Amalgamation of DNAzymes and Nanozymes in a Coronazyme

High-power "nesting-doll" biofuel cell enabled by free-standing electrodes with inherent enzymatic function

Biofuel cell (BFC) is a type of green energy device based on the biocatalyst-mediated redox reaction. However, their relatively low performance has limited their wider application. Here, we proposed a novel all-in-one strategy to design the free-standing electrodes with the inherent enzyme-like activity and high conductivity, in which, the dynamic limitations of the enzyme-electrode interface were eliminated. This approach facilitated rapid electron transfer by removing the need to coat enzymes on the electrode. Furthermore, the enzyme-mimic characteristic enhanced the stability of BFC. Notably, the step-by-step "ionic corrosion-electrografting coordination" of Cu foam yielded the free-standing cathode, which exhibited excellent laccase-like activity. Concurrently, the in-situ loading of gold particles on the Ni foam can serve as an exemplary mimic of the glucose oxidase. Furthermore, a "nesting doll" nanozyme BFC device was developed, in which, the anode was placed inside the cathode to create a multi-shell coaxial configuration. The four-tier devices demonstrated an elevated open-circuit voltage of 1.7 V, and the output power density was 3639.0 μW cm⁻2 measured by resistance method, which was superior to that of the reported literatures. This study presents a pioneering approach to improving output performance and stability, thereby broadening the potential scope of BFC application.

Target-driven functionalized DNA hydrogel capillary sensor for SARS-CoV-2 dual-mode detection

Coronavirus disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused secondary pandemic, which still poses a serious threat to physical health and economic development. Herein, the target-driven functionalized DNA hydrogel capillary sensor based on cascade signal amplification and carbon coated cobalt manganese modified by prussian blue and platinum nanoparticles (MnCo@C-Pt-PB NPs) has been successfully developed for dual-mode detection of SARS-CoV-2. The cascade signal amplification triggered by target RNA causes the permeability of the DNA hydrogel loaded in the capillary to be destroyed, thereby releasing the embedded MnCo@C-Pt-PB NPs as signal molecules into 3,3',5,5'-tetramethylbenzidine/hydrogen peroxide (TMB/H2O2) solution under the driving of capillarity. The colorless TMB is then catalyzed to blue oxidation products (oxTMB) due to peroxidase-like activity of MnCo@C-Pt-PB NPs, and MnCo@C-Pt-PB NPs and oxTMB with photothermal properties synergistically increase the system temperature under near-infrared irradiation, which are recorded by portable devices to achieve dual-mode detection. Signals intensity are proportional to the logarithm of T-RNA concentration in a wide detection range (100 aM-100 pM), with a detection limit of 100 aM. Moreover, the reliability of the developed method in oropharyngeal swabs samples has also been validated. The signal conversion and amplification function of functionalized DNA hydrogel enhances the convenience, sensitivity and versatility of the developed method, which is promising to be applied in environmental safety, molecular diagnostic assays and disease prevention.

Nanozyme-catalyzed and zwitterion-modified swabs based for the detection of Listeria monocytogenes in complex matrices

In recent years, nanozymes have been widely used in the field of biosensing and food safety testing due to their advantages of low cost, high stability, easy modification and adjustable catalytic activity. However, how to reduce the signal interference generated by reducing substances, macromolecules and colored substances in the food matrix in nanozymes-based colorimetric sensing is still a major challenge. In this paper, using Listeria monocytogenes as a model analyte, sodium sulfonyl methacrylate (SBMA) polymers were modified onto cotton swabs by photothermal polymerization and combined with Listeria monocytogenes-specific aptamer (Apt1) to prepare swabs that can specifically capture and isolate Listeria monocytogenes from complex matrices (SBMA/Apt1 cotton swab). In addition, in combination with the inhibitory effect of the aptamer (Apt2) on the oxidase activity of Mn3O4 NPs, a colorimetric biosensor based on nanozymes that can quantitatively, sensitively, and specifically identify Listeria monocytogenes in food products was constructed. The results showed that the colorimetric signal of the method was linear with the concentration of Listeria monocytogenes in the range of 2.83-2.83 × 105 CFU/mL, and the limit of detection was 2.64 CFU/mL, which can be used for the detection of Listeria monocytogenes in complex environments and food samples.

