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Carbazole‐ and fluorene‐substituted benzidine blocks have been functionalized with two different solubilizing pendant groups, in order to enhance the material's solubility in greener solvents. Preserving the optical and electrochemical properties, the aromatic function and substitution showed an important influence on the solvent affinity, achieving concentrations up to 150 mg/mL in o‐xylenes for the glycol‐containing materials and decent solubility in alcohols for the compounds functionalized with ionic chains. The latter solution proved to be ideal for the preparation of luminescence slot‐die coating film on top of flexible‐substrates up to 33 cm×2 cm. As a proof of concept, the materials have been implemented in different organic electronic devices, highlighting the low turn‐on voltage (4 V) presented by organic light‐emitting diodes (OLEDs), which is comparable with vacuum‐processed devices. A structure‐solubility relationship and a synthetic strategy are disentangled in this manuscript to tailor organic semiconductors and adapt their solubility towards the desired solvent and application. [ABSTRACT FROM AUTHOR]

We investigated sequence-specific and simultaneous microRNA (miRNA) detections by surface plasmon resonance (SPR) imaging measurements on SPR chips possessing an Au spot array modified with probe DNAs based on a miRNA-detection-selective SPR signal amplification method. MiRNAs were detected with the detection limit of the attomole level by SPR imaging measurements for different miRNA concentrations on a single chip. SPR signals were enhanced based on a combination process of sequence-specific hybridization of the miRNA to the probe DNAs, extension reaction of polyadenine (poly(A)) tails by poly(A) polymerase, binding of a ternary complex of T30-biotin/horseradish peroxidase (HRP)-biotin/streptavidin to the poly(A) tails, and the oxidation reaction of tetramethylbenzidine (TMB) on the HRP by providing a blue precipitate on the surface. This process sequence-specifically and dramatically amplified the SPR signals. This is a simple, cost-effective, and feasible signal amplification method based on the organic compound TMB instead of metal nanoparticles.

The carcinogenic effects of benzidine (BZ) on bladder cancer are well documented, but its potential for promoting upper urinary tract urothelial carcinoma (UTUC) remains unclear. The ability of emodin, a natural pharmaceutical compound, to prevent BZ‑associated UTUC has not been previously explored. To the best of our knowledge, the present study is the first to reveal that BZ significantly enhanced the survival and migration of UTUC cell lines in vitro . Furthermore, in vivo experiments demonstrated that BZ promoted an increase in the size of subcutaneous tumors in nude mice. Further investigation revealed that BZ upregulated the expression of protein kinase A (PKA) and cyclooxygenase 2 (COX2), along with downstream matrix metalloproteinase 9 (MMP9) and vascular endothelial growth factor (VEGF), in UTUC cells. Moreover, BZ increased the levels of cyclic adenosine monophosphate (cAMP) and prostaglandin E2 (PGE2) in cell lysates. By contrast, emodin reduced the PKA and COX2 expression levels compared with the BZ‑treated group. Similarly, the in vivo experiments demonstrated that emodin significantly inhibited tumor growth in BZ‑pretreated nude mice, accompanied by reductions in the cAMP, PGE2, MMP9 and VEGF levels. These findings elucidated the role of BZ in promoting UTUC progression. Additionally, emodin has emerged as a novel inhibitor of BZ‑induced UTUC development through PKA/COX2 inhibition, suggesting its potential as a natural therapeutic agent against BZ‑associated UTUC.

α-Glucosidase (α-Glu) is implicated in the progression and pathogenesis of type II diabetes (T2D). In this study, we developed a rapid colorimetric technique using platinum nanoparticles stabilized by chitosan (Ch-PtNPs) to detect α-Glu activity and its inhibitor. The Ch-PtNPs facilitate the conversion of 3,3',5,5'-tetramethylbenzidine (TMB) into oxidized TMB (oxTMB) in the presence of dissolved O 2 . The catalytic hydrolysis of 2-O-α-D-glucopyranosyl-L-ascorbic acid (AA-2G) by α-Glu produces ascorbic acid (AA), which reduces oxTMB to TMB, leading to the fading of the blue color. However, the presence of α-Glu inhibitors (AGIs) hinders the generation of AA, allowing Ch-PtNPs to re-oxidize colorless TMB back to blue oxTMB. This unique phenomenon enables the colorimetric detection of α-Glu activity and AGIs. The linear range for α-Glu was found to be 0.1-1.0 U mL -1 and the detection limit was 0.026 U mL -1 . Additionally, the half-maximal inhibition value (IC 50 ) for acarbose, an α-Glu inhibitor, was calculated to be 0.4769 mM. Excitingly, this sensing platform successfully detected α-Glu activity in human serum samples and effectively screened AGIs. These promising findings highlight the potential application of the proposed strategy in clinical diabetes diagnosis and drug discovery., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.)

