Electrochemical Sensor for Carbonyl Groups in Oxidized Proteins

Nanozyme Catalytic Performance Enhancement through Defect and Electronic Structure Regulation of Metal-Doped NiCo2O4@Pd

Spinel oxides have emerged as a promising candidate in the realm of nanozymes with variable oxidation states, while their limited active sites and low conductivity hinder further application. In this work, we synthesize a series of metal-doped NiCo2O4 nanospheres decorated with Pd, which are deployed as highly efficient nanozymes for the detection of cancer biomarkers. Through meticulous modulation of the molar ratio between NiCo2O4 and Pd, we orchestrated precise control over the oxygen vacancies and electronic structure within the nanozymes, a key factor in amplifying the catalytic prowess. Leveraging the superior H2O2 reduction catalytic properties of Fe-NiCo2O4@Pd, we have successfully implemented its application in the electrochemical detection of biomarkers, achieving unparalleled analytical performance, much higher than that of Pd/C and other reported nanozymes. This research paves the way for innovative electron modification strategies in the design of high-performance nanozymes, presenting a formidable tool for clinical diagnostic analyses.

Coaxial dual-path electrochemical biosensing and logic strategy-based detection of lung cancer-derived exosomal PD-L1

Exosomal programmed death ligand-1 (ExoPD-L1) is a vital marker of immune activation in the early stages of tumor therapy and it can inhibit anti-tumor immune responses. However, due to the low expression of ExoPD-L1 in cancer cells, it is difficult to perform highly sensitive assays and accurately differentiate cancer sources. Therefore, we constructed a coaxial dual-path electrochemical biosensor for highly accurate identification and detection of ExoPD-L1 from lung cancer based on chemical-biological coaxial nanomaterials and nucleic acid molecular signal amplification strategies. The measurements showed that the detected ExoPD-L1 concentrations ranged from 6 × 102 particles per mL to 6 × 108 particles per mL, and the detection limit was 310 particles per mL. Compared to other sensors, the electrochemical biosensor designed in this study has a lower detection limit and a wider detection range. Furthermore, we also successfully identified lung cancer-derived ExoPD-L1 by analyzing multiple protein biomarkers expressed on exosomes through the "AND" logic strategy. This sensor platform is expected to realize highly sensitive detection and accurate analysis of multiple sources of ExoPD-L1 and provide ideas for the clinical detection of ExoPD-L1.

Rapid Cryptococcus electroporated-lysis and sensitive detection on a miniaturized platform

Fast and accurate detection of Cryptococcus and precise differentiation of its subtypes is of great significance in protecting people from cryptococcal disease and preventing its spread in populations. However, traditional Cryptococcus identification and detection techniques still face significant challenges in achieving high analysis speed as well as high sensitivity. In this work, we report an electric microfluidic biochip. Compared to conventional methods that take several hours or even a day, this chip can detect Cryptococcus within 20 min, and achieve its maximum detection limit within 1 h, with the ability to differentiate between the Cryptococcus neoformans (NEO) and rare Cryptococcus gattii (GAT) efficiently, which accounts for nearly 100%. This device integrated two functional zones of an electroporation lysis (EL) zone for rapid cell lysis (<30 s) and an electrochemical detection (ED) zone for sensitive analysis of the released nucleic acids. The EL zone adopted a design of microelectrode arrays, which obtains a large electric field intensity at the constriction of the microchannel, addressing the safety concerns associated with high-voltage lysis. The device enables a limit of detection (LOD) of 60 pg/mL for NEO and 100 pg/mL for GAT through the modification of nanocomposites and specific probes. In terms of the detection time and sensitivity, the integrated microfluidic biochip demonstrates broad potential in Cryptococcus diagnosis and disease prevention.

