Redox Indicator Research Articles

A graphitic nano-onion/molybdenum disulfide nanosheet composite as a platform for HPV-associated cancer-detecting DNA biosensors

An electrochemical DNA sensor that can detect human papillomavirus (HPV)-16 and HPV-18 for the early diagnosis of cervical cancer was developed by using a graphitic nano-onion/molybdenum disulfide (MoS2) nanosheet composite. The electrode surface for probing DNA chemisorption was prepared via chemical conjugation between acyl bonds on the surfaces of functionalized nanoonions and the amine groups on functionalized MoS2 nanosheets. The cyclic voltammetry profile of an 1:1 nanoonion/MoS2 nanosheet composite electrode had an improved rectangular shape compared to that of an MoS2 nanosheet elecrode, thereby indicating the amorphous nature of the nano-onions with sp2 distancing curved carbon layers that provide enhanced electronic conductivity, compared to MoS2 nanosheet only. The nanoonion/MoS2 sensor for the DNA detection of HPV-16 and HPV-18, respectively, was measured at high sensitivity through differential pulse voltammetry (DPV) in the presence of methylene blue (MB) as a redox indicator. The DPV current peak was lowered after probe DNA chemisorption and target DNA hybridization because the hybridized DNA induced less effective MB electrostatic intercalation due to it being double-stranded, resulting in a lower oxidation peak. The nanoonion/MoS2 nanosheet composite electrodes attained higher current peaks than the MoS2 nanosheet electrode, thereby indicating a greater change in the differential peak probably because the nanoonions enhanced conductive electron transfer. Notably, both of the target DNAs produced from HPV-18 and HPV-16 Siha and Hela cancer cell lines were effectively detected with high specificity. The conductivity of MoS2 improved by complexation with nano-onions provides a suitable platform for electrochemical biosensors for the early diagnosis of many ailments in humans.Graphical

A proteoglycan isolated from Ganoderma lucidum attenuates diabetic kidney disease by inhibiting oxidative stress-induced renal fibrosis both in vitro and in vivo.

Ganoderma lucidum (G. lucidum) was regarded as "miraculous herb" by the Chinese and recorded detailly in the "Shen Nong Ben Cao Jing" as a tonic to improve health and prolong life. A proteoglycan (namely, FYGL) was extracted from Ganoderma lucidum, which was a water-soluble hyperbranched proteoglycan, and was found to be able to protect pancreatic tissue against oxidative stress damage. Diabetic kidney disease (DKD) is a complication of diabetes, but the effective treatment is still lack. Chronic hyperglycemia in diabetic patients induce the accumulation of ROS, which injure the renal tissue and lead to the renal dysfunction. In this work, the efficacy and target mechanics of FYGL on diabetic renal function were investigated. In the present study, the mechanism of the reno-protection of FYGL was analyzed on diabetic db/db mice and rat glomerular mesangial cells (HBZY-1) induced by high glucose (HG) with palmitate (PA) (HG/PA). In vitro, the levels of reactive oxygen species (ROS), malondialdehyde (MDA) and superoxide dismutase (SOD) were evaluated by commercial kits. the expressions of NOX1 and NOX4, phosphorylation of MAPK and NF-κB, and pro-fibrotic proteins were measured by Western blot. In vivo, diabetic db/db mice were gavaged with FYGL for 8 weeks, body weight and fasting blood glucose (FBG) were tested weekly. On 8th week, the serum, urine and renal tissue were collected for glucose tolerance test (OGTT), redox indicator (SOD, CAT, GSH and MDA), lipid metabolism (TC, TG, LDL and HDL), blood urea nitrogen (BUN), serum creatinine (Scr), uric acid (UA), 8-oxo-deoxyguanosine (8-OHdG), and the changes of histopathology and expression of collagen IV and AGEs. The results in vitro showed that FYGL significantly inhibited the HG/PA-induced HBZY-1cells proliferation, ROS generation, MDA production, promoted SOD activity, and suppressed NOX1, NOX4, MAPK, NF-κB, and pro-fibrotic proteins expression. In addition, FYGL markedly alleviated blood glucose, antioxidant activity and lipid metabolism, improved renal functions, and relieved renal histopathological abnormalities, especially renal fibrosis. The antioxidant activity of FYGL can reduce ROS caused by diabetes and protect renal from oxidative stress-induced dysfunction, thereby improving renal function. This study shows that FYGL has the potential to treat diabetic kidney disease.

