Combining a Genetically Engineered Oxidase with Hydrogen-Bonded Organic Frameworks (HOFs) for Highly Efficient Biocomposites

Enzymes incorporated into hydrogen‐bonded organic frameworks (HOFs) via bottom‐up synthesis are promising biocomposites for applications in catalysis and sensing. Here, we explored synthetic incorporation of d‐amino acid oxidase (DAAO) with the metal‐free tetraamidine/tetracarboxylate‐based BioHOF‐1 in water. N‐terminal enzyme fusion with the positively charged module Z(basic2) strongly boosted the loading (2.5‐fold; ≈500 mg enzyme g(material) (−1)) and the specific activity (6.5‐fold; 23 U mg(−1)). The DAAO@BioHOF‐1 composites showed superior activity with respect to every reported carrier for the same enzyme and excellent stability during catalyst recycling. Further, extension to other enzymes, including cytochrome P450 BM3 (used in the production of high‐value oxyfunctionalized compounds), points to the versatility of genetic engineering as a strategy for the preparation of biohybrid systems with unprecedented properties

Thermal-induced phase transitions in self-assembled mesostructured films studied by small-angle X-ray scattering

Two examples of phase transition in self-assembled mesostructured hybrid thin films are reported. The materials have been synthesized using tetraethoxysilane as the silica source hydrolyzed with or without the addition of methyltriethoxysilane. The combined use of transmission electron microscopy, small-angle X-ray scattering and computer simulation has been introduced to achieve a clear identification of the organized phases. A structural study of the self-assembled mesophases as a function of thermal treatment has allowed the overall phase transition to be followed. The initial symmetries of mesophases in as-deposited films have been linked to those observed in samples after thermal treatment. The monodimensional shrinkage of silica films during calcination has induced a phase transition from face-centered orthorhombic to body-centered cubic. In hybrid films, instead, the phase transition has not involved a change in the unit cell but a contraction of the cell parameter normal to the substrate

Influence of domestic and environmental weathering in the self-cleaning performance and durability of TiO2 photocatalytic coatings

Weathering of photocatalytic TiO2 coatings represents an important issue for the successful application of TiO2- based self-cleaning materials. Photocatalytic efficiency of the as-prepared materials is crucial for commercialization; however, changes in the coating performance due to weathering become a critical factor for practical applications. Moreover, chemical durability should be considered as weathering can promote the release of photocatalyst nanoparticles, which can pollute the environment and be hazardous for human health. In this study, two photocatalytic TiO2 coatings with different microstructures (namely compact and mesoporous) were exposed to chemical treatments to simulate domestic and environmental weathering. Results show that dense TiO2 coatings with a slow photocatalytic activity are suitable for domestic applications as minimum leaching of photoactive material was observed. Conversely, once exposed to chemical solutions commonly present in domestic environments, the initially highly active mesoporous TiO2 coatings showed a dramatic drop of the selfcleaning performance and a significant release of nanoparticles in the surrounding environment. It is expected that the results reported here will be of particular relevance for the construction sector, as the manuscript discloses important knowledge for the development of TiO2-based self-cleaning materials once exposed to indoor or outdoor environments

Self-Assembly of Oriented Antibody-Decorated Metal–Organic Framework Nanocrystals for Active-Targeting Applications

Antibody (Ab)-targeted nanoparticles are becoming increasingly important for precision medicine. By controlling the Ab orientation, targeting properties can be enhanced; however, to afford such an ordered configuration, cumbersome chemical functionalization protocols are usually required. This aspect limits the progress of Abs-nanoparticles toward nanomedicine translation. Herein, a novel one-step synthesis of oriented monoclonal Ab-decorated metal–organic framework (MOF) nanocrystals is presented. The crystallization of a zinc-based MOF, Zn2(mIM)2(CO3), from a solution of Zn2+ and 2-methylimida-zole (mIM), is triggered by the fragment crystallizable (Fc) region of the Ab. This selective growth yields biocomposites with oriented Abs on the MOF nanocrystals (MOF*Ab): the Fc regions are partially inserted within the MOF surface and the antibody-binding regions protrude from the MOF surface toward the target. This ordered configuration imparts antibody–antigen rec-ognition properties to the biocomposite and shows preserved target binding when compared to the parental antibodies. Next, the biosensing performance of the system is tested by loading MOF*Ab with luminescent quantum dots (QD). The targeting efficiency of the QD-containing MOF*Ab is again, fully preserved. The present work represents a simple self-assembly approach for the fabrication of antibody-decorated MOF nanocrystals with broad potential for sensing, diagnostic imaging, and targeted drug delivery

High‑Throughput Electron Diffraction Reveals a Hidden Novel Metal–Organic Framework for Electrocatalysis

