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The generation of a mesoporous structure in platinum nanoparticles can effectively enhance physical and chemical properties. In this study, mesoporous platinum nanoparticles (MPNs) were synthesized by a soft template-mediated one-pot chemical method. To develop a mesoporous structure, Pluronic F-127 was employed. The Pluronic F-127 surfactant forms self-assembled micelles, and the micelles act as the pore-directing agents in the synthesis of nanoparticles. Scanning electron microscopy results revealed that the MPN had a uniform size of 70 nm on average and a distinct mesoporous structure. The development of a concave mesoporous structure on the surface of the MPNs can increase the surface area and facilitate the efficient transport of reactants. The synthesized MPNs exhibited peroxidase-like activity. Furthermore, the MPNs showed excellent catalytic efficiency compared to HRP, due to the high surface area derived from the presence of the mesoporous structure. The peroxidase-like MPNs were applied to the enzyme-linked immunosorbent assay (ELISA) of C-reactive protein (CRP). The MPN-based ELISA exhibited sensitive CRP detection in the range from 0.24 to 7.8 ng/mL with a detection limit of 0.13 ng/mL. Moreover, the recoveries of the CRP concentrations in spiked human serum were 98.6% and 102%. These results demonstrate that as a peroxidase mimic, the MPNs can replace the natural enzymes in conventional ELISA for sensitive CRP detection. [ABSTRACT FROM AUTHOR]

Chitosan (CS)-stabilized platinum nanoparticles (CS/PtNPs) were employed to develop a novel aptamer-based dual-mode colorimetric and photothermal biosensor for selective detection of kanamycin (KAN). As a peroxidase-like catalyst, the CS/PtNPs showed outstanding catalytic activity for the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H 2 O 2). As a stabilizing agent, CS excelled at fixing the KAN binding aptamer on the surface of the CS/PtNPs, amplifying their catalytic activity and enhancing colloidal dispersion and stability. The oxidized TMB (TMB ox) functioned as a signal for the colorimetric, photothermal aptasensor because of its observable absorbance of light in the visible and near-infrared (NIR) regions. When light from a NIR laser was absorbed by the TMB ox in the reaction solution, heat was generated in inverse proportion to the KAN concentration. The developed colorimetric and photothermal modes of the aptasensor showed a linear detection range of 0.1–50 and 0.5–50 μM, with a limit of detection (LOD) of 0.04 and 0.41 μM, respectively. Moreover, the aptasensor successfully determined KAN concentrations in spiked milk samples, verifying the reliability and reproducibility in practical applications. The dual-mode aptasensor based on CS/PtNPs for KAN detection, utilizing both color change and heat generation signals through a single probe (TMB ox), demonstrates rapid response, simplicity in operation, cost-effectiveness, and high sensitivity. In addition, unlike typical immunoassays, this aptamer-based peroxidase-like nanozyme activation and inhibition strategy required no washing process, which was very effective in terms of reducing the time required for an assay and sustaining a high sensitivity. [Display omitted] [ABSTRACT FROM AUTHOR]

The development of efficient and sensitive point-of-care testing is crucial for preparedness in the post-pandemic era. Although paper-based lateral flow assays have attracted attention and have various advantages for rapid, on-site diagnosis, they have low sensitivity. To overcome the limitations of the existing assays, in this study, we aimed to develop a new, one-step, nanozyme-amplified SlipChip for the sensitive detection of C-reactive protein (CRP). The SlipChip was constructed by combining wax-printed paper with different channel designs. The three-dimensional (3D) fluidic configuration of the SlipChip allowed for the sequential delivery of reagents, enabling mixing and signal amplification with a one-step sliding operation. As a signal-amplifying reagent, peroxidase-mimicking porous platinum nanozyme (pPtNZ) was synthesized using a simple wet chemical method. The pPtNZ conjugated on the test line catalyzes the oxidation of diaminobenzidine (DAB) in the presence of hydrogen peroxide, increasing the color intensity. The immunoassay results of the SlipChip were easily interpreted within 20 min, and the color intensity was visually enhanced by DAB precipitation over time, resulting in up to 6-fold signal amplification. The proposed pPtNZ-SlipChip exhibited high analytical performances for the one-step detection of serum and salivary CRP from 0.1 to 1000 ng/mL, with a limit of detection of 0.03 ng/mL. These results revealed the potential and applicability of the pPtNZ-SlipChip, with the advantages of simplicity, sensitivity, low cost, and portability for on-site detection and point-of-care testing. [ABSTRACT FROM AUTHOR]

