Adaptable graphitic C6N6-based copper single-atom catalyst for intelligent biosensing

Atomically dispersed single-atom catalysts (SACs) and enzymes (SAzymes): synthesis and application in Alzheimer's disease detection

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline and memory loss. Conventional diagnostic methods, such as neuroimaging and cerebrospinal fluid analysis, typically detect AD at advanced stages, limiting the efficacy of therapeutic interventions. Early detection is crucial for improving patient condition by enabling timely administration of treatments that may decelerate disease progression. In this context, single-atom catalysts (SACs) and single-atom nanozymes (SAzymes) have emerged as promising tools offering highly sensitive and selective detection of Alzheimer's biomarkers. SACs, consisting of isolated metal atoms on a support surface, deliver unparalleled atomic efficiency, increased reactivity, and reduced operational costs, although certain challenges in terms of stability, aggregation, and other factors persist. The advent of SAzymes, which integrate SACs with natural metalloprotease catalysts, has further advanced this field by enabling controlled electronic exchange, synergistic productivity, and enhanced biosafety. Particularly, M-N-C SACs with M-Nx active sites mimic the selectivity and sensitivity of natural metalloenzymes, providing a robust platform for early detection of AD. This review encompasses the advancements in SACs and SAzymes, highlighting their pivotal role in bridging the gap between conventional enzymes and nanozyme and offering enhanced catalytic efficiency, controlled electron transfer, and improved biosafety for Alzheimer's detection.

Incorporation of Bimetallic Sulfide with Carbon Nitride for Advanced Na-Ion Batteries

Sodium-ion batteries (SIBs) have received tremendous attention owing to their low cost, high working voltages, and energy density. However, the design and development of highly efficient SIBs represent a great challenge. Here, a unique and reliable approach is reported to prepare carbon nitride (CN) hybridized with nickel iron sulfide (NFCN) using simple reaction between Ni-Fe layered double hydroxide and dithiooxamide. The characterization results demonstrate that the hybridization with optimal amount of CN induces local distortion in the crystal structure of the hybrid, which would benefit SIB performance. Systematic electrochemical studies with a half-cell configuration show that the present hybrid structure exhibits a promising reversible specific capacity of 348 mAh g-1 at 0.1 A g-1 after 100 cycles with good rate capability. Simulation result reveals that the iron atoms in nickel iron sulfide act as a primary active site to accommodate Na+ ions. At last, with a full cell configuration using NFCN and Na3V2(PO4)2O2F as the anode and cathode, respectively, the specific capacity appears to be ≈95 mAh g-1 after 50 cycles at 0.1 A g-1 condition. This excellent performance of these hybrids can be attributed to the synergistic effect of the incorporated CN species and the high conductivity of nickel-iron sulfide.

Cu Single-Atom Nanozyme-Mediated Electrochemiluminescence Biosensor for Highly Sensitive Detection of MicroRNA-622

MicroRNA (miRNA) detection is a critical aspect of disease diagnosis, and recent studies indicate that miRNA-622 could be a potential target for lung cancer. Herein, Cu single atoms were anchored on graphitic carbon nitride (Cu SAs@CN) as a coreaction accelerator applied in luminol-H2O2 system, thereby establishing an efficient and sensitive electrochemiluminescence (ECL) biosensor for miRNA-622 detection. Cu SAs@CN was explored to possess excellent enzyme-like activities that promote the generation of abundant reactive oxygen species, which amplified ECL emission. Meanwhile, in order to improve the accuracy and sensitivity for miRNA-622 detection, the highly specific trans-cleavage ability of CRISPR/Cas12a was combined with a catalytic hairpin assembly strategy. Therefore, an ECL biosensor for miRNA-622 detection was systematically constructed as a proof of concept, achieving an ultralow limit of detection of 1.09 fM, and the feasibility was demonstrated in human serum samples. The findings of this research provide a promising strategy to enhance the ECL response using versatile single-atom catalysts, thus advancing the development of ECL biosensing applications.

