Biomimetic Nanozymes Based on Coassembly of Amino Acid and Hemin for Catalytic Oxidation and Sensing of Biomolecules

What are the inorganic nanozymes? Artificial or inorganic enzymes!

The research on inorganic nanozymes remains very active since the first paper on the “intrinsic peroxidase-like properties of ferromagnetic nanoparticles” was published in Nature Nanotechnology in 2007. However, there is...

Oxygen-Powered Flower-like FeMo6@CeO2 Self-cascade Nanozyme: Turn-on Enhancement Fluorescence Sensor

Enzyme cascade reactions in organisms have sparked tremendous interest for their coupled catalysis-facilitated efficient biochemical reactions. However, multi-enzyme cascade nanozymes remain largely unpracticed. In the work, flower-like porous ceria-based integrated...

In Situ-Grown Heterostructured Co3S4/CNTs/C Nanocomposites with a Bridged Structure for High-Performance Supercapacitors

As one of the most competitive candidates for energy storage devices, supercapacitors have attracted extensive research interest due to their incomparable power density and ultralong cycling stability. However, the large surface area required for charge storage is an irreconcilable contradiction with the requirement of energy density. Therefore, a high energy density is a major challenge for supercapacitors. To solve the contradiction, Co₃S₄/CNTs/C with a bridged structure is designed, where CNTs generated in situ serve as a bridge to connect a porous carbon matrix and a Co₃S₄ nanoparticle, and Co₃S₄ nanoparticles are anchored on the topmost of CNTs. The porous carbon and Co₃S₄ are used for electrochemical double-layer capacitors and pseudocapacitors, respectively. This bridged structure can efficiently utilize the surface of Co₃S₄ nanoparticles to increase the overall energy storage capacity and provide more electrochemically active sites for charge storage and delivery. The materials show an energy density of 41.3 Wh kg^-1 at 691.9 W kg^-1 power density and a retaining energy density of 33.1 Wh kg^-1 at a high power density of 3199.9 W kg^-1 in an asymmetrical supercapacitor. The synthetic technique provides a simple method to obtain heterostructured nanocomposites with a high energy density by maximizing the effect of pseudocapacitor electrode active materials.

Simple and Green Synthesis of Carbonized Polymer dots from Nylon 66 Waste Fibers and its Potential Application

Carbonized polymer dots (CPDs) have attracted widespread attention owing to their unique properties and are usually prepared from monomers of polymers or polymers. To reduce the waste of high-value petropolymers and environmental pollution, a simple and green method for the preparation of CPDs using a hydrothermal technique based on the cross-linking enhanced emission effect was proposed, in which nylon 66 waste fibers were used as a precursor and glutaraldehyde as a cross-linking agent. The as-prepared CPDs possessed polymer/carbon hybrid structures with a 3.5 nm average diameter, and hydroxyl (-OH), carboxyl (-COOH), and amino (-NH₂) groups were present on the surface of CPDs. It can be found that the as-prepared CPDs display excitation-dependent photoluminescence emission, which is mainly attributed to the molecular state luminescence center. Because the molecular state fluorescence of CPDs could be affected by the presence of Fe³⁺ and the change of pH values, the as-prepared CPDs can be used as a probe for the detection of the concentration of Fe³⁺ and the pH variations of solution. The fluorescence intensity of CPDs was selectively quenched by Fe³⁺ in the range from 1 to 145 μM. In virtue of the static quenching of CPDs by Fe³⁺, a sensing system was fabricated for the quantitative detection of Fe³⁺, and its limit of detection was 0.1 μM. Based on the electrostatic doping/charging of CPDs, a pH sensor was fabricated. It showed that the fluorescence intensity of CPDs decreased along with the increase of pH from 2.60 to 12.6. What is more, the CPDs were found to be an alternative to traditional fluorescent inks for encryption and information storage.

