Logic Gates Based on Magnetic Nanoparticles Functionalized with a Bioelectrocatalytic System

Magneto‐controlled OR, AND and INHIB logic gates were designed using cobalt ferrite magnetic nanoparticles (CoFe₂O₄, saturated magnetization ca. 70 emu g^?1, 17±2 nm diameter) functionalized with microperoxidase‐11. Tunable magnetic field generated by three external permanent magnets (NdFeB) upon moving them below the electrochemical cell resulted in translocation of the biofunctionalized magnetic nanoparticles between conductive and nonconductive domains of a solid plate. This resulted in electrochemically readable output signals with the Boolean logic controlled by the magnetic input signals. The current corresponding to the reversible redox process of the heme measured at ?0.4 V (vs. SCE) was considered as “1” output signal, while a small background current obtained from the conducting interface in the absence of the magnetic nanoparticles was considered as “0” output signal. Addition of H₂O₂ to the solution resulted in the generation of a cathodic catalytic current when the microperoxidase‐11‐functionalized magnetic nanoparticles are associated with the conductive domain of the support. This resulted in the amplification of “1” output signal and the increased difference between “1” and “0” signals generated by the cell, thus reducing the possibility of errors in the Boolean logic operations.     

Amplified Electrochemical Response of Phenol by Oxygenation of Tyrosinase Coupling with Electrochemical‐chemical‐chemical Redox Cycle

In this work, an novel electrochemical‐chemical‐chemical (ECC) redox cycle was designed in an enzyme‐based sensor for acquiring additional signal amplification. The tyrosinase (Tyr) was entrapped in a sulfonated polyaniline?chitosan (SPAN?CS) composite which was used as a redox capacitor on a glass carbon electrode. Firstly, the substrate, phenol was catalyzed to catechol and further catalyzed to o‐benzoquinone by Tyr. Next, in the presence of Ru(NH₃)₆Cl₂, the reduced state of SPAN(SPAN_red) was reacted with o‐benzoquinone to form it's oxidized state (SPAN_ox) and catechol, then SPAN_ox was reduced back to SPAN_red by Ru(II) in the solution. Finally, the amplified anodic current of catechol was obtained on electrode through above ECC redox cycle system. In addition, the ECC redox cycling led to a high signal‐to‐background ratio. The voltammetric response showed excellent analytical performance to phenol over two linear range of 3.5 to 200.0 nmol L^?1 and 200.0 to 2000.0 nmol L^?1 with a high sensitivity of 2204 μA mM^?1. The detection limit was obtained to be 0.8 nmol L^?1 (S/N=3). Furthermore, the proposed approach exhibited good repeatability, stability and specificity, and could offer practicality in the detection of phenol in tap water.     

Nanocrystalline ceria–praseodymia and ceria–zirconia solid solutions for soot oxidation

The relative effects of Zr⁴⁺ and Pr^3+/4+ dopants on the structure, redox properties, and catalytic performance of nanosized ceria was studied. The investigated ceria?Czirconia and ceria?Cpraseodymia (CP) solid solutions were prepared by a modified coprecipitation method, characterized by a variety of techniques, and evaluated for soot oxidation. The characterization results indicate that CP has more surface and bulk oxygen vacancies, redox sites, and lattice oxygen mobility, and better thermal stability. Besides having low specific surface area, CP is more active in soot oxidation. This better activity has been attributed to the presence of more surface and bulk oxygen vacancies, which promote the adsorption of gas-phase oxygen and the formation and mobility of large numbers of active oxygen species.     

Monitoring the Glutathione Redox Reaction in Living Human Cells by Combining Metabolic Labeling with Heteronuclear NMR

The glutathione (GSH) redox reaction is critical for defense against cellular reactive oxygen species (ROS). However, direct and real‐time monitoring of this reaction in living mammalian cells has been hindered by the lack of a facile method. Herein, we describe a new approach that exploits the GSH biosynthetic pathway and heteronuclear NMR. [U‐¹³C]‐labeled cysteine was incorporated into GSH in U87 glioblastoma cells, and the oxidation of GSH to GSSG by a ROS‐producing agent could be monitored in living cells. Further application of the approach to cells resistant to temozolomide (TMZ), an anti‐glioblastoma drug, suggested a possible new resistance mechanism involving neutralization of ROS. This result was corroborated by the observation of up‐regulation of glutathione peroxidase 3 (GPx3). This new approach could be easily applied to redox‐dependent signaling pathways and drug resistance involving ROS.     

