Label-free mapping of microstructural organisation in self-aligning cellular collagen hydrogels using image correlation spectroscopy

Hydrogels have emerged as promising biomaterials for regenerative medicine. Despite major advances, tissue engineers have faced challenges in studying the complex dynamics of cellmediated hydrogel remodelling. Second harmonic generation (SHG) microscopy has been a pivotal tool for non-invasive visualization of collagen type I hydrogels. By taking into account the typical polarization SHG effect, we recently proposed an alternative image correlation spectroscopy (ICS) model to quantify characteristics of randomly oriented collagen fibrils. However, fibril alignment is an important feature in many tissues that needs to be monitored for effective assembly of anisotropic tissue constructs. Here we extended our previous approach to include the orientation distribution of fibrils in cellular hydrogels and show the power of this model in two biologically relevant applications. Using a collagen hydrogel contraction assay, we were able to capture cell-induced hydrogel modifications at the microscopic scale and link these to changes in overall gel dimensions over time. After 24 h, the collagen density was about 3 times higher than the initial density, which was of the same order as the decrease in hydrogel area. We also showed that the orientation parameters recovered from our automated ICS model match values obtained from manual measurements. Furthermore, regions axial to cellular processes aligned at least 1.5 times faster compared with adjacent zones. Being able to capture minor temporal and spatial changes in hydrogel density and collagen fibril orientation, we demonstrated the sensitivity of this extended ICS model to deconstruct a complex environment and support its potential for tissue engineering research

Improving the mechanical stability of zirconium-based metal-organic frameworks by incorporation of acidic modulators

Acidic modulating ligands have been shown to stabilize UiO metal-organic frameworks against structural collapse under ball-milling.T.D.B. would like to thank Trinity Hall for funding, along with Professor Anthony K. Cheetham for use of lab facilities. D.D.V. is grateful to IWT (MOF Shape), KU Leuven for support in the Metusalem grant CASAS and IAP 7/05 Functional Supramolecular Systems. I.S. and B.B. thank Research Foundation – Flanders (FWO) for Ph.D. fellowships.This is the accepted manuscript. The final published version is available from RSC at http://pubs.rsc.org/en/Content/ArticleLanding/2015/TA/c4ta06396a#!divAbstract

Towards metal-organic framework based field effect chemical sensors: UiO-66-NH2 for nerve agent detection

We present a highly sensitive gas detection approach for the infamous 'nerve agent' group of alkyl phosphonate compounds. Signal transduction is achieved by monitoring the work function shift of metal-organic framework UiO-66-NH2 coated electrodes upon exposure to ppb-level concentrations of a target simulant. Using the Kelvin probe technique, we demonstrate the potential of electrically insulating MOFs for integration in field effect devices such as ChemFETs: a three orders of magnitude improvement over previous work function-based detection of nerve agent simulants. Moreover, the signal is fully reversible both in dry and humid conditions, down to low ppb concentrations. Comprehensive investigation of the interactions that lead towards this high sensitivity points towards a series of confined interactions between the analyte and the pore interior of UiO-66-NH2

Evaluatie en waardering van de archeologische sites Rooiveld-Papenvijvers(Oostkamp, provincie West-Vlaanderen)

Dit rapport beschrijft de resultaten van het waarderend onderzoek op de archeologische sites Rooiveld-Papenvijvers in Oostkamp (West-Vlaanderen). De oudste sporen van menselijke activiteit in dit gebied gaan terug tot het mesolithicum. De bewoning tijdens het neolithicum is goed gedocumenteerd. Naast de opgegraven nederzetting te Waardamme Vijvers, leverde het proefsleuvenonderzoek te Papenvijvers een finaal-neolithische site (3de millennium cal BC). Verder leverden de beperkte prospecties op verschillende plaatsen, waaronder Oostkamp Nieuwenhove en Hertsberge Papevijvers, lithische artefacten op die naar alle waarschijnlijkheid tot een niet nader te bepalen fase van het neolithicum behoren. Deze situatie is vrij uniek voor Vlaanderen. Neolithische bewoning in de zandige delen van Vlaanderen ontbrak tot nog toe vrijwel, met uitzondering van enkele graven van de Klokbekercultuur. De opgraving te Waardamme Vijvers is bijzonder vanwege de ontdekking van de eerste en vooralsnog enige huisplattegrond uit het neolithicum in Vlaanderen. Sporen uit de bronstijd zijn dankzij de luchtfotografie heel talrijk in het gebied. Het desktop onderzoek leverde in totaal een negental cirkelvormige structuren op die naar alle waarschijnlijkheid mogen geïnterpreteerd worden als resten van grafheuvels uit de vroege en midden-bronstijd. Het is ook duidelijk dat de regio in de bronstijd bewoond was, o.a. door de opgraving op de site Waardamme Vijvers. Voor de ijzertijd is de situatie vermoedelijk gelijklopend. De enige nederzetting die uit deze periode werd aangetroffen komt eveneens uit de opgraving in Waardamme Vijvers. Voor de Romeinse periode beschikken we slechts over de sporen van een grafveld op Waardamme Vijvers en keramiekvondsten. Latere periodes zijn alleen via cartografische bronnen gedocumenteerd. Het rapport eindigt met aanbevelingen voor verder onderzoek en beheer van dit gebied

