Oxidase-like Catalytic Activity Research Articles

A convenient smartphone-assisted colorimetric for 6-Mercaptopurine detection using enhanced oxidase-like activity of β-cyclodextrin modified MnO2 nanosheets

6-mercaptopurine (6-MP) is widely used in the treatment of many diseases, but exhibits some serious side effects due to its toxicity. Therefore, it is important and imperative to effectively control and monitoring concentration of 6-MP. Herein, we designed a smartphone-assisted colorimetric sensing platform for 6-MP detection, based on an excellent β-cyclodextrin modified MnO2 nanosheets (β-CD@MnO2 NNS) mediated oxidase-like activity. β-CD@MnO2 NNS can directly oxidizes 3,3′,5,5′-tetramethylbenzidine (TMB) into oxidized TMB with color changes, yielding more than 3-fold higher oxidase-like catalytic activity compared with individual MnO2 NNS. After adding 6-MP, β-CD@MnO2 NNS can be reduced to Mn2+ and lose their oxidase-like properties, resulting in a color and absorbance change for sensitive and selectivity detection of 6-MP. Meanwhile, the smartphone-based color recognition application can intuitively and simply measure the concentration of 6-MP. The limits of detection UV–vis instrument and smartphone were 0.35 μM and 0.86 μM, respectively. This method has also been successfully applied to the detection of real samples. Finally, this study provides a new promising platform for detection of 6-MP and is expected to be used in application of pharmaceutical analysis and biomedicine.

Porphyrin-based covalent organic framework as oxidase mimic for highly sensitive colorimetric detection of pesticides.

A covalent organic framework-based strategy was designedfor label-free colorimetric detection of pesticides. Covalent organic framework-based nanoenzyme with excellent oxidase-like catalytic activity was synthesized. Unlike other artificial enzymes, porphyrin-based covalent organic framework (p-COF) as the oxidase mimic showed highly catalytic chromogenic activity and good affinity toward TMB without the presence of H2O2, which can be used as substitute for peroxidase mimics and H2O2 system in the colorimetric reaction. Based on the fact that the pesticide-aptamer complex can inhibit the oxidase activity of p-COF and reduced the absorbance at 650nm in UV-Vis spectrum, a label-free and facile colorimetric detection of pesticides was designed and fabricated. Under the optimized conditions, the COF-based colorimetric probe for pesticide detection displayed high sensitivity and selectivity. Taking fipronil for example the limit of detection was 2.7ng/mL and the linear range was 5-500,000ng/mL. The strategy was successfully applied to the detection of pesticides with good recovery , which was in accordance with that of HPLC-MS/MS. The COF-based colorimetric detection was free of complicated modification H2O2, which guaranteed the accuracy and reliability of measurements. The COF-based sensing strategy is a potential candidate for the sensitive detection of pesticides of interests.

Spatially confining copper atom in flowerlike-CoFe hydroxides for smartphone-based ratiometric colorimetric dual-mode detection of nitrite

Great progress in nanozyme catalysis for distinct catalytic reactions have been made. However, more current nanozyme-induced sensing platforms are depended on oxidase-like nanozymes with multienzymatic catalytic behavior, which can affect the determination accuracy and reliability. Designing high active and stable advanced nanozymes for enzyme-like catalysis remains a huge challenge for analytic chemistry. Herein, a three-atom site catalyst of CoFeCu hydroxide nanozyme is rationally prepared for constructing sensing platform by utilizing oxidase-like catalytic activity. The CoFeCu nanozyme can mimic the behavior of oxidase by trigging O2 into O2·− via its highly dispersed metal active sites, which exhibits good oxidase-like activities with of 2.22 mM and of 3.69 × 10−8 M·s−1 toward 3, 3′, 5, 5′-tetramethylbenzidine (TMB). Specifically, the elaborate doping of low content Cu leads to higher catalytic activity and adequate detection sensitivity. Interestingly, with the addition of nitrite, a redox and diazotized reaction can be induced to generate visual color change from blue to yellow, resulting in the nitrite level-related ratio variation for the absorbance intensity at 665 and 450 nm. Besides, to the realize the demand of point-of-care monitor of nitrite, a portable sensor was built containing a dark box by a UV lamp and an intelligent smartphone. In the colorimetry-smartphone modes, the linear ranges of nitrite are 1–290, and 3.3–250 μM, with related detection limits of 0.9, and 2.96 μM, respectively. This strategy was further used to detect nitrite in river water with outstanding results with the dual mode. Therefore, the proposed dual-mode detection approach provides promising potential for self-house monitor of nitrite, which will greatly improve the analysis efficiency and large-scale determination in human life quality.