Logic control of microfluidics with smart colloid

We report the successful realization of a microfluidic chip with switching and corresponding inverting functionalities. The chips are identical logic control components incorporating a type of smart colloid, giant electrorheological fluid (GERF), which possesses reversible characteristics via a liquid-solid phase transition under external electric field. Two pairs of electrodes embedded on the sides of two microfluidic channels serve as signal input and output, respectively. One, located in the GERF micro-channel is used to control the flow status of GERF, while another one in the ither micro-fluidic channel is used to detect the signal generated with a passing-by droplet (defined as a signal droplet). Switching of the GERF from the suspended state (off-state) to the flowing state (on-state) or vice versa in the micro-channel is controlled by the appearance of signal droplets whenever they pass through the detection electrode. The output on-off signals can be easily demonstrated, clearly matching with GERF flow status. Our results show that such a logic switch is also a logic IF gate, while its inverter functions as a NOT gate.     

CuII Ions and the Stilbene–Chroman Hybrid with a Catechol Moiety Synergistically Induced DNA Damage,and Cell Cycle Arrest and Apoptosis of HepG2 Cells: An Interesting Acid/Base‐Promoted Prooxidant Reaction

Development of potential cancer treatment strategies by using an exogenous reactive oxygen species (ROS)‐generating agent (prooxidant) or redox intervention, has attracted much interest. One effective ROS generation method is to construct a prooxidant system by polyphenolic compounds and Cu^II ions. This work demonstrates that Cu^II and the stilbene–chroman hybrid with a catechol moiety could synergistically induce pBR322 plasmid DNA damage, as well as cell cycle arrest and apoptosis of HepG2 cells. Additionally, an interesting acid/base‐promoted prooxidant reaction was found. The detailed chemical mechanisms for the reaction of the hybrid with Cu^II in acid, neutral and base solutions are proposed based on UV/Vis spectral changes and identification of the related oxidative intermediates and products.     

Nanoplatform-based cellular reactive oxygen species regulation for enhanced oncotherapy and tumor resistance alleviation

The cancer cells realize their proliferation and metastasis activities based on the special redox adaptation to increased reactive oxygen species(ROS) level, which inversely makes them sensitive to external interference with their redox state. In view of this, in recent decades, researchers have made great efforts to construct a series of novel nanoplatform-based ROS-mediated cancer therapies through increasing ROS generation and inhibiting the ROS elimination. Besides, the multidrug resistance ...     

Fast Antioxidation Kinetics of Glutathione Intracellularly Monitored by a Dual-Wire Nanosensor

The glutathione (GSH) system is one of the most powerful intracellular antioxidant systems for the elimination of reactive oxygen species (ROS) and maintaining cellular redox homeostasis. However, the rapid kinetics information (at the millisecond to the second level) during the dynamic antioxidation process of the GSH system remains unclear. As such, we specifically developed a novel dual-wire nanosensor (DWNS) that can selectively and synchronously measure the levels of GSH and ROS with high temporal resolution, and applied it to monitor the transient ROS generation as well as the rapid antioxidation process of the GSH system in individual cancer cells. These measurements revealed that the glutathione peroxidase (GPx) in the GSH system is rapidly initiated against ROS burst in a sub-second time scale, but the elimination process is short-lived, ending after a few seconds, while some ROS are still present in the cells. This study is expected to open new perspectives for understanding the GSH antioxidant system and studying some redox imbalance-related physiological.     

Stimuli‐Responsive Circularly Polarized Organic Ultralong Room Temperature Phosphorescence

Purely organic materials showing room temperature phosphorescence (RTP) and ultralong RTP (OURTP) have recently attracted much attention. However, it is challenging to integrate circularly polarized luminescence (CPL) into RTP/OURTP. Here, we show a strategy to realize CPL‐active OURTP (CP‐OURTP) by binding an achiral phosphor group directly to the chiral center of an ester chain. Engineering of this flexible chiral chain enables efficient chirality transfer to carbazole aggregates, resulting in strong CP‐OURTP with a lifetime of over 0.6 s and dissymmetry factor of 2.3×10^?3 after the conformation regulation upon photo‐activation. The realized CP‐OURTP is thus stable at room temperature but can be deactivated quickly at 50 °C to CP‐RTP with high CPL stability during the photo‐activation/thermal‐deactivation cycles. Based on this extraordinary photo/thermal‐responsive and highly reversible CP‐OURTP/RTP, a CPL‐featured lifetime‐encrypted combinational logic device has been successfully established.     