Electrochemical DNA-Sensor Based on Macrocyclic Dendrimers with Terminal Amino Groups and Carbon Nanomaterials.

The assembling of thiacalix[4]arene-based dendrimers in cone, partial cone, and 1,3-alternate configuration on the surface of a glassy carbon electrode coated with carbon black or multiwalled carbon nanotubes has been characterized using cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. Native and damaged DNA were electrostatically accumulated on the modifier layer. The influence of the charge of the redox indicator and of the macrocycle/DNA ratio was quantified and the roles of the electrostatic interactions and of the diffusional transfer of the redox indicator to the electrode interface indicator access were established. The developed DNA sensors were tested on discrimination of native, thermally denatured, and chemically damaged DNA and on the determination of doxorubicin as the model intercalator. The limit of detection of doxorubicin established for the biosensor based on multi-walled carbon nanotubes was equal to 1.0 pM with recovery from spiked human serum of 105-120%. After further optimization of the assembling directed towards the stabilization of the signal, the developed DNA sensors can find application in the preliminary screening of antitumor drugs and thermal damage of DNA. They can also be applied for testing potential drug/DNA nanocontainers as future delivery systems.

Isolation of a polyethylene-degrading bacterium, Acinetobacter guillouiae, using a novel screening method based on a redox indicator

Plastic, a polymer synthesized from petrochemicals, is used worldwide. However, natural degradation of plastic is difficult, causing environmental pollution, with microplastics posing a serious threat to human health. In this study, we aimed to use a new screening method based on the oxidation-reduction indicator, 2,6-dichlorophenolindophenol, to isolate a polyethylene-degrading bacterium, Acinetobacter guillouiae, from insect larvae. Plastic-degrading strains are identified by the color change in the redox indicator from blue to colorless as plastic metabolism occurs. Polyethylene biodegradation by A. guillouiae was verified through weight loss, surface erosion, physiological evidence, and chemical changes on the plastic surface. In addition, we analyzed the characteristics of hydrocarbon metabolism in polyethylene-degrading bacteria. Results suggested that alkane hydroxylation and alcohol dehydrogenation were key steps in polyethylene degradation. This novel screening method will pave the way for high-throughput screening of polyethylene-degrading microorganisms and extending its application to other types of plastics may potentially address plastic pollution.

Electrochemical DNA-nano biosensor for the detection of cervical cancer-causing HPV-16 using ultrasmall Fe3O4-Au core-shell nanoparticles

This paper reports a label-free biosensor for detecting human papillomavirus type 16 (HPV-16). For this purpose, the surface of the screen-printed carbon electrodes (SPCEs) was coated with Fe3O4-Au core-shell nanoparticles (NPs) using a green and facile eco-friendly method. The modified surfaces of the electrodes were then functionalized with thiolated single-strand DNA (ssDNA) probe human papillomavirus (HPV) DNA sequences. Next, the hybridization events with the immobilized probe DNA were monitored by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) using [Fe(CN)6]3‐/4− as the redox indicator. Our results demonstrate that the modified electrodes could distinguish the redox current signals of [Fe(CN)6] 3−/4− due to the absence/presence of the immobilized probe DNA. Furthermore, quantitative estimations of the concentration of the probe DNA were also possible. Optimal performance was obtained for probe DNA concentrations between 1 and 10 μM. The best performance of our HPV biosensor was obtained for probe DNA concentration of 5 μM, for which the limit of detection and sensitivity of our developed sensor resulted to be 0.1 nM and 2.4 μA/nM, respectively.

Engineered Escherichia coli as a Controlled-Release Biocarrier for Electrochemical Immunoassay.

Micro/nanocarriers hold great potential in bioanalysis for molecular recognition and signal amplification but are frequently hampered by harsh synthesis conditions and time-consuming labeling processes. Herein, we demonstrate that Escherichia coli (Ec) can be engineered as an efficient biocarrier for electrochemical immunoassay, which can load ultrahigh amounts of redox indicators and simultaneously be decorated with detection antibodies via a facile polydopamine (PDA)-mediated coating approach. Compared with conventional carrier materials, the entire preparation of the Ec biocarrier is simple, highly sustainable, and reproducible. Moreover, immune recognition and electrochemical transduction are performed independently, which eliminates the accumulation of biological interference on the electrode and simplifies electrode fabrication. Using human epidermal growth factor receptor 2 (HER2) as the model target, the proposed immunosensor exhibits excellent analytical performance with a low detection limit of 35 pg/mL. The successful design and deployment of Ec biocarrier may provide new guidance for developing biohybrids in biosensing applications.

