Rosette-shaped graphitic carbon nitride acts as a peroxidase mimic in a wide pH range for fluorescence-based determination of glucose with glucose oxidase

Signal-off colorimetric and signal-on fluorometric dual-mode aptasensor for ultrasensitive detection of Salmonella Typhimurium using graphitic carbon nitride

Food safety is severely burdened by the prevalence of foodborne pathogens and the diseases they cause, necessitating the development of rapid, easy-to-use, highly sensitive, and reliable detection methods. Here, a signal-off colorimetric and signal-on fluorometric dual-mode detection method for Salmonella Typhimurium (S. typhimurium) was developed based on its unique interaction with aptamer DNA and graphitic carbon nitride (GCN). In the absence of a target Salmonella species, 6-carboxyfluorescein (FAM)-labeled aptamers are adsorbed on the surface of GCN primarily via a π-π interaction, resulting in reduced fluorescence of FAM through GCN-mediated quenching as well as improved peroxidase-like activity of GCN to generate intense blue color through facilitated electrostatic attraction between the negatively charged aptamer and positively charged 3,3',5,5'-tetramethylbenzidine (TMB) substrate. The introduction of S. typhimurium to the sample solution causes the detachment of the aptamer from GCN due to its higher affinity for S. typhimurium than GCN, thereby rapidly reducing the colorimetric signal and recovering the fluorescence. We successfully determined the number of S. typhimurium using this method in a remarkably short duration (10-30 min), highlighting its rapidity. The limit of detection values for S. typhimurium were as low as 8 and 3 CFU/mL when using colorimetric and fluorometric methods, respectively. Moreover, this method can be used to detect S. typhimurium spiked in real vegetable extract and milk with high reproducibility and reliability. This method serves as a convenient route to the rapid, sensitive, selective, and reliable detection of pathogens from complex food samples, with the potential to replace conventional yet laborious methods currently in use.

Tailoring osteoimmunity and hemostasis using 3D-Printed nano-photocatalytic bactericidal scaffold for augmented bone regeneration

Bone hemorrhage, infection, and large bone defects following surgical treatment of traumatic bone injury have raised potential concerns, underscoring the urgent need to develop multifunctional therapeutic platforms that can effectively address traumatic bone regeneration. Advancements in three-dimensional (3D) printing technology have propelled the development of several engineering disciplines, such as tissue engineering. Nevertheless, 3D-printed frameworks with conventional materials often lack multifunctional capabilities to promote specific activities for diverse regeneration purposes. In this study, we developed a highly oxidized two-dimensional (2D) graphitic carbon nitride (Ox-gCN) as a nano-photocatalyst to reinforce alginate/gelatin (ALG)-based hydrogel scaffolds (ALG/CN) to achieve an anti-inflammatory and osteo-immunomodulatory niche with superior hemostatic ability for traumatic bone injury repair. Sulfuric acid oxidation enhances the oxygen-containing functional groups of the g-CN surface and promotes cell adhesion and differentiation of human bone marrow-derived mesenchymal stem cells (hBMSCs) in vitro. Moreover, the excellent visible light-activated photocatalytic characteristics of the ALG/CN scaffold were used in antibacterial studies. In addition, the ALG/CN bio/nanocomposite scaffold facilitates M2 polarization of macrophages than did pristine ALG scaffolds. Furthermore, ALG/CN scaffold induced hBMSCs differentiation by upregulating ERK and MAPKs phosphorylation during osteo-immunomodulation. In a rat calvaria defect model, the fabricated ALG/CN scaffolds induced new bone formation through collagen deposition and activation of osteocalcin proteins without inflammation in vivo. These results highlight the potential of 3D-printed functionalized 2D carbon nitrides in regulating the bone immune microenvironment, which may be beneficial for developing advanced tissue constructs, especially for traumatic bone regeneration in clinical settings.

Carbon-based nanozymes: design, catalytic mechanisms, and environmental applications

Carbon-based nanozymes are synthetic nanomaterials that are predominantly constituted of carbon-based materials, which mimic the catalytic properties of natural enzymes, boasting features such as tunable catalytic activity, robust regenerative capacity, and exceptional stability. Due to the impressive enzymatic performance similar to various enzymes such as peroxidase, superoxide dismutase, and oxidase, they are widely used for detecting and degrading pollutants in the environment. This paper presents an exhaustive review of the fundamental design principles, catalytic mechanisms, and prospective applications of carbon-based nanozymes in the environmental field. These studies not only serve to augment the comprehension on the intricate operational mechanism inherent in these synthetic nanostructures, but also provide essential guidelines and illuminating perspectives for advancing their development and practical applications. Future studies that are imperative to delve into the untapped potential of carbon-based nanozymes within the environmental domain was needed to be explored to fully harness their ability to deliver broader and more impactful environmental preservation and management outcomes.