The in situ synthesis is reported of citric acid-functionalized ultra-fine bimetallic PtRu alloy nanoparticles (CA@PtRu ANPs) through a simple one-pot wet chemical method. The cost-efficient CA@PtRu ANPs with an average diameter of 3.2 nm revealed to have enhanced surface area, peroxidase-like activity, high stability, and adequate availability of functional groups to bind biomolecules. Along with nanoparticle surface area, the surface charge has also significantly affected the peroxidase-like activity and the colloidal suspension stability. As an excellent immobilization matrix and peroxidase mimic, the CA@PtRu ANPs were utilized to develop non-enzymatic colorimetric immunoassay for rapid, selective, and sensitive quantification of C-reactive protein (CRP) biomarkers. In this immunoassay, CA@PtRu ANPs serve as enzyme mimic that significantly amplifies the color signals, and amine-functionalized silica-coated magnetic microbeads (APTES/SiO2@Fe3O4) act as CRP-recognizing capture probes. The absorbance curves of colorimetric immunoassay were measured in wavelengths between 550 and 750 nm, and the maximum absorbance at 652 nm was used to establish a linear relationship between absorbance and CRP concentrations. The developed colorimetric immunoassay showed rapid and sensitive quantification of CRP levels from 0.01 to 180 μg mL−1 with a LOD of 0.01 μg mL−1. Moreover, the mean recovery of CRP from spiked human serum samples lies between 97 and 109% (n = 3), which indicates that the proposed nanozyme-linked immunoassay has the potential to be used in rapid point-of-care applications. [ABSTRACT FROM AUTHOR]

Nanozymes are effective substitutes for natural enzymes and offer multiple advantages. Here, synthesized Prussian blue nanoparticles (PBNPs) exhibited excellent peroxidase-like activity, catalyzing the oxidation of 3,5,3′,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide within 1 min. Oxidized TMB (TMB ox) underwent a color change from transparent to blue and then yellow by a stop solution. Moreover, the TMB ox could be reduced on an indium tin oxide electrode, generating an electrochemical current, indicating that TMB can be used as a colorimetric and electrochemical indicator. The PBNPs modified with 3-aminophenylboronic acid (APBA) captured glycated albumin (GA) with a boronate affinity sandwich assay. As boronic acid binds to glycoproteins using cis -diol bonding, it can be used to detect GA. The APBA-modified PBNPs (PBBA) were involved with a sandwich complex formation and employed as nanozymes for the quantitative analysis of GA using colorimetric and electrochemical methods. Both methods showed strong linearities for different concentrations of GA. The results show that PBBA is a suitable alternative for natural enzymes and can be applied to sensitive determination of GA. Image 1 • Prussian blue nanozymes showed an excellent peroxidase-like activity. • Boronate affinity sandwich assays were developed to detect glycated albumin (GA). • The nanozymes were used in colorimetric and electrochemical assays of GA. • The developed assays were capable of accurate determination of GA in real samples. [ABSTRACT FROM AUTHOR]

We developed a new nanozyme-based electrochemical immunoassay method for the monitoring of glycated albumin (GA) known to reflect short-term glycaemic levels. For this study, we synthesized urchin-like Pt nanozymes (uPtNZs) and applied them to colorimetric and electrochemical assays for sensitive determination of GA in total human serum albumin (tHSA) using 3,3′,5,5′-tetramethylbenzidine (TMB) and thionine as substrates, respectively. The uPtNZs showed peroxidase-mimic activity in the presence of hydrogen peroxide. Boronic acid (BA)-agarose bead was used to capture GA through specific cis-diol interactions. uPtNZs were modified with GA antibody (GA-Ab) to form sandwich complexes with GA/BA-agarose bead. The amount of Ab-uPtNZ/GA/BA-agarose bead complex increased with increasing percentage of GA in 50 mg/mL tHSA. The colorimetric assay exhibited linearity from 0.02 to 10% (10 µg/mL – 5 mg/mL) GA with an LOD of 0.02% (9.2 µg/mL). For electrochemical assay, GA was detected from 0.01 to 20% (5 µg/mL – 10 mg/mL) with an LOD of 0.008% (3.8 µg/mL). The recovery values of measured GA in human plasma samples were from 106 to 107%. These results indicate that electrochemical assay using uPtNZs is a promising method for determining GA. [ABSTRACT FROM AUTHOR]

