73 research outputs found
Unidirectional Neuronal Cell growth and Differentiation on Aligned Polyhydroxyalkanoate Blend Microfibres with Varying Diameters
Polyhydroxyalkanoates (PHAs) are a family of prokaryotic-derived biodegradable and biocompatible natural polymers known to exhibit neuroregenerative properties. In this work, poly(3-hydroxybutyrate), P(3HB) and poly(3-hydroxyoctanoate), P(3HO), have been combined to form blend fibres for directional guidance of neuronal cell growth and differentiation. A 25:75 P(3HO)/P(3HB) blend (PHA blend) was used for the manufacturing of electrospun fibres as resorbable scaffolds to be used as internal guidance lumen structures in nerve conduits. The biocompatibility of these fibres was studied using neuronal and Schwann cells. Highly aligned and uniform fibres with varying diameters were fabricated by controlling electrospinning parameters. The resulting fibre diameters were 2.4 ± 0.3 ”m, 3.7 ± 0.3 ”m and 13.5 ± 2.3 ”m for small, medium and large diameter fibres respectively. The cell response to these electrospun fibres was investigated with respect to growth and differentiation. Cell migration observed on the electrospun fibres showed topographical guidance in accordance with the direction of the fibres. The correlation between fibre diameter and neuronal growth under two conditions; individually and in co-culture with Schwann cells was evaluated. Results obtained from both assays revealed that all PHA blend fibre groups were able to support growth and guide aligned distribution of neuronal cells and there was a direct correlation between the fibre diameter and neuronal growth and differentiation. This work has led to the development of a family of unique biodegradable and highly biocompatible 3D substrates capable of guiding and facilitating the growth, proliferation and differentiation of neuronal cells as internal structures within nerve conduits
Nerve tissue engineering using blends of poly(3-hydroxyalkanoates) for peripheral nerve regeneration
The only types of polyhydroxyalkanoates (PHAs) that have been explored for use in nerve regeneration are poly(3âhydroxybutyrate), P(3HB), and poly(3âhydroxybutyrateâcoâ3âhydroxyhexanoate) (P(3HBâcoâ3HHx)). However, nerve regeneration induced by these PHAs is inferior to that of autologous nerve grafting. The aim of this work was to study novel PHA blends as resorbable biomaterials for the manufacture of nerve guidance conduits. PHA blend films with varying ratios of poly(3âhydroxyoctanoate)/poly(3âhydroxybutyrate) (P(3HO)/P(3HB)) were produced using the solventâcasting method. Neat films of P(3HO) and P(3HB), along with 25:75, 50:50, and 75:25 blend films of P(3HO)/P(3HB), were characterized with respect to chemical, material, and biological properties. On surface analysis, the blends exhibited higher values of roughness compared with the neat films. The differential scanning calorimetry characterization of the blends confirmed that P(3HO) and P(3HB) formed immiscible blends. FTIR and XRD analysis of the blends showed a decrease in crystallinity along with an increase of the proportion of P(3HO) . However, an increase in the stiffness of the blends was observed when the proportion of P(3HB) increased. Although all of the blends were biocompatible with NG108â15 neuronal cells, the 25:75 P(3HO)/P(3HB) blend showed significantly better support for growth and differentiation of these cells. The mechanical properties of PHA blends correspond to the reported properties of peripheral nerves. Therefore, they could serve as base material for the manufacture of nerve guidance conduits
Modulation of neuronal cell affinity of composites scaffolds based on polyhydroxyalkanoates and bioactive glasses
Biocompatibility and neuron regenerating properties of various bioactive glass (BG)/Polyhydroxyalkanoate (PHA) blend composites were assessed in order to study their suitability for peripheral nerve tissue applications, specifically as lumen structures for nerve guidance conduits (NGCs). BG/PHA blend composites were fabricated using Bioactive glassŸ 45S5 (BG1) and BG 1393 (BG2) with the 25:35 poly(3-hydroxyoctanoate/poly3-hydroxybutyrate), 25:75 P(3HO)/P(3HB) blend (PHA blend). Various concentrations of each BG (0.5, 1.0 and 2.5 wt%) were used to determine the effect of BG on neuronal growth and differentiation, in single culture using NG108-15 neuronal cells and in a co-culture along with RN22 Schwann cells. NG108-15 cells exhibited good growth and differentiation on all the PHA blend composites showing that both BGs have good biocompatibility at 0.5, 1.0 and 2.5 wt% within the PHA blend. The Young's modulus values displayed by all the PHA blend/BG composites ranged from 385.6 MPa to 1792.6 MPa, which are able to provide the required support and protective effect for regeneration of peripheral nerves. More specifically, the tensile strength obtained in the PHA blend/BG1 (1.0 wt%) (10.0 ± 0.6 MPa) was found to be similar to that of rabbit peroneal nerve. This composite also exhibited the best biological performance in supporting growth and neuronal differentiation among all the substrates. The neurite extension on this composite was found to be remarkable with the neurites forming a complex connection network
Characterization of modular deposits for urban drainage networks using CFD techniques
[EN] The growing urban development of population centers in much of the world joined with the significant effects of
climate change are causing an increasingly important and recurring increase of the damage caused by flooding. Much
of the drainage networks of cities were designed for precipitation characteristics and return periods that have proved
to be insufficient with the lapse of time. Therefore, solutions need to be addressed both to reduce runoff generated
flows as to control circulating ones through the rainwater drainage networks.
All these flow control rain technologies are commonly known as SUDS (Sustainable Urban Drainage), term that
encompasses a multitude of solutions to control runoff although many of them require significant costs that make
them practically unviable. Therefore, not only should focus on reducing runoff input to the network but also in the
flow control techniques development. The idea is to design strategies to reduce flow rain peaks and maximize the
capacity of existing networks.
The use of detention and storm tanks for flood control is a solution increasingly used as an alternative one to control
increased rainfall caused by climate change [1].
Nature and execution of storm tanks can be very diverse, from conventional way based on concrete structures to
the most innovative ones in which modular structures are employed to improve the construction speed if many modular
units are required at the same time that minimizing urban supply disruption is achieved.
Currently, a wide range of modular structures exists on the market with both, different geometries and sizes. In this
study the Aquacell brand supplied by Mexichem-PAVCO in Colombia shown in Fig. 1 has been chosen for the
development of this study.S849218
The fourth-order single-switch improved super-boost converter with reduced input current ripple
This paper introduces a new single switch DC-DC fourth-order boost converter. The proposed converter is the improved version of an existing converter known as the super-boost converter. The improved super-boost ISP converter achieves a smaller input current ripple than the super-boost converter when the same parameters in passive components are used. Conversely, smaller components can be used to achieve the same input current ripple, which leads to a compact and cheaper design. A comparative evaluation showed a reduction of 37.3% of stored energy in inductors to comply with a required input current ripple in comparison with the super-boost converter for a particular design. Experimental results are provided to corroborate this benefit of the ISB proposed topology
MetodologĂa para la DeterminaciĂłn de la Capacidad de Carga de Visitantes, en las Ăreas Marinas Protegidas de Cuba
Abiotic variability among different aquatic systems of the central Amazon floodplain during drought and flood events
Fluvial lateral environments in RĂo de La Plata basin: effects of hydropower damming and eutrophication
TRY plant trait database â enhanced coverage and open access
Plant traitsâthe morphological, anatomical, physiological, biochemical and phenological characteristics of plantsâdetermine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of traitâbased plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traitsâalmost complete coverage for âplant growth formâ. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and traitâenvironmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives
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