Transition metal-doped germanium oxide nanozyme with enhanced enzyme-like activity for rapid detection of pesticide residues in water samples

Designing highly active nanozymes for bioanalysis and environmental sensing remains a challenge. In this study, transition metal, palladium (Pd) and iron (Fe), doped germanium oxide (GeO₂) nanozyme was designed and optimized. Compared with the pristine GeO₂ nanozyme, the transition metal doped GeO₂ nanozyme have lower Michaelis-Menten constants and higher catalytic activity, indicating that the Pd and Fe doped GeO₂ nanozyme not only enhance their affinity for the substrate but also improve its catalytic activity. In addition, a colorimetric sensor based on the GeO₂@Pd-H₂O₂-TMB system was constructed for the visual detection of simazine in water samples due to the good affinity between TMB and simazine. This sensor has good selectivity and sensitivity with a detection limit of 6.21 μM because of the highest catalytic performance of GeO₂@Pd nanozyme. This study broadens the application of nanozymes in environmental field and other nanozymes can also be enhanced in activity by simple transition metal doping.

Nanozyme's catalytic activity at neutral pH: reaction substrates and application in sensing

Nanozymes exhibit their great potential as alternatives to natural enzymes. In addition to catalytic activity, nanozymes also need to have biologically relevant catalytic reactions at physiological pH to fit in the definition of an enzyme and to achieve efficient analytical applications. Previous reviews in the nanozyme field mainly focused on the catalytic mechanisms, activity regulation, and types of catalytic reactions. In this paper, we discuss efforts made on the substrate-dependent catalytic activity of nanozymes at neutral pH. First, the discrepant catalytic activities for different substrates are compared, where the key differences are the characteristics of substrates and the adsorption of substrates by nanozymes at different pH. We then reviewed efforts to enhance reaction activity for model chromogenic substrates and strategies to engineer nanomaterials to accelerate reaction rates for other substrates at physiological pH. Finally, we also discussed methods to achieve efficient sensing applications at neutral pH using nanozymes. We believe that the nanozyme is catching up with enzymes rapidly in terms of reaction rates and reaction conditions. Designing nanozymes with specific catalysis for efficient sensing remains a challenge.

Role of Leptin with hypothyroidism in Iraqi diabetic type 2 patients

In thyroid subjects, leptin hormone and thyroid-stimulating hormone levels connect; both are emphatically corresponding with adiposity. “Leptin hormone was essentially raised in the hypothyroid topic,” to levels like those seen in corpulent thyroid topic. This study aimed to determine leptin hormone levels, T3, T4, TSH, HbA1c %, FBG, lipid profile in diabetic and diabetic with hypothyroidism patients and compare the outcome with the healthy group. 90 samples were registered in this study with their ages ranging between (40 - 65) years that dole out into 3 groups as follows: thirty healthy groups (G1), thirty patients with diabetes (G2), and category three (G3) include diabetic patients and hypothyroidism as an associated disease. This study revealed a slightly significant elevated leptin in G3, contrasting to G2 and G1. Meantime no significant elevated spotted between G2 and G1. The conclusion could be from this investigation that leptin levels were changed in patients’ gatherings that might be utilized in checking and early analysis of thyroid dysfunction in these patients relying upon the significant connection for leptin chemical with T3, T4, and TSH.

Colorimetric determination of phenolic compounds using peroxidase mimics based on biomolecule-free hybrid nanoflowers consisting of graphitic carbon nitride and copper

Hybrid nanoflowers consisting of graphitic carbon nitride (GCN) and copper were successfully constructed without the involvement of any biomolecule, by simply mixing them at room temperature to induce proper self-assembly to achieve a flower-like morphology. The resulting biomolecule-free GCN-copper hybrid nanoflowers (GCN-Cu NFs) exhibited an apparent peroxidase-mimicking activity, possibly owing to the synergistic effect from the coordination of GCN and copper, as well as their large surface area, which increased the number of catalytic reaction sites. The peroxidase-mimicking GCN-Cu NFs were then employed in the colorimetric determination of selected phenolic compounds hydroquinone (HQ), methylhydroquinone (MHQ), and catechol (CC). For samples without phenolic compounds, GCN-Cu NFs catalyzed the oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H₂O₂, producing an intense blue color signal. Conversely, in the presence of phenolic compounds, the oxidation of TMB was inhibited, resulting in a significant reduction of the color signal. Using this strategy, HQ, MHQ, and CC were selectively and sensitively determined in a linear range up to 100 μM with detection limits down to 0.82, 0.27, and 0.36 μM, respectively. The practical utility of this assay system was also validated by using it to detect phenolic compounds spiked in tap water, yielding a good recovery of 97.1-108.9% and coefficient of variation below 3.0%, demonstrating the excellent reliability and reproducibility of this strategy. Colorimetric determination of phenolic compounds using peroxidase mimics based on biomolecule-free hybrid nanoflowers consisting of graphitic carbon nitride and copper.

