A promising electrochemical sensor based on PVP-induced shape control of a hydrothermally synthesized layered structured vanadium disulfide for the sensitive detection of a sulfamethoxazole antibiotic.

The presence of sulfamethoxazole (SMX) in natural waters has become a significant concern recently because of its detrimental effects on human health and the ecological environment. To address this issue, it is of utmost urgency to develop a reliable method that can determine SMX at ultra-low levels. In our research, we utilized PVP-induced shape control of a hydrothermal synthesis method to fabricate layer-like structured VS2, and employed it as an electrode modification material to prepare an electrochemical sensor for the sensitive determination of SMX. Thus, our prepared VS2 electrodes exhibited a linear range of 0.06-10.0 µM and a limit of detection (LOD) as low as 47.0 nM (S/N = 3) towards SMX detection. Additionally, the electrochemical sensor presented good agreement with the HPLC method, and afforded perfect recovery results (97.4-106.8%) in the practical analysis. The results validated the detection accuracy of VS2 electrodes, and demonstrated their successful applicability toward the sensitive determination of SMX in natural waters. In conclusion, this research provides a promising approach for the development of electrochemical sensors based on VS2 composite materials.

An Overview to Molecularly Imprinted Electrochemical Sensors for the Detection of Bisphenol A.

Bisphenol A (BPA) is an industrial chemical used extensively in plastics and resins. However, its endocrine-disrupting properties pose risks to human health and the environment. Thus, accurate and rapid detection of BPA is crucial for exposure monitoring and risk mitigation. Molecularly imprinted electrochemical sensors (MIES) have emerged as a promising tool for BPA detection due to their high selectivity, sensitivity, affordability, and portability. This review provides a comprehensive overview of recent advances in MIES for BPA detection. We discuss the operating principles, fabrication strategies, materials, and methods used in MIES. Key findings show that MIES demonstrate detection limits comparable or superior to conventional methods like HPLC and GC-MS. Selectivity studies reveal excellent discrimination between BPA and structural analogs. Recent innovations in nanomaterials, novel monomers, and fabrication techniques have enhanced sensitivity, selectivity, and stability. However, limitations exist in reproducibility, selectivity, and stability. While challenges remain, MIES provide a low-cost portable detection method suitable for on-site BPA monitoring in diverse sectors. Further optimization of sensor fabrication and characterization will enable the immense potential of MIES for field-based BPA detection.

A novel electrochemical aptasensor based on eco-friendly synthesized titanium dioxide nanosheets and polyethyleneimine grafted reduced graphene oxide for ultrasensitive and selective detection of ciprofloxacin.

Developing a rapid, sensitive, and efficient analytical method for the trace-level determination of highly concerning antibiotic ciprofloxacin (CIP) is desirable to guarantee the safety of human health and ecosystems. In this work, a novel electrochemical aptasensor based on polyethyleneimine grafted reduced graphene oxide and titanium dioxide (rGO/PEI/TiO2) nanocomposite was constructed for ultrasensitive and selective detection of CIP. Through the in-situ electrochemical oxidation of Ti3C2Tx nanosheets, TiO2 nanosheets with good electrochemical response were prepared in a more convenient and eco-friendly method. The prepared TiO2 nanosheets promote charge transferring on electrode interface, and [Fe(CN)6]3-/4- as electrochemical active substance can be electrostatically attracted by rGO/PEI. Thus, electrochemical detection signal of the aptasensor variates a lot after specific binding with CIP, achieving working dynamic range of 0.003-10.0 µmol L-1, low detection limit down to 0.7 nmol L-1 (S/N = 3) and selectivity towards other antibiotics. Additionally, the aptasensor exhibited good agreement with HPLC method at 95% confidence level, and achieved good recoveries (96.8-106.3%) in real water samples, demonstrating its suitable applicability of trace detection of CIP in aquatic environment.

Highly Sensitive and Selective Dopamine Determination in Real Samples Using Au Nanoparticles Decorated Marimo-like Graphene Microbead-Based Electrochemical Sensors.