Point-of-care testing has been extensively utilized for in-home diagnosis, customized testing, and pandemic monitoring. The current study aims to develop a nanozyme-mediated dual-readout (colorimetric and photothermal) bioassay for straightforward and sensitive detection of cholesterol. The nanozyme, cauliflower-like platinum nanostructures (CS@Pt NS) were synthesized by chemically reducing the Pt precursor in the chitosan (CS) solution. CS as a stabilizer excels at controlling the surface properties, enhancing peroxidase-like activity, and improving colloidal dispersion, and stability. The dual-readout sensor for cholesterol detection was proposed by combining cholesterol oxidase-catalyzed cholesterol oxidation with CS@Pt NS-catalyzed TMB oxidation. The oxidized TMB (TMBox) acts as a probe for both colorimetric and photothermal readouts because of having excellent absorbance in visible and near-infrared (NIR) regions. The absorption of NIR laser-driven light by the TMBox in the reaction solution generates heat, which is proportional to the concentration of cholesterol. The dual-readout sensor shows a linear detection range of 0–2 mM, with a limit of detection (LOD) of 45 µM for the colorimetric assay and 25 µM for the photothermal assay. Furthermore, the sensor successfully detects cholesterol in spiked human serum with acceptable accuracy. • Surprisingly, CS as a stabilizer enhances the peroxidase-like activity of CS@Pt NS. • Colorimetric & photothermal dual-readout biosensor developed for cholesterol detection. • A portable thermal imaging camera allows quick and accurate measurement of temperature. • Photothermal detection stands out for being more straightforward, convenient, and accurate. • The dual-readout sensor accurately detects cholesterol in spiked human serum. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mesoporous platinum nanozymes (MPNs) were fabricated by a surfactant-based self-assembly method. • MPNs showed the higher peroxidase-mimic activity than horseradish peroxidase. • MPNs were applied to colorimetric vitamin D detection using a competitive immunoassay. • MPNs-based immunoassay exhibited good linearity for vitamin D detection with a LOD of 1.0 ng/mL. In this study, mesoporous platinum nanozymes (MPNs) were fabricated by a surfactant-based self-assembly method and then used to develop a novel competitive immunoassay for sensitive detection of 25-hydroxyvitamin D 3 (25(OH)VD 3). The MPNs showed enhanced peroxidase-like activity that catalyzes the reaction between hydrogen peroxide (H 2 O 2) and 3,3′,5,5′-tetramethylbenzidine (TMB). The excellent peroxidase-like MPNs were employed to develop a competitive immunoassay for the sensitive colorimetric detection of 25(OH)VD 3. The immunoassay detected 25(OH)VD 3 in the range of 1.6 to 100 ng/mL, with a detection limit of 1.0 ng/mL. The recovery values of 25(OH)VD 3 from the spiked human serum samples were between 104% and 95%. These results indicate the applicability of MPNs as alternatives for natural enzymes and the feasibility for sensitive 25(OH)VD 3 detection. [ABSTRACT FROM AUTHOR]

Lysophosphatidylcholine (LPC) can be used as a biomarker for diseases such as cancer, diabetes, atherosclerosis, and sepsis. In this study, we demonstrated the ability of nanozymes to displace the natural derived enzyme in enzyme-based assays for the measurement of LPC. Synthesized polyvinylpyrrolidone-stabilized platinum–ruthenium nanozymes (PVP/PtRu NZs) had a uniform size of 2.48 ± 0.24 nm and superb peroxidase-mimicking activity. We demonstrated that the nanozymes had high activity over a wide pH and temperature range and high stability after long-term storage. The LPC concentration could be accurately analyzed through the absorbance and fluorescence signals generated by the peroxidation reaction using the synthesized nanozyme with substrates such as 3,3′,5,5′-tetramethylbenzidine (TMB) and 10-acetyl-3,7-dihydroxyphenoxazine (Ampliflu™ Red). LPC at a concentration of 0–400 µM was used for the analysis, and the coefficient of determination (R2) was 0.977, and the limit of detection (LOD) was 23.1 µM by colorimetric assay. In the fluorometric assay, the R2 was 0.999, and the LOD was 8.97 µM. The spiked recovery values for the determination of LPC concentration in human serum samples were 102–115%. Based on these results, we declared that PVP/PtRu NZs had an ability comparable to that of the native enzyme horseradish peroxidase (HRP) in the enzyme-based LPC detection method. [ABSTRACT FROM AUTHOR]