Silver Nanoparticles‐Silsesquioxane Nanomaterial Applied to the Determination of 4‐Nitrophenol as a Biomarker

A novel silsesquioxane material was synthetized and used as a stabilizing agent for silver nanoparticles. This hybrid material was characterized by FTIR, ²⁹Si CP‐MAS NMR, ¹³C DEPT 135° NMR and TGA techniques and the silver nanoparticles were characterized from DLS, UV‐Vis spectroscopy, zeta‐potential, TEM and SAXS results. The silver nanoparticles obtained were spherical in shape with a diameter of 3.74 nm. The nanomaterial was successfully applied in the modification of a glassy carbon electrode and a pronounced current response was obtained in the determination of the biomarker 4‐nitrophenol. Quantum chemical calculations, using density functional theory, were also performed in order to evaluate the redox properties of the analyte. Two different linear ranges were obtained applying optimal square wave voltammetry conditions. The reduction peak currents obtained were linear for 4‐NP concentrations in the ranges of 0.29 to 1.50 μmol L^?1 (E_d=?0.6 V and t_d=20 s) and 2.75 to 31.5 μmol L^?1, with a theoretical (signal to noise=3) limit of detection of 0.05 μmol L^?1 (t_d=20 s). The proposed method was successfully applied to the determination of 4‐NP in synthetic serum samples at different levels of 4‐NP with a recovery range of 94–101 %. Validation was performed using a comparative method through the capillary electrophoresis (CE) technique.     

An Enzyme‐Based Half‐Adder and Half‐Subtractor with a Modular Design

A half‐adder and a half‐subtractor have been realized using enzymatic reaction cascades performed in a flow cell device. The individual cells were modified with different enzymes and assembled in complex networks to perform logic operations and arithmetic functions. The modular design of the logic devices allowed for easy re‐configuration, enabling them to perform various functions. The final output signals, represented by redox species [Fe(CN)₆]^3?/4? or NADH/NAD⁺, were analyzed optically to derive the calculation results. These output signals might be applicable in the future for actuation processes, for example, substance release activated by logically processed signals.     

Molybdenum trioxide hybridized kaempferol: double-powered nanosystem for salvaging oxidative stress and electrochemical immunoprobing of interleukin-6

Intracellular reactive oxygen species (iROS) are the culprit in inflammation-linked diseases. Excessive radical generation triggers an inflammation cascade involving interleukin-6 (IL-6) and other cytokines release, causing oxidative stress to cells. Developing healthcare materials with dual-functionality controlling iROS and diagnosing IL-6 would be extremely beneficial for chronic inflammatory disease management. Herein, molybdenum trioxide hybridized kaempferol nanoparticles (MoHK NPs) have been synthesized with iROS scavenging and in situ electrochemical redox property for immunoassay of IL-6. Physicochemical integrity of nanosystem comprising MoHK NPs is characterized by X-ray absorption/photoelectron, Raman, and fourier transform infrared (FT-IR) spectroscopy as well as scanning transmission electron microscopy–high-angle annular dark field microscopic analysis. In vitro radical scavenging mechanism of MoHK NPs was studied by electron paramagnetic spectroscopy. Distinctly, these MoHK NPs exhibit a clinically significant antioxidant function and cytocompatibility with RAW 264.7 macrophage cell line. Bioaffinity layer–assisted monoclonal antibodies of IL-6 immobilized on MoHK electrode enable superior selectivity, electrochemical signal transduction (sensitivity 0.63 μA/fM/cm²), and rapid analytical response time even at ultralow IL-6 concentrations (detection limit 0.91 fM). This work demonstrates that hybridizing redox-active and antioxidant-rich phytochemical on metal oxide nanosystem can be a promising strategy for multifunctional theranostics.     

