A Novel Hydrogen Peroxide Sensor via the Direct Electrochemistry of Horseradish Peroxidase Immobilized on Colloidal Gold Modified Screen-printed Electrode

The direct electrochemistry of horseradish peroxidase (HRP) immobilized on a colloidal gold modified screen-printed carbon electrode (HRP-Au-SPCE) and its application as a disposable sensor were studied. The immobilized HRP displayed a couple of stable and well-defined redox peaks with a formal potential of –0.338 V (vs. SCE) and a heterogeneous electron transfer rate constant of (0.75±0.04) s-1 in 0.1 M pH 7.0 PBS. It showed a highly thermal stability, fast amperometric response and an electrocatalytic activity to the reduction of hydrogen peroxide (H2O2) without the aid of an electron mediator. The biosensor exhibited high sensitivity, good reproducibility, and long-term stability for the determination of H2O2 with a linear range from 0.8 μM to 1.0 mM and a detection limit of 0. 4 μM at 3σ. The variation coefficients are 2.7 % and 2.3 % for over 10 successive assays at the H2O2 concentrations of 8.0 and 20 μM, respectively. The K M app for H2O2 sensor was determined to be 1.3 mM

A Novel Hydrogen Peroxide Sensor via the Direct Electrochemistry of Horseradish Peroxidase Immobilized on Colloidal Gold Modified Screen-printed Electrode

Abstract: The direct electrochemistry of horseradish peroxidase (HRP) immobilized on a colloidal gold modified screen-printed carbon electrode (HRP-Au-SPCE) and its application as a disposable sensor were studied. The immobilized HRP displayed a couple of stable and well-defined redox peaks with a formal potential of –0.338 V (vs. SCE) and a heterogeneous electron transfer rate constant of (0.75±0.04) s-1 in 0.1 M pH 7.0 PBS. It showed a highly thermal stability, fast amperometric response and an electrocatalytic activity to the reduction of hydrogen peroxide (H2O2) without the aid of an electron mediator. The biosensor exhibited high sensitivity, good reproducibility, and long-term stability for the determination of H2O2 with a linear range from 0.8 M to 1.0 mM and a detection limit of 0. 4 M at 3σ. The variation coefficients are 2.7 % and 2.3 % for over 10 successive assays at the H2O2 concentrations of 8.0 and 20 M, respectively. The K M app for H2O2 sensor was determined to be 1.3 mM

Integrated Tyramide and Polymerization-Assisted Signal Amplification for a Highly-Sensitive Immunoassay

A novel strategy for ultrasensitive detection of model protein based on the integration of tyramide signal amplification (TSA) and polymerization-assisted signal amplification was proposed. The surface-initiated atom transfer radical polymerization (SI-ATRP) of glycidyl methacrylate (GMA) was triggered by the initiator-coupled protein immobilized on the electrode surface through sandwiched immunoreactions. Growth of long chain polymeric materials provided numerous epoxy groups for subsequent coupling of horseradish peroxidase (HRP), which in turn significantly increased the loading of quantum dots (QDs) labeled tyramide in the presence of hydrogen peroxide. As a result, electrochemiluminescence (ECL) and square-wave voltammetric (SWV) measurements showed 9.4- and 10.5-fold increase in detection signal in comparison with the unamplified method, respectively. To demonstrate the feasibility of this approach, human immunoglobulin G antigen (IgG) as a model target protein was employed and the detection limits were 0.73 and 0.09 pg mL^–1 for ECL and SWV, respectively. The results showed that sensitivity of the presented immunoassay significantly increased by one-order of magnitude and offered great application promises in providing a sensitive, specific, and potent method for biological detection

Quantitative Detection of Potassium Ions and Adenosine Triphosphate via a Nanochannel-Based Electrochemical Platform Coupled with G‑Quadruplex Aptamers

The development of synthetic nanopores and nanochannels that mimick ion channels in living organisms for biosensing applications has been, and still remains, a great challenge. Although the biological applications of nanopores and nanochannels have achieved considerable development as a result of nanotechnology advancements, there are few reports of a facile way to realize those applications. Herein, a nanochannel-based electrochemical platform was developed for the quantitative detection of biorelated small molecules such as potassium ions (K⁺) and adenosine triphosphate (ATP) in a facile way. For this purpose, K⁺ or ATP G-quadruplex aptamers were covalently assembled onto the inner wall of porous anodic alumina (PAA) nanochannels through a Schiff reaction between −CHO groups in the aptamer and amino groups on the inner wall of the PAA nanochannels under mild reaction conditions. Conformational switching of the aptamers confined in the nanochannels occurs in the presence of the target molecules, resulting in increased steric hindrance in the nanochannels. Changes in steric hindrance in the nanochannels were monitored by the anodic current of indicator molecules transported through the nanochannels. As a result, quantitative detection of K⁺ and ATP was realized with a concentration ranging from 0.005 to 1.0 mM for K⁺ and 0.05 to 10.0 mM for ATP. The proposed platform displayed significant selectivity, good reproducibility, and universality. Moreover, this platform showed its potential for use in the detection of other aptamer-based analytes, which could promote its development for use in biological detection and clinical diagnosis

