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Physiological stimulus-specific cargo release from nanoparticle carriers is a holy grail of drug delivery research. While the majority of such work is carried out in vitro with cell lines, widespread use of common mammalian model systems – mice and rats – is difficult due to the associated cost and regulatory restrictions. Here we use the inexpensive, easily reared, excellent genetic model system Drosophila melanogaster to test pH responsive cargo release from widely used mesoporous silica nanoparticles (MSNs) coated with pH sensitive polydopamine (PDA) and polyethylene glycol (PEG) polymers. We synthesized 650 ± 75 nm diameter PDA or PEG coated mesoporous silica nanoparticles loaded with a fluorescent dye and fed to individual adult flies. Subsequently, the passage of the particles were monitored through the fly gut. As in mammals, the fly intestine has multiple pH specific zones that are easily accessible for imaging and also genetic, biochemical or physiological manipulations. We observed that both the species of MSNs ruptured around the acidic (pH < 4.0) middle midgut of the flies. PEG coated particles showed sharper specificity of release in the acidic middle midgut of flies than the PDA coated ones and had less tendency to clump together. Our results clearly show that the Drosophila gut can be used as a model to test pH responsive biocompatible materials in vivo. Our work paves the way for greater use of Drosophila as an in vivo complete systemic model in drug delivery and smart materials research. It also suggests that such specific delivery of chemical/biological cargo can be exploited to study basic biology of the gut cells and their communication with other organs.

The effect of different buffers on in vitro release of PEG coated mesoporous silica nanoparticles is discussed in this work. We prepared Rhodamine loaded and PEG coated mesoporous silica nanoparticles (PEG coated RhB@MSNs) of ~ 650 nm size and studied their release behaviour for 5 hours in various buffer solutions (both Na+ and K+ versions) prepared by standard procedure. We observed that Rhodamine release was highest in the citrate buffer. A comparison of different buffer effects on the in vitro release reveals that it is crucial to choose the right buffer for determining the loaded cargo release in each pH zone (acidic, neutral and basic). Clearly, choosing the wrong combination of buffers for different pH zones would result in completely different interpretation of the release behaviour.

Very high surface area, self-assembled, highly crystalline mesoporous SrTiO3 (STO) thin films were developed for photoelectrochemical water splitting. Much improved performance of these mesoporous films compared to planar STO thin films and any other form of STO such as single crystal samples and nanostructures was demonstrated. The high performance resulted from very large surface area films and optimization of carrier concentration.

Three highly crystalline Cu(II)-polyoxometalate (POM) complexes, [Cu1.5(H2O)7.5PW12O40]·4.75H2O and cis- and trans-[Cu2(H2O)10SiW12O40]·6H2O, were successfully synthesized and characterized by single crystal and powder X-ray diffraction as well as thermogravimetric analysis. All complexes feature octahedrally coordinated, Jahn–Teller-distorted CuII centres, which are coordinated by one terminal oxygen atom of the POM anion and five water molecules. The crystal structure of [Cu1.5(H2O)7.5PW12O40]·4.75H2O, reveals four-fold disorder at one of the two Cu-sites, whereas [Cu2(H2O)10SiW12O40]·6H2O crystallizes in two fully-ordered polymorphic forms: a monoclinic structure containing an angled cis configuration of the Cu-POM-Cu molecule and a triclinic structure containing a linear trans configuration. Density functional theory (DFT) calculations show that the cis polymorph of [Cu2(H2O)10SiW12O40]·6H2O is more stable than the trans form by about 30 kJ mol−1.

