Time filter

Source Type

Milano, Italy

Fernandes S.C.M.,University of Aveiro | Fernandes S.C.M.,University of the Basque Country | Sadocco P.,Piazza Leonardo da Vinci | Alonso-Varona A.,University of the Basque Country | And 5 more authors.
ACS Applied Materials and Interfaces | Year: 2013

There has been a great deal of interest in the use of nanostructured bacterial cellulose membranes for biomedical applications, including tissue implants, wound healing, and drug delivery. However, as bacterial cellulose does not intrinsically present antimicrobial properties, in the present study, antimicrobial bacterial cellulose membranes were obtained by chemical grafting of aminoalkyl groups onto the surface of its nanofibrillar network. This approach intends to mimic intrinsic antimicrobial properties of chitosan. Interestingly, these novel grafted bacterial cellulose membranes (BC-NH 2) are simultaneously lethal against S. aureus and E. coli and nontoxic to human adipose-derived mesenchymal stem cells (ADSCs) and thus may be useful for biomedical applications. In addition to these biological properties, the bioactive nanostructured BC-NH2 membranes also present improved mechanical and thermal properties. © 2013 American Chemical Society. Source

Tome L.C.,University of Aveiro | Tome L.C.,New University of Lisbon | Fernandes S.C.M.,University of Aveiro | Perez D.S.,Institute technologique FCBA | And 6 more authors.
Cellulose | Year: 2013

Thin nanocomposite films of thermoplastic starch, chitosan and cellulose nanofibers (bacterial cellulose or nanofibrillated cellulose) were prepared for the first time by solvent casting of water based suspensions of the three polysaccharides. The role of the different bioploymers on the final properties (thermal stability, transparency, mechanical performance and antimicrobial activity) of the films was related with their intrinsic features, contents and synergic effects resulting from the establishment of interactions between them. Thermoplastic starch displays an important role on the thermal stability of the films because it is the most stable polysaccharide; however it has a negative impact on the mechanical performance and transparency of the films. The addition of chitosan improves considerably the transparency (up to 50 % transmittance for 50 % of chitosan, in respect to the amount of starch), mechanical performance and antimicrobial properties (at least 25 % of chitosan and no more than 10 % of cellulose nanofibers are required to observe bacteriostatic or bactericidal activity) but decrease their thermal stability. The incorporation of cellulose nanofibers had the strongest positive impact on the mechanical properties of the materials (increments of up to 15 and 30 MPa on the Young′s modulus and Tensile strength, respectively, for films with 20 % of BC or NFC). Nonetheless, the impact in thermal stability and mechanical performance of the films, promoted by the addition of chitosan and cellulose nanofibres, respectively, was higher than the expected considering their percentage contents certainly because of the establishment of strong and complex interactions between the three polysaccharides. © 2013 Springer Science+Business Media Dordrecht. Source

Martins N.C.T.,University of Aveiro | Freire C.S.R.,University of Aveiro | Neto C.P.,University of Aveiro | Silvestre A.J.D.,University of Aveiro | And 4 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2013

New composites of nanofibrillated cellulose (NFC) and ZnO nanoparticles (NP) have been prepared by electrostatic assembly in aqueous medium and using polyelectrolytes as macromolecular linkers. Selected NFC/ZnO systems were employed as fillers in starch based coating formulations for Eucalyptus globulus-based paper sheets. Using this method, antibacterial paper with low content of ZnO (<0.03%) and slight improvements in air permeability and mechanical properties were obtained. The antibacterial activity of the ZnO/NFC coatings was investigated namely by submitting paper samples to solar light exposure and dark conditions. In both conditions, the paper samples have shown bacteriostatic and/or bactericidal activity against Gram positive (Staphylococcus aureus and Bacillus cereus) and Gram negative (Klebsiella pneumoniae) bacteria. These results seem to support that the mechanism for ZnO antimicrobial activity is not mediated only by the photoactivity of the semiconductor but also by oxidizing species formed at the particles surfaces. © 2012 Elsevier B.V. Source

Martins N.C.T.,University of Aveiro | Freire C.S.R.,University of Aveiro | Pinto R.J.B.,University of Aveiro | Fernandes S.C.M.,University of Aveiro | And 6 more authors.
Cellulose | Year: 2012

Nanofibrillated cellulose offers new technological solutions for the development of paper products. Here, composites of nanofibrillated cellulose (NFC) and Ag nanoparticles (NP) were prepared for the first time via the electrostatic assembly of Ag NP (aqueous colloids) onto NFC. Distinct polyelectrolytes have been investigated as macromolecular linkers in order to evaluate their effects on the building-up of Ag modified NFC and also on the final properties of the NFC/Ag composite materials. The NFC/Ag nanocomposites were first investigated for their antibacterial properties towards S. aureus and K. pneumoniae microorganisms as compared to NFC modified by polyelectrolytes linkers without Ag. Subsequently, the antibacterial NFC/Ag nanocomposites were used as fillers in starch based coating formulations for Eucalyptus globulus-based paper sheets. The potential of this approach to produce antimicrobial paper products will be discussed on the basis of complementary optical, air barrier and mechanical data. © 2012 Springer Science+Business Media B.V. Source

Barata J.F.B.,University of Aveiro | Pinto R.J.B.,University of Aveiro | Vaz Serra V.I.R.C.,University of Aveiro | Vaz Serra V.I.R.C.,University of Lisbon | And 7 more authors.
Biomacromolecules | Year: 2016

Transparent corrole grafted-chitosan films were prepared by chemical modification of chitosan with a corrole macrocycle, namely, 5,10,15-tris(pentafluorophenyl)corrole (TPFC), followed by solvent casting. The obtained films were characterized in terms of absorption spectra (UV-vis), FLIM (fluorescence lifetime imaging microscopy), structure (FTIR, XPS), thermal stability (TGA), thermomechanical properties (DMA), and antibacterial activity. The results showed that the chemical grafting of chitosan with corrole units did not affect its film-forming ability and that the grafting yield increased with the reaction time. The obtained transparent films presented fluorescence which increases with the amount of grafted corrole units. Additionally, all films showed bacteriostatic effect against S. aureus, as well as good thermomechanical properties and thermal stability. Considering these features, promising applications may be envisaged for these corrole-chitosan films, such as biosensors, bioimaging agents, and bioactive optical devices. © 2016 American Chemical Society. Source

Discover hidden collaborations