The present work investigates the capability of single-stranded DNA (ssDNA) in enhancing the intrinsic peroxidase-like activity of the g-C3N4 nanosheets (NSs). We found that ssDNA adsorbed on g-C3N4 NSs could improve the catalytic activity of the nanosheets. The maximum reaction rate of the H2O2-mediated TMB oxidation catalyzed by the ssDNA-NSs hybrid was at least 4 times faster than that obtained with unmodified NSs. The activity enhancement could be attributed to the strong interaction between TMB and ssDNA mediated by electrostatic attraction and aromatic stacking and by both the length and base composition of the ssDNA. The high catalytic activity of the ssDNA-NSs hybrid permitted sensitive colorimetric detection of exosomes if the aptamer against CD63, a surface marker of exosome, was employed in hybrid construction. The sensor recognized the differential expression of CD63 between the exosomes produced by a breast cancer cell line (MCF-7) and a control cell line (MCF-10A). Moreover, a similar trend was detected in the circulating exosomes isolated from the sera samples collected from breast cancer patients and healthy controls. Our work sheds lights on the possibility of using ssDNA to enhance the peroxidase-like activity of nanomaterials and demonstrates the high potential of the ssDNA-NSs hybrid in clinical diagnosis using liquid biopsy.

Pesticide detection based on nanozyme is largely limited in terms of the variety of pesticides. Herein, a spherical and well-dispersed Fe 3 O 4 /graphene oxide nanoribbons (Fe 3 O 4 /GONRs) composite nanozyme was applied to firstly develop an enzyme-free and sensitive colorimetric and fluorescence dual-mode detection of thiophanate-methyl (TM). The synthesized Fe 3 O 4 /GONRs possess excellent dual enzyme-like activities (peroxidase and catalase) and can catalyze H 2 O 2 to oxidize 3,3',5,5'-tetramethylbenzidine (TMB) into oxidized TMB (oxTMB). We found that Fe 3 O 4 /GONRs can adsorb TM through the synergistic effect of multiple forces, thereby inhibiting the catalytic activities of nanozyme. This inhibition can modulate the transformation of TMB to oxTMB, producing dual responses of absorbance decrease (oxTMB) and fluorescence enhancement (TMB). The limits of detection (LODs) of TM were 28.1 ng/mL (colorimetric) and 8.81 ng/mL (fluorescence), respectively. Moreover, the developed method with the recoveries of 94.8-100.8% also exhibited a good potential application in the detection of pesticides residues in water and food samples., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Staphylococcus aureus is a pathogenic bacterium contaminating milk and dairy foods causing food poisoning and foodborne pathogens. In this work, a smartphone-enabled enzyme cascade-triggered colorimetric platform was constructed using a cascade bio-nanozyme formed by immobilized glucose oxidase (GOx) on Fe 3 O 4 @Ag for rapid detection of S. aureus. Benefiting from reasonable experimental design, a bio-nanozyme cascade-triggered reaction was achieved through H 2 O 2 produced by GOx oxidation of glucose, followed by in situ catalysis of 3,3',5,5'-tetramethylbenzidine (TMB) by the inherent peroxidase-like activity of Fe 3 O 4 @Ag to produce color signals. Staphylococcus aureus detection could be performed through naked-eye observation and smartphone measurement, and the developed assay can achieve quantitative and qualitative detection of S. aureus. The on-site nanoplatform had satisfactory specificity and sensitivity with a low detection limit of 6.9 cfu·mL -1 in 50 min. Moreover, the nanoplatform has good practicality in the detection of S. aureus in milk samples. Therefore, the assay has potential application prospects in food safety inspection., (© 2024, The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

