This study investigates the effect of riboflavin on microbiologically influenced corrosion (MIC) of 304 stainless steel induced by Rhodopseudomonas palustris TIE-1. Riboflavin accelerated the MIC process, deepening and expanding corrosion pits. Electrochemical results showed a significant increase in corrosion rate, especially with the addition of 40 ppm riboflavin. X-ray photoelectron spectroscopy (XPS) analysis demonstrated that the passive film underwent a compositional transformation from FeO/FeO/CrO to FeOOH/Cr(OH), accompanied by oxidative conversion of CrO to CrO mediated by riboflavin-facilitated extracellular electron uptake (EEU). High performance liquid chromatography (HPLC) results confirmed riboflavin degradation into lumichrome, which accelerated extracellular electron transfer (EET). Scanning electrochemical microscopy (SECM) analysis demonstrated that lumichrome's redox cycling enhanced EEU efficacy, resulting in the degradation of passive film.

Human epidermal growth factor receptor 2 (HER2) status is an important factor in evaluating the prognosis of breast cancer patients. Therefore, it is particularly important to develop a simple and sensitive method for the detection of HER2-positive breast cancer. Here, an ultra-sensitive electrochemical biosensor for detecting HER2-specific proteins was assembled using gold nanoparticles and Two-dimensional carbides (AuNPs-TiCTx) as a conducting substrate. The prepared AuNPs-TiCTx not only has good electrical conductivity and strong electrochemical signal output, but also provides a large number of active sites for the AuS bonds assembly aptamer. In addition, the antibodies-modified functionalized graphene oxide (GO) as a carrier platform, which provides an additional boost for the detection of trace targets with high sensitivity under optimal conditions. Afterwards,HER2 protein was detected by signal amplification effect of AuNPs-TiCTx and functionalized GO combined with Electron transfer activated regeneration catalyst atomic transfer radical polymerization (ARGET ATRP). In the range of 1 to 10 ng·mL, there was a good linear relationship between the HER2 concentration and the signal intensity, with a limit of detection of 0.19 pg·mL. Moreover, this method has good selectivity and stability, and then still maintains good detection performance and strong anti-interference ability in the complex environment of normal human serum, which is expected to be applied in clinical application.

When a redox enzyme is wired to an electrode under conditions of direct electron transfer (DET), its activity can be simply detected as a current. This approach has been reviewed extensively, but here we address a gap in the literature by discussing the initial qualitative interpretation and assessment of catalytic DET electrochemical data. Topics addressed here include electroactive coverage, turnover frequencies, mass transport limitations, film loss, redox-driven (in)activation, signal corrections, distinction between steady-state and transient responses, and identification of non-ideal behaviors. Based on our group's expertise, we provide explanations, general advice, and prescriptive guidance to help readers understand experimental issues.

Direct electron transfer (DET)-type bioelectrocatalysis, a coupled enzymatic and electrode reaction without redox mediators, provides insights into enzyme properties that facilitate the construction of efficient biomimetic devices. Because many DET-type multimeric dehydrogenases are membrane-bound proteins, obtaining the overall steric structures of these enzymes using conventional X-ray crystallography has proved difficult for many decades. Novel cryo-electron microscopy (cryo-EM) and single-particle image analysis have recently been developed that enable elucidation of the overall structure of membrane-bound DET-type multimeric dehydrogenases. In particular, "structural bioelectrochemistry," a fusion of structural biology and bioelectrochemistry, has enabled rapid hypothesis testing via the analysis of three-dimensional (3D) structures using enzyme engineering and electrochemistry. This review outlines critical related studies in the last decade and the epoch-making breakthroughs leading to next-generation applications.

The effects of electroporation are highly influenced by the shape of the applied waveform. This waveform shape can modify the transmitted energy and current flow patterns, impacting the electric field distribution, temperature rise among others. These interactions, along with their synergies with electroporation, are being explored across various industrial and research domains. For instance, in the biomedical field, high-frequency waveforms such as nanosecond pulses offer distinct advantages, while in the food industry, controlled temperature increases combined with electroporation are beneficial. However, in the medical field, the effects of combining high-frequency waveforms (in the MHz range) with low-frequency waveforms (in the kHz range commonly used in clinical electroporation) have not been thoroughly studied, though hypotheses have been proposed regarding their potential effects. In this paper, proof of concept of the effect of the combination of two harmonics is presented using three different strategies to investigate new electroporation protocols. To support this study, a specialized electrical and thermal test bench was developed to control and evaluate the feasibility and potential of possible synergy between high- and low-frequency waveforms to electroporation using an in vitro model.

