One- vs two-step preparation of antimicrobial coatings composed of laser ablated copper nanoparticles and poly-lactic ac
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One- vs two-step preparation of antimicrobial coatings composed of laser ablated copper nanoparticles and poly-lactic acid Daniela Longano1, Nicoletta Ditaranto1, Nicola Cioffi1, Francesca Di Niso2, Teresa Sibillano2, Francesco P. Mezzapesa2, Antonio Ancona2, Amalia Conte3, Matteo A. Del Nobile3, Luigia Sabbatini1, Luisa Torsi1 1 Dipartimento di Chimica, Università degli Studi di Bari “Aldo Moro”, Via Orabona 4, 70126 Bari, Italy. 2 CNR-IFN, Istituto di Fotonica e Nanotecnologie, Dipartimento Interateneo di Fisica “M. Merlin”, Via Amendola 173, 70126 Bari, Italy. 3 BIOAGROMED, Istituto per la Ricerca e le Applicazioni Biotecnologiche per la Sicurezza e la Valorizzazione dei Prodotti Tipici e di Qualità, Via Napoli 25, 71100 Foggia, Italy ABSTRACT Copper-containing nanomaterials have been developed as antimicrobial additives for food packaging applications. These nano-antimicrobials are composed of copper nanoparticles (CuNPs) embedded in poly-lactic acid (PLA), which has been selected as a biodegradable polymer matrix. Copper nanostructures have been synthesized by laser ablation following two different protocols: (I) one-pot synthesis in presence of PLA and (II) in absence of polymer matrix. In the latter route, the as prepared CuNPs suspension has been subsequently mixed to a PLA solution. The resulting dispersions have been directly drop-cast on several substrates. Nanoantimicrobials have been characterized by UV-Vis and x-ray photoelectron spectroscopies, and transmission electron microscopy. The kinetics of copper release in aqueous solution from antimicrobial nanomaterials have been studied by means of Electro-Thermal Atomic Absorption Spectroscopy. Finally, preliminary biological tests have been performed on Pseudomonas species by JIS methods (Japanese Industrial Standard, JIS Z 2801:2000). INTRODUCTION In our research group, antifungal/antibacterial coatings have been frequently prepared embedding electrosynthesized core-shell NPs in various polymer matrices, the stabilized structure of NPs providing a gradual and controlled release of bioactive metal ions [1-6]. Laser ablation of a metallic copper target in liquids is a novel route to generate metal nanoparticles even in absence of surfactants/stabilizers . In the present study, CuNPs have been synthesized by means of laser ablation in two different ways: (I) one-pot synthesis has been carried out in presence of PLA and (II) in absence of polymer matrix. In the latter route the CuNPs suspensions have been then mixed to PLA dissolved in the same solvent. As reported by other authors, ablation of a Cu target in pure acetone affords the preparation of stable colloids [7-10]. In this study, the choice of copper and PLA components for our composite coatings is aimed at combining the bioactivity of CuNPs with the well-known biodegradability of the polymer matrix. The nanomaterial composition has been characterised by means of different analytical techniques. Moreover, since these antibacterial systems could be used in food packaging field as active packages for f
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