Nitrogen-neighboured single cobalt sites enable heterogeneous oxidase-type catalysis

Development of biomimetic catalytic systems that can imitate or even surpass natural enzymes remains an ongoing challenge 1–3. This is particularly true in the context of accessing non-natural reactions by bioinspired approaches, which offer intriguing possibilities for benign and affordable chemical synthesis 4. Exploiting the untapped potential of inorganic solids by translating complex knowledge in (bio)molecular-based systems may constitute a potentially useful strategy for such purpose 5, but efforts to capitalize on the minimum catalytic unit of a versatile solid matrix have been largely unsuccessful. Here, we show how an all-inorganic biomimetic system bearing robust nitrogen-neighboured single cobalt site/pyridinic-N site (Co-N4/Py-N) pairs can act cooperatively as an oxidase mimic, which renders an engaged coupling of oxygen (O2) reduction with synthetically beneficial chemical transformations. By developing this broadly applicable platform, the scalable synthesis of greater than 100 industrially and pharmaceutically appealing O-silylated compounds via the unprecedented aerobic oxidation of hydrosilane under ambient conditions is demonstrated. Moreover, this heterogeneous oxidase mimic also offers potential for expanding the catalytic scope of enzymatic synthesis. We anticipate that the strategy demonstrated here will pave a new avenue for understanding the underlying nature of redox enzymes and open up a new class of material systems for artificial biomimetics.

Impact of Magneto-optical Properties Depending on the Orientation in the Plane of Cobalt Ferrite Locked in a Silica Matrix

In this work, we discuss the magneto-optical properties according to the orientation of 15nm-sized cobalt ferrite blocked in a silica matrix in comparison to the study done on 20nm-sized cobalt ferrite. This measurement shows that it is possible to increase the remanence of the Faraday effect by creating a magnetic orientation in the solid matrix, which is interesting for the production of self-polarized components. In addition, this remanence is greater for 15 nm than for 20 nm.A gelation field applied perpendicular to the plane of the layer therefore produces a preferential orientation of the magnetic moments in the direction of the field applied during the measurement.

PHOTOLUMINESCENCE OF NANOCRYSTALLINE CdTe, INTRODUCED INTO POROUS SILICON

A method of colloidal synthesis of monodisperse nanocrystals (NC) with high stability, narrow bands of photoluminescence (PL) and high quantum yield has been developed. The process of colloidal synthesis took place at room temperature and for the passivation of NC used a variety of surfactants. The surface of NC CdTe was modified by introducing them into a matrix, organic or crystalline. In our case, the matrix was porous Silicon (PS), that is a composite structure was formed on the basis of the matrix and NC semiconductor. Nanocomposite structures of PS – NC CdTe were obtained by introducing colloidal solutions of NC CdTe into the solid matrix of PS and subsequent processing at a certain temperature regime. The photoluminescent properties of a composite system in which the matrix is microcrystalline PS and the second component is NC CdTe deposited from a colloidal solution of NC CdTe have been studied. The peculiarity of this system is that both components have PL of different intensities.The large difference in PL intensities and different positions of the radiation bands allowed, comparing the PL spectra of the colloidal solution of NC CdTe, PS and NC CdTe – PS at different stages of introduction of CdTe nanoparticles into the porous Silicon surface, to identify the interaction and mutual influence of the two constituent materials. The main disadvantages of the method are its relative novelty, which leads to the need for empirical selection of some parameters of the synthesis. The planned change of properties of PS and colloidal solutions of NC CdTe by variation of technological methods of synthesis and processing methods will allow to control the physical properties of this composite system and use it to develop new principles of design and creation of new generation sensor devices.

Lipid Nanocarriers-Loaded Nanocomposite as a Suitable Platform to Release Antibacterial and Antioxidant Agents for Immediate Dental Implant Placement Restorative Treatment

Immediate implant placement is a single-stage restorative approach for missing teeth widely used to overcome the ridge remodeling process occurring after dental extractions. The success of this procedure relies on opportune osseointegration in the surrounding tissues. To support this process, a multifunctional nanocomposite, to be applied in the fresh post-extraction socket, was here designed, prepared, and characterized. This formulation consists of quercetin (QRC)-loaded nanostructured lipid carriers (NLCs) entrapped in a chitosan-based solid matrix containing ciprofloxacin (CPX). QRC-NLCs were prepared by homogenization followed by high-frequency sonication, and thereafter this dispersion was trapped in a chitosan-based CPX-loaded gel, obtaining the nanocomposite powder (BioQ-CPX) by lyophilization. BioQ-CPX displayed desirable properties such as high porosity (94.1 ± 0.5%), drug amounts (2.1% QRC and 3.5% CPX). and low swelling index (100%). Moreover, the mechanism of drug release from BioQ-CPX and their ability to be accumulated in the target tissue were in vitro and ex vivo elucidated, also by applying mathematical models. When trapped into the nanocomposite, QRC stressed under UV light exposure (50 W) was shown to maintain its antioxidant power, and CPX and QRC under natural light were stable over nine months. Finally, both the measured antioxidant power and the antimicrobial and antibiofilm properties on Staphylococcus aureus demonstrated that BioQ-CPX could be a promising platform to support the single-stage dental restorative treatment.