Cardiovascular disease (CVD) remains a significant worldwide health challenge, with mortality rates rising rapidly. Low-density lipoprotein (LDL) is a crucial serum biomarker for the early diagnosis of CVD, which can significantly improve outcomes and reduce mortality. Herein, a label-free electrochemical aptasensor for rapid detection of LDL was developed based on the titanium carbide-carboxymethyl chitosan-hemin (MXene-CMCS-Hemin) nanocomposites as the electrochemical signal probe. Firstly, gold nanoparticles (Au NPs) were electrodeposited onto a screen-printed carbon electrode (SPCE) to form a conductive substrate. Subsequently, the MXene-CMCS-Hemin nanocomposites were anchored onto the Au NPs/SPCE surface. Then LDL was immobilized on the surface of MXene-CMCS-Hemin/Au NPs/SPCE to construct the electrochemical aptasensor. When LDL specifically bound with the LDL to form LDL-LDL complexes, hindering the electron transfer and reducing the Hemin oxidation current, LDL detection can be achieved via differential pulse voltammetry (DPV). Under optimal circumstances, the changes of Hemin's oxidation current showed a good linear response with LDL concentration in the range of 0.1-4.0 μmol/L with a detection limit of 0.095 μmol/L (S/N = 3). The aptasensor demonstrated good performance with the relative errors of 0.60 % to 6.58 % for the direct detection of LDL in human serum samples, which offers a novel tool for the clinical diagnosis of CVD.

Here we investigate how formaldehyde (HCHO), a known strong inhibitor of [FeFe]‑hydrogenases and a mild inhibitor of [NiFe]‑hydrogenases, may exert more complex effects on this group of metalloenzymes, which reversibly catalyze the 2H/H₂ reaction. We investigated the [NiFe]‑hydrogenase Hyd-2 from E. coli using protein film electrochemistry, a technique that enables the measurement of enzyme activity when the enzyme is adequately adsorbed on the electrode. The effect of HCHO on the electrocatalytic performance of Hyd-2 is highly dependent on the buffer pH and the direction of catalysis. During H₂ production, HCHO consistently acts as an inhibitor of Hyd-2. However, this effect is reversed in acidic pH values, where HCHO can mildly enhance the electrocatalytic H₂ oxidation by Hyd-2. FTIR investigations did not detect any new redox intermediate resulting from the inhibition or activation. Therefore, we propose that HCHO - a natural electrophile that can readily react with nucleophiles and proton acceptors - may facilitate the transfer protons during the rapid transformation of different redox species participating in the catalytic cycle of [NiFe]‑hydrogenases.

This study introduces an innovative electrochemiluminescence (ECL) biosensor for the highly sensitive and specific detection of Argonaute 2 (Ago2) activity. Ago2, a key enzyme in the RNA interference (RNAi) pathway, plays a crucial role in gene regulation, and its dysregulation is associated with diseases such as cancer and viral infections. The biosensor integrates hybridization chain reaction (HCR) amplification and the CRISPR/Cas12a system, leveraging a multi-stage signal amplification strategy. The detection mechanism begins with Ago2-mediated cleavage of a designed hairpin RNA (HP-RNA), releasing single-stranded RNA (ssRNA) that triggers HCR. This amplification step generates long DNA polymers, which serve as activators for the CRISPR/Cas12a system. Cas12a's collateral cleavage activity amplifies the signal further by cleaving a DNA reporter labeled with a ruthenium-based luminophore, enhancing the ECL output. This dual amplification strategy achieves exceptional sensitivity, with a detection limit of 0.126 aM. The biosensor demonstrates excellent specificity, distinguishing Ago2 from other Argonaute proteins, and maintains high reproducibility and stability, retaining 94 % of its signal after two weeks of storage. Real-world applicability was confirmed by accurately detecting Ago2 in spiked cell lysates, with recovery rates exceeding 100 %. The combination of HCR, CRISPR/Cas12a, and ECL establishes a robust platform for biomarker detection, offering superior sensitivity and adaptability for clinical diagnostics, disease monitoring, and therapeutic evaluation. This biosensor represents a significant advancement in the development of next-generation diagnostic tools.

