Potential adoption of electrochemical biosensors for cancer DNA biomarker detection in liquid biopsies: A systematic review.

Fungal flavin-dependent glucose dehydrogenase (FAD-GDH) is now widely preferred as an O2-insensitive alternative to glucose oxidase for 2nd generation blood glucose test strips. FAD-GDH bioelectrodes have potential for continuous glucose monitoring (CGM), but continue to be hampered by poor operational stability, restricted mediator compatibility, and selectivity limitations. Herein, we report new protective biosensor coatings based on covalently photocrosslinked polysaccharides for more robust CGM with FAD-GDH bioelectrodes. The crosslinked hydrogel membranes were prepared from dextran methacrylate (Dex-MA) polymers synthesised with different degrees of substitution (DS = 9%, 18%, and 37%). The polymers were dip-coated then crosslinked via a photoinitiator using a rapid visible light process (λ = 405 nm; 1 min). This study highlights the crucial impact of the polymer DS on redox mediator electroactivity, O2 reactivity, catalytic glucose activity, storage stability and operational stability. A higher polymer DS provided improved mediator stabilisation and up to a 4-fold increase in 1-week storage stability. A high DS of 37% also significantly increased CGM stability and permitted attractive sensor analytics in artificial interstitial fluid (ISF). The three sensors prepared with a DS of 9% to 37% provided practical linear ranges and detection limits for CGM. A CGM lifetime of 54 h was achieved in a complex artificial ISF comprising electroactive interferences, compared to only 16 h for an equivalent biosensor without hydrogel protection. Photocrosslinked polysaccharide hydrogel membranes hold promise for extending bioelectrocatalytic outputs for future biosensors and eventually biofuel cells and bioreactors.

Enabling the nonphotosynthetic bacterium Moorella thermoacetica (M. thermoacetica) to form a photosynthetic biohybrid system could transform carbon dioxide (CO2) into value-added products. However, to ensure an efficient, mechanistic electron-transfer pathway to microbial catalysts, a pivotal nanoplatform that involves multicomponent composite systems for photoexcited electron transfer from the photosensitizer to the bacteria, as well as for enhancing light-harvesting capabilities and efficient electron/hole separation, is crucial. Here, we design panchromatic ternary polymer dots (Pdots) as biocompatible photosensitizers that can broaden the light absorption spectrum up to 800 nm and enhance light utilization due to efficient charge and energy transfer within the Pdots. By matching the energy level of Pdots to the positions of the redox mediators in M. thermoacetica, effective photoexcited electron transfer to the bacterial membrane proteins can be achieved, providing a sufficient driving force to enhance the efficiency of acetate production. The optimal system renders a photobiocatalytic performance of acetic acid production up to 1.6 mM, corresponding to 320 mmol/gPdots after a 3 day experiment at a light intensity of 5 mW cm-2.

Highly synergistic degradation of fluoroquinolones driven by redox dual channel mechanism in Fe(Ⅲ)-mediated thermally activated persulfate system.

Quinones are important oxidants in biology and synthetic chemistry. Herein, we study the kinetics of the oxidation of hydroquinones to quinones with redox-active guanidines and thioguanidines. In the first section, we report the synthesis and characterization of the first redox-active aromatic compounds with two, three, and four thioguanidino groups and compare their redox properties with the corresponding oligoguanidines. The stable salts obtained upon chemical two-electron oxidation of the tetra-thioguanidine were then applied in dehydrogenative P-P coupling reactions at room temperature, demonstrating their superior proton-coupled electron-transfer reactivity compared with previously used oligoguanidines. Oxidation of hydroquinones and halogenated derivatives to the 1,4-benzoquinones is also much faster with the new tetrathioguanidine than with oligoguanidines. Seemingly paradoxically, for tetraguanidines and tetrathioguanidines, oxidations to high-potential halogenated quinones are faster than those to low-potential quinones (due to proton-coupled electron transfer (PCET)), motivating the use of redox-active guanidines as redox mediators.

