In the highly corrosive wellbore environment, the commonly used material for oil casing, P110 steel, often forms a galvanic couple with the sacrificial anode magnesium (Mg) alloy. Sulfate reducing bacteria (SRB) can further exacerbate metal corrosion through their metabolic activities, leading to premature failure of downhole equipment. However, the regulatory mechanism of SRB on the galvanic corrosion behavior of the AZ63 alloy and P110 steel has not yet been well understood. The results in this study showed that SRB could adsorb on the surface of the AZ63 alloy and form a dense biofilm, which enhanced the electrical resistance of the product film. The maximum pitting depth of the coupled Mg alloy decreased from 377 μm in the abiotic solution to 128 μm in the biotic solution. For the P110 steel, even cathodically protected by the Mg alloy, SRB could still accelerate its localized corrosion through multiple pathways. The galvanic current transferred from the Mg alloy provided the energies for SRB metabolism, forming a positive feedback loop of current-enhanced SRB activity-FeS formation-accelerated corrosion. The maximum pitting depth of the coupled P110 steel reached 7.7 μm, significantly greater than the 1.8 μm observed for uncoupled P110 steel in the biotic solution.
Efficiently reducing carbon dioxide (CO2) to high-value organic chemicals in microbial electrosynthesis (MES) systems hinges on the electrochemical performance of electrode materials. This study increased the efficiency of CO2 reduction to acetic and formic acids by creating a carbon felt (CF) cathode co-modified with nickel‑cobalt bimetallic oxide (NiCo2O4) and carbon nanotubes (CNT) coupled with an enriched mixed microbial community derived from anaerobic sludge. Compared to NiCo2O4/CF and CF cathodes, the CNT-NiCo2O4/CF cathode increased acetate yield by 1.3- and 2.3-fold, and formate yield by 1.1- and 2.4-fold, respectively. Within 8 days, the system achieved 742.98 mg/L acetate and 566.37 mg/L formate. Performance gains stem from: (1) the synergistic effect of CNT and NiCo2O4, which increased electrode surface area and electron transfer efficiency; (2) enhanced hydrophilicity, which improved microbe-electrode interactions; and (3) the presence of Co/Ni ions, which boosted CF conductivity and the selective enrichment of electroactive microbes (e.g., Sporomusa and Cupidesulfovibrio). This study provides an innovative strategy for developing high-performance MES electrode materials. Through the synergistic design of bimetallic oxides and nanocarbon materials, the conversion of CO2 to acetic acid and formic acid was achieved, offering a feasible technical pathway toward carbon neutrality.
Plasma l-citrulline is widely recognized as a clinically important biomarker, primarily serving as an indicator of intestinal function; it is used to assess and monitor the severity of intestinal failure and short bowel syndrome, as well as to diagnose congenital citrullinemia associated with urea-cycle disorders. However, its rapid and simple quantification remains challenging. To our knowledge, this is the first report of an amperometric biosensor for l-citrulline. In this work, the biosensor was developed based on mediated electron transfer (MET)-type bioelectrocatalysis of l-citrulline dehydrogenase (CitDH). The enzyme was immobilized on a mesoporous carbon electrode modified with graphene-coated porous silica spheres (G/PSS) and quinoline-5,8-dione (QD). A catalytic current for l-citrulline oxidation was obtained through QD-mediated electron transfer between immobilized CitDH and the electrode. The biosensor exhibited a linear amperometric response to l-citrulline concentrations ranging from 0.040 to 0.787 mM, with a sensitivity of 1.08 ± 0.17 μA cm-2 mM-1. Interference from l-arginine was minimal at low concentrations (approximately 0.1 mM), with a 3.7-fold higher sensitivity observed for l-citrulline within the linear response range. The sensor performance covers clinically relevant concentration ranges for hypercitrullinemia, demonstrating the feasibility of amperometric citrulline sensing. This study provides a new electrochemical platform for practical citrulline detection.