Applications of DNA functionalized gold nanozymes in biosensing

In recent years, nanozymes have emerged as highly potential substitutes, surpassing the performance of natural enzymes. Among them, gold nanoparticles (AuNPs) and their metal hybrids have become a hot topic in nanozyme research due to their facile synthesis, easy surface modification, high stability, and excellent enzymatic activity. The integration of DNA with AuNPs, by precisely controlling the assembly, arrangement, and functionalization of nanoparticles, greatly facilitates the development of highly sensitive and selective biosensors. This review comprehensively elaborates on three core strategies for the combination of DNA with AuNPs, and deeply analyzes two widely applied enzyme activities in the field of sensing technology and the catalytic principles behind them. On this basis, we systematically summarize various methods for regulating the activity of gold nanozymes by DNA. Following that, we comprehensively review the latest research trends of DNA-Au nanozymes in the field of biosensing, with a particular focus on several crucial application areas such as food safety, environmental monitoring, and disease diagnosis. In the conclusion of the article, we not only discuss the main challenges faced in current research but also look forward to potential future research directions.

Discovery of Lipoxygenase-Like Materials for Inducing Ferroptosis

Recent research has highlighted the pivotal role of lipoxygenases in modulating ferroptosis and immune responses by catalyzing the generation of lipid peroxides. However, the limitations associated with protein enzymes, such as poor stability, low bioavailability, and high production costs, have motivated researchers to explore biomimetic materials with lipoxygenase-like activity. Here, we report the discovery of lipoxygenase-like two-dimensional (2D) MoS2nanosheets capable of catalyzing lipid peroxidation and inducing ferroptosis. The resulting catalytic products were successfully identified using mass spectrometry and a luminescent substrate. Unlike native lipoxygenases, MoS2 nanosheets exhibited exceptional catalytic activity at extreme pH, high temperature, high ionic strength, and organic solvent conditions. Structure-activity relationship analysis indicates that sulfur atomic vacancy sites on MoS2 nanosheets are responsible for their catalytic activity. Furthermore, the lipoxygenase-like activity of MoS2 nanosheets was demonstrated within mammalian cells and animal tissues, inducing distinctive ferroptotic cell death. In summary, this research introduces an alternative to lipoxygenase to regulate lipid peroxidation in cells, offering a promising avenue for ferroptosis induction.

DNA Catalysis: Design, Function, and Optimization

Catalytic DNA has gained significant attention in recent decades as a highly efficient and tunable catalyst, thanks to its flexible structures, exceptional specificity, and ease of optimization. Despite being composed of just four monomers, DNA's complex conformational intricacies enable a wide range of nuanced functions, including scaffolding, electrocatalysis, enantioselectivity, and mechano-electro spin coupling. DNA catalysts, ranging from traditional DNAzymes to innovative DNAzyme hybrids, highlight the remarkable potential of DNA in catalysis. Recent advancements in spectroscopic techniques have deepened our mechanistic understanding of catalytic DNA, paving the way for rational structural optimization. This review will summarize the latest studies on the performance and optimization of traditional DNAzymes and provide an in-depth analysis of DNAzyme hybrid catalysts and their unique and promising properties.

Recent Advances in Nanozyme Sensors Based on Metal-Organic Frameworks and Covalent-Organic Frameworks

Nanozymes are nanomaterials that exhibit enzyme-like catalytic activity, which have drawn increasing attention on account of their unique superiorities including very high robustness, low cost, and ease of modification. Metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs) have emerged as promising candidates for nanozymes due to their abundant catalytic activity centers, inherent porosity, and tunable chemical functionalities. In this review, we first compare the enzyme-mimicking activity centers and catalytic mechanisms between MOF and COF nanozymes, and then summarize the recent research on designing and modifying MOF and COF nanozymes with inherent catalytic activity. Moreover, typical examples of sensing applications based on these nanozymes are presented, as well as the translation of enzyme catalytic activity into a visible signal response. At last, a discussion of current challenges is presented, followed by some future prospects to provide guidance for designing nanozyme sensors based on MOFs and COFs for practical applications.