Supramolecular Functions Related to the Redox Activity of Transition Metals

Abstract

The combination of the properties of different subunits in a multicomponent system may give rise to a function which is defined supramolecular. The presence of transition metals in one or more subunits may induce inter-component processes related to their redox and electron transfer (eT) properties, which trigger the supramolecular function (SF). The following examples are considered: (1) a receptor for transition metals is covalently linked to a fluorescent fragment; following recognition, a metal-to-fluorophore eT process quenches the fluorescence. SF: fluorosensing. (2) an azacyclam macrocycle, hosting the Ni^II/Ni^III redox couple, is covalently linked to a photoactive fragment: the Ni^III state quenches the neighboring fluorophore through an eT mechanism, the Ni^II state does not. SF: redox switching of a fluorescent signal. (3) a Cu^II ion is coordinated by two 2,2′-bipyridine molecules, each bearing a cyclam subunit containing a nickel centre; when nickel is in the divalent state, an inorganic anion X^? (N₃ ^?,NCO^?,NCS^?) is bound to Cu^II; on oxidation, X^? moves to the Ni^III centre. SF: electrochemically triggered translocation of X^? from copper to nickel and vice versa.     

The Signal Amplification in Electrochemical Detection of Chloramphenicol Using Sulfonated Polyaniline‐chitosan Composite as Redox Capacitor

In this work, a novel redox capacitor was designed for signal amplification in electrochemical detection. It was fabricated by co‐electrodeposition of a conducting polymer, sulfonated polyaniline (SPAN) and chitosan on a glass carbon electrode, and its function was evaluated for being a localized source to transfer electron between FcCOOH (Fc) and Ru(NH₃)₆Cl₃ in solution via redox cycling. Furthermore, the electrochemical detection of chloramphenicol, a broad‐spectrum antibiotic was performed using the redox capacitor in the presence of Fc. A significant amplification in cathodic current response of chloramphenicol was obtained through a continuous redox‐cycling reaction. The performance of the amplifying signal responded linearly to chloramphenicol in a concentration range of 0.05 to 50.0 μmol L⁻¹ with a low detection limit of 0.01 μmol L⁻¹. The proposed approach exhibited good reproducibility and stability, and could be used for detection of chloramphenicol in eye drops by standard addition method with the recoveries from 96.5 % to 103.0 %.     

A cobalt redox switch driving alcohol dehydrogenation by redox coupled molecular swing

Developing redox switches that not only perform specific mechanical movements but also drive important chemical reactions is important but a great challenge. Herein, we report a redox pair of cobalt species (Co^III/Co^II) that switches through photo-dehydrogenation of alcohol and hydrogenation of azo-ligand. The cobalt species is equipped with a flexible azo-ligand containing two bulky planar substituents. A planar oxidated sate (Co^III species) can be photo-reduced to a saddle-like reduced state (Co^II) with alcohol molecules as electron donors, and in turn the Co^III species can be recovered with azo-ligand as oxidant under acidic surrounding. Both the redox states of the pair are isolated and characterized by single crystal X-ray diffraction. In the switching cycle, alcohol is oxidized to aldehyde by azo-ligand through proton coupled electron transfer and the cobalt complex acts as a redox catalyst. These results provide important insights into alcohol dehydrogenation catalyzed by redox complexes.     

Copper(II)–Graphitic Carbon Nitride Triggered Synergy: Improved ROS Generation and Reduced Glutathione Levels for Enhanced Photodynamic Therapy

Graphitic carbon nitride (g‐C₃N₄) has been used as photosensitizer to generate reactive oxygen species (ROS) for photodynamic therapy (PDT). However, its therapeutic efficiency was far from satisfactory. One of the major obstacles was the overexpression of glutathione (GSH) in cancer cells, which could diminish the amount of generated ROS before their arrival at the target site. Herein, we report that the integration of Cu²⁺ and g‐C₃N₄ nanosheets (Cu²⁺–g‐C₃N₄) led to enhanced light‐triggered ROS generation as well as the depletion of intracellular GSH levels. Consequently, the ROS generated under light irradiation could be consumed less by reduced GSH, and efficiency was improved. Importantly, redox‐active species Cu⁺–g‐C₃N₄ could catalyze the reduction of molecular oxygen to the superoxide anion or hydrogen peroxide to the hydroxyl radical, both of which facilitated the generation of ROS. This synergy of improved ROS generation and GSH depletion could enhance the efficiency of PDT for cancer therapy.     