Enzyme-powered DNA walker suffers from limited loading capacity of substrate strand and incompatible recognition and enzymatic catalysis environments. To improve the sensitivity, AuNPs@Fe3O4 was employed as track interface to construct an enzyme-driven DNA walker, which features magnetic separation characteristic and high specific surface area. Upon recognition of kanamycin, a large amount enzymatic cleavage fragment presented in the supernatant after consecutive cleavage of substrate strand by activated walking strand. To further amplify the signal, these enzymatic cleavage products mediated an in-situ deposition of polyaniline (PANI) on the tetrahedral DNA nanostructure (TDNA) modified electrode enables a label-free detection of kanamycin. Owing to the introduction of magnetic separation, the background signal was substantially reduced compared with that obtained using DNA-AuNPs, resulting in approximately 2.5-fold enhancement in the signal-to-noise ratio (S/N). Under optimal experimental conditions, a good linear relationship was observed between the logarithmic concentration of kanamycin and the current signal difference in the range of 5-100 pM and the limit of detection was 1.1 pM. Furthermore, the practical performance of the proposed method had been well-demonstrated through real sample validation in spiked milk samples, with recoveries ranging from 92.0% to 102%, confirming its practical application capability.
Electrokinetics-assisted phytoremediation of Cd contamination is an effective method. This study conducted a hydroponic experiment to investigate the mechanism by which electric field enhances Cd extraction by hyperaccumulator. AC electric field induced a significant increase in biomass yield and Cd accumulation. Cd concentration in the xylem sap was clearly elevated by AC. Exposure to AC led to a remarkable increase in the proportions and content of Cd in shoot cell wall and soluble component fractions, and Cd distribution in root organelles and soluble component fractions. Furthermore, the level of IAA and ABA in plants was clearly increased by AC. AC application also induced a significant increase in the activities of POD, CAT, and APX in both shoots and roots. Quantitative analysis revealed that the relative expression levels of most genes encoding IRT, ZIP, NRAMP, HMA, MTs, and PCs proteins related to Cd transport and detoxification in S. alfredii were significantly upregulated by AC. Mantel analysis indicated a significant correlation between biomass yield and photosynthesis, phytohormone, nutrient uptake, as well as antioxidase activity. Mantel analysis and PLS-PM revealed that the upregulation of gene expression levels caused by AC stimuli plays a crucial and positive role in Cd enrichment in hyperaccumulator.
TC4 (Ti-6Al-4 V) titanium alloy resists seawater corrosion by forming a TiO2 passive film, yet its integrity is strongly affected by biofilm-induced interfacial heterogeneity. This work examined passive film modification under five conditions: sterile artificial seawater, Bacillus safensis, Pseudoalteromonas nigrifaciens, Chlorella marina, and a bacterial-algal symbiotic system. Electrochemical impedance spectroscopy, polarization curves, Mott-Schottky analysis, X-ray photoelectron spectroscopy, and cell quantification were combined to correlate biofilm features with semiconductor defects and corrosion performance. Bacterial and mixed biofilms developed extracellular polymeric substance (EPS) barriers that stabilized n-type TiO2 with oxygen-vacancy defects, raising electron escape and improving protection. P. nigrifaciens produced a compact, viscous EPS layer that yielded the best corrosion resistance, while B. safensis showed dynamic evolution from early protection to mid-stage defect increase and late partial self-repair. In contrast, the porous algal film of C. marina generated p-type defects, facilitating Cl- ingress and poorer resistance. The symbiotic system balanced these effects through concurrent O2 generation and EPS shielding. The overall corrosion-resistance order was P. nigrifaciens > ASW ≈ B. safensis > Symbiotic > C. marina. These findings reveal how biofilm structural properties mediates passive film semiconductor properties and suggest an EPS-based interfacial design to improve the durability of marine titanium components.
This study developed a novel molecularly imprinted electrochemical cell sensor for ultrasensitive detection of deoxynivalenol (DON). Using o-phenylenediamine as the functional monomer and Caspase-3 as the template molecule, a molecularly imprinted polymer film was synthesized on screen-printed electrodes via electropolymerization. After elution, the sensor was integrated into a three-electrode system. Upon DON exposure, Caspase-3 released from HepG2 cells specifically binds to the imprinted cavities, altering the current response of the electrochemical indicator [Fe(CN)₆]4-/3-. Using differential pulse voltammetry (DPV), the peak current showed a linear relationship with DON concentration from 0.2 to 100 pg/mL, with a detection limit of 0.193 pg/mL (R2 = 0.9977). This work provides a new method for rapid DON detection in food and expands the application of molecular imprinting in mycotoxin analysis.