In this work, a colorimetric aptasensor based on magnetic beads (MBs), gold nanoparticles (AuNPs) and Horseradish Peroxidase (HRP) was prepared for the detection of mucin 1 (MUC1). Complementary DNA of the MUC1 aptamer (Apt) immobilized on the MBs was combined with the prepared AuNPs-Apt-HRP complex (AuNPs@Apt-HRP). In the presence of MUC1, it specifically bound to Apt, resulting in the detachment of gold nanoparticles from the MBs. After magnetic separation, AuNPs@Apt-HRP was separated into the supernatant and reacted with 3,3',5,5'-Tetramethylbenzidine (TMB) to produce color reaction from colorless to blue. The linear range of MUC1 was from 75 to 500 μg/mL (R 2  = 0.9878), and the detection limit was 41.95 μg/mL. The recovery rate of MUC1 in human serum was 99.18 %∼101.15 %. This method is simple and convenient. Moreover, it does not require complex and expensive equipment for detection of MUC1. It provides value for the development of MUC1 colorimetric sensors and a promising strategy for the determination of MUC1 in clinical diagnosis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Paper-based lateral flow immunoassays (LFIAs) are cost-effective, portable, and simple methods for detection of diverse analytes, which however only provide qualitative or semiquantitative results and lack sufficient sensitivity. A combination of LFIA and electrochemical detection, namely, electrochemical lateral flow immunoassay (eLFIA), enables quantitative detection of analytes with high sensitivity, but the integration of external electrodes makes the system relatively expensive and unstable. Herein, the working, counter, and reference electrodes were prepared directly on the nitrocellulose membrane using screen printing, which remarkably simplified the structure of eLFIA and decreased the cost. Moreover, a horseradish peroxidase (HRP)-based electrochemical signal amplification strategy was used for further increasing the analytical sensitivity. HRP captured on the working electrode can catalyze the oxidation of tetramethylbenzidine (TMB) to form the TMB-TMB ox precipitate on the electrode surface, which as an electrochemically active product can output an amplified current for quantification. We demonstrated that the eLFIA could detect low-abundant inflammatory biomarkers in human plasma samples with limits of detection of 0.17 and 0.54 pg mL -1 for interleukin-6 and C-reactive protein, respectively. Finally, a fully portable system was fabricated by integrating eLFIA with a flexible and wireless electrochemical workstation, realizing the point-of-care detection of interleukin-6.

A colorimetric analysis platform has been successfully developed based on FeCo-NC dual-atom nanozyme (FeCo-NC DAzyme) for the detection of organophosphorus pesticides (OPPs). The FeCo-NC DAzyme exhibited exceptional oxidase-like activity (OXD), enabling the catalysis of colorless TMB to form blue oxidized TMB (oxTMB) without the need for H 2 O 2 involvement. By combining acid phosphatase (ACP) hydrolase with FeCo-NC DAzyme, a "FeCo-NC DAzyme + TMB + ACP + SAP" colorimetric system was constructed, which facilitated the rapid detection of malathion. The chromogenic system was applied to detect malathion using a smartphone-based app and an auxiliary imaging interferogram device for colorimetric measurements, which have a linear range of 0.05-4.0 µM and a limit of detection (LOD) as low as 15 nM in real samples, comparable to UV-Vis and HPLC-DAD detection methods. Overall, these findings present a novel approach for convenient, rapid, and on-site monitoring of OPPs., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Herein, we synthesized a novel N-doped carbon layer encapsulated Fe/Co bimetallic nanoparticles (Fe/Co-NC), which exhibited superior oxidase-like activity due to the facilitation of electron penetration and the formation of metal-nitrogen active sites. Fe/Co-NC could catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) to blue oxTMB. Acetylcholinesterase (AChE) could catalyze the hydrolysis of thioacetylcholine to produce reducing thiocholine, which prevented TMB from oxidation. Thus, a portable hydrogel colorimetric sensor was developed for on-site and visual monitoring of AChE with the detection limit of 0.36 U L -1 , and successfully applied to detect AChE in human erythrocyte samples. Furthermore, this platform was used to investigate the inhibition of triazophos on AChE activity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Herein, a novel dual-mode probe for organophosphorus pesticides (OPs) colorimetric and photothermal detection was developed based on manganese modified porphyrin metal-organic framework (PCN-224-Mn). PCN-224-Mn had excellent oxidase-like activity and oxidized colorless 3,3,5,5-tetramethylbenzidine (TMB) to blue-green oxidation state TMB (oxTMB), which exhibited high temperature under near-infrared irradiation. l-ascorbate-2-phosphate was hydrolyzed by acid phosphatase to produce ascorbic acid, which weakened colorimetric and photothermal signals by impacting oxTMB generation. The presence of OPs blocked the production of ascorbic acid by irreversibly inhibiting the activity of acid phosphatase, causing the restoration of chromogenic reaction and the increase of temperature. Under the optimal conditions, the probe showed a good linear response to OPs in the concentration range of 5 ∼ 10000 ng/mL, using glyphosate as the analog. The detection limits of glyphosate in colorimetric mode and photothermal mode were 1.47 ng/mL and 2.00 ng/mL, respectively. The probe was successfully used for sensitive identification of OPs residues in tea, brown rice, and wheat flour. This work proposes a simple and reliable colorimetric/photothermal platform for OPs identification, which overcomes the problem that single-mode detection probes are susceptible to external factors, and has broad application potential in the field of food safety., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: The development of wearable detection devices that can achieve noninvasive, on-site and real-time monitoring of sweat metabolites is of great demand and practical significance for point-of-care testing and healthcare monitoring. Monitoring uric acid (UA) content in sweat provides a simple and promising way to reduce the risk of gout and hyperuricemia. Traditional bioenzyme based UA assays suffer from high cost, poor stability, inconvenience for storage and easy deactivation of bioenzymes. Wearable microfluidic colorimetric detection device for sweat UA detection has not been reported. The development of novel wearable microfluidic colorimetric detection chip with no requirement of bioenzymes for sweat UA detection is of great importance for health care monitoring., Results: Firstly, Co@MnO 2 nanozyme with high oxidase-like activity was synthesized and characterized. Co@MnO 2 can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) directly to generate blue-green colored ox-TMB. Green colored 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) radical (ABTS ·+ ) was produced by the oxidation of ABTS by potassium persulfate. UA exhibits distinct quenching effect on Co@MnO 2 catalyzed TMB colorimetric reaction system and ABTS ·+ based colorimetric system, leading to obvious color fading of the two colorimetric systems. Then, a flexible microfluidic colorimetric detection chip for UA detection was fabricated by assembling Co@MnO 2 /TMB modified paper chips and ABTS ·+ modified paper chips into a polydimethylsiloxane (PDMS) microfluidic chip. The fabricated microfluidic colorimetric detection chip exhibits good linear relationship for sweat UA detection. The linear range is from 20 to 200 μmol/L with detection limit as low as 6.6 μmol/L. Good results were obtained for the detection of UA in actual sweat from three volunteers., Significance: This work provides two bio-enzyme free colorimetric detection systems for UA detection. Furthermore, a simple, low-cost and selective flexible wearable microfluidic colorimetric detection chip was fabricated for noninvasive and on-site detection of sweat UA, which holds great application potential for personal health monitoring and point-of-care testing., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Hybrid nanozyme graphene quantum dots (GQDs) deposited TiO 2 nanotubes (NTs) on titanium foil (Ti/TiO 2 NTs-GQDs) were manufactured by bestowing the hybrid with the advantageous porous morphology, surface valence states, high surface area, and copious active sites. The peroxidase-like activity was investigated through the catalytic oxidation of chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H 2 O 2 , which can be visualized by the eyes. TiO 2 NTs and GQDs comprising oxygen-containing functional groups can oxidize TMB in the presence of H 2 O 2 by mimicking peroxidase enzymes. The peroxidase-mimicking activity of hybrid nanozyme was significantly escalated by introducing light illumination due to the photosensitive features of the hybrid material. The peroxidase-like activity of Ti/TiO 2 NTs-GQDs enabled H 2 O 2 determination over the linear range of 7 to 250 μM, with a LOD of 2.1 µM. The satisfying peroxidase activity is possibly due to the unimpeded access of H 2 O 2 to the catalyst's active sites. The porous morphology provides the easy channeling of reactants and products. The periodic structure of the material also gave rise to acceptable reproducibility. Without material functionalization, the Ti/TiO 2 NTs-GQDs can be a promising substitute for peroxidases for H 2 O 2 detection., (© 2024. The Author(s).)

