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Faria-Tischer P.C.S.,Federal University of Parana | Faria-Tischer P.C.S.,State University Londrina | Costa C.A.R.,National Center for Energy and Materials | Tozetti I.,State University Londrina | And 2 more authors.
RSC Advances

Bacterial cellulose (BC) and poly(aniline) (PANI) composites were successfully synthesized by in situ polymerization of aniline by ammonium persulphate (APS) in the presence and absence of gold nanoparticles. The composites were fully characterized by different techniques such as SEM and AFM (morphology), Raman and FTIR spectroscopy (chemical structure), EFM (electrical conductivity), thermogravimetric analysis (thermal stability), cyclic voltammetry (charge diffusion) and UV-vis (optical properties). The surface roughness is higher in composites and the polymers interact with each other by strong hydrogen bonds, providing high thermal stability in the BC/PANI composite. The phenazine structure was not present in this composite during synthesis; nevertheless, the local conductivity increased even further in the presence of AuNPs, inducing the interchain redox reactions leading the phenazine structures after electrochemical cycling. The electrical conductivity of composites is highly influenced by the APS in the polymerization step, as observed by EFM. Also, the presence of AuNPs leads to easier diffusional processes through the solid material, as observed by more defined voltammetric waves. © 2016 The Royal Society of Chemistry. Source

Lopes J.H.,University of Campinas | Magalhaes J.A.,Federal University of Sao Paulo | Gouveia R.F.,National Center for Energy and Materials | Bertran C.A.,University of Campinas | And 3 more authors.
Journal of the Mechanical Behavior of Biomedical Materials

This paper investigates the microstructure and the mechanical properties of β-tricalcium phosphate (β-TCP) three-dimensional (3D) porous materials reinforced with 45S5 bioactive glass (BG). β-TCP and β-TCP/x%-BG scaffolds with interconnected pores networks, suitable for bone regeneration, were fabricated by gel-casting method. Mechanical properties, porosity, and morphological characteristics were evaluated by compressive strength test, scanning electron microscopy (SEM) and X-ray microtomography analysis, whereas the structures were fully explored by XRD, and Raman spectroscopy. To the best of our knowledge, this is the first time where the mechanism for understanding the effect of bioglass on the mechanical properties and microstruture of β-TCP/45S5-BG scaffolds has been systematically studied. The findings showed that ionic product lixiviated from 45S5 bioactive glass, rich in silicon species and sodium ion, catalyzes a phase transition from β-TCP to Si-TCP by replacement of phosphorus for silicon and contributes to the improvement of scaffolds mechanical properties. The compressive strength of β-TCP/5%-BG and β-TCP/7.5%-BG was improved around 200% in comparison to pure β-TCP. Osteoblast-like cells (MG 63) were exposed to the materials for 24 h through the use of medium conditioned by β-tricalcium phosphate/bioactive glass. Cell viability was measured by MTT assay in the cells and the data obtained were submitted to ANOVA, Tukey[U+05F3]s multiple comparison (p<0.05). The β-TCP/7.5-BG promoted an increase of cell proliferation. The results suggest that compositions and processing method studied may provide appropriate materials for tissue engineering. © 2016 Elsevier Ltd. Source

Ferreira E.S.,National Center for Energy and Materials | Ferreira E.S.,University of Campinas | Lanzoni E.M.,National Center for Energy and Materials | Costa C.A.R.,National Center for Energy and Materials | And 4 more authors.
ACS Applied Materials and Interfaces

(Graph Presented) This work reports, for the first time, the excellent performance of an aqueous alkaline solution of cellulose as an adhesive for wet and dry cellulosic substrates. Uniaxial tensile tests of filter paper and sulfite writing paper strips bonded with this adhesive (5% cellulose and 7% NaOH aqueous solution) show that failure never occurs in the joints but always in the pristine substrate areas, except in butt joint samples prepared with sulfite paper. Tensile test also shows that paper impregnated with cellulose solution is stronger than the original substrate. X-ray microtomography and scanning electron microscopy reveal that dissolved cellulose fills the gaps between paper fibers, providing a morphological evidence for the mechanical interlocking adhesion mechanism, while scanning probe techniques provide a sharp view of different domains in the joints. Additionally, bonded paper is easily reconverted to pulp, which facilitates paper reprocessability, solving a well-known industrial problem related to deposition of adhesive aggregates (stickies) on the production equipment. © 2015 American Chemical Society. Source

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