Biorefineries offer a sustainable model that supports circular economy and nutrient recovery from waste feedstocks. Biorefineries were centered on microalgae for biomass and biofuel generation, but the concept has shifted toward inclusion of more versatile microorganisms to cope with diversity of waste substrates. Purple phototrophic bacteria (PPB) are particularly interesting, as they can treat wastewater while producing biomass, polyhydroxybutyrate (PHB), and carotenoids. Furthermore, PPB can utilize electrodes as extracellular electron donors, enhancing the synthesis of these products. Additionally, electrochemical moving bed reactors have been shown to improve PHB production by supporting electroactivity in planktonic cells. In this study, a photo microbial electrochemical moving bed reactor (photoME-MBR) was scaled up from 250 mL to 50 L, which constitutes the largest example for a bioelectrochemically-assisted PPB case study. The new configuration was operated under cathodic conditions to assess biomass, PHB, and carotenoid production; brewery wastewater treatment efficiency, and bioelectrochemical performance. Synthesis of value-added products at pilot scale was comparable to laboratory-scale productivity, while achieving organic pollutants removal at a rate of 136 gTOC/m3·d. Cathodic polarization significantly enhanced PHB production (100 mgPHB/gDryBiomass) by promoting extracellular electron uptake from the conductive bed. Microbial community analysis identified Rhodopseudomonas sp. and Bradyrhizobium sp. as dominant genera.
The present work reports the development of an electrochemical immunosensor using a metal-organic framework (MOF)/metallic nanocluster electrode surface for the detection of 25-hydroxy vitamin D3 (VitD3). The copper metal-coordinated organic porphyrin linker, 4,4,4,4-(Porphine-5, 10, 15, 20-tetrayl) tetrakis (benzoic acid) (Cu-TCPP) was prepared and utilized for the synthesis of Zirconium-based PCN-222(Cu) MOF, which was further conjugated to gold nanoclusters (AuNC). The fluorine-doped tin oxide (FTO) was sequentially modified with this nanoconjugate, p-phenylenediamine (PDA), bioreceptor antibodies (anti-VitD3), and blocking agent, 6-mercaptohexanol (MCH) to achieve the biosensor electrode, i.e., FTO/AuNC@PCN-222(Cu)/PDA/anti-VitD3/MCH. The electrode was used to detect VitD3 in a wide linear range, i.e., 1 to 108 fg/ml via electrochemical impedance spectroscopy. The detection limit and analytical sensitivity were found to be 0.088 fg/ml and 1.35 × 102 Ω/fgml-1 cm-2, respectively, with retained ∼91.9% of the actual response till 42 days in the presence of 103 fg/ml VitD3. The ultra-sensitivity of the biosensor in spiked human serum and real samples, was validated with the standard ELISA. Its outstanding selectivity and analytical performance open up new avenues for integrating AuNC@PCN-222(Cu)-based electrochemical sensors into miniaturized, cheaper, and real-time diagnostics.
This study aimed to investigate the synergistic effect of cold atmospheric plasma (CAP) and pulsed electric field (PEF) in inducing immunogenic cell death (ICD) in triple-negative breast cancer (TNBC) cells. CAP and PEF devices were self-developed. MDA-MB-231 cell line was used and divided into five groups: Control, CAP, PEF, CAP before PEF, and PEF before CAP. Optical emission spectroscopy confirmed that CAP produced reactive species such as He, OH, N₂ and O, and infrared thermal imaging showed that the maximum temperature during the treatment did not exceed 28.3 °C. CAP could significantly increase the content of H₂O₂, NO₂- and NO₃- in PBS. Scavenger experiments showed that the cytotoxicity of CAP was completely reversed by Catalase and N-Acetylcysteine (NAC), while that of PEF was only reversed by NAC. Furthermore, CAP before PEF treatment had the strongest killing and pro-apoptotic effects on TNBC cells, and the increase in ICD markers was the most significant. Mechanically, pre-treatment with CAP allowing PEF to cause more extensive membrane disintegration. CAP before PEF treatment also triggered the most intense mitochondrial oxidative stress, leading to a significant rise in intracellular reactive oxygen species (ROS) levels.
