A blood-serum sulfide selective electrochemical sensor based on a 9,10-phenanthrenequinone-tethered graphene oxide modified electrode

An anti-poisoning nanosensor for in situ monitoring of intracellular endogenous hydrogen sulfide

Intracellular H₂S plays an important regulatory role in cell metabolism. The limited sensing materials and severe sensor passivation hinder its quantification. We functionalized conductive nanowires with MoS₂ and quercetin in a large-scale manner, developed single nanowire sensors with excellent electrocatalytic and anti-poisoning performance, and achieved the accurate quantification of H₂S within single cells.

Hydrogen sulfide poisoning in forensic pathology and toxicology: mechanism and metabolites quantification analysis

Historically, hydrogen sulfide (H₂S) poisoning has extremely high and irreparable mortality. Currently, the identification of H₂S poisoning needs to combine with the case scene analysis in forensic medicine. The anatomy of the deceased seldom had obvious features. There are also a few reports about H₂S poisoning in detail. As a result, we give a comprehensive analysis of the related knowledge on the forensic aspect of H₂S poisoning. Furthermore, we provide the analytical methods of H₂S and its metabolite-which may assist in H₂S poisoning identification.

Inner filter effect-based upconversion fluorescence sensing of sulfide ions

Upconversion nanocrystals (UCNCs) have emerged as a new type of fluorescent probe for sensing applications. Herein, we designed a 980 nm excited upconversion luminescence system, composed of core-shell-structured NaYF₄ : Yb,Er@NaYF₄ : Yb nanocrystals (csUCNCs) and the triethylenetetramine-Cu complex (complex-I), for quantitative detection of sulfide ions. Taking advantage of the specific recognition of complex-I toward S^2-, the as-formed compound (complex-II) exhibits excellent spectral overlap not only in the range of fluorescence emissions of UCNCs but also in the excitation wavelength for UCNCs; fluorescence quenching of UCNCs occurs where the complex-II acts as the energy acceptor. Due to the electrostatic repulsion between positively charged ligand-free csUCNCs and complex-I, the fluorescence quenching is based on the primary and secondary inner filter effect rather than the fluorescence resonance energy transfer process. The detection limit of S^2- for the upconversion-based system is calculated to be 2.7 μM, exhibiting higher detection sensitivity over the single complex-I compound measured by the spectrophotometric method. Moreover, no significant variation in upconversion luminescence is observed upon the addition of other interfering ions, showing the excellent selectivity of this nanoprobe toward S^2-.

Porous Carbon Nanofiber-Modified Carbon Fiber Microelectrodes for Dopamine Detection

We present a method to modify carbon-fiber microelectrodes (CFME) with porous carbon nanofibers (PCFs) to improve detection and to investigate the impact of porous geometry for dopamine detection with fast-scan cyclic voltammetry (FSCV). PCFs were fabricated by electrospinning, carbonizing, and pyrolyzing poly(acrylonitrile)-b-poly(methyl methacrylate) (PAN-b-PMMA) block copolymer nanofiber frameworks. Commonly, porous nanofibers are used for energy storage applications, but we present an application of these materials for biosensing which has not been previously studied. This modification impacted the topology and enhanced redox cycling at the surface. PCF modifications increased the oxidative current for dopamine 2.0 ± 0.1-fold (n = 33) with significant increases in detection sensitivity. PCF are known to have more edge plane sites which we speculate lead to the two-fold increase in electroactive surface area. Capacitive current changes were negligible providing evidence that improvements in detection are due to faradaic processes at the electrode. The ΔE_p for dopamine decreased significantly at modified CFMEs. Only a 2.2 ± 2.2 % change in dopamine current was observed after repeated measurements and only 10.5 ± 2.8% after 4 hours demonstrating the stability of the modification over time. We show significant improvements in norepinephrine, ascorbic acid, adenosine, serotonin, and hydrogen peroxide detection. Lastly, we demonstrate that the modified electrodes can detect endogenous, unstimulated release of dopamine in living slices of rat striatum. Overall, we provide evidence that porous nanostructures significantly improve neurochemical detection with FSCV and echo the necessity for investigating the extent to which geometry impacts electrochemical detection.