Helical Polyallenes: From Controlled Synthesis to Distinct Properties

Polyallenes with appropriate pendants can form stable helices and exhibit significant optical activity. These helical polyallenes contain reactive double bonds that allow for further functionalization, making them a class of chiral functional materials with broad application prospects. This review article delves into the intricacies of synthesizing well-defined helical polyallenes through controlled synthetic methodologies, including helix-sense selective living polymerization, regioselective and asymmetric living polymerization, and one-pot block copolymerization of allenes with aryl monomers. The systemically outlined characteristics of the resulting helical polyallenes and related copolymers are summarized include their unique chiroptical properties, stimuli-responsiveness, helix-induced chiral self-assembly, and circularly polarized luminescence (CPL). Additionally, current challenges and future perspectives in the research of controlled synthesis, functionalities, and applications of helical polyallenes are discussed in detail.

Creating a suprazyme: integrating a molecular enzyme mimic with a nanozyme for enhanced catalysis

Enzyme mimics, due to their limited complexity, traditionally display low catalytic efficiency. Herein we present a strategy that enables the transformation of a slow-acting catalyst into a highly active one by creating a non-covalent suprastructure, termed "suprazyme". We show that cucurbit[7]uril macrocycles, rudimentary molecular enzyme mimics, embedded within an anionic monolayer on the surface of gold nanoparticles, outperform individual cucurbit[7]urils as well as nanoparticles, which also exhibit catalytic enzyme-like activity and thus act as nanozymes, by over 50 times, showcasing a 1044-fold acceleration in a model oxime formation reaction. The superior performance of such a suprazyme is attributed to a synergistic interplay between the organic monolayer and macrocycles, which is accompanied by a decreased local polarity and pH that favors the acid-catalyzed condensation process. The proposed approach holds promise for developing diverse suprazymes, contingent upon achieving a complementary structure and mechanism of action between the molecular catalyst and nanoparticles.

High fidelity detection of miRNAs from complex physiological samples through electrochemical nanosensors empowered by proximity catalysis and magnetic separation

Electrochemical detection of miRNA biomarkers in complex physiological samples holds great promise for accurate evaluation of tumor burden in the perioperative period, yet limited by reproducibility and bias issues. Here, nanosensors installed with hybrid probes that responsively release catalytic DNAzymes (G-quadruplexes/hemin) were developed to solve the fidelity challenge in an immobilization-free detection. miRNA targets triggered toehold-mediated strand displacement reactions on the sensor surface and resulted in amplified shedding of DNAzymes. Subsequently, the interference background was removed by Fe3O4 core-facilitated magnetic separation. Binding aptamers of the electrochemical reporter (dopamine) were tethered closely to the catalytic units for boosting H2O2-mediated oxidation through proximity catalysis. The one-to-many conversion by dual amplification from biological-chemical catalysis facilitated sufficient homogeneous sensing signals on electrodes. Thereby, the nanosensor exhibited a low detection limit (2.08 fM), and high reproducibility (relative standard deviation of 1.99%). Most importantly, smaller variations (RSD of 0.51-1.04%) of quantified miRNAs were observed for detection from cell lysates, multiplexed detection from unprocessed serum, and successful discrimination of small upregulations in lysates of tumor tissue samples. The nanosensor showed superior diagnostic performance with an area under curve (AUC) of 0.97 and 94% accuracy in classifying breast cancer patients and healthy donors. These findings demonstrated the synergy of signal amplification and interference removal in achieving high-fidelity miRNA detection for practical clinical applications.