Biomimetic two-dimensional nanozymes: synthesis, hybridization, functional tailoring, and biosensor applications

Biological enzymes play important roles in mediating the biological reactions in vitro and in vivo due to their high catalytic activity, strong bioactivity, and high specificity; however, they have also some disadvantages such as high cost, low environmental stability, weak reusability, and difficult production. To overcome these shortcomings, functional nanomaterials including metallic nanoparticles, single atoms, metal oxides, alloys, and others have been utilized as nanozymes to mimic the properties and functions of natural enzymes. Due to the development of the synthesis and applications of two-dimensional (2D) materials, 2D nanomaterials have shown high potential to be used as novel nanozymes in biosensing, bioimaging, therapy, logic gates, and environmental remediation due to their unique physical, chemical, biological, and electronic properties. In this work, we summarize recent advances in the preparation and functionalization, as well as biosensor and immunoassay applications of various 2D material-based nanozymes. To achieve this aim, first we demonstrate the preparation strategies of 2D nanozymes such as chemical reduction, templated synthesis, chemical exfoliation, calcination, electrochemical deposition, hydrothermal synthesis, and many others. Meanwhile, the structure and properties of the 2D nanozymes prepared by conjugating 2D materials with nanoparticles, metal oxides, biomolecules, polymers, ions, and 2D heteromaterials are introduced and discussed in detail. Then, the applications of the prepared 2D nanozymes in colorimetric, electrochemical, fluorescent, and electrochemiluminescent sensors are demonstrated.

Limitation-induced fluorescence enhancement of carbon nanoparticles and their application for glucose detection

Rational design of detection strategy is the key to high-performance fluorescence analysis. In this article, we found that the glucose-induced limitations can greatly enhance the fluorescence of functionalized carbon nanoparticles (CNPs), which are synthesized through one-step thermal pyrolysis method using phenylboronic acid derivative as the precursors. The glucose can assembly onto the surface of the CNPs to form a "shell", limiting the surfaces' intramolecular rotation and reducing non-radiative decay, which hence resulted in enhanced fluorescence of the CNPs. Under optimal conditions, the fluorescence intensity of the CNPs is nearly 70-fold enhanced, and the method has low detection limit (10 μM) and linear response in the concentration range from 50 μM to 2000 μM. Based on this interesting "target-triggered limitation-induced fluorescence enhancement" phenomenon, a simple and effective non-enzymatic fluorescence enhancement method was developed and successfully applied to the determination of glucose in spiked serum samples. This work provides new insight into the design of fluorescence-enhanced detection strategies based on the limitation-induced property.

Two-Dimensional Nanomaterials With Enzyme-Like Properties for Biomedical Applications

Recently, remarkable progress has been made in nanozyme research due to the rapid development of nanomaterials. Two-dimensional nanomaterials such as metal nanosheets, graphene-based materials, transition metal oxides/dichalcogenides, etc., provide enhanced physical and chemical functionality owing to their ultrathin structures, high surface-to-volume ratios, and surface charges. They have also been found to have high catalytic activities in terms of natural enzymes such as peroxidase, oxidase, catalase, and superoxide dismutase. This review provides an overview of the recent progress of nanozymes based on two-dimensional nanomaterials, with an emphasis on their synthetic strategies, hybridization, catalytic properties, and biomedical applications. Finally, the future challenges and prospects for this research are discussed.

Electrochemical Sensors Based on Carbon Nanomaterial Used in Diagnosing Metabolic Disease

Metabolic diseases have become common diseases with the improvement of living standards because of changed dietary habits and living habits, which seriously affect health. Currently, related biomarkers have been widely used as important indicators for clinical diagnosis, treatment, and prognosis of metabolic diseases. Among all detection methods for biomarkers of metabolic diseases, electrochemical sensor technology has the advantages of simplicity, real-time analysis, and low cost. Carbon nanomaterials were preeminent materials for fabricating electrochemical sensors in order to enhance the performance. In this paper, we summarize the research progress in the past 3 years of electrochemical sensors based on carbon nanomaterials in detecting markers of metabolic diseases, which include carbon nanotubes, graphene, carbon quantum dots, fullerene, and carbon nitride. Additionally, we discuss the future prospects for this field.

A facile route for constructing Cu–N–C peroxidase mimics

Cu–N–C single-atom nanozymes were successfully designedviaa one-pot solvothermal method and their excellent peroxidase-mimicking activity has been investigated and applied for H₂O₂and glucose determination.