Highly sensitive colorimetric sensing for ascorbic acid utilizing Co3O4@MnO2 hollow nanocubes as oxidase mimic

The development of oxidase mimic with favorable catalytic activity is of great significance for the rapid and convenient detection of ascorbic acid (AA). Herein, in this work, a synergistic regulation strategy of heterogeneous interface and hollow structure is proposed to effectively solve the problem of limited active sites obtained with Co3O4. The charge rearrangement at heterointerface could improve the catalytic activity of oxidase mimic. Moreover, the hollow nanocubes structure could increase specific surface area and provide rich active sites. As a result, the target material possesses enhanced oxidase-like catalytic activity and desirable stability compared to bare Co3O4 and MnO2, which also catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to form a blue product (ox-TMB) even without hydrogen peroxide. Ox-TMB is reduced to TMB owing to the strong reducibility of AA, which represents a decrease in absorbance at 652 nm and a colorless solution. Moreover, an efficient biosensing method for the detection of AA is developed. The relative absorbance (∆A) of the sensing platform is linearly related to the concentration of AA in the range of 0–200 μM, and the detection limit is 0.11 μM. This work provides a novel method for the rapid, cost-effective and sensitive detection of AA, and possesses a wide range of potential application value.

A dual-mode strategy for diacetyl detection based on colorimetry and surface-enhanced Raman scattering

Diacetyl is an important food additive with rich creamy flavor whose excessive intake may cause various diseases. Herein, for the first time, we designed a dual-mode method for diacetyl detection based on colorimetry and surface-enhanced Raman scattering (SERS) technology. Diacetyl exhibited excellent oxidase-like catalytic activity under light-mediated condition, facilitating the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue ox-TMB for colorimetric detection. Notably, diacetyl could control the oxidation process of TMB by simply adjusting light irradiation, unlike traditional enzymatic reactions that required terminators to stop the reaction. Interestingly, ox-TMB was an ideal Raman marker for SERS analysis. Then, a three-dimensional flower-like zinc oxide/silver (ZnO/Ag) for sensitive SERS detection was prepared, which exhibited outstanding SERS effect with a high enhancement factor of 1.89 × 108 due to effective charge transfer and synergistic effect between ZnO and Ag. Based on these, SERS method was constructed to indirectly detect diacetyl, which has not been reported due to low Raman activity of diacetyl. The linear ranges of colorimetry and SERS were 0.5–60 μM and 10−9-10−5 M respectively, with detection limits of 0.41 μM and 0.73 nM. Obviously, the dual-mode strategy combined the simplicity and practicality of colorimetry and the high sensitivity of SERS, offering great potential applications in practical samples.

PdPtB Electrochemiluminescence Nanoenhancer and SiC@Au-PEDOT Nanowires-Based Detection of β-Amyloid Oligomers in Alzheimer's Disease.

β-Amyloid oligomers (AβOs) are promising biomarkers for the diagnosis of Alzheimer's disease (AD). The present research introduces a novel electrochemiluminescence (ECL) immunosensor based on PdPtB nanoenhancer and SiC@Au-PEDOT nanowires (NWs) for the specific and ultrasensitive detection of AβOs. The PdPtB nanoenhancer exhibited excellent oxidase-like catalytic activity with in situ generation of reactive oxygen species (ROS) to enhance luminol ECL in neutral media. In addition, SiC@Au-PEDOT NWs were utilized as a biocompatible and conductive substrate for the modification of the glassy carbon electrode (GCE). With this design, the ECL immunosensor showed outstanding AβOs analytical performance without exogenous coreactant. The ECL immunosensor demonstrated a favorable linear range of 20 pM to 20 nM and a detection limit of 10 pM under optimized conditions with potential straightforward clinical application. In general, the developed ECL immunosensor provides a promising strategy for the early diagnosis of AD.

