategy for four pyrazole-phenanthridine based D-π-A luminophores, denoted as 2a, 2b, 2c and 2d was developed to investigate the effect of acid on the photo-physical properties of these dyes. Photo-physical studies of the synthesized probes showed distinct absorption and emission under various pH conditions. Theoretical calculations using density functional methods were carried out for understanding the mechanistic aspects of the proton induced fluorescence. The experimentally observed photo-physical properties correlated well with theoretical results. Moreover, probes 2 and 2a can be used to monitor the fluorescence changes in E. coli cells under different pH conditions.

A strategy to promote the electroactive platform adopting poly(o-anisidine)-silver nanocomposites probed for the voltammetric detection of NADH and dopamine

A study on the voltammetric detection of NADH (β-nicotinamide adenine dinucleotide), Dopamine (DA) and their simultaneous determination is presented in this work. The electrochemical sensor was fabricated with the hybrid nanocomposites of poly(o-anisidine) and silver nanoparticles prepared by simple and cost-effective insitu chemical oxidative polymerization technique. The nanocomposites were synthesized with different (w/w) ratios of o-anisidine and silver by increasing the amount of o-anisidine in each, by keeping silver at a fixed quantity. The XRD patterns revealed the semi-crystalline nature of poly(o-anisidine) and the face centered cubic structure of silver. The presence of silver in its metallic state and the formation of nanocomposite were established by XPS analysis. Raman studies suggested the presence of site-selective interaction between poly(o-anisidine) and silver. HRTEM studies revealed the formation of polymer matrix type nanocomposite with the embedment of silver nanoparticles. The sensing performance of the materials were studied via cyclic voltammetry, differential pulse voltammetry and chronoamperometry techniques. Fabricated sensor with 3:1 (w/w) ratio of poly(o-anisidine) and silver exhibited good catalytic activity towards the detection of NADH and DA in terms of potential and current response, when compared to others. Several important electrochemical parameters regulating the performance of the sensor have been evaluated. Under the optimum condition, differential pulse voltammetry method exhibited the linear response in the range of 0.03 to 900μM and 5 to 270μM with a low detection limit of 0.006μM and 0.052μM for NADH and DA, respectively. The modified electrodes exhibited good sensitivity, stability, reproducibility and selectivity with well-separated oxidation peaks for NADH and DA in the simultaneous determination of their binary mixture. The analytical performance of the nanocomposite as an electrochemical sensor was also established for the determination of NADH in human urine and water samples and DA in pharmaceutical dopamine injections with satisfactory coverage.

Synthesis and characterization of chromium(III) Schiff base complexes: antimicrobial activity and its electrocatalytic sensing ability of catechol

A series of acyclic Schiff base chromium(III) complexes were synthesized with the aid of microwave irradiation method. The complexes were characterized on the basis of elemental analysis, spectral analysis such as UV-Visible, Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR) spectroscopies and electrospray ionization (ESI) mass spectrometry. Electrochemical analysis of the complexes indicates the presence of chromium ion in +3 oxidation state. Cr (III) ion is stabilized by the tetradentate Schiff base ligand through its nitrogen and phenolic oxygen. From the spectral studies it is understood that the synthesized chromium(III) complexes exhibits octahedral geometry. Antimicrobial activity of chromium complexes was investigated towards the Gram positive and Gram negative bacteria. In the present work, an attempt was made to fabricate a new kind of modified electrode based on chromium Schiff base complexes for the detection of catechol at nanomolar level.

Synthesis, growth and photoluminescence behaviour of Gd2O2SO4:Eu3+ nanophosphors: the effect of temperature on the structural, morphological and optical properties

Gd₂(SO₄)₃·8H₂O, Gd₂O₂SO₄, and Gd₂O₂SO₄:Eu³⁺ nanoparticles have been synthesized by CTD method.

Manganese sesquioxide to trimanganese tetroxide hierarchical hollow nanostructures: effect of gadolinium on structural, thermal, optical and magnetic properties

Hollow Mn₂O₃ and Mn₃O₄ nanoparticles with different morphologies were obtained from a single precursor, MnC₂O₄.

Inhibition of soluble epoxide hydrolase reduces food intake and increases metabolic rate in obese mice

BACKGROUND AND AIMS

This study evaluated the responses to soluble epoxide hydrolase (s-EH) inhibition, an essential enzyme in the metabolism of arachidonic acid, on food intake, body weight and metabolic parameters in mice fed a high fat-high fructose diet (HFD) for 10 weeks.

METHODS AND RESULTS

After 5 weeks of HFD, mice were divided into two groups: 1) s-EH inhibitor (AR9281, 200mg/kg/day by gavage twice daily), and 2) vehicle (0.3ml per gavage). Food intake, body weight, oxygen consumption (VO(2)), carbon dioxide production (VCO(2)), respiratory quotient (RQ), and motor activity were measured weekly for more 5 weeks. HFD increased body weight (37±1 vs. 26±1g), and plasma of glucose (316±8 vs. 188±27mg/dl), insulin (62.1±8.1 vs. 15.5±5.0μU/ml), and leptin levels (39.4±3.6 vs. 7.5±0.1ng/ml) while reducing VO(2), VCO(2) and motor activity. s-EH inhibition for 5 weeks decreased caloric intake by ~32% and increased VO(2) by ~17% (42.8±1.4 vs. 50.2±1.5ml/kg/min) leading to significant weight loss. Inhibition of s-EHi also caused significant reductions in plasma leptin levels and visceral fat content. Uncoupling protein 1 (UCP1) content in brown adipose tissue was also elevated by ~50% during s-EH inhibition compared to vehicle treatment.

CONCLUSION

These results suggest that s-EH inhibition with AR9281 promotes weight loss by reducing appetite and increasing metabolic rate, and that increased UCP1 content may contribute to the increase in energy expenditure.