Particulate matter stimulates the NADPH oxidase system via AhR-mediated epigenetic modifications

Stimulation of human keratinocytes with particulate matter 2.5 (PM2.5) elicits complex signaling events, including a rise in the generation of reactive oxygen species (ROS). However, the mechanisms underlying PM2.5-induced ROS production remain unknown. Here, we show that PM2.5-induced ROS production in human keratinocytes is mediated via the NADPH oxidase (NOXs) system and the Ca2+ signaling pathway. PM2.5 treatment increased the expression of NOX1, NOX4, and a calcium-sensitive NOX, dual oxidase 1 (DUOX1), in human epidermal keratinocyte cell line. PM2.5 bound to aryl hydrocarbon receptor (AhR), and this complex bound to promoter regions of NOX1 and DUOX1, suggesting that AhR acted as a transcription factor of NOX1 and DUOX1. PM2.5 increased the transcription of DUOX1 via epigenetic modification. Moreover, a link between DNA demethylase and histone methyltransferase with the promoter regions of DUOX1 led to an elevation in the expression of DUOX1 mRNA. Interestingly, PM2.5 increased NOX4 expression and promoted the interaction of NOX4 and Ca2+ channels within the cytoplasmic membrane or endoplasmic reticulum, leading to Ca2+ release. The increase in intracellular Ca2+ concentration activated DUOX1, responsible for ROS production. Our findings provide evidence for a PM2.5-mediated ROS-generating system network, in which increased NOX1, NOX4, and DUOX1 expression serves as a ROS signal through AhR and Ca2+ activation.

Electrochemical approaches based on micro- and nanomaterials for diagnosing oxidative stress

This review article comprehensively discusses the various electrochemical approaches for measuring and detecting oxidative stress biomarkers and enzymes, particularly reactive oxygen/nitrogen species, highly reactive chemical molecules, which are the byproducts of normal aerobic metabolism and can oxidize cellular components such as DNA, lipids, and proteins. First, we address the latest research on the electrochemical determination of reactive oxygen species generating enzymes, followed by detection of oxidative stress biomarkers, and final determination of total antioxidant activity (endogenous and exogenous). Most electrochemical sensing platforms exploited the unique properties of micro- and nanomaterials such as carbon nanomaterials, metal or metal oxide nanoparticles (NPs), conductive polymers and metal-nano compounds, which have been mainly used for enhancing the electrocatalytic response of sensors/biosensors. The performance of the electroanalytical devices commonly measured by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in terms of detection limit, sensitivity, and linear range of detection is also discussed. This article provides a comprehensive review of electrode fabrication, characterization and evaluation of their performances, which are assisting to design and manufacture an appropriate electrochemical (bio)sensor for medical and clinical applications. The key points such as accessibility, affordability, rapidity, low cost, and high sensitivity of the electrochemical sensing devices are also highlighted for the diagnosis of oxidative stress. Overall, this review brings a timely discussion on past and current approaches for developing electrochemical sensors and biosensors mainly based on micro and nanomaterials for the diagnosis of oxidative stress.

Carbon Inks-Based Screen-Printed Electrodes for Qualitative Analysis of Amino Acids

Due to the great significance of amino acids, a substantial number of research studies has been directed toward the development of effective and reliable platforms for their evaluation, detection, and identification. In order to support these studies, a new electrochemical platform based on PANI/ZnO nanowires' modified carbon inks screen-printed electrodes was developed for qualitative analysis of electroactive amino acids, with emphasis on tyrosine (Tyr) and tryptophan (Trp). A comparative investigation of the carbon ink before and after modification with the PANI/ZnO was performed by scanning electron microscopy and by Raman spectroscopy, confirming the presence of PANI and ZnO nanowires. Electrochemical investigations by cyclic voltammetry and electrochemical impedance spectroscopy have shown a higher charge-transfer rate constant, which is reflected into lower charge-transfer resistance and higher capacitance values for the PANI/ZnO modified ink when compared to the simple carbon screen-printed electrode. In order to demonstrate the electrochemical performances of the PANI/ZnO nanowires' modified carbon inks screen-printed electrodes for amino acids analysis, differential pulse voltammograms were obtained in individual and mixed solutions of electroactive amino acids. It has been shown that the PANI/ZnO nanowires' modified carbon inks screen-printed electrodes allowed for tyrosine and tryptophan a peak separation of more than 100 mV, enabling their screening and identification in mixed solutions, which is essential for the electrochemical analysis of proteins within the proteomics research field.