A Novel Electrochemical Immunosensor Based on Anti-IgY and PLA/PEG Nanofibrous Mats Used for Allergens Detection in Farinaceous Products

The present study focuses on the first electrochemical immunosensor built with polymeric mats enriched with nanomaterials, targeting the dust mite protein, for the detection of allergens in flour sources with important implications in allergic reactions. As a proof-of-concept, we have used the Blo t 5 allergen from Blomia tropicalis (target) and established electrochemical parameters to recognize and detect the specific allergen using a polyclonal immunoglobulin (Ig) Y (probe). Detection was performed in a portable potentiostat (EmStat) using a graphite screen-printed electrode. For that, the nanofibrous mats of poly(lactic acid)/poly(ethylene glycol) (PLA/PEG), and carbon nanotubes (CNTs) were placed in contact with the surface of the electrodes. The functionalization that occurs through the deposition of the polymer was induced through the passage of current. Subsequently, the modification was validated by cyclic voltammetry (CV) readings and ferri/ferrocyanide was used as a redox indicator in CV analyses. The novel immunosensor was able to discriminate between allergen-contaminated and uncontaminated farinaceous samples. The immunosensor displays high sensitivity detecting up to 50 μg ml−1 in the calibration curve with a linear response between 5 and 500 μg ml−1. The new biosensor shows great potential in the detection of farinaceous contaminants in laboratories, food factories and in the field.

Biodegradation of paraffin wax using Bacillus sp. SASH for quality improvement of crude oil properties

Biodegradation has become the most preferred and sustainable mean of reducing paraffin wax, removing paraffin deposition in pipelines and improving the flow of petroleum products. The current study focuses on the isolation of bacteria that has the capability to utilize paraffin as a sole carbon source and has been screened using 2,6-dichlorophenol indophenol (DCPIP) dye as redox indicator. The bacterium was identified as Bacillus sp. SASH according to its 16S rRNA gene sequence analysis. It is a moderate halophile that can grow in seawater at pH 7 and 37 °C. Bacillus sp. SASH was able to degrade various paraffinic products such as paraffin wax, heavy wax distillates, and liquid paraffin and it showed up to 84% paraffin wax degradation. Gas chromatography–mass spectrometry analysis revealed that higher carbon chains after retention time of 18 min were removed after treatment of the wax with the bacterium. Bacillus sp. SASH enhanced the flow of different petroleum products by reducing their viscosity and pour point values. It was also able to reduce the viscosity and improve the flow of crude oil by 60%.

Response of redox zoning and microbial community structure in riverbed sediments to the riverbed scouring during bank filtration

Riverbed sediments are an important zone and interface for the interaction of surface water and groundwater; hence, biochemical processes in the riverbed sediments are critical to maintain the ecology of the system and water quality. Riverbed sediment scouring can substantially alter the hydrodynamic conditions of river water infiltration and redox conditions at the surface–groundwater interface, which in turn affects the biochemical processes. Currently, in-depth understanding of the distribution characteristics of the microbial community structure in riverbed sediments, especially their response to riverbed scouring, is lacking. This study revealed the temporal and spatial changes in redox indicators in the Liaohe riverbed sediment and discussed the response of the microbial community to the influence of riverbed scouring. The results showed that during the investigation period (September to November 2020), the riverbed sediments in the river reach were generally in a state of scouring in the low water stage, and the scour depth was 4–9 cm. The redox zone in the nearshore area moved up by 5.5–23 cm, and moved down by 0.1–10 cm in the intermediate transition area and the center of riverbed, and the maximum overlapping depth of the redox zone could reach 50 cm. The relative abundance of dominant bacteria species had a good correlation with the intensity of geochemical reactions, decreasing in low-water levels close to the center of the riverbed, which further indicated the weakening of the reduction rate. Influenced by riverbed scouring, the species of denitrifying bacteria in the surface layer increased, multiple dominant bacteria of iron, manganese and sulfate often coexist in deep riverbed sediments, and were slightly different in the low water level. The results provide a better understanding of the chemical composition of the pore water in the riverbed sediments, which are of great significance for maintaining the ecological safety of river water.