A dual-mode fluorometric/colorimetric sensor for sulfadimethoxine detection based on Prussian blue nanoparticles and carbon dots

A dual-mode (colorimetric/fluorescence) nanoenzyme-linked immunosorbent assay (NLISA) was developed based on Au-Cu nanocubes generating Prussian blue nanoparticles (PBNPs). It is expected that this method can be used to detect the residues of sulfonamides in the field, and solve the problem of long analysis time and high cost of the traditional method. Sulfadimethoxine (SDM) was selected as the proof-of-concept target analyte. The Au-Cu nanocubes were linked to the aptamer by amide interaction, and the Au-Cu nanocubes, SDM and antibody were immobilized on a 96-well plate using the sandwich method. The assay generates PBNPs by oxidising the Cu shells on the Au-Cu nanocubes in the presence of hydrochloric acid, Fe3+ and K3[Fe (CN)6]. In this process, the copper shell undergoes oxidation to Cu2+ and subsequently Cu2 + further quenches the fluorescence of the carbon point. PBNPs exhibit peroxidase-like activity, oxidising 3,3',5,5'-tetramethylbenzidine (TMB) to OX-TMB in the presence of H2O2, which alters the colorimetric signal. The dual-mode signals are directly proportional to the sulfadimethoxine concentration within the range 10- 3~10- 7 mg/mL. The limit of detection (LOD) of the assay is 0.023 ng/mL and 0.071 ng/mL for the fluorescent signal and the colorimetric signal, respectively. Moreover, the assay was successfully applied to determine sulfadimethoxine in silver carp, shrimp, and lamb samples with satisfactory results.

Data-Driven Evolutionary Design of Multienzyme-like Nanozymes

Multienzyme-like nanozymes are nanomaterials with multiple enzyme-like activities and are the focus of nanozyme research owing to their ability to facilitate cascaded reactions, leverage synergistic effects, and exhibit environmentally responsive selectivity. However, multienzyme-like nanozymes exhibit varying enzyme-like activities under different conditions, making them difficult to precisely regulate according to the design requirements. Moreover, individual enzyme-like activity in a multienzyme-like activity may accelerate, compete, or antagonize each other, rendering the overall activity a complex interplay of these factors rather than a simple sum of single enzyme-like activity. A theoretically guided strategy is highly desired to accelerate the design of multienzyme-like nanozymes. Herein, nanozyme information was collected from 4159 publications to build a nanozyme database covering element type, element ratio, chemical valence, shape, pH, etc. Based on the clustering correlation coefficients of the nanozyme information, the material features in distinct nanozyme classifications were reorganized to generate compositional factors for multienzyme-like nanozymes. Moreover, advanced methods were developed, including the quantum mechanics/molecular mechanics method for analyzing the surface adsorption and binding energies of substrates, transition states, and products in the reaction pathways, along with machine learning algorithms to identify the optimal reaction pathway, to aid the evolutionary design of multienzyme-like nanozymes. This approach culminated in creating CuMnCo7O12, a highly active multienzyme-like nanozyme. This process is named the genetic-like evolutionary design of nanozymes because it resembles biological genetic evolution in nature and offers a feasible protocol and theoretical foundation for constructing multienzyme-like nanozymes.

From Molecules to Classrooms: A Comprehensive Guide to Single-Molecule Localization Microscopy

Single-molecule localization microscopy (SMLM) has revolutionized our ability to visualize cellular structures, offering unprecedented detail. However, the intricate biophysical principles that underlie SMLM can be daunting for newcomers, particularly undergraduate and graduate students. To address this challenge, we introduce the fundamental concepts of SMLM, providing a solid theoretical foundation. In addition, we have developed an intuitive graphical interface APP that simplifies these core concepts, making them more accessible for students. This APP clarifies how super-resolved images are fitted and highlights the crucial factors determining image quality. Our approach deepens students' understanding of SMLM by combining theoretical instruction with practical learning. This development equips them with the skills to carry out single-molecule super-resolved experiments and explore the microscopic world beyond the diffraction limit.

