Time filter

Source Type

Aouada F.A.,Sao Paulo State University | Aouada F.A.,National Nanotechnology Laboratory for Agriculture LNNA | Mattoso L.H.C.,National Nanotechnology Laboratory for Agriculture LNNA | Longo E.,Sao Paulo State University
Journal of Thermoplastic Composite Materials

The aim of this article is to propose advances for the preparation of hybrid nanocomposites prepared by the combination of intercalation from solution and melt-processing methods. This research investigates the effect of the laponite RDS content on the thermal, structural, and mechanical properties of thermoplastic starch (TPS). X-ray diffraction was performed to investigate the dispersion of the laponite RDS layers into the TPS matrix. The results show good nanodispersion, intercalation, and exfoliation of the clay platelets, indicating that these composites are true nanocomposites. The presence of laponite RDS also improves the thermal stability and mechanical properties of the TPSmatrix due to its reinforcement effect which was optimized by the high degree of exfoliation of the clay. Thus, these results indicate that the exfoliated TPS-laponite nanocomposites have great potential for industrial applications and, more specifically, in the packaging field. © The Author(s) 2011 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav. Source

Pereira M.M.,Federal University of Juiz de fora | Raposo N.R.B.,Federal University of Juiz de fora | Brayner R.,University Paris Diderot | Teixeira E.M.,National Nanotechnology Laboratory for Agriculture LNNA | And 5 more authors.

Cellulose nanofibers (CNF) have mechanical properties that make them very attractive for applications in the construction of polymeric matrices, drug delivery and tissue engineering. However, little is known about their impact on mammalian cells. The objective of this study was to evaluate the cytotoxicity of CNF and their effect on gene expression of fibroblasts cultured in vitro. The morphology of CNF was analyzed by transmission electron microscopy and the surface charge by Zeta potential. Cell viability was analyzed by flow cytometry assay and gene expression of biomarkers focused on cell stress response such as Heat shock protein 70.1 (HSP70.1) and Peroxiredoxin 1 (PRDX1) and apoptosis as B-cell leukemia (BCL-2) and BCL-2 associated X protein (BAX) by RT-PCR assay. Low concentrations of CNF (0.02-100 μg ml-1) did not cause cell death; however, at concentrations above 200 μg ml-1, the nanofibers significantly decreased cell viability (86.41 ± 5.37%). The exposure to high concentrations of CNF (2000 and 5000 μg ml-1) resulted in increased HSP70.1, PRDX1 and BAX gene expression. The current study concludes that, under the conditions tested, high concentrations (2000 and 5000 μg ml-1) of CNF cause decreased cell viability and affect the expression of stress- and apoptosis-associated molecular markers. © 2013 IOP Publishing Ltd. Source

Aouada F.A.,Sao Paulo State University | Aouada F.A.,National Nanotechnology Laboratory for Agriculture LNNA | Mattoso L.H.C.,National Nanotechnology Laboratory for Agriculture LNNA | Longo E.,Sao Paulo State University
Industrial Crops and Products

A simple method based on the combination of the intercalation from solution and melt-processing preparation methods was used to prepare highly exfoliated and compatible thermoplastic starch (TPS) and montmorillonite clay (MMT) nanocomposites. The effects of the MMT content on the thermal, structural, and mechanical properties of the nanocomposites were investigated. XRD diffraction was used to investigate the MMT exfoliation/intercalation degrees in the TPS matrix. Data from thermogravimetric analysis and differential scanning calorimetry revealed that the addition of MMT increased the thermal stabilities of TPS nanocomposites. Young's modulus and tensile strength increased from 8.0 to 23.8. MPa and 1.5 to 2.8. MPa with an increasing MMT content from 0 to 5. wt% without diminishing their flexibility. The improvement in such properties can be attributed to the good dispersion/exfoliation of MMT in the TPS matrix. Combining both methods, it was possible to obtain homogenous and transparent nanocomposites with excellent thermal and mechanical properties for application as packaging materials. © 2011 Elsevier B.V. Source

Bortolin A.,Federal University of Sao Carlos | Bortolin A.,National Nanotechnology Laboratory for Agriculture LNNA | Aouada F.A.,National Nanotechnology Laboratory for Agriculture LNNA | Aouada F.A.,Sao Paulo State University | And 5 more authors.
Journal of Applied Polymer Science

This article studied the applicability of poly(acrylamide) and methylcellulose (PAAm-MC) hydrogels as potential delivery vehicle for the controlled-extended release of ammonium sulfate (NH4) 2SO4 and potassium phosphate (KH2PO 4) fertilizers. PAAm-MC hydrogels with different acrylamide (AAm) and MC concentrations were prepared by a free radical polymerization method. The adsorption and desorption kinetics of fertilizers were determined using conductivity measurements based on previously built analytical curve. The addition of MC in the PAAm chains increased the quantities of (NH 4)2SO4 and KH2PO4 loaded and extended the time and quantities of fertilizers released. Coherently, both loading and releasing processes were strongly influenced by hydrophilic properties of hydrogels (AAm/MC mass proportion). The best sorption (124.0 mg KH2PO4/g hydrogel and 58.0 mg (NH4) 2SO4/g hydrogel) and desorption (54.9 mg KH 2PO4/g hydrogel and 49.5 mg (NH4) 2SO4/g hydrogel) properties were observed for 6.0% AAm-1.0% MC hydrogels (AAm/MC mass proportion equal 6), indicating that these hydrogels are potentially viable to be used in controlled-extended release of fertilizers systems. © 2011 Wiley Periodicals, Inc. Source

de Lima R.,University of Sorocaba | Feitosa L.O.,University of Sorocaba | Maruyama C.R.,University of Sorocaba | Barga M.A.,University of Sorocaba | And 6 more authors.
International Journal of Nanomedicine

Background: Agricultural products and by products provide the primary materials for a variety of technological applications in diverse industrial sectors. Agro-industrial wastes, such as cotton and curaua fibers, are used to prepare nanofibers for use in thermoplastic films, where they are combined with polymeric matrices, and in biomedical applications such as tissue engineering, amongst other applications. The development of products containing nanofibers offers a promising alternative for the use of agricultural products, adding value to the chains of production. However, the emergence of new nanotechnological products demands that their risks to human health and the environment be evaluated. This has resulted in the creation of the new area of nanotoxicology, which addresses the toxicological aspects of these materials. Purpose and methods: Contributing to these developments, the present work involved a genotoxicological study of different nanofibers, employing chromosomal aberration and comet assays, as well as cytogenetic and molecular analyses, to obtain preliminary information concerning nanofiber safety. The methodology consisted of exposure of Allium cepa roots, and animal cell cultures (lymphocytes and fibroblasts), to different types of nanofibers. Negative controls, without nanofibers present in the medium, were used for comparison. Results: The nanofibers induced different responses according to the cell type used. In plant cells, the most genotoxic nanofibers were those derived from green, white, and brown cotton, and curaua, while genotoxicity in animal cells was observed using nanofibers from brown cotton and curaua. An important finding was that ruby cotton nanofibers did not cause any significant DNA breaks in the cell types employed. Conclusion: This work demonstrates the feasibility of determining the genotoxic potential of nanofibers derived from plant cellulose to obtain information vital both for the future usage of these materials in agribusiness and for an understanding of their environmental impacts. © 2012 de Lima et al, publisher and licensee Dove Medical Press Ltd. Source

Discover hidden collaborations