The hydrolysis of a series of unactivated dipeptides in the presence of a zirconium(IV)-substituted Lindqvist type polyoxometalate, (Me4N)2[W5O18Zr(H2O)3] (designated as ZrW5), was studied by kinetic experiments and NMR spectroscopy. Among the dipeptides examined, those with the X–Ser amino acid sequence were most effectively hydrolyzed. The kinetics of the hydrolysis of histidylserine (His–Ser) was studied in detail; a rate constant of 95.3 (± 0.1) × 10–7 s–1 (pD 7.4 and 60 °C) in the presence of an equimolar amount of ZrW5 was calculated. The binding of His–Ser to ZrW5 was examined by UV/Vis, 1H, 13C, and 183W NMR spectroscopy, and the data indicate that at physiological pD His–Ser chelates the ZrIV through its imidazole nitrogen, amine nitrogen, and amide carbonyl oxygen. In the presence of ZrW5, the pD profile of kobs is bell-shaped, with a maximum reaction rate at pD 7.5. At high pD values an inactive complex is formed as a result of the deprotonation of the amide nitrogen, resulting in inhibition of His–Ser hydrolysis. The effects of pH, temperature, inhibitors, and ionic strength on the hydrolysis rate constant were also investigated, and a full account of the mechanism of this novel reaction is given.

The addition of H 3PW 12O 40 to an aqueous solution of K 2CrO 4 led to the hydrolysis of [PW 12O 40] 3- with its quantitative conversion into K 13[KP 2W 20O 72]. K 13[KP 2W 20O 72] in these chromate-containing solutions was characterized by 183W and 31P NMR, EXAFS, SAXS, and EPR spectroscopy. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Keggin heteropolyacid incorporated Cu3(BTC)2 (BTC = 1,3,5-benzenetricarboxylic acid) thin films were grown on metallic Cu substrates in various solvents at ambient conditions. The Keggin heteropolyacid templated the growth of Cu3(BTC)2 crystals while the Cu substrate served as Cu2+-ion source. To obtain smooth, homogeneous films the optimal growth conditions found were in an ethanolic solution in contact with ambient air. X-ray diffraction measurements showed a preferred (100) orientation of the Cu3(BTC)2 crystals in ethanol while the use of a water-based solvent yielded a dominating (111) orientation.

Researchers in need of an ordered nanoporous material tend to rely on the original synthesis protocols which often demand hydrothermal synthesis and involve harsh chemical conditions, expensive sacrificial templates and long synthesis times. Considerable efforts have been invested in developing new pathways to simplify synthesis procedures. While in the area of zeolites even with optimum templates intrinsic energy barriers of the crystallization process obstruct the development of easy room temperature synthesis, the synthesis of ordered mesoporous materials and metal organic frameworks (MOFs) are examples of materials for which synthesis can be rationalized and simplified. One key element for the development of room temperature synthesis is the selection of highly efficient templates.

An original synthesis approach to prepare Cu 3 (BTC) 2 (BTC = benzene tricarboxylic acid) encapsulated Keggin phosphotungstic acid (HPW) [HPW/Cu 3 (BTC) 2 ] involving mixing of reagents at room temperature, quenching in liquid nitrogen and freeze drying has resulted in the formation of nanocrystals. The catalytic properties of the as-synthesized nanocrystalline materials were assessed using a model esterification reaction of acetic acid with 1-propanol. HPW/Cu 3 (BTC) 2 catalyst is partially dissolved in presence of acetic acid. In the esterification reaction the molar ratio of acetic acid to 1-propanol is critical. At high molar ratio of acetic acid to 1-propanol (1:2) leaching of Cu 2+ and HPW was observed. However, at low molar ratio of acetic acid to 1-propanol (1:40) leaching of Cu 2+ and HPW could be prevented and the catalyst was stable. Nanosized HPW/Cu 3 (BTC) 2 showed higher catalytic activity compared to micron-size Cu 3 (BTC) 2 (HKUST-1), ultrastable Y zeolite and micron-sized HPW/Cu 3 (BTC) 2 catalysts. The stability of the nanosized MOF catalyst in acidic reaction medium after esterification reaction was investigated by powder X-ray diffraction (PXRD), scanning electron microscope (SEM) and N 2 adsorption.

