Enhanced Activity of Enzyme Immobilized on Hydrophobic ZIF-8 Modified by Ni2+ Ions.

The development of efficient enzyme immobilization to promote their recyclability and activity is highly desirable. Zeolitic imidazolate framework-8 (ZIF-8) has been proved to be an effective platform for enzyme immobilization due to its easy preparation and biocompatibility. However, the intrinsic hydrophobic characteristic hinders its further development in this filed. Herein, a facile synthesis approach was developed to immobilize pepsin (PEP) on the ZIF-8 carrier by using Ni2+ ions as anchor (ZIF-8@PEP-Ni). By contrast, the direct coating of PEP on the surface of ZIF-8 (ZIF-8@PEP) generated significant conformational changes. Electrochemical oxygen evolution reaction (OER) was employed to study the catalytic activity of immobilized PEP. The ZIF-8@PEP-Ni composite attains remarkable OER performance with an ultralow overpotential of only 127 mV at 10 mA cm-2 , which is much lower than the 690 and 919 mV overpotential values of ZIF-8@PEP and PEP, respectively.

Anionic Porous Zn-Metalated Porphyrin Metal-Organic Framework with PtS Topology for Gas-Phase Photocatalytic CO2 Reduction.

Presented here are the synthesis and gas-phase photocatalytic CO2 reduction of an anionic porous Zn-metalated porphyrin metal-organic framework (MOF) induced by an ionic liquid. The desired CO2 affinity and deep conduction band position of the MOF catalyst provide strong kinetic and thermodynamic advantages for photocatalytic CO2 to CH4 conversion with high selectivity (∼70%) in H2O vapor.

Isolating Fe-O2 Intermediates in Dioxygen Activation by Iron Porphyrin Complexes.

Dioxygen (O2) is an environmentally benign and abundant oxidant whose utilization is of great interest in the design of bioinspired synthetic catalytic oxidation systems to reduce energy consumption. However, it is unfortunate that utilization of O2 is a significant challenge because of the thermodynamic stability of O2 in its triplet ground state. Nevertheless, nature is able to overcome the spin state barrier using enzymes, which contain transition metals with unpaired d-electrons facilitating the activation of O2 by metal coordination. This inspires bioinorganic chemists to synthesize biomimetic small-molecule iron porphyrin complexes to carry out the O2 activation, wherein Fe-O2 species have been implicated as the key reactive intermediates. In recent years, a number of Fe-O2 intermediates have been synthesized by activating O2 at iron centers supported on porphyrin ligands. In this review, we focus on a few examples of these advances with emphasis in each case on the particular design of iron porphyrin complexes and particular reaction environments to stabilize and isolate metal-O2 intermediates in dioxygen activation, which will provide clues to elucidate structures of reactive intermediates and mechanistic insights in biological processes.

Efficient Energy-Transfer-Induced High Photoelectric Conversion in a Dye-Encapsulated Ionic Pyrene-Based Metal-Organic Framework.

The relationship between the aggregation states of pyrene-based linkers and the photoluminescence/photoelectric performance was well studied by the formation of an anionic metal-organic framework, [BMI]2[Mg3(TBAPy)2(H2O)4]·2dioxane, which shows highly enhanced light-harvesting and photoelectric conversion efficiency by the encapsulation of D-π-A cation dyes.

Hexanuclear Zn(II)-Induced Dense π-Stacking in a Metal-Organic Framework Featuring Long-Lasting Room Temperature Phosphorescence.

A new strategy to enhance the room temperature phosphorescence performance has been developed through hexanuclear Zn(II)-cluster-induced dense π-stacking in a metal-organic framework matrix. The synergistic effect of metal clusters and large overlap of π-conjugated dimers facilitate the phosphorescence emission, migration, and separation of charge carriers for excellent photocatalytic activity.

Highly Dense Packing of Chromophoric Linkers Achievable in a Pyrene-Based Metal-Organic Framework for Photoelectric Response.

Highly dense packing of chromophoric linkers is achieved in a novel pyrene-based metal-organic framework (MOF), [Zn(TBAPy)1/2(H2O)2], induced by an ionic liquid. This MOF displays a quick response to visible-light irradiation (photocurrent density of up to 4.492 µA cm-2) and is capable of repetitive on-off photocurrent switching with a large on-off ratio (37.55).