Oxidase-like manganese oxide nanoparticles: a mechanism of organic acids/aldehydes as electron acceptors and potential application in cancer therapy

Identifying the underlying catalytic mechanisms of synthetic nanocatalysts or nanozymes is important in directing their design and applications. Herein, we revisited the oxidation process of 4,4'-diamino-3,3',5,5'-tetramethylbiphenyl (TMB) by Mn3O4 nanoparticles and revealed that it adopted an organic acid/aldehyde-triggered catalytic mechanism at a weakly acidic or neutral pH, which is O2-independent and inhibited by the pre-addition of H2O2. Importantly, similar organic acid/aldehyde-mediated oxidation was applied to other substrates of peroxidase in the presence of nanoparticulate or commercially available MnO2 and Mn2O3 but not MnO. The selective oxidation of TMB by Mn3O4 over MnO was further supported by density functional theory calculations. Moreover, Mn3O4 nanoparticles enabled the oxidation of indole 3-acetic acid, a substrate that can generate cytotoxic singlet oxygen upon single-electron transfer oxidation, displaying potential in nanocatalytic tumor therapy. Overall, we revealed a general catalytic mechanism of manganese oxides towards the oxidation of peroxidase substrates, which could boost the design and various applications of these manganese-based nanoparticles.

Advances in the Application of Transition-Metal Composite Nanozymes in the Field of Biomedicine

Due to the limitation that natural peroxidase enzymes can only function in relatively mild environments, nanozymes have expanded the application of enzymology in the biological field by dint of their ability to maintain catalytic oxidative activity in relatively harsh environments. At the same time, the development of new and highly efficient composite nanozymes has been a challenge due to the limitations of monometallic particles in applications and the inherently poor enzyme-mimetic activity of composite nanozymes. The inherent enzyme-mimicking activity is due to Au, Ag, and Pt, along with other transition metals. Moreover, the nanomaterials exhibit excellent enzyme-mimicking activity when composited with other materials. Therefore, this paper focuses on composite nanozymes with simulated peroxidase activity that have been prepared using noble metals such as Au, Ag, and Pt and other transition metal nanoparticles in recent years. Their simulated enzymatic activity is utilized for biomedical applications such as glucose detection, cancer cell detection and tumor treatment, and antibacterial applications.

Graphene oxide-enhanced colorimetric detection of Mec A gene based on toehold-mediated strand displacement

Mec A, as a representative gene mediating resistance to β-lactam antibiotics in methicillin-resistant Staphylococcus aureus (MRSA), allows a new genetic analysis for the detection of MRSA. Here, a sensitive, prompt, and visual colorimetry is reported to detect the Mec A gene based on toehold-mediated strand displacement (TMSD) and the enrichment effect of graphene oxide (GO). The Mec A triggers to generate the profuse amount of signal units of single-stranded DNA (SG) composed of a long single-stranded base tail and a base head: the tail can be adsorbed and enriched on the surface of GO; the head can form a G quadruplex structure to exert catalytic function towards 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid). Therefore, through the enrichment effect of GO, the signal units SG reflects different degrees of signal amplification on different substrates (such as aqueous solution or filter membrane). This strategy demonstrates a broad linear working range from 100 pM to 1.5 nM (solution) and 1 pM to 1 nM (filter membrane), with a low detection limit of 39.53 pM (solution) and 333 fM (filter membrane). Analytical performance in real samples suggests that this developed colorimetry is endowed with immense potential for clinical detection applications.

Edge-generated N-doped carbon-supported dual-metal active sites for enhancing electrochemical immunoassay

Development of high-precision human epidermal growth factor receptor 2 (HER2) assay is essential for the early diagnostic and prevention of breast cancer. In this work, an innovative Fe/Mn bimetallic nanozyme at the edge of N-doped carbon defects (FeMn-NCedge) with abundant active sites was prepared through the hydrothermal synthetic method. FeMn-NCedge nanozyme displayed excellent peroxidase-like activity relative to the H2O2-catalyzed 3,3',5,5'-tetramethylbenzidine (TMB) system for generation of the oxidized TMB (oxTMB). As a proof-of-concept application, we constructed an electrochemical immunoassay for the detection of HER2 based on the unique merits of FeMn-NCedge. Initially, a sandwiched immunoreaction was carried out in the microtiter plate coated with monoclonal anti-HER2 capture antibodies using glucose oxidase (GOx)-labeled anti-HER2 as detection antibody. The carried GOx could catalyze glucose to produce H2O2, thus resulting in the formation of oxTMB with the assistance of TMB and FeMn-NCedge nanozyme. The produced oxTMB could be determined on the electrode by the chronoamperometry at an applied potential of +10 mV. Experimental results revealed that the steady-state current increased with the increasing HER2 concentration in the sample, and gave a good linear relationship within the dynamic range of 0.01-10 ng/mL at a limit of detection of 5.4 pg/mL HER2. In addition, good reproducibility, high specificity and acceptable accuracy were acquired for the measurement of human serum samples. Importantly, this method can be extended for quantitative monitoring other disease-related proteins by changing the corresponding antibodies.