As a potent detection method for cancer biomarkers in physiological fluid, a colorimetric and electrochemical dual-mode sensing platform for breast cancer biomarker thioredoxin 1 (TRX1) was developed based on the excellent peroxidase-mimicking and electrocatalytic property of Prussian blue nanoparticles (PBNPs). PBNPs were hydrothermally synthesized using K 3 [Fe(CN) 6 ] as a precursor and polyvinylpyrrolidone (PVP) as a capping agent. The synthesized spherical PBNPs showed a significant peroxidase-like activity, having approximately 20 and 60% lower K m values for 3,3',5,5'-tetramethylbenzidine (TMB) and H 2 O 2 , respectively, compared to those of horseradish peroxidase (HRP). The PBNPs also enhanced the electron transfer on the electrode surface. Based on the beneficial features, PBNPs were used to detect target TRX1 via sandwich-type immunoassay procedures. Using the strategies, TRX1 was selectively and sensitively detected, yielding limit of detection (LOD) values as low as 9.0 and 6.5 ng mL -1 via colorimetric and electrochemical approaches, respectively, with a linear range of 10-50 ng mL -1 in both strategies. The PBNP-based TRX1 immunoassays also exhibited a high degree of precision when applied to real human serum samples, demonstrating significant potentials to replace conventional HRP-based immunoassay systems into rapid, robust, reliable, and convenient dual-mode assay systems which can be widely utilized for the identification of important target molecules including cancer biomarkers.

