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Santiago de Compostela, Spain

Rodriguez-Velazquez E.,Institute Ortopedia Y Banco Of Tejidos Musculoesqueleticos | Silva M.,Institute Ortopedia Y Banco Of Tejidos Musculoesqueleticos | Taboada P.,Grupo de Fisica de Coloides y Polimeros | Mano J.F.,University of Minho | And 7 more authors.
Biomacromolecules | Year: 2014

It is well accepted that the surface modification of biomaterials can improve their biocompatibility. In this context, techniques like ion etching, plasma-mediated chemical functionalization, electrospinning, and contact microprinting have successfully been employed to promote the cell adhesion and proliferation of chitosan (CH) substrates. However, they prove to be time-consuming, highly dependent on environmental conditions, and/or limited to the use of expensive materials and sophisticated instruments not accessible to standard laboratories, hindering to a high extent their straightforward application. Filling this gap, this paper proposes the superficial cross-linking of CH as a much simpler and accessible means to modify its superficial properties in order to enhance its cellular affinity. CH membranes were prepared by solvent casting followed by a cross-linking step mediated by the chemical vapor deposition (CVD) of glutaraldehyde (GA). The membranes were characterized against non- and solution cross-linked membranes in terms of their mechanical/surface properties and biological performance. Among others, the CVD membranes proved (i) to be more mechanically stable against cell culture and sterilization than membranes cross-linked in solution and (ii) to prompt the adherence and sustained proliferation of healthy cells to levels even superior to commercial tissue culture plates (TCPs). Accordingly, the CVD cross-linking approach was demonstrated to be a simple and cost-effective alternative to the aforementioned conventional methods. Interestingly, this concept can also be applied to other biomaterials as long as GA (or other volatile components alike) can be employed as a cross-linker, making possible the cross-linking reaction at mild experimental conditions, neither requiring sophisticated lab implements nor using any potentially harmful procedure. © 2013 American Chemical Society. Source


Blanco-Loimil M.,Grupo de Fisica de Coloides y Polimeros | Pardo A.,Grupo de Fisica de Coloides y Polimeros | Villar-Alvarez E.,Grupo de Fisica de Coloides y Polimeros | Martinez-Gonzalez R.,Grupo de Fisica de Coloides y Polimeros | And 4 more authors.
RSC Advances | Year: 2016

In this paper, we present a one step, simple, robust and "green" methodology to fabricate high-density ordered arrays of uniform Au nanoparticles (NPs) and Au NP clusters at room temperature over large areas which are suitable for high-performance surface enhanced Raman spectroscopy (SERS). The method is based on the template-guided self-assembly process undergone by polystyrene-b-poly(4-vinylpyridine) copolymer (PS-b-P4VP), in which gold salt is incorporated within the micellar cores (P4VP) and subsequently reduced by HEPES buffer salt in a reduction process at room temperature to give single and clustered NP arrays with hexagonal order. Sizes of P4VP domains are nearly constant (ca. 27 nm) and contain clusters of tiny Au NPs of ca. 4 nm separated 2-3 nm each other. Moreover, the clusters can be transformed either on singly dispersed anisotropic ("nanocrescent-like") or spherical NPs only by their exposure to O2 plasma. Excellent SERS performance with high signal intensities (as evidenced by high enhancement factors >8 × 105) and excellent reproducibility were found for the cluster arrays. This is because of the uniform size and gap distance of the gold clusters in large areas. The anisotropic and isotropic dispersed NP metallic substrates also displayed good sensitivities but with relatively slightly lower enhancement factors (ca. 104 to 105). All these metallic substrates can be achievable without the use of any expensive equipment or clean room processing enabling the potential obtention of low-cost and high-throughput production of chips for (bio)sensing applications. © 2016 The Royal Society of Chemistry. Source


Cambon A.,Grupo de Fisica de Coloides y Polimeros | Figueroa-Ochoa E.,University of Guadalajara | Juarez J.,University of Sonora | Villar-Alvarez E.,Grupo de Fisica de Coloides y Polimeros | And 5 more authors.
Journal of Physical Chemistry B | Year: 2014