Modified cellulose nanofibril aerogel: Tunable catalyst support for treatment of 4-Nitrophenol from wastewater

4-Nitrophenol (4-NP) is a hazardous aromatic compound widely used for various industries. Catalytic reduction of 4-NP using metal nanoparticles (NPs) is a highly effective method to treat 4-NP from waste effluent. Even though lots of methods have investigated to prepare efficient metal NPs composites, the nano and/or micro size of composites makes it hard to recover after wastewater treatment, limiting its practical use. Here, we fabricate 3-dimensional polyethylene imine grafted cellulose nanofibril (CNF-PEI) aerogel as a porous support material for platinum (Pt) NPs to practically and effectively treat 4-NP from wastewater. The Pt NPs are formed in-situ mode on cylindrical CNF-PEI aerogel by adsorption reaction with amine groups of PEI and subsequently reduction with NaBH₄. Control of PEI grafting density and the initial concentration of Pt ions allows manipulation of the loading mass, size, and distribution of Pt NPs on 3D scaffold of CNF-PEI aerogel. The composite aerogel shows high catalytic activity for conversion of 4-NP. The 4-NP conversion activity is strongly affected by the size of Pt NPs and effective surface area of aerogels. The 2.74 nm size Pt NPs with even distribution in the aerogel show fast reaction kinetics (k = 0.12 min^-1). Finally, 4-NP reduction efficiency does not decrease during 5 times reuse cycle of Pt NPs loaded CNF-PEI aerogel. This CNF-PEI aerogel loaded with Pt NPs is recovered easily from wastewater after treatment, so it is reusable and offers high potential as a practical recyclable environmental catalyst.

A new biomimetic nanozyme of hemin/graphdiyne oxide with superior peroxidase-like activity for colorimetric bioassays

Graphdiyne oxide (GDYO) is a novel type of two-dimensional carbon allotrope nanomaterial consisting of a large conjugated system and excellent chemical stability. To date, application of GDYO as a nanozyme in biosensing has been rarely reported. In this study, a novel ultrasensitive colorimetric bioassay was constructed using a hemin/GDYO nanocomposite (H/GDYO) as a new nanozyme with superior peroxidase-like activity for the detection of H₂O₂ and glucose. It was discovered that H/GDYO exhibited 6-fold higher peroxidase-like activity than pure hemin. Catalytic kinetic analysis showed that H/GDYO had a much higher affinity for H₂O₂ and glucose than that of hemin. The designed colorimetric bioassay displayed excellent sensitivity for H₂O₂ and glucose detection with a wide linear range of 0.015-0.5 mM and 0.1-10 mM, respectively, while the limit of detection (LOD) was as low as 4.39 μM and 38 μM, respectively. Moreover, it was successfully applied for the analysis of H₂O₂ in milk and glucose in real human serum samples with acceptable recoveries. Importantly, the developed colorimetric bioassay shows good agreement with the results obtained from a commercial blood glucose meter. We believe that the proposed method could provide a promising prospect for medical diagnosis and biotechnology.

Morphology-Dependent Peroxidase Mimicking Enzyme Activity of Copper Metal-Organic Polyhedra Assemblies

The morphology of nanomaterials (geometric shape and dimension) play a significant role in its various physical and chemical properties. Thus, it is essential to link morphology with performance in specific applications. For this purpose, the morphology of copper metal-organic polyhedra (Cu-MOP) can be modulated through distinct assembly process, which facilitates the exploration of the relationship between morphology and catalytic performance. In this work, the assemblies of Cu-MOP with three different morphologies (nanorods, nanofibers and nanosheets) were facilely prepared by the variation of solvent mixture of N, N-dimethylformamide (DMF) and methanol, revealed the important role of the interaction between the surface group and the solvent on the morphology of these assemblies. Cu-MOP nanofibers exhibited the highest mimetic peroxidase enzyme activity over the Cu-MOP nanosheets and nanorods, which have been utilized in the detection of glucose. Cu-MOPs assemblies with tunable morphology accompanied with adjustable mimic peroxidase activity, had great potential applications in the field of bioanalytical chemistry and biomedicals.

Self-Assembly Dual-Responsive NO Donor Nanoparticles for Effective Cancer Therapy

Drug resistance and the serious side effects caused by classical chemotherapy drugs necessitate the development of novel targeted drug delivery systems. The high lipophilicity and short half-life of nitric oxide (NO), a gas with strong antitumor activity, make it difficult to reach the tumor site and result in a poor therapeutic effect in vivo. In order to overcome the deficiencies of the existing NO donors and NO delivery vehicles, a novel strategy was proposed to deliver NO for cancer chemotherapy by the prodrug dimer self-assembly nanoparticles of NO donors. Specifically, phenylsulfonylfuroxan (FZ) was chosen as the NO donor to synthesize the prodrug dimer precursor (FZ-SS-FZ) by disulfide linkages and ester bonds. The insertion of disulfide linkages promotes the self-assembly of FZ-SS-FZ in water. After this, the dual-responsive and tumor-targeting NO delivery system (FZ-SS-FZ@FA NPs) will finally be fabricated by further introducing folic acid on the surface of nanoparticles. FZ-SS-FZ can self-assemble to form uniform nanoparticles in water, which can effectively deliver NO to the tumor site and be uptaken by tumor cells, thus resulting in specific NO release in tumor cells and inducing tumor cell apoptosis. FZ-SS-FZ@FA NPs significantly improve the drug loading and delivery efficiencies of NO for chemotherapy, while enhancing its efficacy, providing a novel strategy for the tumor-targeted delivery of NO and at the same time laying a theoretical basis for the clinical translation of NO-based gas chemotherapy, opening up a new approach for cancer chemotherapy.