Clinically Applicable Homogeneous Assay for Serological Diagnosis of Alpha-Fetoprotein by Impact Electrochemistry

Tumor protein quantification with high specificity, sensitivity, and efficiency is of great significance to enable early diagnosis and effective treatment. The existing methods for protein analysis usually suffer from high cost, time-consuming operation, and insufficient sensitivity, making them not clinically friendly. In this work, a label-free homogeneous sensor based on the nano-impact electroanalytic (NIE) technique was proposed for the detection of tumor protein marker alpha-fetoprotein (AFP). The detection principle is based on the recovery of current of single PtNP catalyzed hydrazine oxidation due to the release of the pre-adsorbed passivating aptamers on PtNPs from the competition of the stronger binding between the specific interaction of the AFP aptamer and AFP. The intrinsic one-by-one analytical ability of NIE allows highly sensitive detection, which can be further improved by reducing the reaction/incubation volume. Meanwhile, the current sensor avoids a laborious labeling procedure as well as the separation and washing steps due to the in situ characteristic of NIE. Accordingly, the current sensor enables efficient, highly sensitive, and specific AFP analysis. More importantly, the reliable detection of AFP in diluted real sera from hepatocellular carcinoma (HCC) patients is successfully achieved, indicating that the impact electrochemistry-based sensing platform has great potential to be applied in point-of-care devices for HCC liquid biopsy.

Rapid 16S rDNA electrochemical sensor for detection of bacteria based on the integration of target-triggered hairpin self-assembly and tripedal DNA walker amplification

Diseases caused by bacteria pose great challenges to human health. The key to reduce disease transmission and mortality is to develop accurate and rapid methods for the detection and identification of bacteria. Herein, a rapid bacteria 16S rDNA electrochemical sensor based on target-triggered hairpin self-assembly and tripedal DNA walker (TD walker) amplification strategy was constructed. Specific variable region of 16S rDNA fragment of bacteria was used as biomarker. The target-triggered hairpin self-assembly strategy was used to prepare a TD walker. The hairpin DNA probes labeled with ferrocene (F_c) were designed and modified on surface of electrode. The "legs" of TD walker hybridized with three hairpin probes and opened their hairpin structures. Exo III enzyme recognised hybrid duplexes and selectively digest hairpin probes. The "legs" of TD walker was released and hybridized with the other three hairpin probes. In this way, the enzyme drived the walkers to walk along electrode interface, until hairpin DNA probes were all removed from the electrode, the F_c was far away from electrode interface. A significantly current reduction signal was obtained and bacteria were detected by recording this response. This strategy was low-cost and scalable, it could continuously recycle low-concentration targets, thus enhanced the detection sensitivity. As the proof-of-concept work, the electrochemical sensor was utilized as detector. The limit of detection (LOD) of detecting Staphylococcus aureus (S. aureus) was 20 CFU mL^-1 and detection time was less than 3 h. It was expected to be widely used in clinical early diagnosis.