Construction of core–shell MOF@COF hybrid materials as highly efficient light-responsive oxidase-like nanozymes for colorimetric detection of glutathione

In this work, a novel and light-responsive nanozyme, with enzyme-like characteristics, was synthesized based on core–shell MOF@COF hybrid materials. The donor–acceptor type COF (as shell) synthesized by 1,3,6,8-tetrakis(4-aminophenyl)pyrene (Py, donor) and thieno[3,2-b]thiophene-2,5-dicarbaldehyde (Tt, acceptor) was wrapped on the NH2-Cu-MOF (robust catalyst, as core) through a sequential growth strategy. Surprisingly, with visible-light irradiation, the core–shell Cu-MOF@Py-Tt hybrid materials exhibited extremely high oxidase-like enzymatic catalytic activity attributing to the high separation efficiency of photogenerated carriers in core–shell hybrid materials and the shell with the characteristics of large π-conjugated and D-A electronic structure. With the light-control catalytic activity, Cu-MOF@Py-Tt can form the O2•- that can catalyze the TMB to blue color. Consequently, a light-control, sensitive and rapid colorimetric method for determination of glutathione (GSH) was designed based on light-responsive oxidase mimic of core–shell Cu-MOF@Py-Tt with the linear range of 0.2–70 μM and limit of detection of 0.17 μM. The proposed method demonstrated the future potential of core–shell MOF@COF hybrid materials to obtain excellent nanozyme activity.

Achieving smartphone-based colorimetric assay for Hg2+ with a bimetallic site strategy based on Hg2+-triggered oxidase-like catalytic activity of NSC/Co6Ni3S8 nanocomposite

Modulation of the nanozyme's catalytic activity is crucial for its real applications in detecting target analytes. Herein, we fabricated the nanocomposite (NSC/Co6Ni3S8) of N, S co-doped carbon and Co6Ni3S8 by a facile sol-gel approach. Compared to NSC/Ni9S8, NSC/Co6Ni3S8 with bimetallic active sites displayed better enzyme-mimetic activity. This nanocomposite could catalyze O2 to form ·O2− and oxidize colorless 3, 3′, 5, 5′-tetramethylbenzidine (TMB) into blue oxTMB. The other two free radicals (h+ and ·OH) played minor roles during the catalytic reaction. Hg2+ could integrate with S2− to form HgS and the surface charges of O2 were transferred to Hg2+ to promote O2 adsorption. DFT theoretical calculations highlight that the main reasons for the enhancing effect of Hg2+ on color development results from electron transfer and increased adsorption energy of O2 molecules onto the surface of NSC/Co6Ni3S8. By employing the oxidase-like activity of NSC/Co6Ni3S8 and Hg2+-triggered promoting effect, a colorimetric sensing platform was established for Hg2+ assay with a linear range of 10–200 μg/L and detection limit of 3 μg/L. Through integration with a smartphone-based APP “Thing Identify” software, a visual colorimetric assay for Hg2+ was constructed with a detection limit of 5 μg/L. Compared to the data detected by the mercury vapor meter, the relative recoveries of 92.4–108.1% evidenced the higher accuracy of this smartphone-based visual detection. Overall, the NSC/Co6Ni3S8-based colorimetric assay is convenient, rapid, and visual, and can be applied for routine monitoring of Hg2+ in real-world waters under outdoor conditions.

Platinum Palladium Bimetallic Nanozymes Stabilized with Vancomycin for the Sensitive Colorimetric Determination of L-cysteine.