Cytotoxicity and internalization properties of novel alpha7 nicotinic receptor selective peptides.

Cell-penetrating peptides (CPPs) contain ≤30 residues and have the unique ability to enter cells, making them attractive agents for Central Nervous System (CNS)-targeted drug delivery. Examples are CPPs derived from the rabies virus glycoprotein (RVG). RVG-derived peptides make use of a nicotinic acetylcholine receptor (nAChR)-mediated mechanism to enter the mouse CNS and deliver cargo. However, previously developed RVG-derived peptides lack selectivity for distinct nAChR subtypes, which are associated with different neurological diseases. As an example, dysregulation of the homomeric α7-nAChR is involved in Alzheimer's disease and depression. In an effort to develop an α7-nAChR-selective CPP, we hypothesized that combining regions of the RVG with those of a protein known to specifically interact with the α7-nAChR subtype could create a chimeric peptide with CPP properties that is α7-nAChR selective. However, insertion of protein segments into RVG brings possibility for altering cytotoxic and cell internalization properties. To investigate these changes for our RVG-chimeric peptides, we cultured and transfected neuronal-like cells with α7 subunits and the nAChR chaperone NACHO, and verified expression using fluorescent tags. We treated cells with RVG or fusion peptides using a range of concentrations to obtain their cytotoxic profiles using a redox indicator for cell viability. Separately, α7-nAChR cells were treated with the lead peptide containing the fluorescent tag FITC and visualized using live cell confocal fluorescence microscopy. We did not observe significant cytotoxic effects of the original RVG or chimeric peptides for concentrations ranging from 0.3 nM to 100 μM. Additionally, our data suggests that the lead chimeric peptide can enter neuronal-like cells by using an α7-nAChR-mediated mechanism. An α7-nAChR subtype-selective therapeutic agent has the potential to aid in depression treatment, without creating unwanted off-target effects. Moreover, it may be useful as vehicle for CNS-targeted drug delivery.

Towards the maximization of nanochannels blockage through antibody-antigen charge control: Application for the detection of an Alzheimer’s disease biomarker

Although size and charge effects in nanochannels have been previously approached for electrochemical immunosensing, as far as we know, thorough studies on the effect of both the antibody and the antibody/antigen immunocomplex charges at different pHs have not been deeply reported. In this context, we present here an unprecedented study of such parameters, applied also for the first time for the detection of an Alzheimer’s disease (AD) biomarker. AD detection is currently based in time consuming and expensive techniques, so that the development of alternative analytical strategies for facilitating its diagnosis is still a need. To reach that purpose, we propose here the development of a nanochannel-based system for the electrochemical monitoring of Tau protein, an important AD biomarker. Tau protein is selectively captured by specific antibodies immobilized in the inner walls of the nanochannels of nanoporous alumina membranes. The captured Tau protein blocks the nanochannel and difficulties the passage of red-ox indicator ions, which is voltammetrically monitored using an indium tin oxide/poly(ethylene terephthalate) (ITO/PET) electrode as transducer. The charges of both the antibody and the Tau antigen at different pHs and their effect on the diffusion of the red-ox indicator ions to the electrode are carefully evaluated to maximize the electrostatic blocking of the nanochannels upon the immunocomplex formation. The developed biosensing system allows the determination of Tau protein with a detection limit of 4.3 ng/mL, which is within the range of clinical interest, showing also excellent recovery percentages in human plasma samples.

Strategies in the optimization of DNA hybridization conditions and its role in electrochemical detection of dengue virus (DENV) using response surface methodology (RSM).