Facile Preparation of a Rhodamine B Derivative-Based Fluorescent Probe for Visual Detection of Iron Ions

Iron ions play an important role in our lives. Excessive or lack of iron ion intake leads to many diseases. At the same time, the water environment is easily polluted by these metal ions with the acceleration of industrialization. Therefore, the detection of iron ions in the water environment and the human body is particularly important. In this paper, we prepared a RhB-EDA fluorescent probe by condensing rhodamine B (RhB) with ethylenediamine (EDA) for high recognition of Fe3+. A RhB-EDA molecule itself is colorless and has no fluorescence emission in an alcohol solution. When Fe3+ was added, the lactam ring structure of the fluorescent probe opened, and the UV and fluorescence spectra changed. At the same time, the color of the mixed solution gradually deepened toward pink. Therefore, dual spectral detection and naked-eye observation of Fe3+ were realized. In addition, with the decrease of the pH value and the prolongation of chelating time, the ultraviolet absorbance and fluorescence emission intensity were enhanced and the color of the mixed solution deepened. The RhD-EDA fluorescent probe is simple and accurate and provides good technical support for the detection of Fe3+.

Lanthanide upconversion and downshifting luminescence for biomolecules detection

Biomolecules play critical roles in biological activities and are closely related to various disease conditions. The reliable, selective and sensitive detection of biomolecules holds much promise for specific and rapid biosensing. In recent years, luminescent lanthanide probes have been widely used for monitoring the activity of biomolecules owing to their long luminescence lifetimes and line-like emission which allow time-resolved and ratiometric analyses. In this review article, we concentrate on recent advances in the detection of biomolecule activities based on lanthanide luminescent systems, including upconversion luminescent nanoparticles, lanthanide-metal organic frameworks, and lanthanide organic complexes. We also introduce the latest remarkable accomplishments of lanthanide probes in the design principles and sensing mechanisms, as well as the forthcoming challenges and perspectives for practical achievements.

Nanozymes-Hitting the Biosensing "Target"

Nanozymes are a class of artificial enzymes that have dimensions in the nanometer range and can be composed of simple metal and metal oxide nanoparticles, metal nanoclusters, dots (both quantum and carbon), nanotubes, nanowires, or multiple metal-organic frameworks (MOFs). They exhibit excellent catalytic activities with low cost, high operational robustness, and a stable shelf-life. More importantly, they are amenable to modifications that can change their surface structures and increase the range of their applications. There are three main classes of nanozymes including the peroxidase-like, the oxidase-like, and the antioxidant nanozymes. Each of these classes catalyzes a specific group of reactions. With the development of nanoscience and nanotechnology, the variety of applications for nanozymes in diverse fields has expanded dramatically, with the most popular applications in biosensing. Nanozyme-based novel biosensors have been designed to detect ions, small molecules, nucleic acids, proteins, and cancer cells. The current review focuses on the catalytic mechanism of nanozymes, their application in biosensing, and the identification of future directions for the field.

Chitosan based macromolecular probes for the selective detection and removal of Fe3+ ion

Chitosan has been widely used due to its biodegradable, cost-effective and environmentally friendly properties. Modification of chitosan attracts much attention as promising methods to detect and remove organic and inorganic pollutants. In this work, chitosan-based macromolecular probes were designed and synthesized. The probes can detect Fe³⁺ in the presence of other metal ions. The detection mechanism is investigated as well. The probe's fluorescence quenching upon the addition of Fe³⁺ ion could be ascribed to the complexation between the electron-deficient ion Fe³⁺ and "C=N" (electron-rich group) of fluorescent chitosan probes. What's more, the obtained fluorescent macromolecular probes can be used for the removal of Fe³⁺ in solution. The probes could adsorb the Fe³⁺ in solution and the removal efficiency can reach as high as 62.0% while the removal efficiency of original chitosan is only 16.0%. The probes have good selective detection for Fe³⁺ and the detection limit reaches 1.2 μM.