Amphiphilic block copolymers have emerged during last years as a fascinating substrate material to develop micellar nanocontainers able to solubilize, protect, transport, and release under external or internal stimuli different classes of cargos to diseased cells or tissues. However, this class of materials can also induce biologically relevant actions, which complement the therapeutic activity of their cargo molecules through their mutual interactions with biologically relevant entities (cellular membranes, proteins, organelles...); these interactions at the same time, are regulated by the nature, conformation, and state of the copolymeric chains. For these reasons, in this paper we investigated the self-assembly process and physico-chemcial properties of two reverse triblock poly(butylene oxide)-poly(ethylene oxide)-poly(butylene oxide) block copolymers, BO14EO 378BO14 and BO21EO385BO 21, which have been recently found to be very useful as drug delivery nanovehicles and biological response modifiers under certain conditions (A. Cambón et al. Int. J. Pharm. 2013, 445, 47-57) in order to obtain a clear picture of the solution behavior of this class or block copolymers and to understand their biological activity. These block copolymers are characterized by possessing long BO blocks and extremely lengthy central EO ones, which provide them with a rich rheological behavior characterized by the formation of flowerlike micelles with sizes ranging from 20 to 40 nm in aqueous solution and the presence of intermicellar bridging even at low copolymers concentrations as denoted by atomic force microscopy. Bridging is also clearly observed by analyzing the rheological response of these block copolymers both storage and loss moduli upon changes on time, temperature, and or concentration. Strikingly, the relatively wide Poisson distribution of the polymeric chains make the present copolymers behave rather distinctly to conventional associative thickeners. The observed rich rheological behavior and their tunability also make these copolymers promising materials to configure drug gelling depots. © 2014 American Chemical Society. Source


Goy-Lopez S.,Grupo de Fisica de Coloides y Polimeros | Taboada P.,Grupo de Fisica de Coloides y Polimeros | Cambon A.,Grupo de Fisica de Coloides y Polimeros | Juarez J.,Grupo de Fisica de Coloides y Polimeros | And 3 more authors.
Journal of Physical Chemistry B | Year: 2010

In the present work, the formation and stabilization of gold nanoparticles in a one-pot water-based synthesis has been achieved in the presence of a four-arm, star-shaped polyoxyethyelene - polyoxypropylene (PEO - PPO) block copolymer, Tetronic T904, which acts as both reductant and stabilizer. The influence of several parameters such as copolymer and gold salt concentration, reaction temperature, and solution pH on both the size and shape of the resulting nanocrystals has been established. Low copolymer/gold salt molar ratios favor the formation of either triangular or hexagonal planar nanostructures due to a low reduction rate which turns the reaction into kinetic control. As the molar ratio increases, reduction becomes faster with the subsequent increase in the number of crystal seeds and, thus, the decrease in particle size. In addition, there is an increase in the reduction rate which causes the reduction reaction to be governed by thermodynamics, and consequently, spherical geometries are favored. A particle spherical shape can also be promoted as a consequence of the accumulation of block copolymer molecules on different crystallographic planes, homogenizing the metal surface structure and disabling the growth in different crystallographic directions. The same behavior was observed when the reaction temperature was raised. The size and shape of gold nanoparticles could also be controlled by varying the pH of the medium. As the pH becomes more acidic, protons prevent the oxyethylene part of the copolymer from the reduction of metal ions, and consequently, the number of nuclei decreases. This explains the overall increase in the particle size and the change in shape when the synthesis is carried out in acid medium. Finally, comparison with nanoparticles obtained in the presence of a structurally related linear block copolymer Pluronic P105, with a similar number of EO and PO units as T904, denoted an important incidence of the arrangement of PEO and PPO blocks on the reduction reaction rate and the size and shape of the resulting nanoparticles. © 2010 American Chemical Society. Source


Cambon A.,Grupo de Fisica de Coloides y Polimeros | Figueroa-Ochoa E.,University of Guadalajara | Blanco M.,Grupo de Fisica de Coloides y Polimeros | Barbosa S.,Grupo de Fisica de Coloides y Polimeros | And 3 more authors.
RSC Advances | Year: 2014

Triblock polyethyelene oxide-polybutylene oxide-based block copolymers overcome some of the synthetic drawbacks of commercially available Pluronic block copolymers as well as providing a more hydrophobic environment to solubilise poorly aqueous-soluble compounds. These facts can be exploited to use this class of copolymers as efficient drug delivery nanocarriers (A. Cambón et al., Int. J. Pharm., 2013, 445, 47-57), and their interactions with biologically relevant entities and biological performance should be regulated by the nature, conformation and state of the copolymeric chains. For this reason, in this work we investigated the self-assembly process of two of these reverse triblock poly(butylene oxide)-poly(ethylene oxide)-poly(butylene oxide) block copolymers, BO8EO90BO8 and BO20EO411BO20, to obtain a clear picture of their self-assembly behaviour in order to correlate it with their biological performance. As a consequence of their particular structure, BO20EO411BO20 possesses a rich rheological behavior characterized by the formation of flower-like micelles (ca. 10 to 30 nm in size) and intermicellar bridging at low copolymer concentrations, as shown by atomic force microscopy and rheology data. Conversely, BO8EO90BO8 displays a behaviour more similar to that observed for diblock EOmBOm and direct triblock EOmBOnEOn copolymers, with single non-associated micelles at low concentrations, and a flow behaviour typical of mesoscopic ordered cubic structures. Strikingly, the relatively wide Poisson distribution of the copolymeric chains makes the present copolymers behave also rather distinctly to conventional associative thickeners. © The Royal Society of Chemistry 2014. Source

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