In this work, a colorimetric and fluorescent dual-mode probe controlled by NH 2 -MIL-88 B (Fe, Ni) nanozymes was developed to visually detect tetracycline antibiotics (TCs) residues quantitatively, as well as accurately distinguish the four most widely used tetracycline analogs (tetracycline (TC), chrycline (CTC), oxytetracycline (OTC), and doxycycline (DC)). Colorless substrate 3,3',5,5'-tetramethylbenzidine (TMB) may be oxidized to blue oxidized TMB by the Fe Fenton reaction, which was catalyzed by the NH 2 -MIL-88 B (Fe, Ni) nanozyme with POD-like activity. The colorimetric detection system allows TCs to interact with NH 2 -MIL-88 B (Fe, Ni). This inhibits the production of ·OH, weakens the oxidation process of TMB, and ultimately lightens the blue color in the system by blocking the electron transfer between NH 2 -MIL-88 B (Fe, Ni) and H 2 O 2 . Furthermore, TCs can interact with NH 2 -MIL-88 B (Fe, Ni) as a result of the internal filtering effect, which causes the fluorescence intensity to decrease as TCs concentration increases. Additionally, a portable instrument that combines a smartphone sensing platform with colorimetric and fluorescent signals was created for the quick, visual quantitative detection of TCs. The colorimetric and fluorescent dual-mode nano platform enables color change, with detection limits (LODs) of 0.182 μM and 0.0668 μM for the spectrometer and smartphone sensor, respectively, based on the inhibition of fluorescence and enzyme-like activities by TCs. Overall, the colorimetric and fluorescence dual-mode sensor has good stability, high specificity, and an efficient way to eliminate false-positive issues associated with a single detection mode., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The preparation of cobalt-based nanozymes with high oxidase-like activity still needs more efforts. In this paper, we report the synthesis of a CoO/Co-tryptophan-functional graphene quantum dot hybrid (CoO/Co-Try-GQD). Firstly, cobalt ions coordinate with the indole nitrogen on Try-GQD to form a complex, followed by thermal reduction and oxidation. The resulting hybrid presents a three-dimensional network structure, and CoO/Co nanoparticles are uniformly dispersed on the graphene sheet with an average size of 10 ± 0.24 nm. This unique structure improved the oxidase-like activity of the hybrid, enabling it to catalyze the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to rapidly produce deep blue ox-TMB with a strong absorbance at 652 nm ( A 652 ). A colorimetric method was developed for the highly sensitive determination of L-cysteine (L-cys) based on the inhibition of the hybrid's oxidase-like activity and low A 652 caused by the binding of L-cys with Co atoms on CoO/Co via the Co-S bond. The A 652 linearly decreased with increasing L-cys concentration in the range of 0.05-2 μM, and the detection limit was 0.032 μM. Further, the established method has been successfully applied to the determination of L-cys in milk.

Introduction: Thoracoabdominal normothermic regional perfusion (TA-NRP) following cardiac death is an emerging multivisceral organ procurement technique. Recent national studies on outcomes of presumptive TA-NRP-procured organs are limited by potential misclassification since TA-NRP is not differentiated from donation after cardiac death (DCD) in registry data., Methods: We studied 22 donors whose designees consented to TA-NRP and organ procurement performed at our institution between January 20, 2020 and July 3, 2022. We identified these donors in SRTR to describe organ utilization and recipient outcomes and compared them to recipients of traditional DCD (tDCD) and donation after brain death (DBD) organs during the same timeframe., Results: All 22 donors progressed to cardiac arrest and underwent TA-NRP followed by heart, lung, kidney, and/or liver procurement. Median donor age was 41 years, 55% had anoxic brain injury, 45% were hypertensive, 0% were diabetic, and median kidney donor profile index was 40%. TA-NRP utilization was high across all organ types (88%-100%), with a higher percentage of kidneys procured via TA-NRP compared to tDCD (88% vs. 72%, p = .02). Recipient and graft survival ranged from 89% to 100% and were comparable to tDCD and DBD recipients (p ≥ .2). Delayed graft function was lower for kidneys procured from TA-NRP compared to tDCD donors (27% vs. 44%, p = .045)., Conclusion: Procurement from TA-NRP donors yielded high organ utilization, with outcomes comparable to tDCD and DBD recipients across organ types. Further large-scale study of TA-NRP donors, facilitated by its capture in the national registry, will be critical to fully understand its impact as an organ procurement technique., (© 2024 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The distribution of gold nanoparticles (AuNPs) on the surface of a metal-organic framework (MOF) plays a crucial role in the catalytic performance of MOF-AuNP composites. This study describes how the physical adsorption (PH@AuNPs-on-U) and chemical modification of AuNPs on the surface of UiO-66-NH 2 (U) affect the composites' catalytic efficiency. After 2-vinyl-4,4-dimethyl-2-oxazolin-5-one (VD) linked to poly( N -2-hydroxypropyl methacrylamide) (PH) with U (UVD-PH), UVD-PH@AuNPs composites were constructed with PH as the capping and reducing reagent. The composites exhibited higher peroxidase (POD)-like activity than PH@AuNPs-on-U for oxidising 3,3'5,5'-tetramethylbenzidine (TMB) with H 2 O 2 . The approach demonstrated that the proposed composite-based nanozymes could significantly enhance their catalytic activity and had a highly uniform distribution of PH@AuNPs on the surface of UVD. An assay with the nanozymes for visual detection of homocysteine (Hcy) was developed, displaying a good linear relationship ( R 2 = 0.998) ranging from 3.34 μM to 30.0 μM and a detection of limit of 0.3 μM. Additionally, the UVD-PH@AuNPs-TMB-H 2 O 2 system successfully monitored serum Hcy after intraperitoneal injection in rats. This study paves a new way for developing MOF-AuNPs with highly uniform surface distribution of polymer@AuNPs to boost its catalytic activity and to detect drugs in real bio-samples.