A sensitive and selective electrochemical dopamine (DA) sensor has been developed using gold nanoparticles decorated marimo-like graphene (Au NP/MG) as a modifier of the glassy carbon electrode (GCE). Marimo-like graphene (MG) was prepared by partial exfoliation on the mesocarbon microbeads (MCMB) through molten KOH intercalation. Characterization via transmission electron microscopy confirmed that the surface of MG is composed of multi-layer graphene nanowalls. The graphene nanowalls structure of MG provided abundant surface area and electroactive sites. Electrochemical properties of Au NP/MG/GCE electrode were investigated by cyclic voltammetry and differential pulse voltammetry techniques. The electrode exhibited high electrochemical activity towards DA oxidation. The oxidation peak current increased linearly in proportion to the DA concentration in a range from 0.02 to 10 µM with a detection limit of 0.016 µM. The detection selectivity was carried out with the presence of 20 µM uric acid in goat serum real samples. This study demonstrated a promising method to fabricate DA sensor-based on MCMB derivatives as electrochemical modifiers.

A Double-Deck Structure of Reduced Graphene Oxide Modified Porous Ti3C2Tx Electrode towards Ultrasensitive and Simultaneous Detection of Dopamine and Uric Acid.

Considering the vital physiological functions of dopamine (DA) and uric acid (UA) and their coexistence in the biological matrix, the development of biosensing techniques for their simultaneous and sensitive detection is highly desirable for diagnostic and analytical applications. Therefore, Ti3C2Tx/rGO heterostructure with a double-deck layer was fabricated through electrochemical reduction. The rGO was modified on a porous Ti3C2Tx electrode as the biosensor for the detection of DA and UA simultaneously. Debye length was regulated by the alteration of rGO mass on the surface of the Ti3C2Tx electrode. Debye length decreased with respect to the rGO electrode modified with further rGO mass, indicating that fewer DA molecules were capable of surpassing the equilibrium double layer and reaching the surface of rGO to achieve the voltammetric response of DA. Thus, the proposed Ti3C2Tx/rGO sensor presented an excellent performance in detecting DA and UA with a wide linear range of 0.1-100 µM and 1-1000 µM and a low detection limit of 9.5 nM and 0.3 µM, respectively. Additionally, the proposed Ti3C2Tx/rGO electrode displayed good repeatability, selectivity, and proved to be available for real sample analysis.

Intertwined Carbon Nanotubes and Ag Nanowires Constructed by Simple Solution Blending as Sensitive and Stable Chloramphenicol Sensors.

Chloramphenicol (CAP) is a harmful compound associated with human hematopathy and neuritis, which was widely used as a broad-spectrum antibacterial agent in agriculture and aquaculture. Therefore, it is significant to detect CAP in aquatic environments. In this work, carbon nanotubes/silver nanowires (CNTs/AgNWs) composite electrodes were fabricated as the CAP sensor. Distinguished from in situ growing or chemical bonding noble metal nanomaterials on carbon, this CNTs/AgNWs composite was formed by simple solution blending. It was demonstrated that CNTs and AgNWs both contributed to the redox reaction of CAP in dynamics, and AgNWs was beneficial in thermodynamics as well. The proposed electrochemical sensor displayed a low detection limit of up to 0.08 µM and broad linear range of 0.1-100 µM for CAP. In addition, the CNTs/AgNWs electrodes exhibited good performance characteristics of repeatability and reproducibility, and proved suitable for CAP analysis in real water samples.

A triple-chamber microbial fuel cell enabled to synchronously recover iron and sulfur elements from sulfide tailings.

Bioleaching by coupling iron oxidization with microbial growth is a process frequently used to extract target metals from sulfide tailing piles. However, the slower leaching, longer operational times, and lower efficiency compared to those of other extracting processes are the most important reasons that make this approach unattractive for the recovery of target elements. A triple-chamber microbial fuel cell (MFC) was explored to elevate the dissolution of sulfide tailings via in-situ removal of bioleached Fe3+/Fe2+ and SO42-, during which iron and SO42- ions were synchronously recovered as Fe(OH)3 and S° in the first and second cathode chambers, respectively. 107.9 % of iron and 99.8 % of sulfur contained in the sulfide tailings was bioleached over 50 h, with 80.0 % iron and 22.1 % sulfur elements synchronously recovered. The purities of the Fe(OH)3 and S° precipitates with high metallurgical values were up to 93.1 % and 90.2 %, respectively. The excellent leaching performance of the explored triple-chamber MFC was attributed to the synergistic effect of Acidithiobacillia catalysis and electrochemical oxidation. The explored approach, by virtue of having the higher bioleaching efficiency, less aggressive conditions and shorter operating times than the conventional bioleaching, is of potential commercial value.