Nanozymes, or artificial enzymes, have received a great deal of attention in recent years because of their superior enzyme-like capabilities over natural enzymes. The transition-metals are being investigated for their intrinsic nanozyme activity in various applications, including biosensors, antimicrobials, cytoprotection, anticancer, tissue engineering, and drug delivery. Especially, silver (Ag) is one of the transition-metals that has been investigated intensively since the turn of the century because of its biological activity and catalytic properties. This review discussed various Ag-based hybrid nanozymes preparation and their enzyme-like activity by combining Ag with other metals, salts, and organic molecules. Ag-based hybrid nanozymes in the form of metal–organic frameworks, complexes, bimetallic, hexacyanoferrate structures were summarized. Based on the literature results, Ag-based hybrid nanozymes are rapid, sensitive, and selective detection of various compounds, ions, and biological species such as hydrogen peroxide, glucose, phosphatase, glucose oxidase, acetylcholinesterase, cysteine, hepatitis E virus, sulfamethazine, uric acid, hypoxanthine, spermine, and gonadotropin. Moreover, Ag-based nanozymes are being investigated for antibacterial, cell protection, and anticancer applications. Future perspectives on Ag-based nanozymes were discussed at the end of the review. As a result, Ag-based hybrid nanozymes offer great potential for clinical trial applications and commercialization. [ABSTRACT FROM AUTHOR]

[Display omitted] • An electrochemical cytosensor was developed for SK-MEL 28 cancer cell detection. • The electrical signal intensity of the cancer cell was used to monitor cell viability. • The cytosensor could detect the cancer cells from 2,880 to 40,000 cells per device. • The cytosensor enabled a sensitive and fast assessment of the anticancer effect of saponin. Discovering new anticancer agents and analyzing their activities is a vital part of drug development, but it requires a huge amount of time and resources, leading to the increasing demands for more-effective techniques. Herein, a novel and simple cell-based electrochemical biosensor, referred to as a cytosensor, was proposed to investigate the electrochemical behavior of human skin malignant melanoma (SK-MEL28) cells and the anticancer effect of saponin on cell viability. To enhance both electrocatalytic properties and biocompatibility, gold nanoparticles were electrochemically deposited onto a conductive substrate, and poly-L-lysine was further added to the electrode surface. Electric signals from SK-MEL28 cells on the electrodes were obtained from cyclic voltammetry and differential pulse voltammetry. The cathodic peak current was proportional to the cell viability and showed a detection range of 2,880–40,000 cells per device with an excellent linear cell number-intensity relationship ( R 2 = 0.9952). Furthermore, the anticancer effect of saponin on SK-MEL28 cells was clearly established at concentrations higher than 20 μM , which was highly consistent with conventional assays. Moreover, the developed electrochemical cytosensor for evaluating anticancer effects enabled rapid (<2 min), sensitive (LOQ: 2,880 cells/device), and non-invasive measurements, thus providing a new avenue for assessing the anticancer drugs in vitro. [ABSTRACT FROM AUTHOR]

The combination of Pt with low-cost transition metal is an effective way to diminish the bulk utilization of costly Pt and to design new nanostructured materials with improved enzyme-like activity. In the present work, citric acid-functionalized platinum–nickel hollow nanospheres (CA@PtNi hNS) were synthesized through a simple one-pot wet chemical method, which involves the galvanic replacement reaction between the Ni nanoparticles and the Pt precursor that leads to the formation of hollow nanostructures. Transmission electron spectroscopic images revealed the uniformity of the CA@PtNi hNS, with an average diameter of 10.3 ± 2 nm. Moreover, zeta potential, FTIR, and XPS measurements confirmed the existence of citric acid in the CA@PtNi hNS. During synthesis, the use of citric acid not only facilitates monodispersity but also provides a negative surface charge (−11 mV) to the CA@PtNi hNS that electrostatically attracts the 3,3′,5,5′-Tetramethylbenzidine (TMB) substrate. As-prepared CA@PtNi hNS possessed excellent peroxidase-like activity due to rich Pt surfaces, large surface area, and heterogeneous interaction between Pt and Ni atoms. Furthermore, a nanozyme-linked immunosorbent assay (NLISA) for human serum albumin (HSA) detection was developed by replacing the enzyme in a standard enzyme-linked immunosorbent assay with CA@PtNi hNS. The CA@PtNi hNS based-NLISA showed sensitive detection of HSA concentrations ranging from 0 to 400 ng mL−1 with a LOD of 0.19 ng mL−1 and an average of 112% recovery of HSA from the spiked human plasma samples. The outcomes of the present study confirm the applicability of CA@PtNi hNS as substitutes for natural enzymes. Unlabelled Image • Novel CA@PtNi hNS was used to develop enzyme-free ELISA for monitoring of HSA. • CA@PtNi hNS as peroxidase mimic was synthesized through one-pot wet chemical method. • CA@PtNi hNS showed excellent activity due to rich Pt surfaces and synergistic effect. • NLISA method was developed by replacing the enzyme in the ELISA kit for HSA with CA@PtNi hNS. • NLISA revealed 120% better sensitivity as compared to standard ELISA. [ABSTRACT FROM AUTHOR]

