l-Cysteine-Tuned the Hierarchical Structure Based on Benzimidazole: Synthesis, Characterization, and Application in Ratiometric Electrochemiluminescence Immunoassay.

Efficient and robust electrochemiluminescence (ECL) emitters are crucial for enhancing the ECL immunosensor sensitivity. This study introduces a novel ECL emitter, CoBIM/Cys, featuring a hierarchical core-shell structure. The core of the structure is created through the swift coordination between the sulfhydryl and carboxyl groups of l-cysteine (l-Cys) and cobalt ions (Co2+), while the shell is constructed by sequentially coordinating benzimidazole (BIM) with Co2+. This design yields a greater specific surface area and a more intricate porous structure compared to CoBIM, markedly enhancing mass transfer and luminophore accessibility. Moreover, the l-Cys and Co2+ core introduces Co-S and Co-O catalytic sites, which improve the catalytic decomposition of H2O2, leading to an increased production of hydroperoxyl radicals (OOH•). This mechanism substantially amplifies the ECL performance. Leveraging the competitive interaction between isoluminol and BIM for OOH• during ECL emission, we developed a ratiometric immunosensor for cardiac troponin I (cTnI) detection. This immunosensor demonstrates a remarkably broad detection range (1 pg mL-1 to 10 ng mL-1), a low detection limit (0.4 pg mL-1), and exceptional reproducibility and specificity.

A Conductive Microcavity Created by Assembly of Carbon Nanotube Buckypapers for Developing Electrochemically Wired Enzyme Cascades.

We describe the creation of a conductive microcavity based on the assembly of two pieces of carbon nanotube buckypaper for the entrapment of two enzymes, horseradish peroxidase (HRP) and glucose oxidase (GOx), as well as a redox mediator: 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid diammonium salt (ABTS). The hollow electrode, employing GOx, HRP, and the mediator, as an electrochemical enzyme cascade model, is utilized for glucose sensing at a potential of 50 mV vs. Ag/AgCl. This bienzyme electrode demonstrates the ability to oxidize glucose by GOx and subsequently convert H2O2 to water via the electrical wiring of HRP by ABTS. Different redox mediators (ABTS, potassium hexacyanoferrate (III), and hydroquinone) are tested for HRP wiring, with ABTS being the best candidate for the electroenzymatic reduction of H2O2. To demonstrate the possibility to optimize the enzyme cascade configuration, the enzyme ratio is studied with 1 mg HRP combined with variable amounts of GOx (1-4 mg) and 2 mg GOx combined with variable amounts of HRP (0.5-2 mg). The bienzyme electrode shows continuous operational stability for over a week and an excellent storage stability in phosphate buffer, with a decay of catalytic current by only 29% for 1 mM glucose after 100 days.

Fine tuning of porphyrin based-paddlewheel framework by imidazole derivative to boost electrochemiluminescence performance.

Precise tuning the structure of catalytic center is of great importance for the construction of enhanced electrochemiluminescence (ECL) emitters and the development of ECL amplification strategies, which is a key factor in improving the sensitivity of biosensors. In this work, we report the enhanced ECL emitters based on the porphyrin-based paddlewheel framework (PPF) with axial coordinated imidazole-like ligands (PPF/X, X = 2-methylimidazole (MeIm), imidazole (Im), benzimidazole (BIM)). In this system, the electron-donating ability of the axial ligands is positively correlated to its coordination ability to the paddlewheel units and the catalytic ability of the axially coordinated paddlewheel units. In addition, the electrochemical and ECL behavior of PPF/X (X = MeIm, Im, BIM) with different axial coordinated ligands are explored.

Micelle-Assisted Confined Coordination Spaces for Benzimidazole: Enhanced Electrochemiluminescence for Nitrite Determination.

