A Magnetic Biomimetic Nanocatalyst for Cleaving Phosphoester and Carboxylic Ester Bonds under Mild Conditions

Proving Cooperativity of a Catalytic Reaction by Means of Nanoscale Geometry: The Case of Click Reaction

Establishing whether a reaction is catalyzed by a single-metal catalytic center or cooperatively by a fleeting complex encompassing two such centers may be an arduous pursuit requiring detailed kinetic, isotopic, and other types of studies─as illustrated, for instance, by over a decade-long work on single-copper versus di-copper mechanisms of the popular "click" reaction. This paper describes a method to interrogate such cooperative mechanisms by a nanoparticle-based platform in which the probabilities of catalytic units being proximal can be varied systematically and, more importantly, independently of their volume concentration. The method relies on geometrical considerations rather than a detailed knowledge of kinetic equations, yet the scaling trends it yield can distinguish between cooperative and non-cooperative mechanisms.

Nanobody and Nanozyme-Enabled Immunoassays with Enhanced Specificity and Sensitivity

Immunoassay as a rapid and convenient method for detecting a variety of targets has attracted tremendous interest with its high specificity and sensitivity. Among the commonly used immunoassays, enzyme-linked immunosorbent assay has been widely used as a gold standard method in various fields that consists of two main components including a recognition element and an enzyme label. With the rapid advances in nanotechnology, nanobodies and nanozymes enable immunoassays with enhanced specificity and sensitivity compared with conventional antibodies and natural enzymes. This review is focused on the applications of nanobodies and nanozymes in immunoassays. Nanobodies advantage lies in their small size, high specificity, mass expression, and high stability. Nanozymes with peroxidase, phosphatase, and oxidase activities and their applications in immunoassays are highlighted and discussed in detail. In addition, the challenges and outlooks in terms of the use of nanobodies and the development of novel nanozymes in practical applications are discussed.

Poly-histidine grafting leading to fishbone-like architectures

A small series of Morita–Baylis–Hillman derivatives was synthesized and made to react with N-acetylhexahistidine to give polymeric materials characterized by the presence of biadduct residues.

Detoxification of organophosphates using imidazole-coated Ag, Au and AgAu nanoparticles

Organophosphate (OP) detoxification is a worldwide problem due to the high stability of P–O bonds.

Role of solvent in the phosphatase activity of a dinuclear nickel(ii) complex of a Schiff base ligand: mechanistic interpretation by DFT studies

A biomimetic metallohydrolase has been synthesized and its catalytic mechanism and the related solvent effect were elucidated using theoretical modeling.

Palladium nanoparticles supported on agarose-functionalized magnetic nanoparticles of Fe3O4 as a recyclable catalyst for C–C bond formation via Suzuki–Miyaura, Heck–Mizoroki and Sonogashira–Hagihara coupling reactions

Palladium nanoparticles supported on agarose functionalized Fe₃O₄ catalyzed C–C bond formation reactions.

An approach for catalyst design in artificial photosynthetic systems: focus on nanosized inorganic cores within proteins

Some enzymes can be considered as a catalyst having a nanosized inorganic core in a protein matrix. In some cases, the metal oxide or sulfide clusters, which can be considered as cofactors in enzymes, may be recruited for use in other related reactions in artificial photosynthetic systems. In other words, one approach to design efficient and environmentally friendly catalysts in artificial photosynthetic systems for the purpose of utilizing sunlight to generate high energy intermediates or useful material is to select and utilize inorganic cores of enzymes. For example, one of the most important goals in developing artificial photosynthesis is hydrogen production. However, first, it is necessary to find a "super catalyst" for water oxidation, which is the most challenging half reaction of water splitting. There is an efficient system for water oxidation in cyanobacteria, algae, and plants. Published data on the Mn-Ca cluster have provided details on the mechanism and structure of the water oxidizing complex as a Mn-Ca nanosized inorganic core in photosystem II. Progress has been made in introducing Mn-Ca oxides as efficient catalysts for water oxidation in artificial photosynthetic systems. Here, in the interest of designing efficient catalysts for other important reactions in artificial photosynthesis, a few examples of our knowledge of inorganic cores of proteins, and how Nature used them for important reactions, are discussed.