Flexible metal-organic frameworks (MOFs) can undergo fascinating structural transitions triggered by external stimuli, such as adsorption/desorption of specific guest molecules or temperature changes. In this detailed study we investigate the potentials and limitations of tuning framework flexibility systematically by exploiting the powerful concept of mixed-linker solid solutions. We chose the prototypical family of functionalized pillared-layer MOFs of the general type Zn2(fu(1)-bdc)2x(fu(2)-bdc)(2-2x)dabco (with x = 1.00, 0.75, 0.50, 0.25 and 0.00; fu-bdc = 2,5-dialkoxy-1,4-benzenedicarboxylate with varying alkoxy chain length, dabco = 1,4-diazabicyclo[2.2.2]octane) and examined their guest responsive, as well as intrinsic temperature dependent structural flexibility by X-ray diffraction, gas physisorption and calorimetric measurements. The ratio of the different fu-bdc linkers can be adjusted freely, offering opportunity for a targeted design of these functional materials by modulating their key features, such as magnitude of framework contraction upon guest removal, breathing behaviour upon CO2 adsorption/desorption, thermoresponsive phase behaviour, and their general thermal expansivity, by the careful choice of fu-bdc linkers and their combination.

Desolvated zeolitic imidazolate framework ZIF-4(Zn) undergoes a discontinuous porous to dense phase transition on cooling through 140 K, with a 23 % contraction in unit cell volume. The structure of the non-porous, low temperature phase was determined from synchrotron X-ray powder diffraction data and its density was found to be slightly less than that of the densest ZIF phase, ZIF-zni. The mechanism of the phase transition involves a cooperative rotation of imidazolate linkers resulting in isotropic framework contraction and pore space minimization. DFT calculations established the energy of the new structure relative to those of the room temperature phase and ZIF-zni, while DSC measurements indicate the entropic stabilization of the porous room temperature phase at temperatures above 140 K.

Low energy permanent magnetic fields (0.5T) applied in hydrodynamically turbulent conditions are observed to enhance self-assembly of materials with magnetically frustrated spin systems (spin-glass, spin-ice or spin–liquid). This effect is demonstrated for the crystallization of vanadium oxide nano-scrolls, manganese oxide nano-tubes and HKUST-1 type Cu3(BTC)2.3H2O Metal-Organic Framework. Crystallization of these spin systems involves spin coupling and alignment of initially isolated paramagnetic metal ions, respectively V(IV), Mn(IV) and Cu(II) into molecular precursor units that self-assemble to the final material. The electromagnetic and hydrodynamic forces applied during magnetohydrodynamic precursor treatment induce a long lived state of collective spin order by the resonant coupling of magnetic field and turbulent structured flow. This altered magnetic alignment in the molecular precursor units consequently assist the self-assembly process resulting in optimised morphology. The presented experimental setup enables precise control over the magnetohydrodynamic conditions during synthesis, essential for elucidation the detailed mechanism. ispartof: Advanced Materials vol:26 issue:30 pages:5173-5178 ispartof: location:Germany status: published

A new concept of luminescent host-guest materials was developed by introduction of Eu3+ into COK-16, a HKUST-1 type hybrid metal-organic framework (MOF) with cation exchange properties. In Eu@COK-16, the luminescent ion resides in the pore system of the MOF. The luminescent properties of Eu@COK-16 have been studied based on excitation and emission, allowing analysis of intramolecular energy-transfer processes from the COK-16 host to the exchanged Eu3+ ions. Both, the framework trimesate (BTC) and encapsulated [PW12O40] 3- ions contribute to energy transfer. Since the antenna molecules (BTC) are part of the framework structure and [PW12O40]3- ions only partly occupy one of the three types of cavities in the structure, a large fraction of the pore volume in this host sensitized luminescent MOF remains available for catalysis applications or adsorption of additional sensitizing molecules. The material structure was determined from a combination of elemental analysis, XAS, XRD, electron and luminescence spectroscopy. crosscheck: This document is CrossCheck deposited related_data: Supplementary Information copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal copyright_licence: The accepted version of this article will be made freely available in the Chemical Sciences Article Repository after a 12 month embargo period history: Received 26 March 2014; Accepted 9 May 2014; Accepted Manuscript published 9 May 2014; Advance Article published 30 May 2014; Version of Record published 19 August 2014 ispartof: Dalton Transactions vol:43 issue:36 pages:13480-13484 ispartof: location:England status: published