Many diseases in the human body are related to the level of L-cysteine. Therefore, it is crucial to establish an efficient, simple and sensitive platform for L-cysteine detection. In this work, we synthesized platinum palladium bimetallic nanoparticles (Van-Ptm/Pdn NPs) using vancomycin hydrochloride (Van) as a stabilizer, which exhibited high oxidase-like catalytic activity. In addition, the catalytic kinetics of the Van-Pt1/Pd1 NPs followed the typical Michaelis-Menten equation, exhibiting a strong affinity for 3,3',5,5'-tetramethylbenzidine substrates. More importantly, we developed a simple and effective strategy for the sensitive colorimetric detection of L-cysteine using biocompatible Van-Pt1/Pd1 NPs. The detection limit was low, at 0.07 μM, which was lower than the values for many previously reported enzyme-like detection systems. The colorimetric method of the L-cysteine assay had good selectivity. The established method for the detection of L-cysteine showed promise for biomedical analysis.

Nanozyme colorimetric sensor array based on monatomic cobalt for the discrimination of sulfur-containing metal salts

The identification of sulfur-containing metal salts (SCMs) is of great interest because they play an important role in many biological processes and diseases. Here, we constructed a ternary channel colorimetric sensor array to detect multiple SCMs simultaneously, relying on monatomic Co embedded in nitrogen-doped graphene nanozyme (CoN4-G). Due to the unique structure, CoN4-G exhibits activity similar to native oxidases, capable of catalysing directly the oxidization of 3,3′,5,5′-tetramethylbenzidine (TMB) by O2 molecules independent of H2O2. Density functional theory (DFT) calculations suggest that CoN4-G has no potential barrier in the whole reaction route, thus presenting higher oxidase-like catalytic activity. Based on different degrees of TMB oxidation, different colorimetric response changes are obtained as "fingerprints" on the sensor array. The sensor array can discriminate different concentrations of unitary, binary, ternary, and quaternary SCMs and has been successfully applied to detect six real samples (soil, milk, red wine and egg white). To advance the field detection of the above four types of SCMs, we creatively propose a smartphone-based autonomous detection platform with a linear range of 1.6–320 μM and a limit of detection of 0.0778–0.218 μM, which demonstrates the potential use of sensor arrays in the application of disease diagnosis and food and environment monitoring.

Metal-free nitrogen-doped carbon nanodots as an artificial nanozyme for enhanced antibacterial activity

Bacterial infections have become a considerable obstacle to public health due to the emergence of antibiotic resistance. Herein, we rationally developed a novel and attractive nitrogen-doped carbon nanodots (N-CNDs) as efficient metal-free artificial nanozymes that synergistically and efficiently inhibit bacterial survival by inheriting the bacteriostatic ability of tea polyphenols and light-triggered oxidase-like catalytic activity. The excellent oxidase-mimicking activity exhibited by N-CNDs in the light was mediated by superoxide radicals (•O2−) with a high maximum reaction rate (1.59 μM⋅s−1) and a low Michaelis constant (0.421 mM). Furthermore, the constructed N-CNDs-based nanozyme was demonstrated to serve as a complex biomaterial platform for efficient sterilization by light-driven oxygen molecule generation of •O2−. Remarkably, the inherent antibacterial ability of N-CNDs can effectively inhibit both Gram-positive and Gram-negative bacteria, particularly against Gram-positive S. aureus at a minimum inhibitory concentration (MIC90) of 375 μg⋅mL−1. The inactivation rates of N-CNDs alone agsinst E. coli and S. aureus were 59.72% and 37.15%, respectively. However, the inactivation rates of E. coli and S. aureus by N-CNDs achieved by light were as high as 97.91% and 80.02%, respectively. Encouragingly, a two-way ANOVA revealed that the concentration of N-CNDs and the duration of light exposure had a synergistic effect on antibacterial behavior, which provided favorable conditions for the sustained eradication of exposed bacteria. This synergistic strategy for bacterial eradication based on a novel metal-free carbon-based nanozyme provides a powerful and feasible approach for bacterial contamination management in food safety and environmental protection.