• An electrochemical technique for live cell patterning was developed. • Various types of cells were patterned by optimizing electrochemical parameters. • Cell arrays patterned in microfluidic chips were used as drug screening platforms. High-resolution cell patterning technology is a versatile tool for studying tissue engineering and in vitro preclinical research, but simple methods that can be implemented easily are lacking. Here, we demonstrate a simple electrochemical approach for arranging cells into various patterns, enabling rapid and accurate localization for cell array formation. A voltage pulse is applied directly to the pre-patterned conducting substrate, causing cellular damage and rapidly forming live/dead cell arrays. The array platform, which focuses on assay miniaturization, is applicable to cell-based drug screening as well as high-content cell culture experiments. [ABSTRACT FROM AUTHOR]

Cancer is a life-threatening disease when it is diagnosed at a late stage or treatment procedures fail. Inhibiting cancer cells in the tumor environment is a significant challenge for anticancer therapy. The photothermal effects of nanomaterials are being studied as a new cancer treatment. In this work, rhenium disulfide (ReS 2) nanosheets were made by liquid exfoliation with gum arabic (GA) and coated with silver nanoparticles (AgNPs) to produce reactive oxygen species that destroy cancer cells. The synthesized AgNP-GA-ReS 2 NPs were characterized using UV, DLS, SEM, TEM, and photothermal studies. According to the DLS findings, the NPs were about 216 nm in size and had a zeta potential of 76 mV. The TEM and SEM analyses revealed that the GA-ReS 2 formed single-layered nanosheets on which the AgNPs were distributed. The photothermal effects of the AgNP-GA-ReS 2 NPs at 50 μg/mL were tested with an 808 nm laser at 1.2 W cm−2, and they reached 55.8 °C after 5 min of laser irradiation. MBA-MB-231 cells were used to test the cytotoxicity of the newly designed AgNP-GA-ReS 2 NPs with and without laser irradiation for 5 min. At 50 μg/mL, the AgNP-GA-ReS 2 showed cytotoxicity, which was confirmed with calcein and EtBr staining. The DCFH-DA and flow cytometry analyses demonstrated that AgNP-GA-ReS 2 nanosheets under NIR irradiation generated ROS with high anticancer activity, in addition to the photothermal effects. [Display omitted] • Gum arabic was the exfoliating agent for the liquid exfoliation of rhenium disulfide nanosheets. • Silver nanoparticles were capped onto gum arabic rhenium disulfide as a photothermal agent. • The silver nanoparticles in the AgNP-GA-ReS 2 generated reactive oxygen species and killed MDA-MB-231 cancer cells with an efficiency of 45.9% without laser treatment. • The synthesized AgNP-GA-ReS 2 showed an excellent photothermal conversion efficiency of 79.6% in MDA-MB-231 cells. • DCFH-DA and flow cytometry analyses demonstrated that reactive oxygen species formation increased during photothermal treatment with AgNP-GA-ReS 2. [ABSTRACT FROM AUTHOR]

A sensitive on-site mercury sensing platform was developed for simple and effective monitoring of mercury levels in the field. The simple and practical mercury detection system was designed by integrating an Au nanoparticle-PEG hydrogel block nanozyme (Au-HBNz) into a polymer film-based colorimetric device. Upon addition of Hg2+ ions, Au-HBNz exhibited excellent peroxidase-like activity, catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine into a blue-colored product, which has a maximum absorbance at 652 nm. The resulting color intensity change was evaluated using a smartphone for simple and rapid Hg2+ detection with a broad detection range (0.008–20 μg∙mL−1) and a linear concentration–response relationship (R2 = 0.96). The detection limit (1.10 ng∙mL−1) was lower than the maximum permissible Hg2+ levels in drinking water set by the World Health Organization (6 ng∙mL−1) and U.S. Environmental Protection Agency (2 ng∙mL−1). The recoveries of Hg2+ determination in river water by spiking Hg2+ samples ranged from 92 to 106%, which indicated high validity and applicability of the Hg2+ detection system for field measurements. Thus, the developed sensor enables highly selective and efficient real-time monitoring of Hg2+. [ABSTRACT FROM AUTHOR]