One-pot synthesis of AuAgPd trimetallic nanoparticles with peroxidase-like activity for colorimetric assays

In this work, AuAgPd trimetallic nanoparticles (AuAgPd TNPs) with intrinsic and broad-spectrum peroxidase-like activity were synthesized through a one-pot method by co-reduction of HAuCl₄, AgNO₃, and Na₂PdCl₄ with NaBH₄. The morphology and composition of AuAgPd TNPs were characterized. The peroxidase-like activity of AuAgPd TNPs were highly dependent on the composition and nanostructure of AuAgPd TNPs. Rationally designed AuAgPd TNPs could catalyze the oxidation of various chromogenic substrates including 3,3'5,5'-tetramethylbenzidine (TMB), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), and o-phenylenediamine (OPD) by H₂O₂ to generate blue, green, and yellow products, respectively. Kinetic assays indicated that AuAgPd TNPs exhibited high affinity to H₂O₂. Then, sensitive colorimetric assays were developed for H₂O₂ detection by using ABTS, OPD, and TMB as chromogenic substrates, respectively. Lowest limit of detection (LOD) of 3.1 μM with wide linear range of 6-250 μM was obtained by using ABTS as substrate. Hydrogen sulfide ion (HS^-) could effectively inhibit the peroxidase-like activity of AuAgPd TNPs. Thus, a selective colorimetric assay was further fabricated for HS^- detection with LOD of 2.3 μM. This work provides an effective way for the synthesis of trimetallic nanozyme with peroxidase-like activity and also for tailoring their catalytic activity for desired use. Graphical abstract.

Visual detection of S2- with a paper-based fluorescence sensor coated with CdTe quantum dots via headspace sampling

A simple method was developed in this work for facile and visual detection of S^2- using a paper-based fluorescence (FL) sensor coated with CdTe quantum dots (QDs) by headspace sampling. With the addition of hydrochloric acid, the target S^2- in the liquid phase would transform to H₂ S, which was released to headspace and quenched the FL of CdTe QDs in a linear manner through a gas-solid reaction, with any possible liquid-phase interference avoided. The regular quenching caused by S^2- in analyte solution with increased concentration could be easily observed by the naked eye, and the limit of detection (LOD) for this method was 0.13 μM and 0.93 μM for FL and visual sensing, respectively, comparable or not to that by other sensing probes. A relative standard deviation of 1.2% was accomplished from seven replicated measurements, implying the high reproducibility, and the recovery for the spiked water samples ranging from 94 to 103%, and illustrating the satisfactory reliability of this method. Moreover, the preparation of this paper sensor was facile and did not require any complicated or time-consuming procedures for additional modification or functionalization as for other probes previously reported.

Growth of large-scale MoS2 nanosheets on double layered ZnCo2O4 for real-time in situ H2S monitoring in live cells

There is an urgent need to develop in situ sensors that monitor the continued release of H2S from biological systems to understand H2S-related pathology and pharmacology. For this purpose, we have developed a molybdenum disulfide supported double-layered zinc cobaltite modified carbon cloth electrode (MoS2-ZnCo2O4-ZnCo2O4) based electrocatalytic sensor. The results of our study suggest that the MoS2-ZnCo2O4-ZnCo2O4 electrode has excellent electrocatalytic ability to oxidize H2S at physiological pH, in a minimized overpotential (+0.20 vs. Ag/AgCl) with an amplified current signal. MoS2 grown on double-layered ZnCo2O4 showed relatively better surface properties and electrochemical properties than MoS2 grown on single-layered ZnCo2O4. The sensor delivered excellent analytical parameters, such as low detection limit (5 nM), wide linear range (10 nM-1000 μM), appreciable stability (94.3%) and high selectivity (2.5-fold). The practicality of the method was tested in several major biological fluids. The electrode monitors the dynamics of bacterial H2S in real-time for up to 5 h with good cell viability. Our research shows that MoS2-ZnCo2O4-ZnCo2O4/carbon cloth is a robust and sensitive electrode to understand how bacteria seek to adjust their defense strategies under exogenously induced stress conditions.