AbstractMetal‐organic frameworks (MOFs) are known for their versatile combination of inorganic building units and organic linkers, which offers immense opportunities in a wide range of applications. However, many MOFs are typically synthesized as multiphasic polycrystalline powders, which are challenging for studies by X‐ray diffraction. Therefore, developing new structural characterization techniques is highly desired in order to accelerate discoveries of new materials. Here, we report a high‐throughput approach for structural analysis of MOF nano‐ and sub‐microcrystals by three‐dimensional electron diffraction (3DED). A new zeolitic‐imidazolate framework (ZIF), denoted ZIF‐EC1, was first discovered in a trace amount during the study of a known ZIF‐CO3‐1 material by 3DED. The structures of both ZIFs were solved and refined using 3DED data. ZIF‐EC1 has a dense 3D framework structure, which is built by linking mono‐ and bi‐nuclear Zn clusters and 2‐methylimidazolates (mIm−). With a composition of Zn3(mIm)5(OH), ZIF‐EC1 exhibits high N and Zn densities. We show that the N‐doped carbon material derived from ZIF‐EC1 is a promising electrocatalyst for oxygen reduction reaction (ORR). The discovery of this new MOF and its conversion to an efficient electrocatalyst highlights the power of 3DED in developing new materials and their applications

Magnetically Responsive Horseradish peroxidase@ZIF-8 for Biocatalysts

Here, we studied a catalytically active and magnetically responsive porous bio-composite obtained from the synthesis of ZIF-8 in presence of iron oxide magnetic nanoparticles and horseradish peroxidase (HRP) enzyme as guest species. Using a one-pot approach in water the precursors of ZIF-8 (zinc acetate and 2-methylimidazole) spontaneously self-assembles around the guest species. We characterized the composite by means of XRD, SEM, FTIR, AFM, and CLSM. SAXS investigation of the kinetics of crystallization showed how the presence of the guest species can act as nucleation seeds. Moreover, we found that the bio-catalytic activity of the HRP/MNP@ZIF-8 biocomposite is 5 times higher than the analoguous composite without MNPs.</div

Biomimetic replication of microscopic metal-organic framework patterns using printed protein patterns

It is demonstrated that metal–organic frameworks (MOFs) can be replicated in a biomimetic fashion from protein patterns. Bendable, fluorescent MOF patterns are formed with micrometer resolution under ambient conditions. Furthermore, this technique is used to grow MOF patterns from fingerprint residue in 30 s with high fidelity. This technique is not only relevant for crime-scene investigation, but also for biomedical applications.P. F. acknowledges the Australian Research Council (ARC, DECRA Grant DE120102451), and the CSIRO AMTCP scheme. K.L. and J.J.R. acknowledge the OCE Scheme. This work was supported by the MINECO-Spain under Project No. PN MAT2012–30994 and the EC (project FP7 ERC-Co 61594). ICN2 acknowledges support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grant No. SEV-2013–0295. This work was also supported by the ARC Centre of Excellence in Convergent Bio-Nano Science and Technology (Project No. CE140100036) and performed in part at the Materials Characterization and Fabrication Platform (MCFP) at The University of Melbourne and the Victorian Node of the Australian National Fabrication Facility (ANFF).Peer Reviewe

Silica orthorhombic mesostructured films with low refractive index and high thermal stability

Silica mesoporous films have been synthesized via Evaporation Induced Self-Assembling (EISA) using Pluronic F-127 as a templating agent and mesostructures with Fmmm orthorhombic symmetry have been obtained. An optimized thermal process to stabilize the silica walls has been used; the silica films exhibited an excellent thermal stability in a large range of temperatures and the mesostructure remained organized up to 950 °C. Fourier transform infrared spectroscopy has shown that the high thermal stability is correlated with a progressive strengthening of the silica structure during thermally-induced polycondensation reactions and structural rearrangements of 4-fold rings present in the silica walls. The mesostructure after annealing at 850 °C is free of silanols and still maintains a high degree of order. The refractive index, volume porosity, and shrinkage have been studied as a function of the thermal treatment up to 1050 °C. The films have a low refractive index (1.32), upon removal of the organic template via thermal calcination, and show a 30% residual porosity up to 850 °C

Photocurable silica hybrid organic-inorganic films for photonic applications

We report the preparation of hybrid organic–inorganic films deposited by dip-coating from a base-catalyzed sol containing tetraethoxysilane and 3-methacryloxypropyltrimethoxysilane as the silicon source, and ethyl-2,4,6-trimethylbenzoylphenylphosphinate as the photoinitiator. The films were cured with a UV lamp, obtaining a change in refractive index upon UV irradiation through the formation of an interpenetrated silica-methacrylate network. The refractive index increased of Δn = 14 × 10−3 after UV treatment. The synthesis is simple and reproducible and yields films with optical quality which can be useful as materials for applications in optics and information storage