Chemiluminescent Logic Gates Based on Functionalized Gold Nanoparticles/Graphene Oxide Nanocomposites

Label‐free logic gates (AND, OR, and INHIBIT) based on chemiluminescence (CL) as new optical readout signal have been developed by taking advantage of the unique CL activity of luminol‐ and lucigenin‐functionalized gold nanoparticles/graphene oxide (luminol‐lucigenin/AuNPs/GO) nanocomposites. It was found that Fe²⁺ ions could induce the CL emission of luminol‐lucigenin/AuNPs/GO nanocomposites in alkaline solution. On this basis, by using Fe²⁺ ions and NaOH as the inputs and the CL signal as the output, an AND logic gate was fabricated. When the initial reaction system contained luminol‐lucigenin/AuNPs/GO nanocomposites and NaOH, either Fe²⁺ ions or Ag⁺ ions could react with the luminol‐lucigenin/AuNPs/GO nanocomposites to produce a strong CL emission. This result was used to design an OR logic gate using Fe²⁺ ions and Ag⁺ ions as the inputs and CL signal as the output. Moreover, two INHIBIT logic gates for Fe²⁺ and Ag⁺ were also developed using by NaClO and L ‐cysteine as their CL inhibitors, respectively. Furthermore, the proposed logic gates were successfully used to detect Fe²⁺, Ag⁺, and L ‐cysteine, respectively. The developed logic gates may find future applications in sensing, clinical diagnostics, and environmental monitoring.     

EXAFS structural studies of electrodeposited Co and Ni hexacyanoferrate films

XAS (EXAFS and XANES), XPS and IR spectroscopies were used to extract redox compositional and structural information on films of electrodeposited Co and Ni hexacyanoferrates whose redox state was manipulated electrochemically. The X-ray methods provided direct information on the metal species and IR provided indirect information via the behaviour of the ligand vibration. XPS responses showed that the electrochemical response of Co hexacyanoferrate is attributable to Co (except for a small amount of Fe^II oxidation at very positive potentials), and of Ni hexacyanoferrate to Fe; XANES edge shifts confirm these deductions. Local structure around the metal atoms was extracted from EXAFS data in terms of M′–N, M′–C and M′–Fe (M′ = Co or Ni) distances and the associated Debye-Waller factors as functions of film charge state. For Co hexacyanoferrate, the redox variation of static disorder was consistent with a molecular model involving discrete Co^II and Co^III sites, whose populations respond to potential, but not with a solid-state model.     

Hydroxyl Radical Generation and DNA Nuclease Activity: A Mechanistic Study Based on a Surface‐Immobilized Copper Thioether Clip‐Phen Derivative

Coordination compounds of copper have been invoked as major actors in processes involving the reduction of molecular oxygen, mostly with the generation of radical species the assignment for which has, so far, not been fully addressed. In the present work, we have carried out studies in solution and on surfaces to gain insights into the nature of the radical oxygen species (ROS) generated by a copper(II) coordination compound containing a thioether clip‐phen derivative, 1,3‐bis(1,10‐phenanthrolin‐2‐yloxy)‐N‐(4‐(methylthio)benzylidene)propan‐2‐amine (2CP‐Bz‐SMe), enabling its adsorption/immobilization to gold surfaces. Whereas surface plasmon resonance (SPR) and electrochemistry of the adsorbed complex indicated the formation of a dimeric Cu^I intermediate containing molecular oxygen as a bridging ligand, scanning electrochemical microscopy (SECM) and nuclease assays pointed to the generation of a ROS species. Electron paramagnetic resonance (EPR) data reinforced such conclusions, indicating that radical production was dependent on the amount of oxygen and H₂O₂, thus pointing to a mechanism involving a Fenton‐like reaction that results in the production of OH^..     

Precise Formation of a Hollow Carbon Nitride Structure with a Janus Surface To Promote Water Splitting by Photoredox Catalysis

The precise modification of redox species on the inner and outer surfaces of hollow nanostructures is relevant in catalysis, surface science, and nanotechnology, but has proven difficult to achieve. Herein, we develop a facile approach to specifically fabricate Pt and Co₃O₄ nanoparticles (NPs) onto the interior and exterior surface of hollow carbon nitride spheres (HCNS), respectively, to promote the surface redox functions of the polymer semiconductors. The photocatalytic water splitting activities of HCNS with spatially separated oxidation and reduction centers at their nanodomains were enhanced. The origin of the enhanced activity was attributed to the spatially separated reactive sites for the evolution of H₂ and O₂ and also to the unidirectional migration of the electron and hole on the Janus surfaces, thereby preventing the unwanted reverse reaction of water splitting and decreasing charge recombination.