Atomically Co-dispersed nitrogen-doped carbon for sensitive electrochemical immunoassay of breast cancer biomarker CA15-3

The development of an ultrasensitive and precise measurement of a breast cancer biomarker (cancer antigen 15-3; CA15-3) in complex human serum is essential for the early diagnosis of cancer in groups of healthy populations and the treatment of patients. However, currently available testing technologies suffer from insufficient sensitivity toward CA15-3, which severely limits early large-scale screening of breast cancer patients. We report a versatile electrochemical immunoassay method based on atomically cobalt-dispersed nitrogen-doped carbon (Co-NC)-modified disposable screen-printed carbon electrode (SPCE) with alkaline phosphatase (ALP) and its metabolite, ascorbic acid 2-phosphate (AAP), as the electrochemical labeling and redox signaling unit for sensitive detection of low-abundance CA15-3. During electrochemical detection by differential pulse voltammetry (DPV), it was found that the Co-NC-SPCE electrode did not have a current signal response to the AAP substrate; however, it had an extremely favorable response current to ascorbic acid (AA). Based on the above principle, the target CA15-3-triggered immunoassay enriched ALP-catalyzed AAP produces a large amount of AA, resulting in a significant change in the system current signal, thereby realizing the highly sensitive detection of CA15-3. Under the optimal AAP substrate concentration and ALP catalysis time, the Co-NC-SPCE-based electrochemical immunoassay demonstrated a good DPV current for CA15-3 in the assay interval of 1.0 mU/mL to 10,000 mU/mL, with a calculated limit of detection of 0.38 mU/mL. Since Co-NC-SPCE has an excellent DPV current response to AA and employs split-type scheme, the constructed electrochemical immunoassay has the merits of high preciseness and anti-interference, and its clinical diagnostic results are comparable to those of commercial kits.

Nanohybrids of BCN-Fe1-xS for Sodium and Lithium Hybrid Ion Capacitors

Hybrid ion capacitors (HIC) are receiving a lot of attention due to their potential to achieve high energy and power densities, but they remain insufficient. It is imperative to explore outstanding and environmentally benign electrode materials to achieve high-performing HIC systems. Here, a unique boron carbon nitride (BCN)-based HIC system that comprises a microporous BCN structure and Fe1-xS nanoparticle incorporated BCN nanosheets (BNF) as cathode and anode, respectively is reported. The BNF is prepared through a facile one-pot calcination process using dithiooxamide (DTO), boric acid, and iron source. In situ, crystal growth of Fe1-xS facilitates the formation of BCN structure through the creation of holes/defects in the polymeric structure. The first principle density functional (DFT) theory simulations demonstrate the structural and electronic properties of the hybrid of BCN and Fe1-xS as compelling anode materials for HIC applications. The DFT calculations reveal that both BCN and BNF structures have excellent metallic characters with Li+ storage capacities of 128.4 and 1021.38 mAh g-1 respectively. These findings are confirmed experimentally where the BCN-based HIC system delivers exceptional energy and power densities of 267.5 Wh kg-1/749.5 W kg-1 toward Li+ storage, which outweighs previous HIC performances and demonstrates favorable performance for Li+ and Na+ storages.

The biomedical application of inorganic metal nanoparticles in aging and aging-associated diseases

Aging and aging-associated diseases (AAD), including neurodegenerative disease, cancer, cardiovascular diseases, and diabetes, are inevitable process. With the gradual improvement of life style, life expectancy is gradually extended. However, the extended lifespan has not reduced the incidence of disease, and most elderly people are in ill-health state in their later years. Hence, understanding aging and AAD are significant for reducing the burden of the elderly. Inorganic metal nanoparticles (IMNPs) predominantly include gold, silver, iron, zinc, titanium, thallium, platinum, cerium, copper NPs, which has been widely used to prevent and treat aging and AAD due to their superior properties (essential metal ions for human body, easily synthesis and modification, magnetism). Therefore, a systematic review of common morphological alternations of senescent cells, altered genes and signal pathways in aging and AAD, and biomedical applications of IMNPs in aging and AAD is crucial for the further research and development of IMNPs in aging and AAD. This review focus on the existing research on cellular senescence, aging and AAD, as well as the applications of IMNPs in aging and AAD in the past decade. This review aims to provide cutting-edge knowledge involved with aging and AAD, the application of IMNPs in aging and AAD to promote the biomedical application of IMNPs in aging and AAD.