Biomarkers of Oxidative Stress and Antioxidant Defense

A number of reactive oxygen and nitrogen species are produced during normal metabolism in human body. These species can be both radical and non-radical and have varying degrees of reactivity. Although they have some important functions in the human body, such as contributing to signal transmission and the immune system, their presence must be balanced by the antioxidant defense system. The human body has an excellent intrinsic enzymatic antioxidant system in addition to different non-enzymatic antioxidants having small molecular masses. An extrinsic source of antioxidants are foodstuffs such as fruits, vegetables, herbs and spices, mostly rich in polyphenols. When the delicate biochemical balance between oxidants and antioxidants is disturbed in favor of oxidants, "oxidative stress" conditions emerge, under which reactive species can cause oxidative damage to biomacromolecules such as proteins, carbohydrates, lipids and DNA. This oxidative damage is often associated with cancer, aging, and neurodegenerative disorders. Because reactive species are extremely short-lived, it is almost impossible to measure their concentrations directly. Although there are certain methods such as ESR / EPR that serve this purpose, they have some disadvantages and are quite costly systems. Therefore, products generated from oxidative damage of proteins, lipids and DNA are often used to quantify the extent of oxidative damage rather than direct measurement of reactive species. These oxidative damage products are usually known as biomarkers. Determination of the concentrations of these biomarkers and changes in the concentration of protective antioxidants can provide useful information for avoiding certain diseases and keep healthy conditions.

4-Hydroxy-2-nonenal, a lipid peroxidation product, as a biomarker in diabetes and its complications: challenges and opportunities

Over 30 million Americans are diagnosed with diabetes and this number is only expected to increase. There are various causes that induce complications with diabetes, including oxidative stress. In oxidative stress, lipid peroxidation-derived reactive carbonyl species such as 4-hydroxy-2-nonenal (4-HNE) is shown to cause damage in organs that leads to diabetic complications. We provided evidence to show that 4-HNE or/and 4-HNE-protein adducts are elevated in various organ systems of diabetic patients and animal models. We then discussed the advantages and disadvantages of different methodologies used for the detection of 4-HNE in diabetic tissues. We also discussed how novel approaches such as electrochemistry and nanotechnology can be used for monitoring 4-HNE levels in biological systems in real-time. Thus, this review enlightens the involvement of 4-HNE in the pathogenesis of diabetes and its complications and efficient methods to identify it. Furthermore, the article presents that 4-HNE can be developed as a biomarker for end-organ damage in diabetes such as diabetic cardiac complications.

Simple electrochemical sensing for mercury ions in dairy product using optimal Cu2+-based metal-organic frameworks as signal reporting

A convenient sensor is developed for electrochemical assay of Hg²⁺ in dairy product using the optimal Cu²⁺-based metal-organic frameworks (Cu-MOFs) as signal reporting. Benefiting from specific recognition between Hg²⁺ and thymine (T)-rich DNA strands, the interferences of milk matrices are effectively eliminated, thereby greatly improving the accuracy of test results. Moreover, the suitable Cu-MOFs offer an efficient carrier for probe design, and the contained Cu²⁺ ions could be directly detected to output electrochemical signal of Hg²⁺ presence without labor- or time-intensive operations. Compared with previous methods, this sensor substantially simplifies the process of electrochemical measurement and facilitates highly sensitive, selective and rapid analysis of Hg²⁺ with detection limit of 4.8 fM, offering a valuable means for monitoring dairy product contamination with Hg²⁺.

Quantitative Profiling of Protein-Derived Electrophilic Cofactors in Bacterial Cells with a Hydrazine-Derived Probe

Post-translational modification of proteins can form electrophilic cofactors that serve as a catalytic center. The derived electrophilic cofactors greatly expand protein activities and functions. However, there are few studies concerning how to profile the electrophiles in bacteria. Herein, we utilized a clickable probe called propargyl hydrazine to profile the protein-derived electrophilic cofactors in Escherichia coli (E. coli) cells. Since the cofactors are mostly carbonyl groups, the hydrazine-based probe can specifically react with the cofactors to form a Schiff base. The labeled proteins were then pulled down for mass spectrometry (MS) analysis. Fourteen proteins were shown to undergo enrichment by the probe and competitive binding by its analogue, propyl hydrazine. The identified proteins were further analyzed with targeted proteomics based on parallel reaction monitoring (PRM). Using this strategy, we obtained a global portrait of protein electrophiles in bacterial cells, among which the proteins of speD and panD were previously reported to derive pyruvoyl group as an electrophilic center while lpp can retain N-terminal formyl methionine. This quantitative chemical proteomics strategy can be used to find out protein electrophiles in bacteria and holds great potential to further characterize the protein functions.