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Nanozymes (NZs) are nanomaterials that mimic enzyme-like catalytic activity. They have attracted substantial attention due to their inherent physicochemical properties for use as promising alternatives to natural enzymes (NEs) in a variety of research fields. Particularly, in biosensing and bioassays, NZs have opened a new horizon to eliminate the intrinsic limitations of NEs, including their denaturation at extreme pH values and temperatures, poor reusability and recyclability, and high production costs. Moreover, the catalytic activity of NZs can be modulated in the preparation step by following an appropriate synthesis strategy. This review aims to gain insight into the potential substitution of NEs by NZs in biosensing and bioassays while considering both the pros and cons. The physicochemical and catalytic properties of nanozymes and natural enzymes are compared to obtain insight into their application in biosensing and bioassays. [Display omitted] • Nanozymes (NZs) are the nanomaterials mimicking the enzyme-like catalytic activity. • NZs and their application in biosensing and bioassay are summarized. • Natural enzymes (NEs) vs NZs in biosensing and bioassay are discussed. • Compositions, modifications, and immobilization strategies and are highlighted. [ABSTRACT FROM AUTHOR]

Mycotoxins, as a food and feed toxins, pose serious health risks for humans and animals and cause huge economic losses. Preventive measures against mycotoxins are not successful, and mycotoxins are commonly present in food and feed, which are easily contaminated. Moreover, this represents entry into the food chain, endangering all, including humans. Graphene oxide (GO) and its composites, thanks to their number of different functional groups on their surface, seem to be a promising tool for capturing and removing mycotoxins from contaminated food and feed without creating health risks or decreasing the quality of products. • Graphene oxide and the composite of graphene oxide with magnetic NPs can adsorb mycotoxins from various food and feed. • The comparison of traditional methods for mycotoxins removal with nanomaterials. • The interactions between nanomaterial and mycotoxins is similar like for antibiotics. • PH values play the most important role in the adsorption of mycotoxins. [ABSTRACT FROM AUTHOR]

This work reports the use of modified reduced graphene oxide (rGO) as a platform for a label-free DNA-based electrochemical biosensor as a possible diagnostic tool for a DNA methylation assay. The biosensor sensitivity was enhanced by variously modified rGO. The rGO decorated with three nanoparticles (NPs)—gold (AuNPs), silver (AgNPs), and copper (CuNPs)—was implemented to increase the electrode surface area. Subsequently, the thiolated DNA probe (single-stranded DNA, ssDNA−1) was hybridized with the target DNA sequence (ssDNA-2). After the hybridization, the double-stranded DNA (dsDNA) was methylated by M.SssI methyltransferase (MTase) and then digested via a HpaII endonuclease specific site sequence of CpG (5′-CCGG-3′) islands. For monitoring the MTase activity, differential pulse voltammetry (DPV) was used, whereas the best results were obtained by rGO-AuNPs. This assay is rapid, cost-effective, sensitive, selective, highly specific, and displays a low limit of detection (LOD) of 0.06 U·mL−1. Lastly, this study was enriched with the real serum sample, where a 0.19 U·mL−1 LOD was achieved. Moreover, the developed biosensor offers excellent potential in future applications in clinical diagnostics, as this approach can be used in the design of other biosensors. [ABSTRACT FROM AUTHOR]

Low-cost, rapid, and easy-to-use biosensors for various cancer biomarkers are of utmost importance in detecting cancer biomarkers for early-stage metastasis control and efficient diagnosis. The molecular complexity of cancer biomarkers is overwhelming, thus, the repeatability and reproducibility of measurements by biosensors are critical factors. Electrochemical biosensors are attractive alternatives in cancer diagnosis due to their low cost, simple operation, and promising analytical figures of merit. Recently graphene-derived nanostructures have been used extensively for the fabrication of electrochemical biosensors because of their unique physicochemical properties, including the high electrical conductivity, adsorption capacity, low cost and ease of mass production, presence of oxygen-containing functional groups that facilitate the bioreceptor immobilization, increased flexibility and mechanical strength, low cellular toxicity. Indeed, these properties make them advantageous compared to other alternatives. However, some drawbacks must be overcome to extend their use, such as poor and uncontrollable deposition on the substrate due to the low dispersity of some graphene materials and irreproducibility of the results because of the differences in various batches of the produced graphene materials. This review has documented the most recently developed strategies for electrochemical sensor fabrication. It differs in the categorization method compared to published works to draw greater attention to the wide opportunities of graphene nanomaterials for biological applications. Limitations and future scopes are discussed to advance the integration of novel technologies such as artificial intelligence, the internet of medical things, and triboelectric nanogenerators to eventually increase efficacy and efficiency. [Display omitted] • The physiochemical properties and roles of graphene nanostructures in fabricating electrochemical biosensors were discussed. • Strategies to improve sensitivity by immobilizing receptors onto the graphene nanostructures were critically reviewed. • Challenges and future directions of the graphene-based biosensing in the diagnostics and PoC devices were discussed. [ABSTRACT FROM AUTHOR]

The removal of selenium from superficial and waste water is a worldwide problem. The maximum limit according to the World Health Organization (WHO) for the selenium in the water is set at a concentration of 10 μg/L. Carbon based adsorbents have attracted much attention and recently demonstrated promising performance in removal of selenium. In this work, several materials (iron oxide based microparticles and graphene oxides materials) and their composites were prepared to remove Se(IV) from water. The graphene oxides were prepared according to the simplified Hummer's method. In addition, the effect of pH, contact time and initial Se(IV) concentration was tested. An electrochemical method such as the differential pulse cathodic stripping voltammetry was used to determine the residual selenium concentration. From the experimental data, Langmuir adsorption model was used to calculate the maximum adsorption capacity. Graphene oxide particles modified by iron oxide based microparticles was the most promising material for the removal of Se(IV) from its aqueous solution at pH 2.0. Its adsorption efficiency reached more than 90% for a solution with given Se(IV) concentration, meanwhile its maximal recorded adsorption capacity was 18.69 mg/g. [ABSTRACT FROM AUTHOR]

