Compact saloplastic membranes of natural polysaccharides for soft tissue engineering

The regeneration of soft biological tissues requires new substitutes that exhibit mechanical properties similar to the native tissue. Herein, thin saloplastic membranes with tunable physical properties are prepared by complexation of chitosan and alginate solutions containing different concentrations of sodium chloride. Polyelectrolyte complexes (PECs) are transferred to flat Petri dishes for compaction into membrane shapes by sedimentation and solvent evaporation. All membranes are resistant to degradation by lysozyme and are stable in solutions with pH values between 1 and 13. Immersing the different membranes in new doping solutions of increasing salt concentrations triggers the typical saloplastic behavior, with a high water absorption and decrease of the rigidity and ultimate tensile strength. The range of such variations is tuned by the sodium chloride amount used in the synthesis: high salt concentrations increase water uptake and tensile moduli, while decreasing the ultimate strength. Cellular assays demonstrate high proliferation rates and viability of L929 fibroblasts seeded onto the most rigid membranes. The results validate the use of saloplastic membranes as soft tissue substitutes for future biomedical applications.Fundação para a Ciencia e Tecnologia (FCT, grants SFRH/BPD/95446/2013, SFRH/BD/101748/2014 and SFRH/BPD/96797/2013), “Fundo Social Europeu“(FSE) and“ Programa Operacional de Potencial Humano“ (POPH

Enzymatic degradation of Polysaccharide-based layer-by-layer structures

The lack of knowledge on the degradation of layer-by-layer structures is one of the causes hindering its translation to preclinical assays. The enzymatic degradation of chitosan/hyaluronic acid films in the form of ultrathin films, freestanding membranes, and microcapsules was studied resorting to hyaluronidase. The reduction of the thickness of ultrathin films was dependent on the hyaluronidase concentration, leading to thickness and topography variations. Freestanding membranes exhibited accelerated weight loss up to 120 h in the presence of the enzyme, achieving complete degradation. Microcapsules with around 5 μm loaded simultaneously with FITC-BSA and hyaluronidase showed that the coencapsulation of such enzyme and protein mixture led to a FITC-BSA release four times higher than in the absence of hyaluronidase. The results suggest that the degradation of LbL devices may be tuned via embedded enzymes, namely, in the controlled release of active agents in biomedical applications.This work was supported by Fundação para a Ciência e Tecnologia (FCT, Postdoctoral Grants SFRH/BPD/95446/ 2013 and SFRH/BPD/96797/2013, and Projects PTDC/ CTM-BIO/1814/2012 and EXPL/CTM-BIO/0646/2013), “Fundo Social Europeu” (FSE), and “Programa Operacional de Potencial Humano” (POPH)

Moldable superhydrophobic surfaces

Moldable superhydrophobic surfaces are produced by freely covering a solid surface with specifically designed microcapsules. Owing to the presence of Fe-particles within the former microcapsules, they can be temporarily fixed on different substrates using a permanent magnet. Such systems are prospective candidates for the fabrication of water/oil repellent surfaces, liquid marbles, or microfluidic channels and as templates for microspheres fabrication.A.M.S.C and S.G.C. acknowledge financial support from Fundação para a Ciência e Tecnologia (FCT) through the grants SFRH/BD/101748/2014 and SFRH/BPD/96797/2013. N.V.D. is grateful for the FCT support through nSTEP project NORTE-07-0124-FEDER-000039.info:eu-repo/semantics/publishedVersio

PH responsiveness of multilayered films and membranes made of polysaccharides

We investigated the pH-dependent properties of multilayered films made of chitosan (CHI) and alginate (ALG) and focused on their postassembly response to different pH environments using a quartz crystal microbalance with dissipation monitoring (QCM-D), swelling studies, ζ potential measurements, and dynamic mechanical analysis (DMA). In an acidic environment, the multilayers presented lower dissipation values and, consequently, higher moduli when compared with the values obtained for the pH used during the assembly (5.5). When the multilayers were exposed to alkaline environments, the opposite behavior occurred. These results were further corroborated by the ability of this multilayered system to exhibit a reversible swellingâ deswelling behavior within the pH range from 3 to 9. The changes in the physicochemical properties of the multilayer system were gradual and different from those of individual solubilized polyelectrolytes. This behavior is related to electrostatic interactions between the ionizable groups combined with hydrogen bonding and hydrophobic interactions. Beyond the pH range of 3â 9, the multilayers were stabilized by genipin cross-linking. The multilayered films also became more rigid while the pH responsiveness conferred by the ionizable moieties of the polyelectrolytes was preserved. This work demonstrates the versatility and feasibility of LbL methodology to generate inherently pH stimulus-responsive nanostructured films. Surface functionalization using pH responsiveness endows several biomedical applications with abilities such as drug delivery, diagnostics, microfluidics, biosensing, and biomimetic implantable membranes.We acknowledge the financial support from the Portuguese Foundation for Science and Technology (FCT) through the doctoral and postdoctoral grants with reference numbers SFRH/BD/81372/2011 (J.M.S.), SFRH/BPD/96797/2013 (S.G.C.), and SFRH/BPD/95446/2013 (R.R.C.). This work was financially supported by the Foundation for Science and Technology (FCT) via Project PTDC/FIS/115048/2009. We also acknowledge the project novel smart and biomimetic materials for innovative regenerative medicine approaches (RL1-ABMR-NORTE-01-0124-FEDER-000016) cofinanced by the North Portugal Regional Operational Programme (ON.2-O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF). C.P. acknowledges the European Commission (FP7) for funding via an ERC grant (GA259370)