Injectable hydrogels capable of in situ gelation under physiological conditions are highly attractive for minimally invasive surgery and locoregional drug delivery. We herein report three novel injectable hydrogels composed of gelatin methacrylate (GelMA) and poly(ethyleneglycol) dimethacrylate (PEGDA), crosslinked through a Fenton-like radical polymerization mediated by cytochrome C (CyC) in the presence of H2O2 and L-ascorbic acid. To the best of our knowledge, this is the first example of an injectable hydrogel formulation in which CyC is used as a redox mediator for radical polymerization. CyC enables the replacement of transition metals while maintaining polymerization kinetics comparable to those of hydrogels synthesized via traditional Fenton systems. The resulting hydrogels, undergoing a sol-gel transition within 1.0 and 2.0 minutes, are biocompatible, and their properties are highly tunable. Indeed, rheological analysis showed that mechanical properties and the linear viscoelastic region (LVR) can be easily modulated by varying the concentrations of the starting methacryl-functionalized gelatin and the crosslinker. Structural characterization and biodegradation studies revealed that enzymatic degradation is strongly dependent on the degree of crosslinking. All hydrogels were readily injectable and showed no detectable cytotoxicity in conditioned-medium assays. Sustained release of rhodamine 101, as a drug-mimicking system, reached ∼70% over 7 days.

Chlorinated hexaazatrinaphthylene as an efficient solid-state redox mediator for membrane-free acidic decoupled water electrolysis.

Air-fed electrochemical H2O2 production via the two-electron oxygen reduction reaction (2e- ORR) offers a sustainable alternative to conventional processes, yet its efficiency is fundamentally constrained by low O2 availability and intrinsically coupled electron-proton transfer. Here, we construct a bifunctional covalent organic polymer interface integrating carbonyl electron-relay units and quaternary ammonium cationic motifs on commercial carbon black (QSPIP-TMC@CB), enabling efficient H2O2 electrosynthesis directly from air. The QSPIP-TMC@CB delivers a H2O2 production rate of 3410.1 mmol·h-1·g-1 with 91.4% H2O2 Faradaic efficiency (FEH2O2) under air, and sustains stable operation at 100.0 mA·cm-2 for 35.0 h. Mechanistically, carbonyl motifs function as reversible redox mediators that facilitate electron injection into O2, while quaternary ammonium cations enrich interfacial O2 and regulate proton accessibility via Donnan repulsion, suppressing excessive protonation of the *OOH intermediate and preventing O─O bond cleavage. This cooperative regulation decouples electron transfer from proton supply, thereby stabilizing the 2e- pathway under O2-lean conditions. The strategy is readily extendable to representative ORR catalysts (Co─N─C and ZnO) and enables gram-scale H2O2 production (4.8g h-1 at 5.0 A, 1.0 wt% within 5min), establishing functionalized-interface electron-proton decoupling as a general and scalable design paradigm for air-fed H2O2 electrosynthesis.

Utilizing redox mediators (RMs) in aprotic Li-O2 batteries as catalysts provides promising solutions to several challenges, including high overpotential, cathode passivation, and electrolyte instability, while enabling the solution-phase catalysis. Despite these advantages, the fundamental origin of their electrochemical activity and how it governs the solution-phase pathway remain poorly understood. To bridge this gap, we systematically explored the stability of reactive intermediates and their influence on solution-phase Li2O2 formation using a series of anthraquinone-based RMs: anthraquinone (AQ), 1-nitroanthraquinone (MNAQ), 1,5-dinitroanthraquinone (1,5-DNAQ), and 1,8-dinitroanthraquinone (1,8-DNAQ). All the studied RMs facilitate the formation of stable intermediate complexes with Li+, O2•-, and LiO2•, thereby promoting the solution-phase Li2O2 formation pathway. Among them, 1,8-DNAQ exhibits the enhanced coordination with Li+ through cooperative participation of carbonyl and nitro oxygens, highlighting the role of the NO2 functional group in dual-site binding. The introduction of electron-withdrawing NO2 groups systematically raises the reduction potential (AQ < MNAQ < 1,5-DNAQ < 1,8-DNAQ), approaching the ideal value of 2.96 V, which is consistent with experimental observations. A correlation is observed between the NO2 substitution, reduction potential, and the LUMO energy, unveiling the underlying origin of the potential shift. Interestingly, the rise in reduction potential is not solely dictated by LUMO energy tuning through functional group modification but also by the thermodynamic stabilization of the reduced species. The involvement of the NO2 group enables electron delocalization, which stabilizes the reduced species and results in an enhanced redox performance compared to the unsubstituted AQ. The following study establishes a structure-property relationship linking the electronic structure, stability of reduced species, and redox activity. It demonstrates how NO2 functionalization correlates with the tuning of reduction potential. These insights provide design principles for developing redox mediators to enhance the catalytic activity and reversibility in next-generation Li-O2 batteries.