A Microfluidic Strategy for Controllable Generation of Water-in-Water Droplets as Biocompatible Microcarriers.

Droplet microfluidics has been widely applied in functional microparticles fabricating, tissue engineering, and drug screening due to its high throughput and great controllability. However, most of the current droplet microfluidics are dependent on water-in-oil (W/O) systems, which involve organic reagents, thus limiting their broader biological applications. In this work, a new microfluidic strategy is described for controllable and high-throughput generation of monodispersed water-in-water (W/W) droplets. Solutions of polyethylene glycol and dextran are used as continuous and dispersed phases, respectively, without any organic reagents or surfactants. The size of W/W droplets can be precisely adjusted by changing the flow rate of dispersed and continuous phases and the valve switch cycle. In addition, uniform cell-laden microgels are fabricated by introducing the alginate component and rat pancreatic islet (ß-TC6) cell suspension to the dispersed phase. The encapsulated islet cells retain high viability and the function of insulin secretion after cultivation for 7 days. The high-throughput droplet microfluidic system with high biocompatibility is stable, controllable, and flexible, which can boost various chemical and biological applications, such as bio-oriented microparticles synthesizing, microcarriers fabricating, tissue engineering, etc.

[Excessive fluoride increases the expression of osteocalcin in the mouse testis].

OBJECTIVE: To observe the influence of excessive fluoride on the levels of osteocalcin and testosterone in the testis of the male mouse. METHODS: Twenty-four C57BL/6J male mice were equally randomized into a normal control and a fluorosis model group, the former fed on distilled water while the latter on a solution of sodium fluoride (100 mg/L) in distilled water, both for 12 weeks. Then, the level of osteocalcin in the testis tissue was measured with the immunohistochemical streptavidin-peroxidase (SP) method and those of osteocalcin and testosterone in the serum determined by ELISA. RESULTS: After 12 weeks of fluoride intervention, the level of serum osteocalcin was significantly higher in the fluorosis models than in the normal controls (ï¼»68.05 ± 5.32ï¼½ vs ï¼»47.50 ± 5.73ï¼½ pg/mL, F = 11.901, P = 0.008), while that of testosterone markedly lower in the former than the latter group (ï¼»8.07 ± 1.35ï¼½ vs ï¼»12.94 ± 3.09ï¼½ ng/mL, F = 2.313, P = 0.006). The results of immunohistochemical SP showed the expression of osteocalcin in the cell membrane and cytoplasm of the fluorosis models, which was evidently higher than in the normal controls. CONCLUSIONS: Twelve-week intake of 100 mg/L fluoride solution can decrease the level of testosterone and increase the expression of osteocalcin in the testis of the male mouse.

Thermochromic luminescent nest-like silver thiolate cluster.

A novel discrete open high-nuclearity nest-like silver thiolate cluster complex, [Ag33 S3 (StBu)16 (CF3 COO)9 (NO3 )(CH3 CN)2 ](NO3 ) (1), has been isolated with nitrate and S(2-) anions acting as structure-directing templates. Its similar nest-like structure has been assembled into an extended layer [Ag31 S3 (StBu)16 (NO3 )9 ]n (2) by adjustment of auxiliary ligand. More interestingly, both complexes exhibit temperature-dependent luminescence of high sensitivity with a large fluorescence enhancement (12-fold for 1, 21-fold for 2), which can be easily recognized by the naked-eye (dramatic red-shift Δ=104 nm for 1, larger Δ=113 nm for 2 at 77 K compared to those at 298 K). The correlation between luminescent thermochromism and temperature-dependent variation of the coordination modes of template NO3 (-) anion, Ag⋅⋅⋅S and Ag⋅⋅⋅Ag distances are also elucidated through variable-temperature single-crystal X-ray crystal structure (VT-SCXRD) analyses.

Broad specific enzyme-linked immunosorbent assay for determination of residual phenothiazine drugs in swine tissues.