Selective and sensitive detection of nitrite has important medical and biological implications. In the present work, to obtain an enhanced electrochemiluminescence (ECL) determination of nitrite, a novel nano-ECL emitter CoBIM/cetyltrimethylammonium bromide (CTAB) was prepared via a micelle-assisted, energy-saving, and ecofriendly method based on benzimidazole (BIM) and CTAB. Unlike conventional micelle assistance, the deprotonated BIM (BIM-) preferential placement was in the palisade layer of cationic CTAB-based micelles. Enriching the original CTAB micelle with BIM- disrupted its stability and resulted in the formation of considerably smaller BIM/CTAB-based micelles, providing a confined coordination environment for BIM- and Co2+. As a result, the growth of CoBIM/CTAB was also limited. Owing to the unusual nitration reaction between BIM and nitrite, the prepared CoBIM/CTAB was successfully applied as a novel ECL probe for the detection of nitrite with a wide linear range of 1-1500 µM and a low detection limit of 0.67 µM. This work also provides a promising ECL platform for ultrasensitive monitoring of nitrite and it was applied with sausages and pickled vegetables.

Post-synthetic modification-driven ZIF reconstruction and functionalization for efficient SARS-CoV-2 ECL detection.

The emergence of novel pathogens, as well as their frequent variants, raises the significance of developing superior and versatile sensing materials and techniques. Herein, a post-modified zeolitic imidazolate framework (pm-ZIF) was synthesized by using ZIF-67 as a parent MOF, and zinc(II) meso-tetra (4-carboxyphenyl) porphine (ZnTCPP) as a successive exchange ligand. Due to the preservation of the tetrahedral Co-N4 units from the ZIF precursor and the introduced porphyrin luminophores, this hybrid material pm-ZIF/P(Zn) enables the linear electrochemiluminescence (ECL) signal conversion of the target DNA concentration. An efficient biosensor that can be used to quantitatively detect SARS-CoV-2 was therefore constructed. The linear range of the sensor was 10-12-10-8 M, with a limit of detection (LOD) reaching 158 pM. Compared with the traditional amplification-based methods, the duration time of our method is significantly shortened and the quantitation of the SARS-Cov-2 RdRp gene can be completed within twenty minutes at room temperature.

Chlorhexidine digluconate exerts bactericidal activity vs Gram positive Staphylococci with bioelectrocatalytic compatibility: High level disinfection for implantable biofuel cells.

Implanted devices destined for contact with sterile body tissues, vasculature or fluids should be free of any microbial contamination that could lead to disease transmission. The disinfection and sterilisation of implantable biofuel cells is a challenging and largely overlooked subject due to the incompatibility of fragile biocatalytic components with classical treatments. Here we report the development of a convenient "soft" chemical treatment based on immersion of enzymatic bioelectrodes and biofuel cells in dilute aqueous chlorhexidine digluconate (CHx). We show that immersion treatment in a 0.5 % solution of CHx for 5 min is sufficient to remove 10-6 log colony forming units of Staphylococcus hominis after 26 h while shorter treatments are less effective. Treatments with 0.2 % CHx solutions were ineffective. Bioelectrocatalytic half-cell voltammetry revealed no loss in activity at the bioanode after the bactericidal treatment, while the cathode was less tolerant. A maximum power output loss of ca. 10 % for the glucose/O2 biofuel cell was observed following the 5 min CHx treatment, while the dialysis bag had a significant negative impact on the power output. Finally, we report a proof-of-concept in vivo operation for 4 days of a CHx-treated biofuel cell with a 3D printed holder and additional porous surgical tissue interface. Further assessments are necessary to rigorously validate sterilisation, biocompatibility and tissue response performance.

Artificial Light-Harvesting System Based on Zinc Porphyrin and Benzimidazole: Construction, Resonance Energy Transfer, and Amplification Strategy for Electrochemiluminescence.