In recent years, limited research has been conducted on enhancing DNA hybridization-based biosensor approaches using statistical models. This study explores the application of response surface methodology (RSM) to improve the performance of a DNA hybridization biosensor for dengue virus (DENV) detection. The biosensor is based on silicon nanowires decorated with gold nanoparticles (SiNWs/AuNPs) and utilizes methylene blue as a redox indicator. The DNA hybridization process between the immobilized DNA probe and the target DENV gene was monitored using differential pulse voltammetry (DPV) based on the reduction of methylene blue. Fourier-transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS) were employed to confirm successful DNA hybridization events on the modified screen-printed gold electrode (SPGE) surface. Several parameters, including pH buffer, NaCl concentration, temperature, and hybridization time, were simultaneously optimized, with NaCl concentration having the most significant impact on DNA hybridization events. This study enhances the understanding of the role of each parameter in influencing DNA hybridization detection in electrochemical biosensors. The optimized biosensor demonstrated the ability to detect complementary oligonucleotide and amplified DENV gene concentrations as low as 0.0891 ng µL-1 (10 pM) and 2.8 ng µL-1, respectively. The developed biosensor shows promise for rapid clinical diagnosis of dengue virus infection.

MiOXSYS® and OxiSperm® II assays appear to provide no clinical utility for determining oxidative stress in human sperm-results from repeated semen collections.

Oxidative stress in semen contributes up to 80% of all infertility diagnosis. Diagnostics to measure oxidative stress in semen was recently added to the 6th edition WHO methods manual, although diagnostic predictive values need to be interpreted with caution as there are still several research questions yet to be answered. To determine the natural fluctuations in semen redox indicators (MiOXSYS® and OxiSperm® II) within and between men and their association with markers of sperm oxidative stress. Total, 118 repeat semen samples from 31 generally healthy men aged 18-45 years, over 6 months. Standard semen analysis as per 5th WHO manual. Semen redox levels measured via MiOXSYS® and OxiSperm® II. Additional attributes of sperm quality; HBA® binding assay and sperm hyperactivation and oxidative stress; DNA fragmentation (Halo® Sperm) and lipid peroxidation (BODIPY™ 581/591 C11) were assessed. Samples with high redox-potential (MiOXSYS® ≥1.47 sORP/106 sperm/ml) had lower sperm, motility, morphology and higher DNA fragmentation (P<0.05). Upon further analysis, these associations were driven solely by the adjustment of sperm concentration (106 /ml) in normalised redox-potential. No significant associations between NBT-reactivity (OxiSperm® II) and measures of the sperm function or oxidative stress were observed (P>0.05). Fluctuations in semen redox levels varied greater between men than within men over the study period. Neither MiOXSYS® nor OxiSperm® II assays were predictive of sperm function or sperm oxidative stress. This was likely due at least in part to limited understanding of their biochemistry and clinical application. As a result, these assays seem to provide no additional clinical utility beyond that of a standard semen analysis, highlighting the imperative for the development of new robust point-of-care devices for accurately determining sperm oxidative stress. These findings suggest that MiOXSYS® and OxiSperm® II systems for the measurement of sperm oxidative stress may have limited diagnostic potential.

An electrochemical aptasensor for Δ9-tetrahydrocannabinol detection in saliva on a microfluidic platform

We present a novel “on-off”, cost-effective, rapid electrochemical aptasensor combined with a microfluidics cartridge system for the detection of Δ9-THC (Δ9-tetrahydrocannabinol) in human saliva via differential pulse voltammetry. The assay relied on the competitive binding between the Δ9-THC and a soluble redox indicator methylene blue, using an aptamer selected via FRELEX. We found that the aptasensor can detected 1 nM of Δ9-THC in PBS in a three-electrode cell system, while the sensitivity and both the dissociation constant (Kd) and association constant (Kb) were dependent on the aptamer density. The aptamer also showed great affinity towards Δ9-THC when tested against cannabinol and cannabidiol. The same limit of detection of 1 nM in PBS was achieved in small volume samples (∼60 μL) using the aptamer-modified gold screen-printed electrodes combined with the microfluidic cartridge setup, however, the presence of 10% raw human saliva had a negative effect which manifested in a 10-fold increase in the LOD due to interfering elements. Filtering the saliva, improved the tested volume to 50% and the LOD to 5 nM of Δ9-THC which is lower than the concentrations associated with impairment (6.5–32 nM). The aptasensor showed a good storage capability up to 3 days, however, the reusability significantly dropped from 10 cycles (freshly prepared) to 5 cycles. The results clearly demonstrate the feasibility of the aptasensor platform with the microfluidics chamber towards a point-of-care testing application for the detection of Δ9-THC in saliva.