Au@PtNP/GO nanozymes were prepared as peroxidase mimics. The nanozymes showed remarkable peroxidase-like activity by the synergistic catalytic effect. For the electrochemical detection of H 2 O 2 , the nanozymes were integrated into POC devices. The developed POC devices were capable of accurate determination of H 2 O 2 in real samples. Nanostructured artificial enzymes, known as nanozymes, have been considered effective alternatives for natural enzymes with the attractive advantages. Herein, bimetallic Au and Pt nanoparticles with graphene oxide (GO) were immobilized chemically on the surface of agarose microbeads. Due to the synergistic effect of the bimetallic nanoparticles and GO (Au@PtNP/GO), this hybrid nanostructure exhibited strong peroxidase-like catalytic activity toward 3,3′,5,5′-tetramethylbenzidine (TMB) substrate in the presence of H 2 O 2. Colorimetric determination of H 2 O 2 , indicated by the blue color of the oxidized TMB within 1 min, was observed using the Au@PtNP/GO nanozymes. To demonstrate practical application of the nanozymes, the Au@PtNP/GO microbeads were packed into a film-based electrochemical point-of-care (POC) device for sensitive and rapid H 2 O 2 detection. Upon introduction of TMB substrate solution containing H 2 O 2 , the catalytically oxidized TMB was electrochemically reduced on the electrode surfaces, resulting in a broader detection range of H 2 O 2 (1 μM – 3 mM) and a lower LOD (1.62 μM) than achievable with the colorimetric detection method. Moreover, the developed POC devices showed the capability of accurate determination of H 2 O 2 with strong repeatability and reproducibility in real sample test using artificial urine. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tumor microenvironment (TME)-activatable metal–organic frameworks (MOF) were developed for targeted tumor therapy. • pH-responsive breakdown of the framework gradually released glucose oxidase/Prussian Blue nanozyme, boosting tumor specificity. • Starvation therapy mediated by glucose oxidase was used to enhance chemodynamic therapy as well as to starve tumor cells. • Cascade catalytic reactions promoted ROS-induced DNA cleavage, growth inhibition, and finally tumor cell apoptosis. • The antitumor nanocomposites enabled chemodynamic/starvation synergism, high therapeutic efficiency, and minimal side effects. Targeted tumor therapy through tumor microenvironment (TME)-responsive nanoplatforms is an emerging treatment strategy used to enhance tumor-specificity to selectively kill cancer cells. Here, we introduce a nanosized zeolitic imidazolate framework-8 (ZIF-8) that simultaneously contains natural glucose oxidase (GOx) and Prussian blue nanoparticles (PBNPs) to construct multi-component metal-organic framework nanocomposites (denoted as ZIF@GOx@PBNPs), which possess cascade catalytic activity selectively within the TME. Once reaching a tumor site, GOx and PBNPs inside the nanocomposites are sequentially released and participate in the cascade catalytic reaction. In weak acidic TME, GOx, which effectively catalyzes the oxidation of intratumoral glucose to hydrogen peroxide (H 2 O 2) and gluconic acid, not only initiates starvation therapy by cutting off the nutrition source for cancer cells but also produces the reactant for sequential Fenton reaction for chemodynamic therapy. Meanwhile, PBNPs, which are released from the ZIF-8 framework dissociated by acidified pH due to the produced gluconic acid, convert the generated H 2 O 2 into harmful radicals to melanomas. In this way, the cascade catalytic reactions of ZIF@GOx@PBNPs enhance reactive oxygen species production and cause oxidative damage to DNA in cancer cells, resulting in remarkable inhibition of tumor growth. The tumor specificity is endowed by using the biomolecules overexpressed in TME as a "switch" to initiate the first catalytic reaction by GOx. Given the significant antitumor efficiency both in vitro and in vivo, ZIF@GOx@PBNPs could be applied as a promising therapeutic platform enabling starvation/chemodynamic synergism, high therapeutic efficiency, and minimal side effects. [ABSTRACT FROM AUTHOR]