ß-Cyclodextrin-Immobilized Ni/Graphene Electrode for Electrochemical Enantiorecognition of Phenylalanine.

In this work, a Ni/graphene (Ni/G) electrode was designed and fabricated by plasma-enhanced chemical vapor deposition (PECVD) for the ultrasensitive recognition of d- and l-phenylalanine. Through a single-step PECVD process, the Ni/G electrode can achieve better hydrophilicity and larger catalytic surface area, which is beneficial for the electrochemical recognition of bio-objects. After surface modification with ß-cyclodextrin, the Ni/G electrode can distinguish d-phenylalanine from l-phenylalanine according to a 0.09 V peak shift in differential pulse voltammetry tests. Moreover, this Ni/G electrode achieved a detection limit as low as 1 nM and a wide linear range from 1 nM to 10 mM toward l-phenylalanine, with great storage stability and working stability.

Selective guanosine binding and cytotoxicity of a benzimidazole derived dinickel complex.

A water-soluble dinickel(II) complex of ethylene glycol-bis(beta-aminoethyl ether) N,N,N',N'-tetrakis(2-benzimidazoyl) (EGTB) was synthesized and fully characterized. The complex crystallizes in a monoclinic system with space group P2(1)/c, a=10.125(1)A, b=28.393(3)A, c=11.026(1)A, and beta=98.966(2) degrees. The hexa-coordinated nickel(II) centers in the centrosymmetric complex adopt a distorted octahedron geometry. The complex binds to purine nucleotides covalently and shows a clear preference for guanosine-5'-monophosphate (5'-GMP) over adenosine-5'-monophosphate (5'-AMP). Its binding to calf thymus DNA (CT-DNA) induces a remarkable conformational variation. The cytotoxic activity of the complex was tested against diverse cell lines including human leukemic cell line U937, macrophage cell line Raw 264.7, human cervical cancer cell line Hela, and human hepatocytes cell line L02. The complex shows a significant inhibition against U937 and Raw 264.7 but little inhibition against Hela and L02.

A trinuclear copper(II) complex of 2,4,6-tris(di-2-pyridylamine)-1,3,5-triazine shows prominent DNA cleavage activity.

A highly water soluble 3:2 complex of copper(II) and 2,4,6-tris(di-2-pyridylamine)-1,3,5-triazine (TDAT) has been synthesized and structurally characterized. The complex crystallized in a triclinic P1 space group with a molecular formula of [Cu3(TDAT)2Cl3]Cl3.2H2O (1), where each copper ion is coordinated by four pyridine nitrogen atoms and an apical chloride. The trinuclear complex is stable at physiological relevant conditions. It can bind to DNA through electrostatic attraction and cleave efficiently the supercoiled pBR322 DNA into its nicked and linear forms at micromolar concentrations. Active oxygen intermediates such as hydroxyl radicals and singlet oxygen generated in the presence of 1 may act as active species for the DNA scission.

Oxidative DNA cleavage promoted by multinuclear copper complexes: activity dependence on the complex structure.

