Nanocomposite hyaluronic acid-based hydrogel for the treatment of esophageal fistulas

Fistulas are abnormal connections between two body parts that can impair the quality of life. The use of biological glues represents the least invasive procedure to fill the fistula; however, it is limited by the need of multiple injections, the persistence of infection and the failure in the treatment of high-output fistulas. We describe herein the use of an injectable nanocomposite hydrogel that is able to form in situ a tissue-mimicking matrix as an innovative material for the treatment of esophageal fistulas. Injectable hydrogels that have the dual advantage of being implantable with a minimally invasive approach and of adapting their shape to the target cavity, while the introduction of mesoporous silica nanoparticles opens the possibility of drug/biomolecules delivery.

The hydrogel is based on hyaluronic acid (HA), the crosslinking process occurs at physiological conditions leading to a hydrogel made of >96% by water and with a large-pore micro-architecture. The kinetic profile of the hydrogel formation is studied as a function of HA molecular weight and concentration with the aim of designing a material that is easily injectable with an endoscopic needle, is formed in a time compatible with the surgical procedure and has final mechanical properties suitable for cell proliferation. The in vivo experiments (porcine model) on esophageal-cutaneous fistulas, showed improved healing in the animals treated with the hydrogel compared with the control group.

Stabilisation effects of phosphane ligands in the homogeneous approach of sunlight induced hydrogen production

Most of the systems for photochemical hydrogen production are not stable and suffer from decomposition. With bis(bidentate) tetraphosphane ligands the stability increases enormously, up to more than 1000 h. This stability was achieved with a system containing osmium(ii) as a light harvesting antenna and palladium(ii) as a water reduction catalyst connected with a bis(bidentate) phosphane ligand in one molecule with the chemical formula [Os(bpy)₂(dppcb)Pd(dppm)](PF₆)₄. With the help of electrochemical measurements as well as photophysical data and its single crystal X-ray structure, the electron transfer between the two active metal centres (light harvesting antenna, water reduction catalyst) was analysed. The distance between the two active metal centres was determined to be 7.396(1) Å. In a noble metal free combination of a copper based photosensitiser and a cobalt diimine-dioxime complex as water reduction catalyst a further stabilisation effect by the phosphane ligands is observed. With the help of triethylamine as a sacrificial donor in the presence of different monophosphane ligands it was possible to produce hydrogen with a turnover number of 1176. This completely novel combination is also able to produce hydrogen in a wide pH-range from pH = 7.0 to 12.5 with the maximum production at pH = 11.0. The influence of monophosphane ligands with different Tolman cone angles was investigated. Monophosphane ligands with a large Tolman cone angle (>160°) could not stabilise the intermediate of the cobalt based water reduction catalyst and so the turnover number is lower than for systems with an addition of monophosphane ligands with a Tolman cone angle smaller than 160°. The role of the monophosphane ligand during sunlight-induced hydrogen production was analysed and these results were confirmed with DFT calculations. Furthermore the crystal structures of two important Co(i) intermediates, which are the catalytic active species during the catalytic pathway, were obtained. The exchange of PPh₃ with other tertiary phosphane ligands can have a major impact on the activity, depending on the coordination properties. By an exchange of monophosphane ligands with functionalised phosphane ligands (hybrid ligands) the hydrogen production was raised 2.17 times.

Unusual stability of dyads during photochemical hydrogen production

Heterodimetallic dyads containing Os and Pd are connected by a bis(bidentate) phosphine and show an excellent stability for the water splitting application.

RETRACTED: Ultrahigh magnetoresistance at room temperature in molecular wires

Systems featuring large magnetoresistance (MR) at room temperature and in small magnetic fields are attractive owing to their potential for applications in magnetic field sensing and data storage. Usually, the magnetic properties of materials are exploited to achieve large MR effects. Here, we report on an exceptionally large (>2000%), room-temperature, small-field (a few millitesla) MR effect in one-dimensional, nonmagnetic systems formed by molecular wires embedded in a zeolite host crystal. This ultrahigh MR effect is ascribed to spin blockade in one-dimensional electron transport. Its generic nature offers very good perspectives to exploit the effect in a wide range of low-dimensional systems.

Electroluminescent device with reversible switching between red and green emission

Research on new materials for organic electroluminescence has recently focused strongly on phosphorescent emitters, with the aim of increasing the emission efficiency and stability. Here we report the fabrication of a simple electroluminescent device, based on a semiconducting polymer combined with a phosphorescent complex, that shows fully reversible voltage-dependent switching between green and red light emission. The active material is made of a polyphenylenevinylene (PPV) derivative molecularly doped with a homogeneously dispersed dinuclear ruthenium complex, which fulfils the dual roles of triplet emitter and electron transfer mediator. At forward bias (+4 V), the excited state of the ruthenium compound is populated, and the characteristic red emission of the complex is observed. On reversing the bias (-4 V), the lowest excited singlet state of the polymer host is populated, with subsequent emission of green light. The mechanism for the formation of the excited state of the PPV derivative involves the ruthenium dinuclear complex in a stepwise electron transfer process that finally leads to efficient charge recombination reaction on the polymer.

Metallocyclodextrins as building blocks in noncovalent assemblies of photoactive units for the study of photoinduced intercomponent processes

Cyclodextrin cups have been employed to build supramolecular systems consisting of metal and organic photoactive/redox-active components; the photoinduced communication between redox-active units assembled in water via noncovalent interactions is established. The functionalization of a beta-cyclodextrin with a terpyridine unit, ttp-beta-CD, is achieved by protection of all but one of the hydroxyl groups by methylation and attachment of the ttp unit on the free primary hydroxyl group. The metalloreceptors [(beta-CD-ttp)Ru(ttp)][PF(6)](2), [(beta-CD-ttp)Ru(tpy)][PF(6)](2), and [Ru(beta-CD-ttp)(2)][PF(6)](2) are synthesized and fully characterized. The [(beta-CD-ttp)Ru(ttp)][PF(6)](2) metalloreceptor exhibits luminescence in water, centered at 640 nm, from the (3)MLCT state with a lifetime of 1.9 ns and a quantum yield of Phi = 4.1 x 10(-)(5). Addition of redox-active quinone guests AQS, AQC, and BQ to an aqueous solution of [(beta-CD-ttp)Ru(ttp)](2+) results in quenching of the luminescence up to 40%, 20%, and 25%, respectively. Measurement of the binding strength indicates that, in saturation conditions, 85% for AQS and 77% for AQC are bound. The luminescence quenching is attributed to an intercomponent electron transfer from the appended ruthenium center to the quinone guest inside the cavity. Control experiments demonstrate no bimolecular quenching at these conditions. A photoactive osmium metalloguest, [Os(biptpy)(tpy)][PF(6)], is designed with a biphenyl hydrophobic tail for insertion in the cyclodextrin cavity. The complex is luminescent at room temperature with an emission band maximum at 730 nm and a lifetime of 116 ns. The osmium(III) species are formed for the study of photoinduced electron transfer upon their assembly with the ruthenium cyclodextrin, [(beta-CD-ttp)Ru(ttp)](2+). Time-resolved spectroscopy studies show a short component of 10 ps, attributed to electron transfer from Ru(II) to Os(III) giving an electron transfer rate 9.5 x 10(9) s(-)(1).