In this study, a novel generic hapten of phenothiazine drugs was synthesized by derivatization of 2-chlorophenothiazine with sodium bromoacetate. Then the hapten was coupled to bovine serum albumin for production of the monoclonal antibody. Results showed that the obtained monoclonal antibody recognized five phenothiazine drugs simultaneously: chlorpromazine, promethazine, acepromazine, perphenazine, and fluphenazine. After evaluation of different coating antigens, a heterologous competitive indirect enzyme-linked immunosorbent assay was developed to determine the residues of the five phenothiazine drugs in swine tissues (muscle, liver, and kidney). The cross-reactivities to the five analytes were in the range of 71 to 98%, and the limits of detection were in the range of 0.2 to 0.4 ng/ml, depending on the drug. Their recoveries from the fortified blank samples were in the range of 73.8 to 96.2%, with coefficients of variation in the range of 4.1 to 14.3%. This is the first study reporting a broad specific immunoassay for multi-determination of the residues of five phenothiazine drugs in animal-derived foods.

Models for evaluating glioblastoma invasion along white matter tracts.

White matter tracts (WMs) are one of the main invasion paths of glioblastoma multiforme (GBM). The lack of ideal research models hinders our understanding of the details and mechanisms of GBM invasion along WMs. To date, many potential in vitro models have been reported; nerve fiber culture models and nanomaterial models are biocompatible, and the former have electrically active neurons. Brain slice culture models, organoid models, and microfluidic chip models can simulate the real brain and tumor microenvironment (TME), which contains a variety of cell types. These models are closer to the real in vivo environment and are helpful for further studying not only invasion along WMs by GBM, but also perineural invasion and brain metastasis by solid tumors.

Back acupoint location method based on prior information and deep learning.

Acupuncture points have a positive effect on the auxiliary prevention and treatment of diseases, so medical devices such as acupuncture robots often need to combine acupuncture points to improve the treatment effect when working, however, intelligent acupoint selection technology is not yet mature, the automatic rapid and accurate positioning of acupoints is still challenging. Therefore, this paper proposes a method of back acupoint location and an evaluation index of acupoint location. First, we propose an improved Keypoint RCNN network for the preliminary location of back acupoints and introduce a channel and spatial attention mechanism module (CBAM) to improve the performance of the model. Then, we set up a posterior median line positioning method to improve the accuracy of acupoint positioning. Finally, expand and locate other acupoints according to the prior information of acupoints. According to the experimental results, the accuracy of acupoint positioning was 87.32%. After the correction of acupoint positioning, the accuracy was increased by 2.8%, which was 90.12%. In this paper, the application of depth learning in automatic location of back acupoints is realized for the first time. Only one image can be used to locate the back acupoints, with an accuracy of 90.12%.

[One-step generation of droplet-filled hydrogel microfibers for 3D cell culture using an all-aqueous microfluidic system].

Hydrogel microfibers, which are characterized by flexible mechanical properties, a uniform spatial distribution, large surface areas, and excellent biocompatibility, hold great potential for various biomedical applications. However, the fabrication of heterogeneous hydrogel microfibers with high cell-loading capacity and the ability to carry multiple components via an environmentally friendly method remains challenging. In this study, we developed a novel pneumatic pump-assisted all-aqueous microfluidic system that enables the one-step fabrication of all-aqueous droplet-filled hydrogel microfibers with unique morphologies and adjustable configurations. By designing a pump-valve cycling system and selecting two immiscible fluids with stable water interfaces (dextran and polyethylene glycol), we successfully fabricated alginate microfibers with equidistantly arranged droplets through the ionotropic gelation reaction between sodium alginate and calcium chloride. The droplet size, interdroplet spacing, and microfiber dimensions could be flexibly controlled by adjusting the flow rates of the inner-phase, middle-phase, and outer-phase inlets. The results showed that the system enabled the high-throughput in situ formation of functional three-dimensional cell spheroids. The generated cell spheroids exhibited excellent cell viability and drug-testing functionality, indicating their potential applications in cell cultures. The developed technique offers strong support for future biomedical research and applications, and provides a new approach for the preparation of multifunctional hydrogel microfibers for materials science, tissue engineering, and drug testing.

Mn(II) coordination polymers based on bi-, tri-, and tetranuclear and polymeric chain building units: crystal structures and magnetic properties.