Single-Molecule Spectroscopy Reveals the Plasmon-Assisted Nanozyme Catalysis on AuNR@TiO2

Gold nanoparticles are frequently employed as nanozyme materials due to their capacity to catalyze various enzymatic reactions. Given their plasmonic nature, gold nanoparticles have also found extensive utility in chemical and photochemical catalysis owing to their ability to generate excitons upon exposure to light. However, their potential for plasmon-assisted catalytic enhancement as nanozymes has remained largely unexplored due to the inherent challenge of rapid charge recombination. In this study, we have developed a strategy involving the encapsulation of gold nanorods (AuNRs) within a titanium dioxide (TiO2) shell to facilitate the efficient separation of hot electron/hole pairs, thereby enhancing nanozyme reactivity. Our investigations have revealed a remarkable 10-fold enhancement in reactivity when subjected to 530 nm light excitation following the introduction of a TiO2 shell. Leveraging single-molecule kinetic analyses, we discovered that the presence of the TiO2 shell not only amplifies catalytic reactivity by prolonging charge relaxation times but also engenders additional reactive sites within the nanozyme's intricate structure. We anticipate that further enhancements in nanozyme performance can be achieved by optimizing interfacial interactions between plasmonic metals and semiconductors.

A comprehensive exploration of the latest innovations for advancements in enhancing selectivity of nanozymes for theranostic nanoplatforms

Nanozymes have captured significant attention as a versatile and promising alternative to natural enzymes in catalytic applications, with wide-ranging implications for both diagnosis and therapy. However, the limited selectivity exhibited by many nanozymes presents challenges to their efficacy in diagnosis and raises concerns regarding their impact on the progression of disease treatments. In this article, we explore the latest innovations aimed at enhancing the selectivity of nanozymes, thereby expanding their applications in theranostic nanoplatforms. We place paramount importance on the critical development of highly selective nanozymes and present innovative strategies that have yielded remarkable outcomes in augmenting selectivities. The strategies encompass enhancements in analyte selectivity by incorporating recognition units, refining activity selectivity through the meticulous control of structural and elemental composition, integrating synergistic materials, fabricating selective nanomaterials, and comprehensively fine-tuning selectivity via approaches such as surface modification, cascade nanozyme systems, and manipulation of external stimuli. Additionally, we propose optimized approaches to propel the further advancement of these tailored nanozymes while considering the limitations associated with existing techniques. Our ultimate objective is to present a comprehensive solution that effectively addresses the limitations attributed to non-selective nanozymes, thus unlocking the full potential of these catalytic systems in the realm of theranostics.

Chromogenic Mechanisms of Colorimetric Sensors Based on Gold Nanoparticles

The colorimetric signal readout method is widely used in visualized analyses for its advantages, including visualization of test results, simple and fast operations, low detection cost and fast response time. Gold nanoparticles (Au NPs), which not only exhibit enzyme-like activity but also have the advantages of tunable localized surface plasmon resonance (LSPR), high stability, good biocompatibility and easily modified properties, provide excellent platforms for the construction of colorimetric sensors. They are widely used in environmental monitoring, biomedicine, the food industry and other fields. This review focuses on the chromogenic mechanisms of colorimetric sensors based on Au NPs adopting two different sensing strategies and summarizes significant advances in Au NP-based colorimetric sensing with enzyme-like activity and tunable LSPR characteristics. In addition, the sensing strategies based on the LSPR properties of Au NPs are classified into four modulation methods: aggregation, surface modification, deposition and etching, and the current status of visual detection of various analytes is discussed. Finally, the review further discusses the limitations of current Au NP-based detection strategies and the promising prospects of Au NPs as colorimetric sensors, guiding the design of novel colorimetric sensors.