This paper describes a simple electrochemical sensing platform based on single-walled carbon nanotube (SWCNT) electrodes for glucose detection. The device fabrication using O2-plasma treatment allows precision and uniformity for the construction of three SWCNT electrodes on the flexible plastic substrate. Glucose assay can be simply accomplished by introducing a glucose sample into the fabricated biosensor. The marked electrocatalytic and biocompatible properties of biosensors based on SWCNT electrodes with the incorporation of ferrocenecarboxylic acid and polyethylene glycol enable effective amperometric measurement of glucose at a low oxidation potential (0.3 V) with low interferences from coexisting species. The device shows efficient electroanalytical performances with high sensitivity (5.5 μA·mM−1·cm−2), good reproducibility (CV less than 3%), and long-term stability (over a month). A linear range of response was found from 0 to 10 mM of glucose with a fast response time of 10 s. This attractive electroanalytical device based on GOx/FCA/PEG/SWCNT electrodes offers a promising system to facilitate a new approach for diverse biosensors and electrochemical devices. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides (TMDs) have gained considerable attention for a broad range of applications, including cancer therapy. Production of TMD nanosheets using liquid exfoliation provides an inexpensive and facile route to achieve high yields. In this study, we developed TMD nanosheets using gum arabic as an exfoliating and stabilizing agent. Different types of TMDs, including MoS 2 , WS 2 , MoSe 2 , and WSe 2 nanosheets, were produced using gum arabic and were characterized physicochemically. The developed gum arabic TMD nanosheets exhibited a remarkable photothermal absorption capacity in the near-infrared (NIR) region (808 nm and 1 W⋅cm−2). The drug doxorubicin was loaded on the gum arabic–MoSe 2 nanosheets (Dox–G–MoSe 2), and the anticancer activity was evaluated using MDA-MB-231 cells and a water-soluble tetrazolium salt (WST-1) assay, live and dead cell assays, and flow cytometry. Dox–G–MoSe 2 significantly inhibited MDA-MB-231 cancer cell proliferation under the illumination of an NIR laser at 808 nm. These results indicate that Dox-G-MoSe 2 is a potentially valuable biomaterial for breast cancer therapy. [Display omitted] • The liquid exfoliation method was used to prepare transition metal dichalcogenide nanosheets (MoS 2 , WS 2 , MoSe 2 , and WSe 2). • Gum arabic was used as the exfoliating and stabilizing agent. • Doxorubicin loaded on gum arabic–MoSe 2 nanosheets (Dox–G–MoSe 2) exhibited photothermal efficiency. • Dox–G–MoSe 2 inhibited MDA-MB-231 cell proliferation and induced apoptosis. [ABSTRACT FROM AUTHOR]

Highlights • Graphene oxide (GO)-gold nanozymes were prepared as peroxidase mimics. • The nanozymes exhibited more enhanced activity than GO and AuNP alone. • The nanozymes were used for an electrochemical H 2 O 2 sensor. • The detection limit was much lower than that by colorimetric method. Abstract We fabricated a nafion/graphene oxide-gold nanoparticle (GO-AuNP) hybrid modified indium tin oxide (ITO) electrode and proposed an electrochemical method to detect hydrogen peroxide (H 2 O 2) using 3,3,5,5,-tetramethylbenzidine (TMB) as a redox mediator. The GO-AuNP hybrids were employed as nanozymes, which function as peroxidase mimics and show highly effective catalytic activity. Based on the high catalytic activity, enzyme mimics were entrapped on the ITO electrode to construct an electrochemical H 2 O 2 sensor by coating nafion polymer. During the catalytic reaction, the peroxidase substrate TMB was oxidized to form the TMB oxidation product, which not only produces a blue color detected by absorbance change, but also generates an electrochemical current. As a result, both spectrophotometric and electrochemical methods were used to determine H 2 O 2 concentration. The spectrophotometric detection displayed a linearity for H 2 O 2 concentration from 10 μM to 5 mM (r2 = 0.989), with an estimated detection limit of 2 μM. In the electrochemical detection, the TMB peak current had a good linear relationship with H 2 O 2 concentration from 10 nM to 10 mM, with an estimated detection limit of 1.9 nM, which was much lower than that of the spectrophotometric method result. [ABSTRACT FROM AUTHOR]