Self-Powered Immunoassay of Norovirus in Human Stools by π-Electron-Rich Homojunction for Enhanced Charge Transfer

Norovirus (NoV) stands as a significant causative agent of nonbacterial acute gastroenteritis on a global scale, presenting a substantial threat to public health. Hence, the development of simple and rapid analytical techniques for NoV detection holds great importance in preventing and controlling the outbreak of the epidemic. In this work, a self-powered photoelectrochemical (PEC) immunosensor of NoV capsid protein (VP1) was proposed by the π-electron-rich carbon nitride homojunction (ER-CNH) as the photoanode. C4N2 ring derived from π-rich locust bean gum was introduced into the tri-s-triazine structure, creating a large π-delocalized conjugated carbon nitride homojunction. This strategy enhances the C/N atomic ratio, which widens light utilization, narrows the bandgap, and optimizes the electronic band structure of carbon nitride. By introduction of a π-rich conjugated structure, p-type domains were induced within n-type domains to build the internal electric field at the interface, thus forming a p-n homojunction to boost carrier separation and transfer. The ER-CNH photoanode exhibited excellent photoelectric performance and water oxidation capacity. Since VP1 inhibits the water oxidation of the ER-CNH photoanode, the open-circuit potential of the as-prepared PEC immunosensor system was reduced for detecting NoV VP1. The self-powered PEC immunosensor achieved a remarkably low detection limit (∼5 fg mL-1) and displayed high stability and applicability for actual stool samples. This research serves as a foundation concept for constructing immunosensors to detect other viruses and promotes the application of self-powered systems for life safety.

Decoupling of the Confused Complex in Oxidation of 3,3',5,5'-Tetramethylbenzidine for the Reliable Chromogenic Bioassay

Regulation of the reaction pathways is a perennial theme in the field of chemistry. As a typical chromogenic substrate, 3,3',5,5'-tetramethylbenzidine (TMB) generally undertakes one-electron oxidation, but the product (TMBox1) is essentially a confused complex and is unstable, which significantly hampers the clinic chromogenic bioassays for more than 50 years. Herein, we report that sodium dodecyl sulfate (SDS)-based micelles could drive the direct two-electron oxidation of TMB to the final stable TMBox2. Rather than activation of H2O2 oxidant in the one-electron TMB oxidation by common natural peroxidase, activation of the TMB substrate by SDS micelles decoupled the thermodynamically favorable complex between TMBox2 with unreacted TMB, leading to an unusual direct two-electron oxidation pathway. Mechanism studies demonstrated that the complementary spatial and electrostatic isolation effects, caused by the confined hydrophobic cavities and negatively charged outer surfaces of SDS micelles, were crucial. Further cascading with glucose oxidase, as a proof-of-concept application, allowed glucose to be more reliably measured, even in a broader range of concentrations without any conventional strong acid termination.

Single-atom nanozymes: classification, regulation strategy, and safety concerns

Nanozymes, nanomaterials possessing enzymatic activity, have been studied extensively by researchers. However, their complex composition, low density of active sites, and inadequate substrate selectivity have hindered the maturation and widespread acceptance of nanozymes. Single-atom nanozymes (SAzymes) with atomically dispersed active sites are leading the field of catalysis due to their exceptional performance. The maximum utilization rate of atoms, low cost, well-defined coordination structure, and active sites are the most prominent advantages of SAzymes that researchers favor. This review systematically categorizes SAzymes based on their support type and describes their specific applications. Additionally, we discuss regulation strategies for SAzyme activity and provide a comprehensive summary of biosafety challenges associated with these enzymes.

Stabilized and Controlled Release of Radicals within Copper Formate-Based Nanozymes for Biosensing

Fenton-like radical processes are widely utilized to explain catalytic mechanisms of peroxidase-like nanozymes, which exhibit remarkable catalytic activity, cost-effectiveness, and stability. However, there is still a need for a comprehensive understanding of the formation, stabilization, and transformation of such radicals. Herein, a copper formate-based nanozyme (Cuf-TMB) was fabricated via a pre-catalytic strategy under ambient conditions. The as-prepared nanozyme shows comparable catalytic activity (Km, 1.02 × 10-5 mM-1; Kcat, 3.09 × 10-2 s-1) and kinetics to those of natural peroxidase toward H2O2 decomposition. This is attributed to the feasible oxidation by *OH species via the *O intermediate, as indicated by density functional theory calculations. The key ·OH radicals were detected to be stable for over 52 days and can be released in a controlled manner during the catalytic process via in situ electron spin-resonance spectroscopy measurements. Based on the understanding, an ultrasensitive biosensing platform was constructed for the sensitive monitoring of biochemical indicators in clinic settings.