Cardiac troponin I (cTnI) is the primary disease marker for acute myocardial infarction (AMI). In this study, we successfully constructed an electrochemical immunosensor based on diazotization reaction to achieve ultrasensitive detection of cTnI. Taking their structural advantages, gold nanostars (Au NSs) were introduced to combine more capture antibodies. Through diazotization reaction, graphene aerogels (GAs) successfully captured thionine (Thi) molecules obtaining GAs-Thi. Specifically, the three-dimensional porous network structure of GAs was utilized to capture more Thi molecules and the chemical bond effect ensures a stable signal output. Meanwhile, the structural advantages of GAs also contribute to the anchoring of detection antibodies. Under the specific recognition effect of antigens and antibodies, a sandwich-like biosensor was successfully constructed, which showed a wide detection range (1 × 10-4 - 100 ng mL-1) and a low detection limit (27.2 fg mL-1). Given the stable signal output, the signal reproducibility of sensors from different batches was excellent with a relative standard deviation (RSD) of only 1.07%. Even more surprisingly, the sensor's signal response remained at 90.35% of the initial value after 3 weeks. Finally, the biosensor demonstrated good accuracy in human serum samples, conforming its high potential for biomedical applications.
Heavy metal contamination is persistent due to non-biodegradability and toxicity. Here, a hierarchical MXene/NiCo2O4/PANI-modified carbon felt anode was developed to enhance extracellular electron transfer (EET) and thereby improve cathodic Cu2+ removal in microbial fuel cells (MFCs). The engineered anode reduced interfacial charge-transfer resistance, promoted electroactive biofilm formation, and reshaped the microbial community toward exoelectrogenic taxa (e.g., Geobacteraceae), leading to a markedly improved power output (Pmax = 2.47 ± 0.08 W m-2). In the cathode chamber, rapid Cu2+ remediation was achieved (99.2 ± 0.1% within 15 h at 30 mg L-1), following a dual-pathway process involving initial interfacial capture and subsequent electroreduction to insoluble Cu0/Cu2O. Moreover, stable Cu2+ removal under intermittent operation was enabled by the pseudocapacitive charge-buffering behavior of the NiCo2O4/PANI framework. This work clarifies how anodic interfacial engineering governs cathodic metal reduction and provides a scalable strategy for coupling metal remediation with energy recovery.
This study details the development of a highly sensitive electrochemical lateral flow assay (ELFA) for the detection of SARS-CoV-2 immunoglobulin G (IgG). The assay utilizes novel polyethylene glycol (PEG)-coated Fe₃O₄ nanoparticles decorated with gold (Fe₃O₄@PEG@Au) as electrochemical labels, integrated with custom-fabricated screen-printed electrodes (c-SPEs). The Fe₃O₄@PEG@Au nanoplatforms were synthesized hydrothermally and thoroughly characterized using techniques including Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), and Dynamic Light Scattering (DLS), confirming their successful formation and ferrocene carboxylic acid (Fc) conjugation. The optimized ELFA demonstrated sensitive and reliable IgG detection in buffer, with optimal performance achieved using sodium tetraborate. Crucially, the assay exhibited robust detection capabilities in complex human serum, particularly in diluted samples where matrix effects were minimized. Performance comparison with both commercial rapid lateral flow assays and the gold-standard ELISA method showed comparable results in human serum. This research establishes the significant promise of Fe₃O₄@PEG@Au nanoplatforms within electrochemical LFAs, offering a path toward rapid, sensitive, and robust point-of-care SARS-CoV-2 IgG diagnostics.