We present the preparation of CoCu bimetallic nanoclusters (Co@Cu-BNCs) by a hydrothermal and one-step pyrolysis method to build a colorimetric and electrochemical dual-mode sensing platform for uric acid (UA) detection. In the presence of H 2 O 2 , Co@Cu-BNCs with peroxidase-mimicking activity may convert colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue-colored oxidized TMB (oxTMB). However, due to the inhibitory effect of uric acid (UA) on the oxidation process of TMB, the characteristic absorption peak intensity of oxTMB decreased when UA was added into a mixed solution. In this approach, a colorimetric assay platform for the detection of UA was demonstrated, with a linear range of 0.1-195 μM and a low limit of detection of 0.06 μM (S/N ratio of 3). In addition, an even wider detection range is achieved in the electrochemical method, due to the pronounced electrocatalytic activity of Co@Cu-BNCs. The surface of the glassy carbon electrode was modified with Co@Cu-BNCs to build an electrochemical sensor for detecting UA. The sensor achieves a wider linear range from 2 to 1000 μM and a limit of detection of 0.61 μM (S/N ratio of 3). Moreover, the detection of UA in a human serum sample showed satisfactory results. The results proved that the colorimetric and electrochemical dual-mode detection platform was sensitive, convenient and accurate.

Inflammation plays a key role in the progression of choroidal neovascularization (CNV). Regular intravitreal injection of anti-VEGF medication is required for many patients to sustain eye condition as CNV always recurs due to persistent chronic inflammation in the retina and choroid. Marine bromophenols (BDB) have been widely studied due to their diverse bioactivities, including anti-inflammatory effect, though the mechanism of which remained unclear. Our study demonstrated that BDB could restricted endothelial cells' function and suppressed choroidal explants both in vitro and in vivo without out affecting the cells viability. BDB also significantly reduced numerous inflammatory cytokines in both raw cells and choroidal tissue, including IL-1β, IL-6, TNF-α, IL-4 and MMP-9. Moreover, we demonstrated that BDB down regulated phosphorylation of NF-κB p65 in the raw cells. By Co-IP assay, HUWE1 was found to be bound with BDB and the binding location was at sequences position 4214. When overexpressed HUWE1 in HUVECs, the suppression of endothelial cells' function by BDB became more significant. Taken together, the findings in this study showed that BDB suppressed endothelial cells' function and choroidal neovascularization by targeting HUWE1 through NF-κB pathway, which suggested that BDB could be a potential therapeutic candidate in treating chronic inflammation in choroidal neovascularization., Competing Interests: Declaration of competing interest The authors declare that there is no known competing financial interests or personal relationships that could have appeared to influence the work in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Hyaluronidase (HAase) is an important endoglycosidase involved in numerous physiological and pathological processes, such as apoptosis, senescence, and cancer progression. Simple, convenient, and sensitive detection of HAase is important for clinical diagnosis. Herein, an easy-to-operate multicolor visual sensing strategy was developed for HAase determination. The proposed sensor was composed of an enzyme-responsive hydrogel and a nanochromogenic system (gold nanobipyramids (AuNBPs)). The enzyme-responsive hydrogel, formed by polyethyleneimine-hyaluronic acid (PEI-HA), was specifically hydrolyzed with HAase, leading to the release of platinum nanoparticles (PtNPs). Subsequently, PtNPs catalyzed the mixed system of 3,3',5,5'-tetramethylbenzidine (TMB) and H 2 O 2 to produce TMB 2+ under acidic conditions. Then, TMB 2+ effectively etched the AuNBPs and resulted in morphological changes in the AuNBPs, accompanied by a blueshift in the localized surface plasmon resonance peak and vibrant colors. Therefore, HAase can be semiquantitatively determined by directly observing the color change of AuNBPs with the naked eye. On the basis of this, the method has a linear detection range of HAase concentrations between 0.6 and 40 U/mL, with a detection limit of 0.3 U/mL. In addition, our designed multicolor biosensor successfully detected the concentration of HAase in human serum samples. The results showed no obvious difference between this method and enzyme-linked immunosorbent assay, indicating the good accuracy and usability of the suggested method., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

