Edible bio-based nanostructures: delivery, absorption and potential toxicity

The development of bio-based nanostructures as nanocarriers of bioactive compounds to specific body sites has been presented as a hot topic in food, pharmaceutical and nanotechnology fields. Food and pharmaceutical industries seek to explore the huge potential of these nanostructures, once they can be entirely composed of biocompatible and non-toxic materials. At the same time, they allow the incorporation of lipophilic and hydrophilic bioactive compounds protecting them against degradation, maintaining its active and functional performance. Nevertheless, the physicochemical properties of such structures (e.g., size and charge) could change significantly their behavior in the gastrointestinal (GI) tract. The main challenges in the development of these nanostructures are the proper characterization and understanding of the processes occurring at their surface, when in contact with living systems. This is crucial to understand their delivery and absorption behavior as well as to recognize potential toxicological effects. This review will provide an insight into the recent innovations and challenges in the field of delivery via GI tract using bio-based nanostructures. Also, an overview of the approaches followed to ensure an effective deliver (e.g., avoiding physiological barriers) and to enhance stability and absorptive intestinal uptake of bioactive compounds will be provided. Information about nanostructures potential toxicity and a concise description of the in vitro and in vivo toxicity studies will also be given.Joana T. Martins, Oscar L. Ramos, Ana C. Pinheiro, Ana I. Bourbon, Helder D. Silva and Miguel A. Cerqueira (SFRH/BPD/89992/2012, SFRH/BPD/80766/2011, SFRH/BPD/101181/2014, SFRH/BD/73178/2010, SFRH/BD/81288/2011, and SFRH/BPD/72753/2010, respectively) are the recipients of a fellowship from the Fundacao para a Ciencia e Tecnologia (FCT, POPH-QREN and FSE, Portugal). The authors thank the FCT Strategic Project PEst-OE/EQB/LA0023/2013 and the project "BioInd-Biotechnology and Bioengineering for improved Industrial and Agro-Food processes," REF.NORTE-07-0124-FEDER-000028, co-funded by the Programa Operacional Regional do Norte (ON.2-O Novo Norte), QREN, FEDER. We also thank to the European Commission: BIOCAPS (316265, FP7/REGPOT-2012-2013.1) and Xunta de Galicia: Agrupamento INBIOMED (2012/273) and Grupo con potencial de crecimiento. The support of EU Cost Action FA1001 is gratefully acknowledged

The free-energy landscape of a mechanically bistable DNA origami

Molecular simulations using coarse-grained models allow the structure, dynamics and mechanics of DNA origamis to be comprehensively characterized. Here, we focus on the free-energy landscape of a jointed DNA origami that has been designed to exhibit two mechanically stable states and for which a bistable landscape has been inferred from ensembles of structures visualized by electron microscopy. Surprisingly, simulations using the oxDNA model predict that the defect-free origami has a single free-energy minimum. The expected second state is not stable because the hinge joints do not simply allow free angular motion but instead lead to increasing free-energetic penalties as the joint angles relevant to the second state are approached. This raises interesting questions about the cause of this difference between simulations and experiment, such as how assembly defects might affect the ensemble of structures observed experimentally

Synthesis, structural characterization and solution dynamics of osmium-rhodium mixed-metal cluster [Os4Rh(µ-H)4(CO)13(η2-NC5H4C2H2)]

Reaction of [Os3Rh(μ-H)3(CO)12] 1 with an excess amount of 2-vinylpyridine in refluxing CHCl3 afforded a new cluster, [Os4Rh(μ-H)4(CO)13(η2-NC5H4C2H2)] 2, in moderate yield. A pair of isomers 2a and 2b, which differ in configuration of the metallated vinylpyridine exist in the solution of 2. Through the variable temperature EXSY experiment, the activation barrier (ΔG≠) for the isomerisation of 2 was determined to be 89.8kJ mol-1