Polymer indicator displacement assay (PIDA) with boronic acid receptors on graphene foam electrodes for self-optimised impedimetric lactic acid determination

Synthetic organic receptor molecules are employed based on boronic acids attached to graphene to provide functionality and selectivity in competitive analyte binding. Here, a new electrochemical sensor concept based on a surface redox polymer indicator displacement (avoiding traditional solution redox indicators) is proposed and demonstrated on graphene foam electrodes. A pyrene-derivatised boronic acid chemo-receptor for lactic acid is adsorbed onto graphene foam and coated with poly-nordihydroguaiaretic acid (poly-NHG) as an electrochemically active polymer indicator. When bound to the boronic acid, poly-NHG remains redox silent. Dynamic displacement with lactic acid results in a concentration-dependent Faradaic current response. Effects of pH and detection methodology (voltammetry, chronoamperometry, and impedance spectroscopy) are investigated. Self-optimised impedimetric sensing based on the interfacial electron transfer resistance is demonstrated. While lactic acid sensing in human serum is possible, the sensor response is lower. Surface-active components from human serum are shown to modify the sensor response without affecting performance. Lactic acid sensing in artificial sweat at pH 4.7 is shown to result in a Langmuirian binding curve with apparent binding constant K = 40 M-1.

Enhancing Electrochemical Biosensor Performance for 17β-Estradiol Determination with Short Split-Aptamers.

Chronic exposure of 17β-estradiol (E2) even at low concentration can disorganize the endocrine system and lead to undesirable health problems in the long run. An electrochemical biosensor for rapid detection of E2 in water samples was successfully developed. The biosensor was based on split DNA aptamers attached onto poly (methacrylic acid-co-n butyl acrylate-succinimide) microspheres deposited on polypyrrole nanowires coated electrode (PPY/PMAA-NBA). The sandwich paired of split DNA aptamers used were truncated from 75 mer parent aptamers. These two strands of 12-mer and 14-mer split DNA aptamers were then immobilized on the PMAA-NBA microspheres. In the presence of E2, the split DNA aptamers formed an apt12-E2-apt14 complex, where the binding reaction on the electrode surface led to the detection of E2 by differential pulse voltammetry using ferrocyanide as a redox indicator. Under optimum conditions, the aptasensor detected E2 concentrations in the range of 1 × 10-4 M to 1 × 10-12 M (R2 = 0.9772) with a detection limit of 4.8 × 10-13 M. E2, which were successfully measured in a real sample with 97-104% recovery and showed a good correlation (R2 = 0.9999) with the established method, such as high-performance liquid chromatography. Interactions between short and sandwich-type aptamers (split aptamers) demonstrated improvement in aptasensor performance, especially the selectivity towards several potential interferents.

Cyclic Voltammetric-Paper-Based Genosensor for Detection of the Target DNA of Zika Virus.

Zika virus (ZIKV), a positive-sense single-stranded RNA virus, has been declared as the cause of a 'worldwide public health emergency' by the WHO since the year 2016. In cases of acute infections, it has been found to cause Guillain-Barre syndrome and microcephaly. Considering the tropical occurrence of the infections, and the absence of any proper treatments, accurate and timely diagnosis is the only way to control this infectious disease. Currently, there are many diagnostic methods under investigation by the scientific community, but they have some major limitations, such as high cost, low specificity, and poor sensitivity. To overcome these limitations, we have presented a low-cost, simple-to-operate, and portable diagnosis system for its detection by utilizing silver nanoparticles. silver nanoparticles were synthesized via chemical methods and characterization was confirmed by UV/TEM and XRD. The paper platform was synthesized using a graphene-based conductive ink, methylene blue as the redox indicator, and a portable potentiostat to perform the cyclic voltammetry to ensure true point-of-care availability for patients in remote areas.