A dilatant, two-layer debris flow model validated by flow density measurements at the Swiss illgraben test site

We propose a dilatant, two-layer debris flow model validated by full-scale density/saturation measurements obtained from the Swiss Illgraben test site. Like many existing models, we suppose the debris flow consists of a matrix of solid particles (rocks and boulders) that is surrounded by muddy fluid. However, we split the muddy fluid into two fractions. One part, the inter-granular fluid, is bonded to the solid matrix and fills the void space between the solid particles. The combination of solid material and inter-granular fluid forms the first layer of the debris flow. The second part of the muddy fluid is not bonded to the solid matrix and can move independently from the first layer. This free fluid forms the second layer of the debris flow. During flow the rocky particulate material is sheared which induces dilatant motions that change the location of the center-of-mass of the solid. The degree of solid shearing, as well as the amount of muddy fluid and of solid particles, leads to different flow compositions including debris flow fronts consisting of predominantly solid material, or watery debris flow tails. De-watering and the formation of muddy fluid washes can occur when the solid material deposits in the runout zone. After validating the model on two theoretical case studies, we show that the proposed model is able to capture the streamwise evolution of debris flow density in time and space for real debris flow events.

Delivery and Diffusion of Retinal in Dermis and Epidermis Through The Combination of Prodrug Nanoparticles and Detachable Dissolvable Microneedles

To minimize fast chemical degradation of retinal, we convert this aldehyde into proretinal nanoparticles (PRNs) by forming retinylidene moieties on chitosan and allowing the grafted polymers to assemble into nanoparticles, and then load the obtained PRNs into detachable microneedles made of 1:1 (by weight) hyaluronic acid/maltose. An embedment of the PRNs in the solid matrix of microneedles helps improving chemical stability of the grafted retinal; the loaded device can be kept at 25 °C for three months (longest time experimented) with less than 30% degradation of the retinylidene moieties. The presence PRNs in the hyaluronic acid-maltose matrix also help improving mechanical strength of the needles. Administration of PRN-loaded detachable microneedles on fresh porcine ear skin results in complete deposition of an array of microneedles in the skin tissue at the dept that spans both epidermis and dermis, as observed by stereomicroscopic and confocal fluorescence microscopic analyses of the cross-sectioned tissue pieces. Obvious diffusion of the PRNs from the originally embedded site of the needles in the skin tissue to the nearby location can be observed, and even distribution in the tissue is reached at 4 h post administration. Rats administered with single dose of PRN-loaded microneedles show significant increased epidermal thickness as compared to rats administered with unloaded microneedles. Both PRN-loaded microneedles and unloaded microneedles produce no skin irritation in rats.

Resolving the Near-Infrared Spectrum of Articular Cartilage

Objective Spectroscopic techniques, such as near-infrared (NIR) spectroscopy, are gaining significant research interest for characterizing connective tissues, particularly articular cartilage, because there is still a largely unmet need for rapid, accurate and objective methods for assessing tissue integrity in real-time during arthroscopic surgery. This study aims to identify the NIR spectral range that is optimal for characterizing cartilage integrity by ( a) identifying the contribution of its major constituents (collagen and proteoglycans) to its overall spectrum using proxy constituent models and ( b) determining constituent-specific spectral contributions that can be used for assessment of cartilage in its physiological state. Design The NIR spectra of cartilage matrix constituent models were measured and compared with specific molecular components of organic compounds in the NIR spectral range in order to identify their bands and molecular assignments. To verify the identified bands, spectra of the model compounds were compared with those of native cartilage. Since water obscures some bands in the NIR range, spectral measurements of the native cartilage were conducted under conditions of decreasing water content to amplify features of the solid matrix components. The identified spectral bands were then compared and examined in the resulting spectra of the intact cartilage samples. Results As water was progressively eliminated from cartilage, the specific contribution of the different matrix components was observed to correspond with those identified from the proxy cartilage component models. Conclusion Spectral peaks in the regions 5500 to 6250 cm−1 and 8100 to 8600 cm−1 were identified to be effective for characterizing cartilage proteoglycan and collagen contents, respectively.

Effect of Local Thermal Non-Equilibrium On the Stability of the Flow in a Vertical Channel Filled with Nanofluid Saturated Porous Medium

The stability of nanofluid flow in a vertical channel packed with a porous medium is examined for the local thermal non-equilibrium state of the fluid, particle and solid-matrix phases. The effects of Brownian motion along with thermophoresis are incorporated in the nanofluid model. The Darcy-Brinkman model for the flow in a porous medium and three-field model, each representing the fluid, particle and solid-matrix phases separately, for temperature is used. A normal mode analysis is used to obtain the eigenvalue problem for the perturbed state, which is then solved using the Chebyshev spectral collocation technique. The critical Rayleigh number and corresponding wavenumber are presented graphically for the effect of different local thermal non-equilibrium parameters. It is noticed that the influence of LTNE parameters on the convective instability is significant.