Ultrasensitivity by molecular titration in spatially propagating enzymatic reactions

Delineating design principles of biological systems by reconstitution of purified components offers a platform to gauge the influence of critical physicochemical parameters on minimal biological systems of reduced complexity. Here we unravel the effect of strong reversible inhibitors on the spatiotemporal propagation of enzymatic reactions in a confined environment in vitro. We use micropatterned, enzyme-laden agarose gels which are stamped on polyacrylamide films containing immobilized substrates and reversible inhibitors. Quantitative fluorescence imaging combined with detailed numerical simulations of the reaction-diffusion process reveal that a shallow gradient of enzyme is converted into a steep product gradient by addition of strong inhibitors, consistent with a mathematical model of molecular titration. The results confirm that ultrasensitive and threshold effects at the molecular level can convert a graded input signal to a steep spatial response at macroscopic length scales.

Preparation and characterization of novel magnetic nanocomposite-bonded metalloporphyrins as biomimetic nanocatalysts

In this work, novel magnetic nanocomposite-bonded metalloporphyrins were synthesized by an effective silanation approach between 3-aminopropyltriethoxysilane derivatized metalloporphyrins and silica-coated magnetic Fe3O4 nanoparticles. The initial metalloporphyrin derivatives were synthesized by the amidation reaction of metalloporphyrin acyl chloride with 3-aminopropyltriethoxysilane. After the metalloporphyrin derivatives were adsorbed on the surface of silica-coated magnetic Fe3O4 nanoparticles, the solid mixture was heated under vacuum at 110 °C for 3 h and then thoroughly washed with chloroform. The obtained magnetic nanocomposite-bonded metalloporphyrins were characterized by elemental analyzer, low-temperature N2 adsorption (BET method), transmission electron microscopy, UV-vis spectroscopy, and infrared spectroscopy. Interestingly, using this particular silanation method, metalloporphyrins could be quantitative-immobilized in magnetic nanocomposites by controlling the input ratio of metalloporphyrins and silica-coated magnetic Fe3O4 nanoparticles. The excellent catalytic activity and recyclability of the magnetic nanocomposite-bonded metalloporphyrins were demonstrated in the cyclohexane oxidation with iodosylbenzene.

Experimental design of application of nanoscale iron-nickel under sonication and static magnetic field for mixed waste remediation

In this paper, the degradation of simulated mixed organics commonly found in nuclear waste streams was studied under a combined influence of sonication and magnetic field. Nanoscale bimetallic iron-nickel was used as source of Fenton reaction. The data were fitted to obey second order kinetics. The extent of degradation followed the trend: TBP-EDTA-citric acid greater than TBP-EDTA, greater than TBP alone. The influence of the three variables that govern degradation behaviour viz. sonication energy, magnetic field and time were evaluated with response surface methodology. The model could predict the ratio of total organic carbon content to a maximum error of only ∼ 6%.

Functionalization of magnetic nanoparticles with organic molecules: Loading level determination and evaluation of linker length effect on immobilization

A general method is introduced to immobilize organic molecules on magnetic nanoparticles through silanization reactions and determine the maximum loading level by UV-vis spectroscopy. Loading levels of 1.5 x 10(-3) mol per gram of nanoparticle were obtained with structurally diverse compounds such as rhodamine B and glucosamine. The length of the linker did not have a significant effect on loading as comparable maximum amounts of rhodamine B were immobilized on magnetic nanoparticles regardless of the linker length. Interestingly, rhodamine B derivatives lost conjugation during synthetic manipulations due to reversible spiroisobenzofuran formation. Full regeneration of conjugation was found to be slow with rhodamine B attached on magnetic nanoparticles. The results obtained from these studies will be useful for studying surface functionalization of MNPs in general.