Porous solids with organized multiple porosity are of scientific and technological importance for broadening the application range from traditional areas of catalysis and adsorption/separation to drug release and biomedical imaging. Synthesis of crystalline porous materials offering a network of uniform micro- and mesopores remains a major scientific challenge. One strategy is based on variation of synthesis parameters of microporous networks, such as, for example, zeolites or metal organic frameworks (MOFs). Here, we show the rational development of an hierarchical variant of the microporous cubic Cu-3(BTC)(2) (BTC = 1,3,5-benzenetricarboxylate) HKUST-1 MOF having strictly repetitive S inn wide mesopores separated by uniform microporous walls in a single crystal structure. This new material coined COK-15 (COK = Centrum voor Oppervlaktechemie en Katalyse) was synthesized via a dual-templating approach. Stability was enhanced by Keggin type phosphotungstate (HPW) systematically occluded in the cavities constituting the walls between the mesopores.

The molecular steps involved in the self-assembly of Cu(3)(BTC)(2) (BTC=1,3,5-benzenetricarboxylic acid) metal-organic frameworks that enclose Keggin-type H(3)PW(12)O(40) heteropolyacid molecules were unraveled by using solution (17)O, (31)P, and (183)W NMR spectroscopy, small-angle X-ray scattering, near-IR spectroscopy, and dynamic light scattering. In aqueous solution, complexation of Cu(2+) ions with Keggin-type heteropolyacids was observed. Cu(2+) ions are arranged around the Keggin structure so that linking through benzenetricarboxylate groups results in the formation of the Cu(3)(BTC)(2) MOF structure HKUST-1. This is a unique instance in which a templating mechanism that relies on specific molecular-level matching and leads to explicit nanoscale building units can be observed in situ during formation of the synthetic nanoporous material.

The solvent dependent solubility of HKUST-1 metal–organic framework (MOF) with encapsulated Keggin 12-tungstophosphoric acid (HPW@Cu3(BTC)2) was exploited to liberate homogeneous heteropolyacid catalyst in a reaction medium and to recover the catalyst by encapsulation in the MOF upon addition of hexane. The application of the new Keggin type heteropolyacid catalyst recovery concept was demonstrated in the esterification of acetic acid with 1-propanol and salicylic acid with ethanol.

Cu-3(BTC)(2) with an incorporated Keggin polyoxometalate was demonstrated to be stable under steaming conditions up to 483 K, while the isostructural HKUST-1 degrades and transforms into [Cu2OH(BTC)(H2O)](n)center dot 2nH(2)O from 343 K onwards. ispartof: Chemical Communications vol:47 issue:28 pages:8037-8039 ispartof: location:England status: published

HKUST-1 is one of the popular metal-organic frameworks (MOFs). The formation of this MOF is significantly accelerated by adding Keggin polyoxometalate anions to the synthesis solution. In this paper the chemistry behind this observation was investigated. Upon addition of Keggin type H 3PW12O40 heteropolyacid the speciation of Cu2+ cations in ethanol:H2O mixture drastically changes. Combining EPR and XANES measurements with accurate pH measurements and prediction of Cu2+ hydrolysis provides strong evidence for surface induced hydrolysis and consequent dimerisation of monomeric Cu2+ species on Keggin ions in acidic conditions. This enables paddle wheel formation, hence explaining the instantaneous precipitation of Cu 3(BTC)2 at room temperature and the systematic encapsulation of Keggin ions in its pores. Fil: Bajpe, Sneha R.. Katholikie Universiteit Leuven; Bélgica Fil: Breynaert, Eric. Katholikie Universiteit Leuven; Bélgica Fil: Mustafa, Danilo. Katholikie Universiteit Leuven; Bélgica Fil: Jobbagy, Matias. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina Fil: Maes, André. Katholikie Universiteit Leuven; Bélgica Fil: Martens, Johan A.. Katholikie Universiteit Leuven; Bélgica Fil: Kirschhock, Christine E. A.. Katholikie Universiteit Leuven; Bélgica

Nanomaterial of Cu(3)(BTC)(2) (BTC = benzene tricarboxylic acid) incorporating Keggin heteropolyacid conveniently prepared at room temperature and recovered by freeze drying outperforms ultrastable Y zeolite in acid catalysed esterification reaction.