Abstract We developed a novel micro-patterning technique for single-walled carbon nanotubes (SWCNTs) on nitrocellulose (NC) membranes and characterized the mechanical and electrical properties of the patterned SWCNTs. The SWCNT patterns were successfully fabricated on wax-printed NC membrane by a vacuum filtration method within 15 min. The well-deposited SWCNT layer on the NC membrane exhibited strong adhesion and high conductivity due to the interconnection of the SWCNT layer in the porous structure of the NC membrane. The distinguishable patterns were resolved down to approximately 100 μm. The patterned SWCNT had an average resistivity of less than 100 Ω/sq and showed excellent mechanical properties in repeated bending tests. The suitability of the patterned SWCNT electrodes for electronic devices was demonstrated successfully via a simple light emitting diode array. Moreover, for the application of the patterned SWCNT to electrochemical paper-based analytical devices (ePADs), the gold nanoparticles (AuNPs) were directly deposited on the SWCNT electrode for non-enzymatic glucose determination. The oxidation peak had a linear response with glucose concentration in the range between 0.5 and 10 mM. The ePADs exhibited a sensitivity of 240 μA/mM·cm2 and a detection limit of 148 μM, which was derived from the electro-catalytic property of AuNPs toward glucose. Based on these results, we believe that the developed SWCNT patterning technique on paper substrates has great potential in ePADs. Graphical abstract Unlabelled Image Highlights • Micro-patterns of single-walled carbon nanotubes (SWCNTs) were successfully fabricated on wax-printed papers. • AuNPs were deposited on the SWCNT electrodes for the application to electrochemical paper-based analytical devices. • The developed devices were applied successfully to non-enzymatic glucose determination. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polyvinylpyrrolidone (PVP) was used to enhance the dispersity and homogeneity of bimetallic nanozymes. • PVP-stabilized PtRu nanozymes (PVP/PtRu NZs) exhibited excellent peroxidase-mimic activity. • Cascade reaction of glucose oxidase and PVP/PtRu NZs was used for colorimetric and fluorometric glucose detection. • Glucose recovery test using human serum and artificial urine showed excellent recovery values. Nanozymes have significant advantages over natural enzymes. The intrinsic peroxidase-like activity of Pt-based nanomaterials can be enhanced by alloying with other transition metals, such as Ru, that have great catalytic activity. In this study, we used polyvinylpyrrolidone (PVP) to synthesize well-dispersed and homogeneous nanostructures. PVP-stabilized Pt-Ru nanozymes (PVP/PtRu NZs) were synthesized and characterized. The PVP/PtRu NZs had an average size of 3.54 ± 0.84 nm and exhibited an intense peroxidase-like activity. The PVP/PtRu NZs were used as peroxidase mimics for colorimetric and fluorometric glucose determination by the glucose oxidase and PVP/PtRu NZs cascade reaction. In the colorimetric assay, the linearly detectable range was 0.25–3.0 mM, with an R2 and limit of detection (LOD) of 0.988 and 138 μM, respectively. In the fluorometric assay, a linear relationship was found when the glucose concentration was between 5.0 and 300 μM (R2 = 0.997), with an LOD of 1.11 μM. Compared to the colorimetric assay, the fluorometric assay had greater sensitivity and a lower detection limit for the determination of glucose. Moreover, the PVP/PtRu NZs had high storage stability over a month and great recovery values in human serum and artificial urine, with a range of 94–106 %. From these results, PVP/PtRu NZs are expected to be used as promising peroxidase mimics in various fields such as biosensing, pharmaceutical processing, and the food industry. [ABSTRACT FROM AUTHOR]

Self-monitoring of glycated albumin (GA), a useful glycemic marker, is an established method for preventing diabetes complications. Here, the paper-based lateral flow assay devices were developed for the sensitive detection of GA and the total human serum albumin (tHSA) in self-monitoring diabetes patients. Boronic acid-derived agarose beads were packed into a hole on a lateral flow channel. These well-coordinated agarose beads were used to capture GA through specific cis-diol interactions and to enhance the colorimetric signals by concentrating the target molecules. The devices exhibited large dynamic ranges (from 10 μg/ml to 10 mg/ml for GA and from 10 mg/ml to 50 mg/ml for tHSA) and low detection limits (7.1 μg/ml for GA and 4.7 mg/ml for tHSA), which cover the range of GA concentration in healthy plasma, which is 0.21–1.65 mg/ml (0.6%–3%). In determining the unknown GA concentrations in two commercial human plasma samples, the relative percentage difference between the values found by a standard ELISA kit and those found by our developed devices was 2.62% and 8.80%, which are within an acceptable range. The measurements of GA and tHSA were completed within 20 min for the total sample-to-answer diagnosis, fulfilling the demand for rapid analysis. Furthermore, the recovery values ranged from 99.4% to 110% in device accuracy tests. These results indicate that the developed paper-based device with boronic acid-derived agarose beads is a promising platform for GA and tHSA detection as applied to self-monitoring systems. [ABSTRACT FROM AUTHOR]