A new method to position and functionalize metal-organic framework crystals

With controlled nanometre-sized pores and surface areas of thousands of square metres per gram, metal-organic frameworks (MOFs) may have an integral role in future catalysis, filtration and sensing applications. In general, for MOF-based device fabrication, well-organized or patterned MOF growth is required, and thus conventional synthetic routes are not suitable. Moreover, to expand their applicability, the introduction of additional functionality into MOFs is desirable. Here, we explore the use of nanostructured poly-hydrate zinc phosphate (α-hopeite) microparticles as nucleation seeds for MOFs that simultaneously address all these issues. Affording spatial control of nucleation and significantly accelerating MOF growth, these α-hopeite microparticles are found to act as nucleation agents both in solution and on solid surfaces. In addition, the introduction of functional nanoparticles (metallic, semiconducting, polymeric) into these nucleating seeds translates directly to the fabrication of functional MOFs suitable for molecular size-selective applications

Placental-fetal distribution of carbon particles in a pregnant rabbit model after repeated exposure to diluted diesel engine exhaust

BACKGROUND: Airborne pollution particles have been shown to translocate from the mother's lung to the fetal circulation, but their distribution and internal placental-fetal tissue load remain poorly explored. Here, we investigated the placental-fetal load and distribution of diesel engine exhaust particles during gestation under controlled exposure conditions using a pregnant rabbit model. Pregnant dams were exposed by nose-only inhalation to either clean air (controls) or diluted and filtered diesel engine exhaust (1 mg/m 3) for 2 h/day, 5 days/week, from gestational day (GD) 3 to GD27. At GD28, placental and fetal tissues (i.e., heart, kidney, liver, lung and gonads) were collected for biometry and to study the presence of carbon particles (CPs) using white light generation by carbonaceous particles under femtosecond pulsed laser illumination. RESULTS: CPs were detected in the placenta, fetal heart, kidney, liver, lung and gonads in significantly higher amounts in exposed rabbits compared with controls. Through multiple factor analysis, we were able to discriminate the diesel engine exposed pregnant rabbits from the control group taking all variables related to fetoplacental biometry and CP load into consideration. Our findings did not reveal a sex effect, yet a potential interaction effect might be present between exposure and fetal sex. CONCLUSIONS: The results confirmed the translocation of maternally inhaled CPs from diesel engine exhaust to the placenta which could be detected in fetal organs during late-stage pregnancy. The exposed can be clearly discriminated from the control group with respect to fetoplacental biometry and CP load. The differential particle load in the fetal organs may contribute to the effects on fetoplacental biometry and to the malprogramming of the fetal phenotype with long-term effects later in life

Two-photon image-scanning microscopy with SPAD array and blind image reconstruction

Two-photon excitation (2PE) laser scanning microscopy is the imaging modality of choice when one desires to work with thick biological samples. However, its spatial resolution is poor, below confocal laser scanning microscopy. Here, we propose a straightforward implementation of 2PE image scanning microscopy (2PE-ISM) that, by leveraging our recently introduced single-photon avalanche diode (SPAD) array detector and a novel blind image reconstruction method, is shown to enhance the effective resolution, as well as the overall image quality of 2PE microscopy. With our adaptive pixel reassignment procedure similar to 1.6 times resolution increase is maintained deep into thick semi-transparent samples. The integration of Fourier ring correlation based semi-blind deconvolution is shown to further enhance the effective resolution by a factor of similar to 2 - and automatic background correction is shown to boost the image quality especially in noisy images. Most importantly, our 2PE-ISM implementation requires no calibration measurements or other input from the user, which is an important aspect in terms of day-to-day usability of the technique. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen

Chemical diversity in a metal-organic framework revealed by fluorescence lifetime imaging

The presence and variation of chemical functionality and defects in crystalline materials, such as metal–organic frameworks (MOFs), have tremendous impact on their properties. Finding a means of identifying and characterizing this chemical diversity is an important ongoing challenge. This task is complicated by the characteristic problem of bulk measurements only giving a statistical average over an entire sample, leaving uncharacterized any diversity that might exist between crystallites or even within individual crystals. Here we show that by using fluorescence imaging and lifetime analysis, both the spatial arrangement of functionalities and the level of defects within a multivariable MOF crystal can be determined for the bulk as well as for the individual constituent crystals. We apply these methods to UiO-67, to study the incorporation of functional groups and their consequences on the structural features. We believe that the potential of the techniques presented here in uncovering chemical diversity in what is generally assumed to be homogeneous systems can provide a new level of understanding of materials properties

Evolution of form in metal-organic frameworks

Self-assembly has proven to be a widely successful synthetic strategy for functional materials, especially for metal-organic materials (MOMs), an emerging class of porous materials consisting of metal-organic frameworks (MOFs) and metal-organic polyhedra (MOPs). However, there are areas in MOM synthesis in which such self-assembly has not been fully utilized, such as controlling the interior of MOM crystals. Here we demonstrate sequential self-assembly strategy for synthesizing various forms of MOM crystals, including double-shell hollow MOMs, based on single-crystal to single-crystal transformation from MOP to MOF. Moreover, this synthetic strategy also yields other forms, such as solid, core-shell, double and triple matryoshka, and single-shell hollow MOMs, thereby exhibiting form evolution in MOMs. We anticipate that this synthetic approach might open up a new direction for the development of diverse forms in MOMs, with highly advanced areas such as sequential drug delivery/release and heterogeneous cascade catalysis targeted in the foreseeable future.ope