Electrochemical biosensors are central to wearable diagnostics, point-of-care testing, and continuous health monitoring due to their low power requirements, compatibility with miniaturized electronics, and proven clinical impact. Despite these advantages, the development of new electrochemical biosensors remains slow, constrained by limited throughput, complex electrode-biomolecule interfaces, and challenges associated with selectivity and performance in chemically complex environments. This perspective outlines how the next generation of electrochemical biosensors can be enabled by decoupling high-throughput front-end discovery and optimization from electrochemical readouts using nonelectrochemical surrogate assays. Optical, affinity, and cell-sorting platforms, including SELEX, fluorescence-activated cell sorting, and chemically coupled fluorescence assays, allow orders-of-magnitude expansion in accessible design space for recognition elements, enzymes, and redox mediators. These approaches enable data-rich exploration of sequence-function relationships and provide scalable inputs for directed evolution, de novo protein design, and machine-learning-guided optimization. Top-performing constructs obtained from these nonelectrochemical surrogate assays can then be screened and validated electrochemically, ensuring translation into functional electrochemical biosensors. Together, these strategies outline a path toward data-driven, scalable, and predictive electrochemical biosensor design that moves beyond trial-and-error development and accelerates deployment in real-world settings.

A flexible, lightweight and low-cost enzymatic bioanode was developed using a screen-printed silver conductive transparency sheet for enzymatic biofuel cell (EBFC) applications. In this work, indole was electrochemically polymerized directly onto the conductive substrate to form a polyindole (PIn) matrix capable of simultaneously entrapping glucose oxidase (GOx) and redox mediator vitamin K3 (VK3). The study integrates a disposable transparency-sheet platform with an electroactive PIn network that promotes efficient enzyme immobilization and enhanced electron transfer for glucose bioelectrocatalysis. The synergistic interaction between PIn, VK3 and GOx significantly improved charge-transfer kinetics and stabilized the bioelectrocatalytic interface, resulting in enhanced electrochemical performance. The fabricated PIn/VK3/GOx bioanode exhibited a current density of 1.18mA cm- 2 in 40 mM glucose solution, demonstrating efficient glucose-dependent electrocatalytic activity. The conductive PIn framework facilitated rapid electron transport between the buried active sites of GOx and the electrode surface, while VK3 acted as an efficient and biocompatible electron shuttle. The bioanode also displayed good electrical stability, semiconducting behavior, and favorable electrochemical characteristics, highlighting its suitability for flexible and wearable bioelectronic applications.

A simple and environmentally friendly electrochemical method is reported for accessing polysubstituted pyrimido[4,5-b]indoles via the cyclization of 3-substituted indoles with amidines. By employing tetrabutylammonium iodide (nBu4NI) as the electrolyte and 2,2,6,6-tetramethylpiperidinooxy (TEMPO) as a redox mediator, the target heterocycles were efficiently synthesized in moderate to good yields. Mechanistic studies demonstrated that both TEMPO and nBu4NI are indispensable redox mediators and essential for achieving high selectivity in this transformation.