Tailored freestanding multilayered membranes based on chitosan and alginate

Engineering metabolically demanding tissues requires the supply of nutrients, oxygen, and removal of metabolic byproducts, as well as adequate mechanical properties. In this work, we propose the development of chitosan (CHIT)/alginate (ALG) freestanding membranes fabricated by layer-by-layer (LbL) assembly. CHIT/ALG membranes were cross-linked with genipin at a concentration of 1 mg· mL−1 or 5 mg·mL−1. Mass transport properties of glucose and oxygen were evaluated on the freestanding membranes. The diffusion of glucose and oxygen decreases with increasing cross-linking concentration. Mechanical properties were also evaluated in physiological-simulated conditions. Increasing cross-linking density leads to an increase of storage modulus, Young modulus, and ultimate tensile strength, but to a decrease in the maximum hydrostatic pressure. The in vitro biological performance demonstrates that cross-linked films are more favorable for cell adhesion. This work demonstrates the versatility and feasibility of LbL assembly to generate nanostructured constructs with tunable permeability, mechanical, and biological properties.The authors acknowledge the financial support by the Portuguese Foundation for Science and Technology (FCT) through the doctoral and Postdoctoral grants with the reference numbers SFRH/BD/81372/2011 (JMS) and SFRH/BPD/96797/2013 (SGC), respectively. This work was financially supported by the FCT, by the project PTDC/FIS/115048/2009, and by the European Commission/FP7 programme (ERC Starting Grant, GA 259370 to C.P.). The authors would also like to acknowledge the project novel smart and biomimetic materials for innovative regenerative medicine approaches (ref.: RL1 - ABMR - NORTE-01-0124-FEDER-000016) cofinanced by the North Portugal Regional Operational Programme (ON.2 0 Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF)

Tuning cell adhesive properties via layer-by-layer assembly of chitosan and alginate

Understanding the mechanisms controlling cell-multilayer film interactions is crucial to the successful engineering of these coatings for biotechnological and biomedical applications. Herein, we present a strategy to tune the cell adhesive properties of multilayers based on marine polysaccharides with and without cross-linking and/or coating with extracellular matrix proteins. Chemical cross-linking of multilayers improved mechanical properties of the coatings but also elicited changes in surface chemistry that alter the adhesion of human umbilical vein endothelial cells. We evaluated a strategy to decouple the mechanical and chemical properties of these films, enabling the transition from cell-adhesive to cellresistant multilayers. Addition of chitosan/alginate multilayers on top of cross-linked films decreased endothelial cell adhesion, spreading, and proliferation to similar levels as uncross-linked films. Our findings highlight the key role of surface chemistry in cell-multilayer film interactions, and these engineered nanocoatings represent a tunable model of cell adhesive and non-adhesive multilayered films.The authors acknowledge the financial support by the LusoAmerican Foundation and the USA National Institutes of Health (R01 AR062920). Joana M. Silva would also like to acknowledge the Portuguese Foundation for Science and Technology (FCT) for her PhD grant.info:eu-repo/semantics/publishedVersio

Layer-by-layer assembly for biofunctionalization of cellulosic fibers with emergent antimicrobial agents

Series title: Advances in polymer science series, ISSN 0065-3195, vol. 271Coating with polyelectrolyte multilayers has become a generic way to functionalize a variety of materials. In particular, the layer-by-layer (LbL) technique allows the coating of solid surfaces to give them several functionalities, including controlled release of bioactive agents. At present there are a large number of applications of the LbL technique; however, it is still little explored in the area of textiles. In this review we present an overview of LbL for textile materials made from synthetic or natural fibers. More specifically, LbL is presented as a method for obtaining new bioactive cotton (as in cellulosic fibers) for potential application in the medical field. We also review recent progress in the embedding of active agents in adsorbed multilayers as a novel way to provide the system with a “reservoir” where bioactive agents can be loaded for subsequent release.The authors would like to thank Fundação para a Ciência e Tecnologia (FCT) for the funding granted for the project PTDC/EBB-BIO/113671/2009 (FCOMP-01-0124-FEDER- 014752) Skin2Tex. Also, we would like to thank Fundo Europeu de Desenvolvimento Regional (FEDER) through COMPETE – Programa Operacional Factores de Competitividade (POFC) for co-funding