Alzheimer's disease (AD) is the leading cause of dementia, and early identification of molecular biomarkers in blood offers a promising avenue for diagnosis and monitoring treatment. Tau-441 stands out as a particularly promising biomarker among the potential molecular targets. This research describes the development of a highly sensitive and cost-effective biomimetic sensor, capable of selectively detecting Tau-441 at femtomolar concentrations. This is achieved through the synergistic combination of gold nanoparticles (AuNPs) with molecularly imprinted polymer (MIP) technology. The MIP layer was sensitised by electropolymerising phenylenediamine (o-PDA) in the presence of Tau-441 and AuNPs onto a gold screen-printed electrode (Au-SPE) using cyclic voltammetry (CV). After polymerisation, the entrapped proteins were removed by proteolytic digestion, generating well-defined imprinted cavities within the polymer matrix. Scanning electron microscopy (SEM) and Raman analysis were conducted to monitor the surface modification of the Au-SPE working electrode. The device displayed linear responses to Tau-441 protein within the range 2.0 pg mL-1 to 200 ng mL-1, with a limit of detection of 1.51 fg mL-1. The analytical performance of the device was validated in complex matrices, including Cormay serum and cell media from primary cultures of hippocampal neurons, using a competitive assay. The platform showed high sensitivity, good reproducibility, and reliable performance in biologically relevant media, demonstrating strong robustness. Its excellent analytical characteristics, together with the potential for integration into portable electrochemical devices, make this sensor a promising tool for rapid and accurate point-of-care testing, enhancing the detection and monitoring of AD.
Seasonal temperature fluctuations in buried thermal pipelines strongly affect microbial growth and associated corrosion. This study examines the influence of temperature and carbon source concentration on Q235B steel corrosion induced by Desulfovibrio ferrophilus. Results demonstrate that D. ferrophilus remains metabolically active even at 85 °C, indicating high thermal adaptability. Corrosion current densities increased with temperature and carbon availability, reaching 5.44 μA·cm-2 at 85 °C under high lactate. Surface analyses (SEM and CLSM) reveal pitting corrosion driven primarily by microbial adhesion, which is enhanced at elevated carbon levels. Electrochemical studies indicate that at 37 °C, carbon concentration significantly affects both anodic and cathodic reactions, reflecting extracellular electron transfer (EET) activity. Corrosion products are dominated by pyrite (FeS), with content modulated by temperature and carbon supply. Overall, high temperature and microbial activity synergistically accelerate Q235B steel corrosion, while localized corrosion is closely linked to microbial biofilms and EET processes. These findings elucidate the mechanistic role of temperature and nutrient availability in microbiologically influenced corrosion of thermal pipeline steel under realistic operational conditions.
This study investigated the microbiologically influenced corrosion (MIC) of Al-Zn-In-Cd sacrificial anode in the simulated marine tidal environment, elucidating the corrosion mechanism arising from the interaction between microorganisms and dynamic marine tide. Results revealed significant spatial variations in corrosion distribution, with the fully immersed zone (FIZ) exhibiting the most severe corrosion. Metabolic activity of Pseudomonas sp. enhanced anodic dissolution, markedly increasing the corrosion rate and raising the corrosion current density (icorr) by an order of magnitude. Furthermore, it altered the composition of corrosion products, forming loose and porous iron-rich products that compromised the protective qualities of corrosion products. Periodic wet-dry cycles further destabilized the corrosion products and accelerated pitting. These findings offer insights that inform the optimization of material design and improve the service life of Al-Zn-In-Cd sacrificial anodes in marine tidal environments.
Microbiologically influenced corrosion (MIC) of carbon steel by sulfate-reducing bacteria (SRB) is a major challenge in oil and gas systems, particularly because of its strong tendency to cause localized attack. Cementite is a common conductive microstructural phase in carbon steels, yet its role in SRB-induced MIC has not been well clarified. In this work, pure iron, 10# steel, and 45# steel with different cementite contents were investigated in sterile and SRB-containing media using surface characterization, corrosion product analysis, pitting quantification, and electrochemical measurements. The results showed that increasing cementite content was associated with more severe localized corrosion, as evidenced by the increased maximum pit depth and broader pit size distribution, while the average corrosion rate did not exhibit a clear monotonic trend. Etched specimens with greater cementite exposure showed further aggravation of pitting, indicating that exposed cementite plays an important role in the corrosion process. Electrochemical results and surface observations suggest that conductive cementite facilitates interfacial electron transfer between sessile SRB and the steel substrate, thereby promoting localized MIC. These findings provide evidence that steel microstructure, especially cementite-containing phases, is an important factor governing SRB-induced pitting and should be considered in the microstructural design of MIC-resistant carbon steels.