Organic polymerization offers a sustainable water treatment approach that enables resource recovery, yet current oxidant-involved practices suffer from poor selectivity. We present an oxidant-free electrocatalytic system for phenolic pollutant polymerization via iodine-mediated proton-coupled electron transfer (PCET) with an iodine-enriched bismuth-oxyiodide-coated carbon cloth (I-BiOI@CC) anode, achieving 97.1% polymerization selectivity by converting pollutants into insoluble polymerized products. Mechanistic investigations demonstrate that I-BiOI@CC provides reversible redox mediation (3I⁻ ⇆ I₃⁻), enhancing pollutant-electrode interaction and accelerating interfacial charge transfer to facilitate PCET-oxidation of phenols to phenolic radicals that undergo polymerization through thermodynamically favored ortho C-O coupling. Polymerization kinetics depend on proton and electron transfer energetics, wherein phenols with stronger electron-donating capacity and weaker O-H bond strength promote the PCET process. The electrocatalytic system exhibits high energy and cost efficiency, demonstrates negligible biotoxicity, and shows excellent practicality. This work offers a promising proof-of-concept for future development of green and selective electrocatalytic processes for water decontamination.

Lithium sulfide (Li2S) is pivotal for high-energy-density lithium-sulfur (Li─S) batteries due to its high theoretical capacity, abundant sulfur resources, and compatibility with anode-free architectures. However, its application is hindered by its intrinsically insulating nature and sluggish redox kinetics. Furthermore, traditional 1,3-dioxolane/1,2-dimethoxyethane electrolytes cannot withstand high voltages and pose safety hazards due to low flash points. Herein, we propose a synergistic strategy by introducing diisopropyl dithiocarbonate disulfide (DIP) as a multifunctional redox mediator into a high-flash-point, high-voltage-tolerant tetraethylene glycol dimethyl ether electrolyte system. DIP directly converts Li2S to lithium polysulfides, decreasing the activation voltage of the first charge to 2.48 from 3.18 V. Simultaneously, DIP facilitates the formation of an organosulfur-rich solid electrolyte interface on the lithium surface, effectively suppressing lithium dendrite formation and growth. Crucially, this system enables stable cycling in anode-free Cu||Li2S batteries for 160 cycles at 0.3 mAh cm-2. Standard Li||Li2S cells also demonstrate superior durability, achieving an extremely low per-cycle decay rate of 0.037% at 1C. Moreover, this strategy holds promise for other metal-sulfur systems, such as Na─S, K─S, Ca─S, Mg─S, and Zn─S batteries, providing a feasible path for safe, next-generation energy storage.

Industrial red mud establishes redox-active interfaces to steer metabolic pathways toward chain elongation in sludge anaerobic fermentation.

Magnetic bio preconcentration (MBP) for chemical-free cost-effective and low carbon sewage organics recovery.

Copper oxide (CuO) is identified as a promising electrocatalyst for the oxidative upgrading of biomass derivatives, although the catalysis mechanism on CuO-based catalysts remains poorly understood. In this work, we report that cation defects in CuO enable a new electro-oxidation mechanism, designated as the adsorbed hydroxyl-mediated (AHM) pathway. A cation-defective CuO (CD-CuO) is prepared by the self-reconstruction of a vanadium-doped cuprous sulfide (V-Cu2S) precatalyst, which exhibits high product yield and Faradaic efficiency exceeding 90% for the electro-oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA). By combining operando Raman spectroscopy with density functional theory-based Raman spectrum simulations, we identify that hydroxyl species adsorbed on high-valence copper sites (Cu2+δO-OH*) act as a redox mediator for HMF oxidation. The cation defects are found to lower the energy barrier for Cu2+δO-OH* formation and enhance HMF adsorption, thereby promoting catalytic activity. Furthermore, the high performance of CD-CuO is well-maintained for more than 100 h in an anion exchange membrane electrolyzer. This work provides new insights into the catalytic mechanism and structure-performance relationships of copper-based catalysts.