Core promoter-selective function of HMGA1 and Mediator in Initiator-dependent transcription

Eukaryotic transcriptional control is mediated by regulatory DNA elements in enhancer regions and core promoter elements located within the promoter region. Martinez and colleagues identify and characterize factors that regulate the TFIID-dependent transcription stimulatory function of the Initiator (INR) core promoter element and the TATA box. The authors demonstrate that these factors are the protein HMGA1, which regulates transcription machinery, and the Mediator coregulator complex, which functions by stimulating the core promoter through the INR element in the presence of HMGA1. These studies significantly advance our understanding of eukaryotic gene regulation

Fe-N-C Nanozyme with Both Accelerated and Inhibited Biocatalytic Activities Capable of Accessing Drug-Drug Interaction

Emerged as a cost-effective and robust enzyme mimic, nanozymes have drawn increasing attention with broad applications ranging from cancer therapy to biosensing. Developing nanozymes with both accelerated and inhibited biocatalytic properties in a biological context is highly envisioned for perusing more advanced functions of natural enzymes, such as in drug-drug interaction, but remains challenging. By re-visiting the well-known Fe-N-C electrocatalyst that has a heme-like Fe-Nx coordination active center, herein, we report that the Fe-N-C with a minimum graphitization had an even superior cytochrome P450 (CYP)-like biocatalytic activity. Moreover, the drug metabolization by the Fe-N-C upon co-existence of other foods and drugs demonstrated a trend of inhibition similar to CYP, indicating its great potential as a replacement for drug dosing guide and outcome prediction. Beyond boosting the enzyme-like activity, this work would open a new vista of nanozymes with inhibited behavior for keeping up more demanding applications, enabled by further mimicking the molecular structure of enzymes.</p

Diverse Metal Coordination Center in M-N-C Enabling Different Type of Enzyme-Mimic Reactions

The epoch-making breakthrough of nanoscience has brought new perspective to empolder new generation of nanozymes with enzyme-like structure and further to propel the comprehending of the structure-property relationship. Here, we report that the regulation of metal coordination center in M-N-C nanozymes (M = Fe, Co, Mn, Ni, and Cu) greatly altered their biocatalytic activities so as to selectively drive different types of enzymatic reactions. It was revealed that the intrinsic selectivity in interaction and activation of ROS by different M-Nx was the origin to promote disparate types of enzyme-like reactions. This work would open a new vista of nanozymes to selectively catalyze different types of reactions, enabled by mimicking the molecular structure of natural enzymes and a further modulation.</a

Electrochemiluminescent Detection of hNQO1 and Associated Drug Screening Enabled by Futile Redox Cycle Reaction

Human NAD(P)H: quinone oxidoreductase 1 (hNQO1), a proteinase that engages in detoxification of quinones and capable of activating anti-tumor drugs, has drawn increasing attention as tumor biomarker and drug target. To date, the detection of hNQO1 primarily uses stimulus-responsive probes, involving metabolization of synthetic quinone-functionalized substrates, which however, remain challenging to improve the sensing signal-to-noise ratio, and are lack of sufficient stability. Herein, we report a facile but general way for hNQO1 detection and associated drug screening as well by ECL sensing of the metabolic H2O2 enabled by futile redox cycle reaction. Taking advantage of the intrinsic circulatory amplification and the luminol-modified nickel foam electrode, the sensing system exhibited a record-level performance in electrochemiluminescent detection of hNQO1. The same strategy was also successfully applied to rapidly screening hNQO1-directed anti-tumor candidate drugs. The proposed new principle for hNQO1 detection would stimulate ECL as a promising tool that combines diagnostic and drug screening functions for the popularization of proteinases in cancer management

Endowing Nanozymes High Biocatalytic Selectivity by Substrates Channeling and Screening

As an alternative to surmount the weakness of natural enzymes, nanozymes have recently attracted extensive attention from early disease diagnosis to tumor therapy. However, due to the lack of enzyme-like molecular recognition units, the poor substrate selectivity of nanozyme-catalyzed reaction significantly restricts their widespread applications. By biomimicking the ingenuity of metabolism process in living, herein we report a multiple-nanozymes system capable of improving the substrate selectivity via cascade reactions in a confined space. As a showcase, the nitrogen-doped carbon nanocages (NCNC) and Prussian blue nanoparticles (PB NPs) were successfully coupled in a microfluidic device to highly selective oxidation and detection of ascorbic acid (AA, an important electron donor and catalyst for alleviation of oxidative stress) against other interferences. It was revealed that the products of the prior nanozymatic reaction were effectively screened as the reactants of the next one, thus stepwise improving the overall selectivity of the all-nanozyme system. This work may open a new door to improve the selectivity of all-nanozyme-system for prospect applications