Gd doped molybdenum selenide/carbon nanofibers: an excellent electrocatalyst for monitoring endogenous H2S

Design and synthesis of Gd doped molybdenum selenide/carbon nanofibers for monitoring H₂S.

Cellulose nanofiber-based electrode as a component of an enzyme-catalyzed biofuel cell

Many types of flexible, wearable, and disposable electronic devices have been developed as chemical and physical sensors, and many solar cells contain plastics. However, because of environmental pollution caused by microplastics, plastic use is being reduced worldwide. We have developed an enzyme-catalyzed biofuel cell utilizing cellulose nanofiber (CNF) as an electrode component. The electrode was made conductive by mixing multi-walled carbon nanotubes with the CNF. This prepared biofuel cell was wearable, flexible, hygroscopic, biodegradable, eco-friendly, and readily disposable like paper. The CNF-based enzyme-catalyzed biofuel cell contained a flavin adenine dinucleotide-dependent glucose dehydrogenase bioanode and laccase biocathode. The maximum voltage and maximum current density of the biofuel cell were 434 mV and 176 μA cm⁻², respectively, at room temperature (15–18 °C). The maximum power output was 27 μW cm⁻², which was converted to 483 (±13) μW cm⁻³.

Cellulose nanofiber-based biofuel cell with flexible, biodegradable, eco-friendly.

Nitric Oxide and Hydrogen Sulfide Regulation of Ischemic Vascular Growth and Remodeling

Ischemic vascular remodeling occurs in response to stenosis or arterial occlusion leading to a change in blood flow and tissue perfusion. Altered blood flow elicits a cascade of molecular and cellular physiological responses leading to vascular remodeling of the macro- and micro-circulation. Although cellular mechanisms of vascular remodeling such as arteriogenesis and angiogenesis have been studied, therapeutic approaches in these areas have had limited success due to the complexity and heterogeneous constellation of molecular signaling events regulating these processes. Understanding central molecular players of vascular remodeling should lead to a deeper understanding of this response and aid in the development of novel therapeutic strategies. Hydrogen sulfide (H₂ S) and nitric oxide (NO) are gaseous signaling molecules that are critically involved in regulating fundamental biochemical and molecular responses necessary for vascular growth and remodeling. This review examines how NO and H₂ S regulate pathophysiological mechanisms of angiogenesis and arteriogenesis, along with important chemical and experimental considerations revealed thus far. The importance of NO and H₂ S bioavailability, their synthesis enzymes and cofactors, and genetic variations associated with cardiovascular risk factors suggest that they serve as pivotal regulators of vascular remodeling responses. © 2019 American Physiological Society. Compr Physiol 9:1213-1247, 2019.

Electrochemical aptasensors for zeatin detection based on MoS2 nanosheets and enzymatic signal amplification

A simple and sensitive electrochemical aptasensor was constructed for zeatin detection, where MoS2 nanosheets were used as the immobilization matrix for gold nanoparticles (AuNPs), and AuNPs were employed as the immobilization matrix to probe DNA. After the aptamer DNA and assist DNA hybridized with probe DNA, Y-type DNA can be formed with two biotins at the terminals of aptamer DNA. Then, avidin modified alkaline phosphatase (Avidin-ALP) can be further modified on the electrode surface through the biotin and avidin interaction. Under the catalytic effect of ALP, p-nitrophenylphosphate disodium (PNPP) can be hydrolyzed to produce p-nitrophenol (PNP). However, in the presence of zeatin, the formed Y-type DNA can be destroyed due to the formation of the zeatin-aptamer conjugate, which further reduces the amount of PNP and leads to the decrease of the oxidation signal of PNP. Under the optimum conditions, the change of the oxidation peak current of PNP was inversely proportional to the logarithm value of zeatin concentration in the range of 50 pM-50 nM. The detection limit was calculated to be 16.6 pM. This electrochemical method also showed good detection selectivity and stability. The potential applicability of this method was proved by detecting zeatin in real samples.