Five new Mn(II) coordination polymers, namely [Mn(2)(tbip)(2)(bix)] (1), [Mn(3)(tbip)(3)(bix)(2)] (2), [Mn(3)(tbip)(2)(Htbip)(2)(bib)(2)]·4H(2)O (3), [Mn(4)(tbip)(4)(bbp)(2)(H(2)O)(2)] (4), and [Mn(4)(tbip)(4)(bip)]·2H(2)O (5), were prepared by hydrothermal reactions of Mn(II) acetate with H(2)tbip (5-tert-butyl isophthalic acid) in the presence of different di-imidazolyl coligands (bix =1,4-bis(imidazol-1-ylmethyl)benzene, bib =1,4-bis(imidazol) butane, bbp =1,3-bis(benzimidazol)propane, bip =1,3-bis(imidazol)propane). All complexes were characterized by elemental analysis, IR spectra, thermogravimetric analysis, single-crystal X-ray crystallography, and powder X-ray diffraction. Single crystal X-ray studies show that these coordination polymers contain homometallic clusters varying from dimeric, trimeric, and tetrameric motifs to polymeric chains depending upon the coligands used. Complex 1 has a 3D 6-connected polycatenane network with dinuclear [Mn(2)O(2)] secondary building units. Complex 2 possesses a 3D 8-connected structure with trinuclear [Mn(3)(COO)(6)] units. Complex 3 shows a 3D pcu net based on trinuclear [Mn(3)(COO)(6)] clusters as nodes. Complex 4 features a 3D 8-connected structure constructed from the distorted square-grid tetranuclear [Mn(4)(µ(2)-COO)(8)(µ(2)-H(2)O)] units. Complex 5 shows a 3D (4,5,6)-connected net containing 1D µ-O/µ-COO alternately bridged chains. Magnetic susceptibility measurements indicate that complexes 1 and 3-5 show weak antiferromagnetic interactions between the adjacent Mn(II) ions, whereas 2 is a three-spin center homometallic ferromagnetic system.

An anthracene based metal-organic framework showing efficient angle-dependent polarized emission, luminescence thermometry, and photoelectronic response.

The development of luminescent metal-organic frameworks (MOFs) has attracted extensive attention due to their applications in photoelectric devices, organic light-emitting diodes (OLEDs), anti-counterfeiting, biological imaging and so on. In this work, a novel anthracene based metal-organic framework, [Cd(DCPA)(DMF)]·(H2O) (1) (H2DCPA = 9,10-di(p-carboxyphenyl)anthracene), has been successfully synthesized under solvothermal conditions. The highly ordered arrangement and special spatial conformation of the anthracene chromophore play a significant role in the photophysical properties of 1. The combination of theoretical calculations and experiments shows that the molecular orbitals have good separation for inhibiting the recombination of electrons and holes. Furthermore, the fluorescence emission of 1 can be instantaneously and reversibly tuned between blue and green at different polarizing angles. Temperature-dependent fluorescence measurements indicate a good linear relationship between the maximum emission intensity/wavelength and the temperature for efficient thermochromism and luminescence thermometry. Photoelectric measurements reveal that 1 shows high performance of photocurrent generation under light illumination. Therefore, our research affords a new perspective to extend the application of luminescent MOFs in the fields of polarized emission, thermometry and photoelectronic response.

High loading of Mn(ii)-metalated porphyrin in a MOF for photocatalytic CO2 reduction in gas-solid conditions.

A high loading of Mn(ii)-metalated porphyrin was achievable in a 2D porphyrin-based Mn-MOF induced by an ionic liquid. The excellent stability, sufficient redox potential, atomically dispersed porphyrin Mn(ii) sites, desired CO2 affinity, high visible light-harvesting and efficient charge separation, endow this MOF with the overall photocatalytic conversion of CO2 to CH4 in gas-solid conditions.

Embellishment of microfluidic devices via femtosecond laser micronanofabrication for chip functionalization.