Graphical abstract showing the nanozyme-enzyme cascade complex system. [Display omitted] • Biomimetic rGO-CeO 2 NC possesses enzyme-mimetic property towards H 2 O 2. • rGO-CeO 2 NC forms a cascade system as NZ-natural enzyme with model enzyme GO x. • CeO 2 NPs was accredited with peroxidase-mimicking and electron acceptor properties. Nanomaterials with enzyme-like activity (nanozymes) are known to be suitable alternatives for natural enzymes tolerating unfavorable pH and temperature conditions. The enzyme-like activity of CeO 2 nanoparticles was already reported and used in electrochemical sensing, where the peroxidase or oxidase-like activities of CeO 2 NPs are mainly used. This work aims to justify the role/s that CeO 2 may play in electrochemical sensing as a nanozyme and acts as a mediator. To this end, a reduced graphene oxide-CeO 2 was prepared and used in two electrochemical sensing configurations. In first configuration, H 2 O 2 reduction was catalyzed at the glassy carbon electrode modified with the rGO-CeO 2 nanocomposite (rGO-CeO 2 NC). The reduction current obtained upon the presence of H 2 O 2 was attributed to a mediator role having a linear range of 100.0–800.0 µmol L−1 with a limit of detection (LOD) and limit of quantification (LOQ) of 15.9 µmol L−1 and 52.9 µmol L−1, respectively. In another configuration, glucose oxidase was used as a model enzyme with the rGO-CeO 2 NC. The oxidation signal obtained upon adding glucose was attributed to the electron-accepting role of the CeO 2 NPs. The analytical figures of merit obtained for both configurations indicated their high sensitivity, selectivity, and reproducibility. The linear detection range for the nanozyme-enzyme cascade system was 100.0–800.0 µmol L−1 with a LOD and LOQ of 18.7 µmol L−1 and 62.3 µmol L−1, respectively. Moreover, the flow injection analysis was enabled due to the short response time in analysis with the prepared sensor. The possibility for applying the developed nanozyme in nanozyme-enzyme cascade system in clinical and food analysis for determination of glucose was verified by studying the interference of various compounds similar to glucose in structure and typical drugs taken by diabetic patients. [ABSTRACT FROM AUTHOR]

Binary-blend films of furcellaran and gelatin (FUR/GEL) and FUR/GEL composite films reinforced with selenium nanoparticles (SeNPs) or silver nanoparticles (AgNPs) were prepared using a solution casting method. The effects of SeNPs and AgNPs on the physical, mechanical, structural, antibacterial properties of the furcellaran/gelatin-based films were examined. It follows from these examinations that the incorporation of SeNPs and AgNPs leads to an increase in thickness, water content, modulus of elasticity, elongation at break, and antimicrobial activity when higher parameters a*, b*, and ΔE are observed in nanocomposite films with AgNPs compared to those enriched with SeNPs. Compared with control film, the addition of nanoparticles significantly decreased solubility and swelling degree. Films containing SeNPs show greater antimicrobial activity against Escherichia coli , Staphylococcus aureus and multi resistant Staphylococcus aureus than films containing AgNPs. [ABSTRACT FROM AUTHOR]

Background: Development of new nanomaterials that inhibit or kill bacteria is an important and timely research topic. For example, financial losses due to infectious diseases, such as diarrhea, are a major concern in livestock productions around the world. Antimicrobial nanoparticles (NPs) represent a promising alternative to antibiotics and may lower antibiotic use and consequently spread of antibiotic resistance traits among bacteria, including pathogens. Results: Four formulations of zinc nanoparticles (ZnA, ZnB, ZnC, and ZnD) based on phosphates with spherical (ZnA, ZnB) or irregular (ZnC, ZnD) morphology were prepared. The highest in vitro inhibitory effect of our NPs was observed against Staphylococcus aureus (inhibitory concentration values, IC50, ranged from 0.5 to 1.6 mmol/L), followed by Escherichia coli (IC50 0.8–1.5 mmol/L). In contrast, methicillin resistant S. aureus (IC50 1.2–4.7 mmol/L) was least affected and this was similar to inhibitory patterns of commercial ZnO-based NPs and ZnO. After the successful in vitro testing, the in vivo study with rats based on dietary supplementation with zinc NPs was conducted. Four groups of rats were treated by 2,000 mg Zn/kg diet of ZnA, ZnB, ZnC, and ZnD, for comparison two groups were supplemented by 2,000 mg Zn/kg diet of ZnO-N and ZnO, and one group (control) was fed only by basal diet. The significantly higher (P < 0.05) Zn level in liver and kidney of all treated groups was found, nevertheless Zn NPs did not greatly influence antioxidant status of rats. However, the total aerobic and coliform bacterial population in rat feces significantly decreased (P < 0.05) in all zinc groups after 30 d of the treatment. Furthermore, when compared to the ZnO group, ZnA and ZnC nanoparticles reduced coliforms significantly more (P < 0.05). Conclusions: Our results demonstrate that phosphate-based zinc nanoparticles have the potential to act as antibiotic agents. [ABSTRACT FROM AUTHOR]