Constructing robust and efficient luminophores is of significant importance in the development of electrochemiluminescence (ECL) amplification strategies. Inspired by the resonance energy transfer in natural light-harvesting systems, we propose a novel ECL amplification system based on ECL resonance energy transfer (ECL-RET), which integrates two luminophores, benzimidazole (BIM) and zinc(II) tetrakis(4-carboxyphenyl)porphine (ZnTCPP), into one framework. Through disassembling and reconstruction processes, numerous BIM surround ZnTCPP in the constructed ZIF-9-ZnTCPP. Combined with the overlapped spectra between the emission of BIM and the absorption of ZnTCPP, the energy of multiple BIM (donor) can be concentrated to a single ZnTCPP (acceptor) to amplify the ECL emission of the acceptor. This work provides a convenient way to design an efficient ECL-RET system, which initiates a brand-new chapter in the development of ECL amplification strategies.

Tuning Dimensionality of Benzimidazole Aggregates by Using Tetraoctylammonium Bromide: Enhanced Electrochemiluminescence Studies.

Exploring the depolymerization strategy of liposoluble luminophores in the aqueous phase is vital for the development of electrochemiluminescence (ECL). In this work, tetraoctylammonium bromide (TOAB) with four long hydrophobic chains and short hydrophilic ends is used as a template to limit the aggregation of benzimidazole (BIM). By adjusting the loading of BIM on the hydrophobic chains of TOAB, a two-dimensional lamellar BIM/TOAB is formed, the ECL intensity of which is 6.4 times higher than that of the aggregated BIM (H2O2 as the coreactant). In terms of ECL spectroscopies, cyclic voltammetry , ECL transients, and the adjustment of the scanning potential range, the ECL mechanism is thoroughly studied. This work provides a new way to depolymerize organic luminophores and reveals a possible pathway in the annihilation ECL mechanism.

Nanostructured electrodes based on multiwalled carbon nanotube/glyconanoparticles for the specific immobilization of bilirubin oxidase: Application to the electrocatalytic O2 reduction.

Here we describe the design and the characterization of novel electrode materials consisting of multi-walled carbon nanotubes coated with glyconanoparticles (GNPs) functionalized with anthraquinone sulfonate. The resulting modified electrodes were characterized by scanning electron microscopy and cyclic voltammetry. Their electrochemical behavior reveals a stable pH-dependent redox signal characteristic of anthraquinone sulfonate. Immobilization of bilirubin oxidase on these three-dimensional electrodes leads to the electroenzymatic reduction of O2 to water with an onset potential of 0.5 V/SCE (saturated calomel electrode). A catalytic cathodic current of 174 µA (0.88 mA cm-2) at 0.1 V/SCE, demonstrates that glyconanoparticles modified by anthraquinone sulfonate were able to interact and orientate bilirubin oxidase by electrostatic interactions.

Regulating the coordination capacity of ATMP using melamine: facile synthesis of cobalt phosphides as bifunctional electrocatalysts for the ORR and HER.

Due to the complexity of the synthetic process of cobalt phosphides (CoP), ongoing efforts concentrate on simplifying the preparation process of CoP. In this work, amino tris(methylene phosphonic acid) (ATMP, L1) and melamine (MA, L2) are assembled into two-dimensional (2D) organic nanostructures by hydrogen bonding and ionic interactions via a supramolecular assembly, which greatly weakens the coordination ability of L1 with Co2+. As the introduced L2 is rich in carbon and nitrogen, it allows the cobalt-organophosphate complex to be placed under a strongly reducing atmosphere during the high-temperature calcination process to achieve an in situ phosphating purpose. The resulting catalyst (N-CoP/NC) exhibits the sought-after enhanced oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) performance. For the ORR in 0.1 M KOH, an enhanced onset potential (0.908 V vs. RHE) and diffusion limiting current (6.280 mA cm-2) can be obtained, which is comparable to those of 20% Pt/C (0.911 V vs. RHE, 5.380 mA cm-2). For the HER in 0.5 M H2SO4, an overpotential of 150 mV is required to drive a current of 10 mA cm-2. Moreover, Density Functional Theory (DFT) calculations reveal the catalytic pathway of N-CoP/NC.