Repeated use of two Chlorella species, C-vulgaris and WW1 for cyclic nickel biosorption

Two living Chlorella species were used to remove nickel from solution containing 30 mug Ni ml(-1) in 10 successive cycles. The present study also examined the continued viability of these two algal species after repeated exposure to nickel. The two species of Chlorella were Chlorella vulgaris (commercially available) and WW1 (indigenous species isolated from domestic sewage and was tentatively identified as Chlorella miniata). The nickel removal percentage of WW1 cells was maintained at around 85\% in the first five cycles, then declined slightly from the fifth cycle onwards, and finally achieved around 70\% removal at the end of the 10th cycle. On the contrary, the removal efficiency of C. vulgaris declined from 50 to 30\% during the 10 cycles of nickel bisorption. At the end of these 10 successive cycles, WW1 accumulated a substantial amount of Ni2+ (the cumulative cellular Ni concentration was 0.92\% dry w.), while the value was only 0.17\% in the case of C. vulgaris. These results suggest that the local isolate, WW1, had more consistent and satisfactory ability fdr removing Ni than the commercial C. vulgaris. Both algal species were still capable of dividing after each nickel treatment cycle, suggesting that the cells were not killed even when significant amounts of nickel were adsorbed/absorbed. However, Ni exposure adversely affected the physiological activity of algal cells as reflected by the decline in division rate and chlorophyll-a activity in both species. Such negative effects became more obvious as the number of cyclic treatments was increased. Nevertheless, WW1 cells appeared to recover from nickel treatment when re-cultivated in commercial medium for 2 weeks. (C) 2001 Elsevier Science Ltd. All rights reserved

Nickel biosorption by two chlorella species, C-Vulgaris (a commercial species) and C-Miniata (a local isolate)

The present study compared the efficiency of two unicellular green algae, Chlorella vulgaris (a commercial species from Carolina Biological Supplies Company) and WW1 (an indigenous species isolated from a local sewage treatment works, tentatively identified as Chlorella miniata) in removing Ni2+ from nickel solutions with concentration ranges similar to that in electroplating effluents. The Ni2+ removal efficiency of C. vulgaris (around 33-41\%) was significantly lower than that of WW1 (more than 99\%) in nickel solutions from 10 to 40 mu g ml(-1). The maximum Ni2+ uptake by C. vulgaris and WW1 under the present batch experiment was 641.76 and 1367.62 mu g g(-1), respectively. According to Langmuir adsorption isotherms the nickel adsorption capacity of WW1 (2985.07 mu g g(-1)) was two times greater than that of C. vulgaris (1282.05 mu g g(-1)). These results demonstrated that WW1 was a more powerful Ni2+ biosorbent than C. vulgaris. In both species, most Ni2+ in solution was sequestered by the algal cells within the first few minutes of treatment. The cellular Ni2+ concentration increased with the concentrations of nickel in solution. After treating Ni-containing wastewater for 24 h, both species were still capable of cell division, but the growth rate was reduced in proportion to the concentrations of nickel in the wastewaters. (C) 2000 Elsevier Science Ltd. All rights reserved

Synthesis and structural characterization of a series of high-hydride content osmium-rhodium carbonyl complexes by the hydrogenation of arene-coordinated clusters