Fe-Single-Atom Nanozyme Catalysts for Sensitive and Selective Detection of Nitrite via Colorimetry and Test Strips

Here, a sensitive and selective strategy for the detection of nitrite via colorimetry and test strips was developed based on Fe-single-atom catalysts (Fe SACs) through the oxidation–reduction and diazotization reactions. Fe SACs possess excellent oxidase-like (OXD) catalytic activity, which can catalyze the oxidation of the colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into blue TMBox with the appearance of an obvious absorbance peak at 652 nm in the presence of oxygen. With the addition of nitrite (NO2–), the oxidation–reduction and diazotization reactions between TMB/TMBox and nitrite can induce the color of the solution to change from blue to green and finally to yellow, with the increase of the peak at 445 nm. Based on this strategy, a dual-signal-ratio colorimetric detection method for nitrite was proposed. Within the concentration range of 1–120 μM, the ratio of A652/A445 has a favorable linear relationship with the logarithm concentration of NO2–, with a detection limit of 0.238 μM. By combining smartphones with the colorimetric method, a more intuitive, visual, and convenient test strip detection platform was developed, which can be utilized for the detection of nitrite within 2–200 μM. The analysis strategy based on the Fe-single-atom nanozyme catalysis integrated with the specific redox/diazotization reaction not only provides a dual-signal ratio sensing with good sensitivity but holds the advantage of good selectivity for the utilization of the specific chemical reaction, which has broad application prospects in food safety supervision and food screening.

Polyhedral MnSe microparticles with specific Hg2+-suppressed oxidase-like activity: Toward a green and low-cost turn-off method for Hg2+ detection

With the attractive advantage of catalytic signal amplification, noble metal-based peroxidase-mimicking nanomaterials have been intensively used to establish optical methods for hypertoxic Hg2+ detection. However, in these methods the requirement of high-concentration H2O2 can lead to secondary pollution, and the noble metals used result in these assays’ high cost. Therefore, exploring new categories of enzyme mimics to develop environmentally friendly and low-cost approaches for Hg2+ sensing is highly desired. Herein we proposed a novel noble metal-free material, MnSe microparticles, featuring specific Hg2+-suppressed oxidase-like catalytic activity, to fabricate a green, cheap, and high-performance turn-off approach for Hg2+ detection. The MnSe microparticles with a polyhedral structure were obtained via a one-pot solvothermal process, showing excellent oxidase-like activity to catalyze the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to its blue product. The introduction of Hg2+ can significantly mask their active sites via forming an inert layer of HgSe outside the MnSe microparticles, thus suppressing the TMB catalytic color reaction. Based on the turn-off principle, colorimetric quantification of Hg2+ was realized with high sensitivity and specificity. By integrating smartphone sensing with 3D-printed accessories and paper strips, a portable platform for the convenient detection of Hg2+ was further established, demonstrating its great practicability in real analysis.

Anti-CD44 antibodies grafted immunoaffinity Fe3O4@MnO2 nanozymes with highly oxidase-like catalytic activity for specific detection of triple-negative breast cancer MDA-MB-231 cells

Cell-enzyme-linked immunosorbent assay (CELISA) is extensively applied for cancer diagnosis and screening because of its simple operation, high sensitivity, and intuitive color change. However, the unstable horseradish peroxidase (HRP), hydrogen peroxide (H2O2) and non-specificity have led to a high false negative rate, which limits its application. In this study, we have developed an innovative immunoaffinity nanozyme aided CELISA based on anti-CD44 monoclonal antibodies (mAbs) bioconjugated manganese dioxide-modified magnetite nanoparticles (Fe3O4@MnO2 NPs) for the specific detection of triple-negative breast cancer MDA-MB-231 cells. The CD44FM nanozymes were fabricated to replace unstable HRP and H2O2 to counteract possible negative effects in conventional CELISA. Results suggested that CD44FM nanozymes displayed remarkable oxidase-like activities over an extensive pH and temperature range. The bioconjugation of CD44 mAbs enabled CD44FM nanozymes to enter MDA-MB-231 cells selectively via over-expressed CD44 antigens on the membrane surface of these cells, and then catalyzed oxidation of the chromogenic substrate TMB, further achieving specific detection of these cells. Additionally, this study exhibited high sensitivity and low detection limit for MDA-MB-231 cells with a quantitation range of just 186 cells. To sum up, this report developed a simple, specific and sensitive assay platform based on CD44FM nanozymes, which could provide a promising strategy for targeted diagnosis and screening of breast cancer.

Regulating the N Coordination Environment of Co Single-Atom Nanozymes for Highly Efficient Oxidase Mimics.