A sensing strategy based on aptamers alkylated with melphalan and graphite nanocrystals in a bed of tetrahedral amorphous carbon for electrochemical detection of lead ions in human urine

We report a voltammetric aptasensor based on the graphite nanocrystals in a bed of tetrahedral amorphous carbon (GNC-TAC) and guanine (G)-rich aptamers alkylated with melphalan anticancer for determination of ultratrace Pb2+ in the clinical samples. In this work, an adhesive and stable layer of GNC-TAC was formed on the cellulose paper by the ion beam sputtering deposition (IBSD) method. This porous conductive nanographite film plays a key role in providing a large area for adsorption of ferrocene carboxylic acid (FC-COOH) anticancer as a redox indicator. Then, melphalan that attaches the alkyl groups to the guanine bases of DNA aptamer was bonded covalently to the carboxylic groups of FC-COOH via the aid of EDC/NHS. The introduction of Pb2+ ions to the aptamer/melphalan/FC-COOH/GNC-TAC/paper electrode leads to the formation of a G-quadruplex (G4)/Pb2+ complex and dissociation of this complex from the modified electrode surface. The target-induced aptamer release from melphalan/FC-COOH/GNC-TAC/paper electrode makes the sensing interface smaller which results in an increase in the current signal. Based on this signal-on mechanism, the sensitive detection of Pb2+ ions in the dynamic linear range (DLR) of 0.5–700.0 μg L−1 is realized (limit of detection (LOD): 0.15 μg L−1). The present strategy shows remarkable advantages including high selectivity and wide detectable range. More importantly, the good consistency of the results obtained with the aptasensor and those by the quality control material (QCM) analysis and atomic absorption spectroscopy equipped with graphite furnace (GF-AAS) technique showed that the proposed strategy has a high potential for Pb2+ detection in the clinical samples.

A sensitive and rapid determination of zinc ion (Zn2+) using electrochemical sensor based on f-MWCNTs/CS/PB/AuE in drinking water

An electrochemical method for detecting the presence of zinc (Zn2+) ions in drinking water was developed using functionalized multi-walled carbon nanotubes (f-MWCNTs) and chitosan (CS). Numerous cylinder-shaped graphene molecules make up f-MWCNTs, which have a high mechanical and electrical conductivity. CS benefits from nanomaterials include biocompatibility, biodegradability, and low toxicity, which are excellent in capacity absorption of metal ions. Dangerous levels of metal ions such as zinc are currently present in drinking water as a result of human and natural activity. Zinc toxicity is associated with a variety of disorders, including Alzheimer’s, Parkinson's, diabetes, and cancer. This study incorporated f-MWCNTs and CS with Prussian blue (PB) immobilised on a gold electrode (AuE). Several parameters, including as buffers, pH, scan rate, redox indicator, accumulation time, and volume, were optimised using the cyclic voltammetry (CV) method. According to the CV method, the optimal parameters were phosphate buffered saline (0.1 M, pH 2), 5 mM Prussian blue, 200 mVs-1 scan rate, and 5 s accumulation time. Under ideal circumstances, the differential pulse voltammetry (DPV) method was used to determine the Zn2+ ions concentration range of 0.2–7.0 ppm. The limit of detection (LOD) was 2.60 × 10–7 mol L-1 with a correlation coefficient of R2 = 0.9777. The recovery rate of the developed sensor (f-MWCNTs/CS/PB/AuE) ranged from 95.78 to 98.96%. The developed sensor showed a variety of advantages for detecting Zn2+ in drinking water, including a quick setup process, quick detection, high sensitivity, and mobility. This study developed the essential sensor for monitoring Zn2+ levels in drinking water in the future.

In-Situ Characterization of Electroreduced Tantalum and Niobium in Deep Eutectic Solvents

Room temperature ionic solvents are expected to possess electrochemical properties suitable for tantalum and niobium redox analogous to high temperature molten salts, in which successful bulk metal electrodeposition is reported. However, with the combination of perplexing multivalent chemistry of niobium and tantalum and alien electrochemical properties of ionic solvents, when compared to better characterized aqueous environments, the fundamental understanding of the electrochemical behavior of niobium and tantalum in these promising, yet compositionally diverse, solvents is severely underpopulated. Herein we report a new toolbox of coordinating additives that form, in many traditional and ionic solvents, chemically-robust reduced niobium and tantalum complexes with distinct photometric and paramagnetic properties, that serve as metal redox indicators and intermediate valence traps during electroreduction. We showcase the utility of these indicator species for clarifying the electrochemical behavior of niobium and tantalum in chemically varied ionic solvent environments by comparing in-situ electrochemical UV-Vis and electron paramagnetic resonance (EPR) observations in a series of chemically dissimilar deep eutectic solvents.