Glucose, an essential biomolecule and a widely used clinical drug, plays a pivotal role in biological processes and disease treatment. Herein, a binary intelligent hydrogel system (PNIPAM-GOD/Co-MoS2) was constructed by integrating cobalt-doped MoS2 (Co-MoS2) nanomaterials and poly(N-isopropylacrylamide) embedded with glucose oxidase (PNIPAM-GOD). Co-MoS2, synthesized using a straightforward hydrothermal method, was modified on a glassy carbon electrode (GCE) as the catalytic inner layer to address the poor conductivity of PNIPAM. PNIPAM-GOD hydrogel was then drop-coated as the outer layer for glucose recognition and stimulus-responsive signal switching. Under optimal conditions, the PNIPAM-GOD/Co-MoS2/GCE demonstrated excellent glucose detection performance with a linear range of 9.0-54.0 mM (R2 = 0.9941) and favorable applicability in real samples. Moreover, using 1,1'-ferrocene dicarboxylic acid (FDA) as an electroactive enzyme mediator, the biosensor displayed reversible electrochemical switching behaviors triggered by temperature, salt, and glucose-mechanisms of which were systematically investigated. Combining these switching properties with the outstanding catalytic activity of Co-MoS2, a series of logic devices were constructed, including a binary 4-input/5-output logic gate network, a 2-to-4 decoder, and a 2-to-1 encoder. These logic gate systems further enhance the complexity of non-conventional computing systems based on biological/pharmaceutical molecules, providing new insights for the development of intelligent biosensors.
Light-driven biohybrid systems that couple semiconductor nanocrystals with enzymes offer a promising strategy for solar-to-chemical energy-conserving reduction reactions, yet are often limited by inefficient hole scavenging. Hole scavenging is critical for maintaining charge separation in the light-absorbing electron donor molecule and, thus, for sustaining catalytic turnover, making quantification essential to improving system efficiency. Here, we introduce a photoelectrochemical approach for real-time monitoring of hole scavenging in cadmium sulfide (CdS) quantum dot (QD)‑nitrogenase MoFe protein biohybrids that catalyze the reduction of H+ and N2. Using hydroquinone (HQ) as the sacrificial electron donor (SED), oxidation of HQ to benzoquinone (BQ) by photogenerated valence-band holes is coupled to the electrochemical reduction of BQ at an electrode, enabling quantification of the hole-scavenging reaction via chronoamperometry. This approach provides a continuous, real-time readout of charge-transfer dynamics under illumination. Systematic variation of light intensity and donor concentration reveals that hole scavenging scales with photon flux and exhibits a non-linear dependence on SED concentration, with an optimum at intermediate HQ concentrations. These results establish chronoamperometry as a powerful tool for probing photoinduced charge transfer, advancing the quantitative understanding of hole-scavenging in biohybrid systems, and offering a generalizable framework for optimizing solar-driven biocatalysis.
Directly connected to an electrode, high potential MCOs catalyse the oxygen reduction reaction (ORR) at low overpotential with high efficiency. MCOs contain two redox centers, a near surface-located mononuclear copper (T1) oxidising a substrate and a buried trinuclear copper center (TNC) reducing dioxygen to water. Which of the two copper centers is directly wired to the electrode during the bioelectrocatalytic reduction of dioxygen is a challenging question to address. Beyond potentially improving the direct electron transfer process, the rational orientation of a high potential MCO should allow to bypass the rate-limiting internal electron transfer from T1 to TNC and enhance the ORR efficiency. Variants of a high potential fungal laccase (LAC3) isolated from Trametes sp. C30 were designed to target two opposite orientations in which the T1 copper center is either as close (T1-orientation) or as far (anti-T1 orientation) as possible from the MWCNT electrode. Analysis of the electrochemical response of these variants under different conditions allow to conclude: (1) the T1 center is the first electron acceptor in randomly adsorbed enzymes, (2) pyrene-enzyme hybrids allow for a selective wiring of T1 and TNC sites to MWCNTs and (3) anti-T1 oriented hybrids are three-fold more efficient for ORR.
