Piazza Leonardo da Vinci

Milano, Italy

Piazza Leonardo da Vinci

Milano, Italy

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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.


Fernandes S.C.M.,University of Aveiro | Fernandes S.C.M.,University of the Basque Country | Sadocco P.,Piazza Leonardo Da Vinci | Causio J.,Piazza Leonardo Da Vinci | And 3 more authors.
Food Hydrocolloids | Year: 2014

In the present work, we propose a simple and straightforward procedure to prepare antibacterial transparent pullulan films by functionalization of pullulan powder with 3-aminopropyltrimethoxysilane. The introduction of active aminopropyl groups into the pullulan polymeric backbone imparts antimicrobial activity against Gram-positive ( Staphylococcus aureus) and Gram-negative bacteria ( Escherichia coli). In addition, the antimicrobial pullulan maintains its filmogenic ability and the films showed reasonable mechanical properties (Young modulus of 1.8GPa and tensile strength of 21MPa) and improved thermal stability (increment of 10°C on the maximum degradation temperature), opening the possibility for application in functional food packaging films and coatings. © 2013 Elsevier Ltd.


Missoum K.,University Grenoble Alpes | Missoum K.,French National Center for Scientific Research | Sadocco P.,Piazza Leonardo da Vinci | Causio J.,Piazza Leonardo da Vinci | And 4 more authors.
Materials Science and Engineering C | Year: 2014

Nanofibrillated cellulose (NFC) and their derivatives were prepared using three chemical surface modification strategies. All grafting was characterized by FTIR and contact angle measurements in order to evaluate the efficiency of grafting. Antibacterial activities of neat and grafted samples were investigated against two kinds of bacteria (i.e. Gram + (Staphylococcus aureus) and Gram - (Klebsiella pneumoniae)). All the grafted samples displayed promising results with at least bacteriostatic effect or bactericidal properties. They also strongly enhanced the photo-catalytic antimicrobial effect of TiO2. This study proves that it is better to use grafted NFC either alone or for functionalization with TiO2 if anti-bacterial properties are desired. The cellulose backbone is known to be easily biodegradable in different biodegradation conditions and environments. The chemical surface modifications applied on NFC in the present work did not negatively influence this valuable property of cellulose but help for monitoring this property, which could be very useful for paper, packaging and composites. © 2014 Published by Elsevier B.V.


Missoum K.,University Grenoble Alpes | Sadocco P.,Piazza Leonardo da Vinci | Causio J.,Piazza Leonardo da Vinci | Belgacem M.N.,University Grenoble Alpes | Bras J.,University Grenoble Alpes
Materials science & engineering. C, Materials for biological applications | Year: 2014

Nanofibrillated cellulose (NFC) and their derivatives were prepared using three chemical surface modification strategies. All grafting was characterized by FTIR and contact angle measurements in order to evaluate the efficiency of grafting. Antibacterial activities of neat and grafted samples were investigated against two kinds of bacteria (i.e. Gram+ (Staphylococcus aureus) and Gram- (Klebsiella pneumoniae)). All the grafted samples displayed promising results with at least bacteriostatic effect or bactericidal properties. They also strongly enhanced the photo-catalytic antimicrobial effect of TiO2. This study proves that it is better to use grafted NFC either alone or for functionalization with TiO2 if anti-bacterial properties are desired. The cellulose backbone is known to be easily biodegradable in different biodegradation conditions and environments. The chemical surface modifications applied on NFC in the present work did not negatively influence this valuable property of cellulose but help for monitoring this property, which could be very useful for paper, packaging and composites. Copyright © 2014 Elsevier B.V. All rights reserved.


PubMed | University of Lisbon and Piazza Leonardo Da Vinci
Type: Journal Article | Journal: 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.


Taliercio A.,Piazza Leonardo da Vinci
International Journal of Solids and Structures | Year: 2014

Approximate expressions for the macroscopic in-plane elastic and creep coefficients of brick masonry with a regular pattern are derived in closed form, using a homogenization approach for periodic media. A microscopic displacement field fulfilling suitable periodicity boundary conditions, and depending on a limited number of degrees of freedom, is formulated over any masonry Representative Volume Element (RVE). According to this field, closed-form expressions for the macroscopic elastic constants are obtained at various degrees of approximation, either using a Method of Cells-type approach, or minimizing the potential energy of the RVE subjected to any given macroscopic stress. Eventually, the results are extended to the description of the global creep behavior of brickwork under service loads, assuming the creep laws of units and mortar to be expressed by Prony series. Using the FE solution as a benchmark, the proposed approach is found to accurately match both the macroscopic constitutive law in linear elasticity and the time evolution of the macroscopic strains of brickwork under sustained macroscopic stress. © 2014 Elsevier Ltd. All rights reserved.


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.


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.


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.


Tome L.C.,University of Aveiro | Fernandes S.C.M.,University of Aveiro | Sadocco P.,Piazza Leonardo Da Vinci | Causio J.,Piazza Leonardo Da Vinci | And 3 more authors.
BioResources | Year: 2012

Antibacterial thermoplastic starch-chitosan based materials were successfully prepared by melt-mixing. The effect of chitosan modification (quaternization and grafting of long carbon chains) on the properties of the materials was also studied. All the ensuing materials were characterized in terms of thermal stability, crystalline structure, mechanical performance, and antibacterial activity. The incorporation of chitosan and its derivatives into the thermoplastic starch matrices resulted in an increment in tensile strengths (up to 85%); however for higher chitosan contents (5 and 7.5 wt.%), a decrease on the Young's modulus (around 50%) was observed, together with an increment in the elongation at break, which can be attributed to the prevention of the retrogradation process. Finally, the thermoplastic starch materials incorporated with 7.5 wt% of the unmodified chitosan and of the water-soluble chitosan derivative had partial (about 20% reduction of CFU) and total bactericidal effect against S. aureus.

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