The most energetic light-induced charge-separation step in nature is driven by photosystem I (PSI), making this photosynthetic protein an attractive candidate for the development of semi-artificial energy conversion devices. Despite significant progress in semiconductor-free bio-photocathodes, the highest photocurrent density was only 322 ± 19 μA cm, achieved by integrating PSI within a pH-dependent poly(vinyl)imidazole Os(bispyridine)Cl redox polymer (T Kothe et al., Chem. Eur. J., 2014, 20, 11029). This study presents a more efficient PSI-based bio-photocathode by incorporating single-walled carbon nanotubes (SWCNTs) into the redox hydrogel composed of the same Osmium-containing redox polymer. The nanostructured redox hydrogel film with SWCNTs serving as electric scaffolds significantly improves the stability, loading amount, and heterogeneous electron transfer rate, resulting in a substantial increase in photocurrent density exceeding 2 mA cm, the highest achieved in a semiconductor-free PSI based photocathode to date. Bioelectrodes constructed by pre-depositing SWCNTs on the electrode surface via covalent bonds outperform those formed by co-immobilizing SWCNTs with the redox hydrogel. The dependence of photocurrent on light intensity and the photocurrent spectrum action demonstrate that the photocurrent unequivocally arises from PSI charge separation. This research lays a promising foundation for the development of semi-artificial photoelectrochemical devices for light-to-energy conversion.

This study explores the combination of jasplakinolide with electroporation (JSP + EP), a method enhancing targeted molecule delivery. CHO-K1 (Chinese hamster ovarian), C2C12 (mouse myoblast), and RD (rhabdomyosarcoma) cells were treated with jasplakinolide (50 nM) in HEPES buffer and exposed to electrical pulses (0.8-1.2 kV/cm). Cell viability was measured via the MTS assay, cytoskeleton structure was assessed with confocal microscopy, and docking studies examined jasplakinolide-actin interactions. The combination of jasplakinolide and electric pulses synergistically affected RMS cells (Rhabdomyosarcoma), causing significant cytoskeletal changes and reduced viability. Docking studies revealed that jasplakinolide interacts with both monomeric and filamentous actin, highlighting a dual mechanism. Confocal imaging showed substantial actin cytoskeleton disruption in cancer cells, with minimal effects on normal cells. Jasplakinolide combined with electric pulses can specifically target cancer cells with less cytotoxicity to normal cells, potentially reducing side effects following the clinical procedure.

Thalassospira species are ubiquitous marine bacteria with poorly understood ecology, and some have been implicated in iron corrosion. To better elucidate the mechanisms and ecological implications of extracellular electron transfer (EET) in oxidative processes, we conducted genomic and bioelectrochemical characterization of Thalassospira xiamenensis strain SN3, an obligate heterotroph isolated from coastal marine sediment cathode-oxidizing enrichments. Physiologic and genomic analyses indicate that SN3 lacks the capacity for lithoautotrophic growth and lacks homologs to genes canonically involved in EET. Bioelectrochemical characterization of SN3 cells shows that inward EET requires a terminal electron acceptor (respiration). Deletion of nitrate reductase catalytic subunit napA abolished current consumption and catalytic activity under nitrate-reducing conditions. Media exchange experiments demonstrate that inward EET in SN3 is facilitated by direct contact with the electrode, with a formal midpoint potential of -153 ± 16 mV vs. SHE. Through deletion of the formate dehydrogenase fdhABCD and electrochemical characterization of mutant cells, we show that inward EET is not a function of Fdh enzyme sorption to the electrode, as has been demonstrated for other organisms. This provides further evidence of a cell-mediated and contact-dependent EET mechanism. This work provides a foundation for investigating this metabolically versatile organism's yet uncharacterized mechanism of EET.

The detection of miRNAs serving as key biomarkers in cancer diagnostics is challenging due to their small size, low abundance, and high sequence similarity, which complicates their sensitive and selective detection. Here, we report a biosensor that combines molecularly imprinted polymers (MIPs) with peptide nucleic acids (PNAs) to achieve a sensitive and highly selective miRNA detection in RNA isolates of cancer cells. MIPs were synthesized by electropolymerization utilizing PNA-supported and pre-oriented miR-21 templates molecules, which serve as both a linker for improved template orientation and an assistive recognition element for miRNA binding. Electrochemical impedance spectroscopy (EIS) was used to detect miR-21 after optimization of the sensor architecture and the experimental parameters. The sensor exhibited excellent sensitivity and selectivity toward miR-21 even when compared to the single mismatched sequence, with a linear response of 0.5-5000 pM and a limit of detection (LoD) of 0.11 ± 0.04 pM without any amplification steps. The sensor was used to quantify miR-21 in artificial serum and in RNA isolates of cancer cells to discriminate between MCF-7 and Hela cells. This approach opens new avenues for the application of MIPs as synthetic antibodies in miRNA research and emphasizes the importance of the synergistic integration of PNA.