In this study, we have developed bridge heterologous ELISA for the detection of 17α- Methyltestosterone by incorporating aromatic spacers between 17α-Methyltestosterone-3-Carboxymethyloxime and Horseradish peroxidase label through N-hydroxysuccinimide mediated carbodiimide reaction method. The immunogen 17α-Methyltestosterone-3-Carboxymethyloxime-Bovine serum albumin used to generate the antibody was also prepared by the N-hydroxysuccinimide mediated carbodiimide reaction without using any spacer. We have studied the impact of bridge/aromatic spacers on functional parameters i.e. sensitivity, affinity and ED 50 of the bridge heterologous assay and compared it with homologous assay. The five combinations of bridge heterologous assay using 17α-Methyl testosterone-3-CMO-BSA antiserum and 17α-MT-3-CMO-4,4'-Diaminodiphenyl sulphide-HRP, 17α MT-3-CMO-4,4'-Oxydianiline-HRP, 17α-MT-3-CMO-Benzidine-HRP, 17α- MT-3-CMO-p-Phenylenediamine-HRP and 17α-MT-3-CMO-Dapson-HRP enzyme conjugates were evaluated. Out of these five combinations, the combination 17α-MT-3-CMO-BSA with 17α-MT-3-CMO-Benzidine-HRP showed the best results. Sensitivity, affinity and ED 50 were improved and found to be 0.02 ng/mL, 0.086 × 10 -8 L/mol and 2.95 ng/mL than homologous assay where Sensitivity, affinity and ED 50 were 0.11 ng/mL, 0.02 × 10 -8 L/mol and 5.78 ng/mL respectively. The cross-reactivity for this bridge heterologous assay combination was seen with only 4 steroids (6-hydrotestosterone- 6%, Testosterone-5.14%, Danazol-0.9% and Nandrolone-0.85%) instead of eight steroids (6-hydrotestosterone-43.75%, Testosterone-38.3%, Danazol-25.14%, Androstenediol-19.16%, Nandrolone-19%, Metandienone-5%, Androstenedione-3.52%, and 17α dimethyltestosterone-2%) as in homologous assay out of 59 structurally related steroids. Thus, the results of this study conclude that the incorporation of aromatic spacer (bridge) in enzyme conjugate has a crucial role in improving sensitivity, specificity, ED 50 and affinity of the developed assay. The assay was then studied for parameters such as recovery (97.4%-108.6%), precision (Inter and Intra-assay coefficient of variation <10%), correlation coefficient (R 2  = 0.96) by comparing with the commercial kit and validated by measuring levels of 17α- methyltestosterone in rat serum after administering them., Competing Interests: Declaration of Competing Interest The authors declare that they have no competing interests., (Copyright © 2023. Published by Elsevier B.V.)

Development of an effective and convenient sensor for sensitive detection of nitrites is of great concern since excessive amounts of nitrites can be harmful to both human health and the environment. In this work, Cu-MOF modified exfoliated graphite paper (EGP) was employed as a signal reporter to enable the visual and electrochemical dual-mode sensing of nitrites. Cu-MOFs were in situ synthesized on EGP, which exhibited an excellent oxidase enzyme-like activity to oxidize 3,3',5,5'-tetramethylbenzidine (TMB) into its oxidation product (oxTMB). The multi-layer structure and the superior electrical conductivity of EGP not only facilitated the loading of the Cu-MOF nanozyme for colorimetric sensing but also enabled its use as an underlying backbone to support electroanalysis. Based on the recognition of nitrite through a highly specific diazo reaction between nitrite and oxTMB, the addition of nitrite caused the colorimetric sensing solution to change color from blue to green, which allowed for the colorimetric sensing of nitrite with a limit of detection (LOD) of 8.5 × 10 -6 mol L -1 . Meanwhile, the Cu-MOF/EGP electrochemical platform was employed for ratiometric detection of nitrite based on the electrochemical oxidation of nitrite and TMB. Compared with the colorimetric mode, the electrochemical mode possessed higher sensitivity with a LOD of 5.4 × 10 -7 mol L -1 , indicating the high sensitivity and accuracy of the proposed dual-mode sensing strategy. Furthermore, the determination of nitrite in different pickled food samples is demonstrated.