The reaction of [Os3Rh(μ-H)3(CO)12] with an excess amount of 4-vinylphenol (as hydride acceptor) in refluxing m-xylene, chlorobenzene or benzene yielded the three new clusters [Os 5Rh2(μ-CO){η6-C6H 4(CH3)2}(CO)16]1, [Os 5Rh2(μ-CO)(η6-C6H 5Cl)(CO)16] 2 and [Os5Rh2(μ-CO) (η6-C5H6)(CO)16] 3. The treatment of [Os3Rh(μ-H)3(CO)12] in refluxing toluene with an excess amount of 4-vinylphenol afforded a new complex, [Os4Rh(μ-H)(η6-C6H5CH 3)(CO)12] 4, which was isolated as a brown complex in 20% yield together with two known compounds, [Os5́Rh2(η 6-C6H5CH3)(μ-CO)(CO) 16] in 10% yield and [Os3Rh4(μ3- η11η1·η1·η 1-C6H5CH3) (CO)13] in 5% yield. Complexes 1-4 were fully characterized by IR, 1H NMR spectroscopy, mass spectroscopy, elemental analysis and X-ray crystallography. The molecular structures of compounds 1-3 are isomorphous, and only differ in the arene-derivatives that attach to the same metal core. Their metal cores can be viewed as a monocapped octahedral, in which an osmium atom caps one of the Os-Os-Os triangular faces of the Os4Rh2 metal framework. Complex 4 has a trigonal-bipyramidal metal core with a C6H5Me ligand that is terminally bound to the Rh atom that lies in the trigonal plane of the metal core. The hydrogenation of [Os5Rh2(η6- C6H5CH3)(μ-CO)(CO)16] with [Os3(μ-H)2(CO)10] in chloroform under reflux resulted in two hydrogen-rich compounds: [Os7Rh3(μ-H) 11(CO)23] 5 and [Os5Rh3Cl(μ-H) 8(CO)18] 6, both in moderate yields. The reaction of [Os5Rh2(η6-C6H 5CH3)(μ-CO)(CO)16] with hydrogen in refluxing chloroform yielded a new cluster compound, [Os5Rh(μ-H) 5(CO)18] 7, in 20% yield, together with a known osmium-rhodium cluster, [Os6Rh(μ-H)7(μ-CO)(CO) 18], as a major compound. Clusters 5, 6 and 7 have been fully characterized by both spectroscopic and crystallographic methods. Additionally, a deuterium-exchange experiment was performed on [Os7Rh 3(μ-H)11(CO)23] 5 and [Os5Rh 3Cl(μ-H)8 (CO)18] 6. Both the compounds proved to be able to exchange the H atom with D in the presence of D 2SO4, and the absence of the hydride signal in the 1H NMR spectrum is consistent with this. Therefore, clusters 5 and 6 may serve as appropriate new hydrogen storage models. © The Royal Society of Chemistry 2005.link_to_subscribed_fulltex

The molecular structure of [Os3Rh4(mu(3)-eta(1):eta(1):eta(1)-C6H5CH3)(CO)(13)]: A face-capping bonding mode for arenes in organometallic clusters

Rhodium gets a new flat cap: A novel face-capping mode of toluene on the title {Os₃Rh₄} cluster is observed (see structure; Os blue, Rh green, C gray, O red, H white). The cluster is obtained from the reaction of [Os₃Rh(μ-H)₃(CO)₁₂] with toluene in the presence of an excess amount of 4-vinylphenol under reflux for 2 h. The new cluster has relatively short metal-metal bonds and an electron count of only 92, which is four electrons less than expected

Characterizing the free-energy landscapes of DNA origamis

We show how coarse-grained modelling combined with umbrella sampling using distance-based order parameters can be applied to compute the free-energy landscapes associated with mechanical deformations of large DNA nanostructures. We illustrate this approach for the strong bending of DNA nanotubes and the potentially bistable landscape of twisted DNA origami sheets. The homogeneous bending of the DNA nanotubes is well described by the worm-like chain model; for more extreme bending the nanotubes reversibly buckle with the bending deformations localized at one or two “kinks”. For a twisted one-layer DNA origami, the twist is coupled to the bending of the sheet giving rise to a free-energy landscape that has two nearly-degenerate minima that have opposite curvatures. By contrast, for a two-layer origami, the increased stiffness with respect to bending leads to a landscape with a single free-energy minimum that has a saddle-like geometry. The ability to compute such landscapes is likely to be particularly useful for DNA mechanotechnology and for understanding stress accumulation during the self-assembly of origamis into higher-order structures