The integration of aptamer chemistry with innovative functional materials such as nanozymes offers new opportunities for the development of the superior electrochemical biosensors. Herein, we introduce a rod-like nanocomposite of Ce-MOF-808@CeO bearing intense nanozymatic activity that prepared through in-situ partial oxidation of Ce-MOF-808 to CeO. Then, the aptamer for tetracycline (TC-Apt) with 5'-PO end was anchored on Ce-MOF-808@CeO modified screen-printed electrode, thereby assembling a label-free electrochemical aptasensor. Electrochemical and spectroscopic assays reveal that the derived CeO can effectively promote the nanozyme activity of Ce-MOF-808 as a cocatalyst. Electrochemical biosensing shows that, the capture of tetracycline (TC) to the electrode surface by the aptamer chemistry significantly inhibits the catalytic activity of Ce-MOF-808@CeO. Thus, TC can be analyzed by monitoring the catalytic signal of the biosensor to HO. Leveraging the exceptional catalytic activity of Ce-MOF-808@CeO, coupled with the high specificity of the aptamer, TC can be analyzed in a wide kinetic range from 1 pM to 100 nM, with a low detection limit of 0.21 pM. The aptasensor is also applicable for the accurate detection of TC residues in fresh shrimp samples, showcasing its potential for practical applications in the monitoring of food safety.

Herein, we report on the development of a phthalocynaine based metal organic frameworks (MOF) for the detection of human epidermal growth factor receptor 2 (HER2). Phthalocyanines (Pcs) exhibit good redox properties, hence their utilization as precursors for the synthesis of Pc based MOFs. The successful preparation of the MOF was confirmed using X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and Brunner Emmet Teller (BET) analysis. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were utilized for electrochemical characterization of the Co octacarboxy Pc (CoOCPc), and Co-CoOCPc-MOF modified glassy carbon electrode (GCE). Differential pulse votammetry was employed for detection of HER2, which is a biomarker for cancer. The selectivity towards HER2 biomarker was accomplished by attaching an aptamer (Apt) onto the MOF modified glassy carbon surface. The GCE/Co-CoOCPc-MOF/Nf/Apt (Nf = Nafion) showed excellent analytical parameters with lowest limit of detection of 5.4 × 10 ng/mL, good repeatability and stability.

The development of highly sensitive methods for detecting infectious diseases is crucial for preventing disease spread. In this study, a novel sensing platform for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pathogens was developed by combining a magnetic metal-organic framework (FeO@MIL-100) with graphene field-effect transistors (GFET). The FeO@MIL-100 magnetic MOF was functionalized with SARS-CoV-2-specific antibodies, enabling highly selective pathogen capture in a phosphate-buffered solution. Following magnetic separation, the captured pathogens were detected using GFETs, with a linear detection range of 1 ag/mL to 10 ng/mL and a detection limit as low as 8.60 ag/mL. Furthermore, the platform has been successfully applied to human serum samples, highlighting its remarkable potential for practical application.

Microbial Electrochemical Fluidized Reactors (ME-FBR) changed the paradigm for growing electroactive bacteria from a biofilm strategy to a planktonic mode, while still performing direct extracellular electron transfer from oxidative metabolism in absence of redox mediators. Glassy carbon was the material selected for growing planktonic Geobacter sulfurreducens in ME-FBR. However, the material was unable to retain cells so applications implying continuous operation have been compromised. In this context, a tailor-made chemical strategy was followed considering the large amount of cytochromes C present on the outermost membrane of bacteria form of the Geobacter genus. In this work, a commercial glassy carbon (GC) was chemically modified with surface oxygen groups (SOGs) mainly carboxylic type with high affinity for heme group of cytochrome C. The functionalized material did conserve the structural and textural features and i) promoted the biofilm formation of Geobacter using acetate as sole carbon and electron donor source, and ii) increased the current density and acetate removal rate in comparison with pristine carbon. Thus, the new material enriched in carboxylic-type SOGs facilitates a-la-carte anchorage of electroactive bacteria to move on from a planktonic-based to a biofilm-based strategy, so ME-FBR operation could be expanded from batch to continuous mode, while electrical current was still possible.