Single-atom catalysts with well-defined atomic structures and precisely regulated coordination environments have been recognized as potential substitutes for natural metalloenzymes. Inspired by the metal coordination structure of natural enzymes, we show here that the oxidase-like activity of single-atom Co catalysts greatly depends on their local N coordination around the Co catalytic sites. We synthesized a series of Co single-atom catalysts with different nitrogen coordination numbers (Co-Nx(C), x = 2, 3, and 4) and demonstrated that the oxidase-like activity of single-atom Co catalysts could be effectively tailored by fine-tuning the N coordination. Among the studied single-atom Co catalysts, the Co-N3(C) with three-coordinate N atoms shows the optimum oxygen adsorption structure and robust reactive oxygen species (ROS) generation, thus presenting the preferable oxidase-like catalytic activity. This work facilitates the future development of rational nanozyme designs for targeting reactions at the atomic level.

SERS Resolving of the Significance of Acetate on the Enhanced Catalytic Activity of Nanozymes

Understanding the structure-activity correlation and reaction mechanism of the catalytic process in an acetic acid-sodium acetate (HAc-NaAc) buffer environment is crucial for the design of efficient nanozymes. Here, we first reported a lattice restructuration of Au-LaNiO3-δ nanofibers (NFs) after acidification with the HAc-NaAc buffer to show a significantly enhanced oxidase-like property. Surface-enhanced Raman spectroscopy (SERS) and density functional theory (DFT) calculation confirm the direct evidence for the formation of specific enhanced intermediate O-O species after acidification, indicating that the insertion of the carboxyl group in the A-Au/LaNiO3-δ NFs plays crucial roles in both producing vacancies in HAc-NaAc solution from its dissociation during the catalytic process and the protection of the vacancies, which can be directly interacted with oxygen in the environment to produce O-O species, realizing the enhanced oxidation of substrate molecules. The insertion of the carboxyl group increased the oxidase-like catalytic activity by 2.38 times and the SERS activity by 5.27 times. This strategy offers a way to construct an efficient nanozyme-linked immunosorbent assay system for the diagnosis of cancer through the highly sensitive SERS identification of exosomes.

Label-free ultra-sensitive colorimetric detection of hepatitis E virus based on oxidase-like activity of MnO2 nanosheets.

Hepatitis E virus (HEV) is an evolving infectious entity that causes viral hepatitis infections worldwide. Current routine methods of identifying and diagnosing HEV are someway laborious and costly. Based on the biomimicking oxidase-like activity of MnO2 nanosheets, we designed a label-free, highly sensitive colorimetric sensing technique for HEV detection. The prepared MnO2 catalyst displays intrinsic biomimicking oxidase-like catalytic activity and efficiently oxidizes the 3,3',5,5'-tetramethylbenzidine (TMB) substrate from colorless to blue colored oxidized TMB (oxTMB) product which can be measured at 652nm by UV-visible spectrum. When the HEV-DNA was added, DNA adsorbed easily on MnO2 surface through physical adsorption and electrostatic interaction which hinders the oxidase-like catalytic activity of MnO2. Upon the introduction of target, the HEV target DNA binds with its complementary ssDNA on the surface of MnO2, the hybridized DNA releases from the surface of MnO2, which leads to recovery of oxidase-like catalytic activity of MnO2. This strategy was applied to construct a colorimetric technique for HEV detection. The approach works in the linear range of 1 fM-100nM DNA concentration with the limit of detection (LOD) of 3.26 fM (S/N = 3) and quantitative limit (LOQ) of 36.08 fM. The TMB-MnO2 platform was highly selective for HEV target DNA detection when compared with potential interferences. Result of serum sample analysis demonstrates that this sensing system can be used for clinical diagnostic applications.