Polynuclear copper complexes with two or three Cu(BPA) (BPA, bis(2-pyridylmethyl)amine) motifs, [Cu2(mTPXA)Cl4]3 H2O (1), [Cu2(pTPXA)Cl4]3 H2O (2), [Cu3(HPTAB)Cl5]Cl3 H2O (3) (mTPXA = N,N,N',N'-tetra-(2-pyridylmethyl)-m-xylylene diamine; pTPXA = N,N, N',N'-tetra-(2-pyridylmethyl)-p-xylylenediamine; HPTAB = N,N,N',N',N'',N''-hexakis(2-pyridylmethyl)-1,3,5-tris-(aminomethyl)benzene) have been synthesized and characterized. The crystal structures of compounds 2 and 3 showed each Cu(BPA) motif had a 4+1 square-pyramidal coordination environment with one chloride occupying the apical position and three N atoms from the same BPA moiety together with another Cl atom forming the basal plane. Fluorescence and circular dichroism (CD) spectroscopy studies indicated that the DNA binding followed an order of 3>2>1 in the compounds. These complexes cleave plasmid pUC19 DNA by using an oxidative mechanism with mercaptopropionic acid (MPA) as the reductant under aerobic conditions. Dinuclear Cu2+ complexes 1 and 2 showed much higher cleavage efficiency than their mononuclear analogue [Cu(bpa)Cl2] at the same [Cu2+] concentration, suggesting a synergistic effect of the Cu2+ centers. Moreover, the meta-dicopper centers in complex 1 facilitated the formation of linear DNA. Interestingly, the additional copper center to the meta-dicopper motif in complex 3 decreased the cleavage efficacy of meta-dicopper motif in complex 1, although it is able to cleave DNA to the linear form at higher [Cu2+] concentrations. Therefore, the higher DNA binding ability of complex 3 did not lead to higher cleavage efficiency. These findings have been correlated to the DNA binding mode and the ability of the Cu2+ complexes to activate oxygen (O2). This work is a good example of the rational design of multinuclear Cu2+ artificial nuclease and the activity of which can be manipulated by the geometry and the number of metal centers.

An asymmetric dizinc phosphodiesterase model with phenolate and carboxylate bridges.

A phosphodiesterase model with two zinc centers has been synthesized and characterized. The compound, [Zn(2)(L(-)(2H))(AcO)(H(2)O)](PF(6)).2H(2)O (Zn(2)L'), was formed using an "end-off" type compartmental ligand, 2,6-bis{[(2-pyridylmethyl)(2-hydroxyethyl)amino]methyl}-4-methylphenol (L), and zinc acetate dihydrate. The X-ray crystallographic analysis shows that Zn(2)L' contains a mu-acetato-mu-cresolato-dizinc(II) core comprised of a quasi-trigonal bipyramidal Zn and a distorted octahedral Zn, and the distance between them is 3.421 Angstroms which is close to the dizinc distance in related natural metalloenzymes. Phosphodiesterase activity of Zn(2)L' was investigated using bis(4-nitrophenyl) phosphate (BNPP) as the substrate. The pH dependence of the BNPP cleavage in aqueous buffer media shows a sigmoid-shaped pH-k(obs) profile with an inflection point around pH 7.13 which is close to the first pK(a) value of 7.20 for Zn(2)L' obtained from the potentiometric titration. The catalytic rate constant (k(cat)) is 4.60 x 10(-6) s(-1) at pH 7.20 and 50 degrees C which is ca. 10(5)-fold higher than that of the uncatalyzed reaction. The deprotonated alcoholic group appended on Zn(2)L' is responsible for the cleavage reaction. The possible mechanism for the BNPP cleavage promoted by Zn(2)L' is proposed on the basis of kinetic and spectral analysis. The dizinc complex formed in situ in anhydrous DMSO exhibits a similar ability to cleave BNPP. This study provides a less common example for the phosphodiesterase model in which the metal-bound alkoxide is the nucleophile.

A novel cytotoxic ternary copper(II) complex of 1,10-phenanthroline and L-threonine with DNA nuclease activity.

A novel ternary copper(II) complex, [Cu(phen)(L-Thr)(H2O)](ClO4) (phen=1,10-phenanthroline, L-Thr=L-threonine), has been synthesized and structurally characterized. The complex crystallized in a triclinic system with space group P1 , a=7.526(15) A, b=11.651(2) A, c=12.127(2) A, alpha=115.41(3) degrees , beta=102.34(3) degrees and gamma=91.33(3) degrees . The copper(II) center is situated in a distorted square-pyramidal geometry. At a concentration of 10(-6) mol L(-1), the complex exhibited potent cytotoxic effects against human leukemia cell line HL-60 and human stomach cancer cell line SGC-7901 with inhibition rates of over 90%, however, less pronounced effects were observed for human liver carcinoma cell line BEL-7402 and human non-small-cell lung cancer cell line A-549. The complex was shown to bind DNA by intercalation and cleave pBR322 DNA in the presence of ascorbate.