Analyzing uracil-DNA glycosylase (UDG) activity is essential for understanding DNA repair mechanisms in disease progression and treatment. This study presents a dual-mode DNA nano-stage biosensing platform integrating electrochemiluminescence (ECL) and electrochemical impedance spectroscopy (EIS) for highly sensitive and specific UDG detection. A DNA-prism-modified electrode immobilizes UDG-responsive elements, forming a stable and efficient detection interface. Upon UDG cleavage, released DNA fragments initiate rapid nano-stage assembly, significantly amplifying the signal output. ECL signals are produced by embedded [Ru(phen)] complexes, while EIS signals result from the reaction of 3,3'-diaminobenzidine (DAB) with HO, catalyzed by manganese tetrakis(4-N-methylpyridyl)porphyrin (MnTMPyP). The platform achieves an exceptional detection limit of 1.0 × 10 U/mL, effectively validating the inhibitory effects of UDG inhibitors. Furthermore, a strong correlation between UDG activity and HeLa cell number is demonstrated. Compared to a commercial UDG detection kit, the biosensor exhibits comparable sensitivity with enhanced versatility. Notably, UDG activity is significantly higher in cancerous cells than in normal cells, reflecting the increased DNA repair demand in malignancy. This capability to distinguish UDG activity among different cell types highlights its potential for cancer diagnostics, while this biosensor platform shows promise for broader applications in clinical diagnostics, cancer research, and drug discovery.

This study demonstrates the straightforward application of scanning electrochemical microscopy (SECM) for characterizing pneumolysin-induced pores in tethered bilayer lipid membranes (tBLMs). Carbon-based nanoelectrodes with a tip radius of approximately 20 nm produced distinct feedback responses during approach curves to the sample. A positive feedback response was observed when approaching the self-assembled monolayer, while the few nanometers thick tBLMs exhibited characteristics of insulating layers, yielding a negative feedback response. Based on the computational calculations, the reconstitution of functional pneumolysin was further confirmed through electrochemical impedance spectroscopy, with a concentration of 5 nM pneumolysin resulting in an average pore density of 0.64 μm. Finally, we demonstrated the practical utility of SECM for visualizing pneumolysin pores within the tBLM system. These experiments highlight the versatility and cost-effectiveness of electrochemical techniques for investigating membrane integrity, toxin activity, and biomolecular interactions at the nanoscale.

The development of implantable glucose sensors is of significant interest in the management of diabetes. This work focuses on developing an implantable, biocompatible nanoporous gold electrode prototype based on Kapton® for the subcutaneous detection of glucose. The electrodes were first modified with a layer containing glucose oxidase and Os(2,2'-bipyridine)Cl·PVI (Os(bpy)Cl PVI). An additional polymeric layer containing poly(2-methacryloyloxyethyl phosphorylcholine-co-glycidyl methacrylate) was then added to reduce biofouling and foreign body reaction effects. The modified electrode had a V of 211 ± 13 μA cm and a K of 6.1 ± 0.8 mM in pseudo physiological conditions, with a linear detection range from 1 to 4 mM and a sensitivity of 28.6 ± 2.1 μA cm mM. In artificial plasma, the response of the sensor was saturated at 3 mM, with a V of 113 ± 10 μA cm and a K of 2.1 ± 0.4 mM with a linear detection range from 1 to 2.5 mM and a sensitivity of 14.6 ± 3.3 μA cm mM. Mechanical stress testing demonstrated that there was a 40 % reduction of the redox polymer coverage after 320 deformation events, however the catalytic activity was still detectable after 160 events. Minimal cytotoxicity effects of the electrodes were observed. When subcutaneously implanted the electrodes showed fairly good mechanical stability after one week and detachment of the metallic layer on some electrodes after 21 days, probably due to electrode bending. A limited foreign body reaction was observed. These results indicated that the electrodes could be implanted for a period of up to 1 week.

This study presents a novel, label-free electrochemical immunosensor for the detection of vascular endothelial growth factor (VEGF), a crucial tumor biomarker. The immunosensor was developed by electrochemical deposition of gold nanoparticles-reduced graphene oxide (AuNPs-rGO) nanocomposite on glassy carbon (GC) and screen-printed carbon (SPC) electrodes. A specific monoclonal antibody against VEGF was immobilized on the electrode surface through a carbodiimide coupling reaction. Field Emission Scanning Electron Microscopy (FE-SEM), X-ray Diffraction (XRD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) have been used to characterize the developed immunosensor. For quantitative measurement of VEGF, fast Fourier transformation admittance voltammetry was employed by applying a special potential waveform on the immunosensor and sampling the currents. The response was determined by measuring changes in the electrode admittance caused by the adsorption of VEGF molecules, without the use of a redox probe. Under optimal conditions, the immunosensor responses were within a linear detection range for VEGF from 0.1 to 10,000 pg/ml and from 10 to 10,000 pg/ml, with notably low detection limits of 29.1 fg/ml and 352 fg/ml for the modified GC and SPC electrodes, respectively. The sensor exhibits minimal interference from common serum proteins, making it a promising candidate for sensitive, low-cost commercialization.