Ascorbate oxidase-like nanozyme with high specificity for inhibition of cancer cell proliferation and online electrochemical DOPAC monitoring

Despite the extensive investigation of the nanozymes exhibit their favorable performance compared to natural enzymes, nevertheless, the highly specific nanozyme still needs to be developed so that it can meet the requirements of exploring the mechanism as well as administration of related diseases and selective monitoring in biological system. In this study, self-assembled glutathione-Cu/Cu2O nanoparticles (GSH-Cu/Cu2O NPs) that exhibits specific ascorbic acid (AA) oxidase-like catalytic activity were constructed for AA-activated and H2O2-reinforced cancer cell proliferation inhibition and selective neurochemical monitoring. Cu/Cu2O NPs demonstrates effective AA oxidase-like activity and no common characteristics of other redox mimic enzymes often present in nanozyme. In particular, we found that the AA oxidase-like activity of GSH-Cu/Cu2O nanozyme was significantly improved by about 40% by improving the activation ability toward oxygen. The synthesized nanozyme can induce the generation of active oxygen by accelerating the oxidation of AA, which effectively suppresses the proliferation of cancer cells. We constructed an online electrochemical system (OECS) though loading nanozyme with enhanced ascorbate oxidase activity into a microreactor and setting it in the upstream of the detector. This GSH-Cu/Cu2O NPs-integrated microreactor can completely eliminate AA interference of the physical level toward 3,4-dihydroxy phenylacetic acid (DOPAC) electrochemical measurement, and the nanozyme-based OECS is able to continuously capture DOPAC alteration in rat brain acidosis model. Our findings may inspire rational design of nanozymes with high specificity as well as nanozyme-based selectivity solution for in vivo detection and show promising opportunities for their involvement in neurochemistry investigation.

Investigation of Sulfur Doping in Mn-Co Oxide Nanotubes on Surface-Enhanced Raman Scattering Properties.

Doping engineering is an efficient strategy to manipulate the optoelectronic properties of metal oxides for sensing, catalysis, and energy applications. Herein, we have demonstrated the fabrication of sulfur (S)-doped Mn-Co oxides to regulate their band and surface electronic structures, which is beneficial to enhancing the charge transfer (CT) between the metal oxides and their adsorbed molecules. As expected, significantly enhanced SERS signals are achieved on S-doped Mn-Co oxide nanotubes, and the minimum detection concentration can reach as low as 10-8 M. Furthermore, the change in the electronic structure caused by S-doping provides different microelectric fields to influence the orientation of the interaction between the probe molecules and the substrate. Additionally, the evaluation of the oxidase-like catalytic activity of the substrate proved that, with an increase in the ratio of Co2+/Co3+ content, the number of electrons on the substrate increases, which promotes the CT process and further increases the degree of CT. The nonmetallic doping route in semiconducting metal oxides can provide effective and stable SERS activity; moreover, it provides a new strategy for exploring the relationship between CT in catalysis and SERS performance of semiconductors.

Self-electrochemiluminescence biosensor based on CRISPR/Cas12a and PdCuBP@luminol nanoemitter for highly sensitive detection of cytochrome c oxidase subunit III gene of acute kidney injury

The cytochrome c oxidase subunit III (COX III) gene is a powerful biomarker for the early diagnosis of acute kidney injury. However, current methods for COX III gene detection are usually laborious and time-consuming, with limited sensitivity. Herein, we report a novel self-electrochemiluminescence (ECL) biosensor for highly sensitive detection of the COX III gene based on CRISPR/Cas12a and nanoemitters of luminol-loaded multicomponent metal-metalloid PdCuBP alloy mesoporous nanoclusters. The nanoemitter with excellent self-ECL in neutral media exhibited a high specific surface area for binding luminol and outstanding oxidase-like catalytic activity toward dissolved O2. Meanwhile, the CRISPR/Cas12a system, as a target-trigger, was employed to specifically recognize the COX III gene and efficiently cleave the interfacial quencher of dopamine-labeled hairpin DNA. As a result, the ECL biosensor showed superior analytical performance for COX III gene detection without exogenous coreactant. Benefiting from the high-efficiency ECL emission of the nanoemitter and Cas12a-mediated interfacial cleavage of the quencher, the developed ECL biosensor exhibited high sensitivity to COX III with a low detection limit of 0.18 pM. The established ECL biosensing method possessed excellent practical performance in urine samples. Meaningfully, the proposed strategy presents promising prospects for nucleic acid detection in the field of clinical diagnostics.