A highly sensitive and facile colorimetric assay is introduced for detecting biogenic gaseous H 2 S using peroxidase (POD)-like catalytic activity of silver core/gold shell nanoplates (Ag@Au NPls). H 2 S can react with Ag@Au NPls to form Ag 2 S or Au 2 S on their surface, which can reduce POD-like activity of Ag@Au NPls and consequently decrease the absorbance at 650 nm due to oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H 2 O 2 ). For in situ and multiple detection of H 2 S, we utilized a microplate cover with 24 polydimethylsiloxane inner wells where Ag@Au NPls reacted with H 2 S gas followed by treatment with TMB/H 2 O 2 . As a result, the change in absorbance at 650 nm showed a linear relationship with the H 2 S concentration in the range 0.33 to 2.96 μM (0.36 absorbance/μM H 2 S in PBS, R 2  = 0.994) with a limit of detection of 263 nM and a relative standard deviation of 4.4%. Finally, this assay could detect H 2 S released from Eikenella corrodens, used as a model bacterium, in a short time (20 min) or at a low number of bacteria (1 × 10 4 colony forming units/mL). Therefore, this assay is expected to be applied for the study of H 2 S signaling in bacterial physiology, as well as measure H 2 S production released from other oral bacteria that cause halitosis and oral diseases, leading to the subsequent diagnosis., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Nanozymes, enzyme-mimicking nanomaterials, have attracted increasing attention due to their low cost, high stability, and catalytic ability compared with natural enzymes. However, the catalytic efficiency of the nanozymes is still relatively low, and catalytic reaction mechanisms remain unclear. To address these issues, herein we prepared nitrogen-riched and sulfur-codoped nano hollow carbons (N/S-HCS) using a green and useful template of CaCO 3 . N/S-HCS exhibits enhanced oxidase-like activity and catalytic kinetic performance. It could directly oxidize the colorless 3,3',5,5'-tetramethylbenzidine (TMB) to the heavy blue colored ox-TMB without H 2 O 2 . The maximum reaction rate ( V max ) is 186.7 × 10 -8 M·s -1 , and Michaelis-Menten constant ( K m ) is 0.162 mM. DFT results show that N and S codoping could work synergistically to provide more active sites, resulting in the superior ability to adsorb oxygen and enhanced catalytic activity. Meantime, we develop a multispectral characterization strategy to unravel catalytic reaction mechanisms about N/S-HCS. It successfully induces the generation of superoxide ( • O 2 - ) and hydroxyl ( • OH) during the colorimetric reaction which are the key intermediate products of the catalytic reaction. Furthermore, N/S-HCS increased the cellular reactive oxygen species level significantly and induced bacteriostasis to more than 95% of Escherichia coli .

Artificial nanozymes have been receiving considerable interest for their outstanding performance and wide application. However, their low activity results in a high concentration of substrates, costs, and environmental pollution. To enhance nanozymic activity, a composite, Fe x Ni 1- x S 2 /hollow carbon spheres (Fe x Ni 1- x S 2 /SC), was facilely synthesized by a solvothermal method. The response surface methodology (RSM) was used to optimize the Ni content in Fe x Ni 1- x S 2 /SC and the experimental conditions, where Fe 0.75 Ni 0.25 S 2 /SC exhibited the highest activity. The K m (Michaelis-Menten's constant) values of Fe 0.75 Ni 0.25 S 2 /SC are 0.025 and 0.021 mM with H 2 O 2 and oxidized 3,3',5,5'-tetramethylbenzidine (TMB) as the substrates, respectively, which are 148 times and 20.5 times lower than those with HRP, 1.88 and 7.19 times lower than those of FeS 2 /SC, and 1.88 and 10.52 times lower than those of Fe 0.8 Ni 0.2 S 2 , meaning a strong affinity of Fe 0.75 Ni 0.25 S 2 /SC for the substrate. The catalytic efficiency ( K cat / K m ) of Fe 0.75 Ni 0.25 S 2 /SC was 5.4 (H 2 O 2 ) and 27.4 times (TMB), and 9.7 (H 2 O 2 ) and 66.2 times (TMB) higher than those of FeS 2 /SC and Fe 0.8 Ni 0.2 S 2 , respectively. The effects of the synergistic interaction between Fe and Ni, the S-C bond formation, and the hollow carbon spheres on the activity were studied. A nanozymic mechanism was proposed. Fe 0.75 Ni 0.25 S 2 /SC could be used to detect cysteine (Cys) at room temperature in 1 min with a detection limit (LOD) of 0.049 μM.