In the present study, Fe3O4@hydrothermal carbon was prepared successfully using rice straw waste. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analysis confirmed that the material had rich and strong redox-active centers on its surface, indicating that it has potential to be used as a redox mediator for electron transfer. Fe3O4@hydrothermal carbon was added into the anaerobic sludge treatment system for the collaboration of dye decolorization. The results showed that azo dye decolorization efficiency reached the maximum value (98.3%) with the presence of Fe3O4@hydrothermal carbon, which was 16.6% higher than control reactor (without Fe3O4@hydrothermal carbon added). In addition, Fe3O4@hydrothermal carbon exhibits good reusability and the dye decolorization rates in the "anaerobic sludge-material" combining system were significantly higher than that in the "sludge-alone" system during the semi-continuous wastewater treatment process. Mechanistic investigations revealed that the enhanced decolorization is driven by a synergistically constructed interspecies electron transfer pathway. Specifically, the addition of Fe3O4@hydrothermal carbon improved the formation of the extracellular polymeric substance (EPS), which had positive effects on sludge stability and its interaction with the material. CV and electron transport system (ETS) activity analysis showed that the sludge exhibited high electrochemical activities with the support of the material, which led to a high electron transfer efficiency between the electron-donating and accepting microbial pairs in the treatment system. The high-throughput sequencing analysis showed that the structure of the microbial community changed during the semi-continuous treatment process; Megasphaera and Clostridium accounted for more than 87.5% of the total abundance of the bacterial community in the anaerobic sludge with material addition. Driven by the material-mediated process, these enriched functional taxa exhibited a high electron transfer efficiency between electron-donating and accepting pairs, accelerating the catalytic cleavage of azo bonds and ultimately improving the overall anaerobic treatment performance.

The strategic design of multifunctional reagents has emerged as a powerful paradigm in modern organic synthesis by integrating activation, fragment delivery, and reaction control within a single chemical entity. This review examines advances from 2005 to 2025, highlighting the evolution of multifunctional reagents from classical systems such as DMSO, DMF, dimethyl carbonate, and isocyanides to sophisticated platforms including silylated lactams, vinylene carbonates, aryldiazonium salts, N-alkoxy- and N-alkenoxypyridinium species, bifunctional polymer-supported systems, and inorganic redox mediators. The discussion is organized by reagent architecture and activation mode, covering molecular, heterogeneous, photochemical, and catalyst-programmable systems. Across cascade reactions, multicomponent processes, and late-stage functionalizations, these reagents enable compression of multistep sequences, improved chemoselectivity, and enhanced step and atom economy. Mechanistic insights from kinetic, spectroscopic, isotopic, and computational studies reveal how integrated functionalities such as internal acid or base activation, redox mediation, and proximity effects govern reactivity across radical, ionic, and photochemical pathways. Comparative analysis underscores trade-offs between efficiency, scalability, and cost, while highlighting challenges in reagent synthesis and process translation. Overall, multifunctional reagent design provides a unifying framework for sustainable and efficient molecular construction in both academic and industrial settings.

The exponential growth of the electric vehicle (EV) market has triggered a massive accumulation of spent lithium-ion batteries (sLIBs), which urgently requires sustainable recycling strategies to reduce environmental risks and ensure the availability of key mineral resources. While traditional pyrometallurgical and hydrometallurgical processes are established for large-scale operations, they are limited by high energy consumption, high reagent consumption, and hazardous secondary emissions. This review systematically evaluates current recycling methods, ranging from traditional smelting and acid-leaching to emerging electrochemical paradigms. A primary focus is placed on the redox-mediated method, a transformative electrochemical strategy designed to overcome the high energy consumption of traditional strategies and the inherent kinetic limitations in direct electrochemical extraction. This method introduces a redox mediator that decouples the electrochemical reaction into the mediator regeneration reaction at the electrode interface and the delithiation reaction at the solid-liquid interface, thereby enabling efficient and targeted energy-supplying recycling. Furthermore, the redox mediator recovery method can be ingeniously combined with value-added processes such as hydrogen production and zinc deposition, significantly reducing energy consumption and carbon footprint compared to traditional methods. This article shows the value of the redox mediator method, which combines waste treatment and resource regeneration.