This paper demonstrates the embellishment of existing microfluidic devices with integrated three dimensional (3D) micronanostructures via femtosecond laser micronanofabrication, which, for the first time, proves two-photon photopolymerization (TPP) to be a powerful technology for chip functionalization. As representative examples, microsieves with various pore shape and adjustable pore size were successfully fabricated inside a conventional glass-based microfluidic channel prepared by wet etching for microparticle separation. Moreover, a fish scale like microfilter was also fabricated and appointed as a one-way valve, which showed excellent performance as we expected. These results indicate that such embellishment of microfluidic devices is simple, low cost, flexible and easy to access. We believe that, combined with TPP, the application of lab-on-chip devices would be further extended.

Ionic liquid induced highly dense assembly of porphyrin in MOF nanosheets for photodynamic therapy.

Two-dimensional (2D) metal-organic framework (MOF) nanosheets have emerged as a new member of 2D nanomaterials for molecular sieving, energy conversion and storage, catalysis and biomedicine. In this paper, a highly dense assembly of porphyrin achievable in porphyrin-integrated MOF nanosheets induced by an ionic liquid is obtained by sonication exfoliation of its bulk crystals. The 2D layered structure MOF, [BMI]2[Ca3(H2TCPP)2(µ2-OH2)2(H2O)2] (1), was firstly prepared by using the ionic liquid assisted synthetic method (H6TCPP = meso-tetra(carboxyphenyl) porphyrin, BMI = 1-butyl-3-methylimidazolium). The laminated layers in 1 clearly indicate a weak interlayer non-covalent interaction but a strong metal-carboxylate bonding within the layers, which facilitates the exfoliation of 1 to form 2D MOF nanosheets (1 NSs). Powder X-ray diffraction (PXRD), high-resolution transmission electron microscopy (HR-TEM) and fast Fourier transform (FFT) patterns revealed that 1 NSs could maintain their crystalline structure after exfoliation. These MOF nanosheets exhibited excellent aqueous dispersibility, biodegradability and high cytotoxicity under light irradiation against MCF-7 cells.

Aqueous-phase detection of antibiotics and nitroaromatic explosives by an alkali-resistant Zn-MOF directed by an ionic liquid.

An alkali-resistant Zn-MOF directed by [BMI]Br ionic liquid, (BMI)2[Zn3(ptptc)2] (1), based on a π-electron-rich terphenyl-tetracarboxylic acid, has been synthesized under the combination of hydro/solvothermal and ionothermal condition (BMI = 1-butyl-3-methylimidazolium, H4ptptc = p-terphenyl-3,3'',5,5''-tetracarboxylic acid). In 1, the trinuclear Zn(ii) clusters are linked by the organic moieties of the ptptc ligands, resulting in a 3D anionic framework structure with highly disordered [BMI]+ cations filled in the pores. 1 exhibits good chemical stability in water and NaOH solutions (pH range of 7-12), which allow it to detect antibiotics and nitroaromatic explosives in an aquatic system. 1 represents high fluorescence quenching efficiency toward NFs (furazolidone, FZD; nitrofurazone, NZF; nitrofurantoin, NFT), NMs (ronidazole, RDZ; metronidazole, MDZ; dimetridazole, DTZ; ornidazole, ODZ) and nitrophenol (2-nitrophenol, 2-NP; 3-nitrophenol, 3-NP; 4-nitrophenol, 4-NP; 2,4,6-trinitrophenol, TNP) in water solution, respectively.

2-Iodo-1,3-dimethoxy-benzene.

Crystals of the title compound, C(8)H(9)IO(2), were obtained from a dimethyl sulfoxide solution of 2,6-dimethoxy-benzoic acid and iodo-benzene diacetate under a nitro-gen atmosphere at 353 K. In the crystal structure, mol-ecules are linked by weak C-H⋯π inter-actions, generating inter-penetrating one-dimensional chains of perpendicularly oriented mol-ecules extending along [011] and [01]. Chains are also formed through non-bonding C-I⋯π contacts extending in the same directions, projecting a zigzag motif in view down [100]. The I⋯Cg distance is 3.695 (2) Šand the C-I⋯Cg angle is 164.17 (14)°. The mol-ecular symmetry m coincides with the mirror plane of the space group Cmc2(1), resulting in a half-mol-ecule in the asymmetric unit (Z' = ½).