[01] M. Carmen Rodríguez-Argüelles, Inorganic Chemistry Department, Faculty of Chemistry, University of Vigo, Vigo, Spain. [02] Noelia González-Ballesteros, Inorganic Chemistry Department, Faculty of Chemistry, University of Vigo, Vigo, Spain. [03] Gregorio Rodríguez-Domínguez, Inorganic Chemistry Department, Faculty of Chemistry, University of Vigo, Vigo, Spain. [04] Marco Campanini, Institute of Materials for Electronics and Magnetism, National Research Council (IMEM-CNR), Parma, Italy. [05] Lucia Nasi, Institute of Materials for Electronics and Magnetism, National Research Council (IMEM-CNR), Parma, Italy. [06] Iria Vázquez, Functional Biology and Health Sciences Department, Microbiology Area, Faculty of Biology, University of Vigo, Vigo, Spain. [07] Carmen Sieiro, Functional Biology and Health Sciences Department, Microbiology Area, Faculty of Biology, University of Vigo, Vigo, Spain.

Due to the problem of resistance of many infectious agents to the usual treatments, this study addresses the ways of obtaining and using new chitosan-silver nanomaterials as antimicrobial agents. Chitosans of medium (CSM) and high (CSH) molecular weights were used as matrices in the formation of small silver nanoparticles (AgNP) when mixed with AgNO₃ under different conditions, such as using the polymer (CS) in acetic acid solutions, as nanoparticles (CS-NP) or in films. The films were prepared by evaporation of the CS-AgNO₃ mixtures at different temperatures and in all cases AgNP was formed. When acetic acid solutions of CS were boiled in the presence of AgNO₃ CS-NP were formed containing AgNP (Ag@CS-NP). It is evident that the size and form of presentation of CS are not factors that can significantly affect the formation of small AgNP. AgNP inserted in different CS matrices presented significant antimicrobial activity (MIC between 0.6-4 μg/mL) against four Gram-positive and five Gram-negative bacteria, and also against three yeasts. It is interesting to emphasize the highest activities achieved for Ag@CSH-NP against B. cereus (0.6 μg/mL) and Ag@CSM-NP against P. pastoris (0.7 μg/mL). Although the antimicrobial activity was dependent on the strain assayed, the overall tendency observed was that the nanocomposites made with CSH are more effective than those prepared with CSM.

Antimicrobial,Chitosan,Nanoparticle,Silver,TEM, UV-Vis

[01] Angebault, C.; Andremont, A. Antimicrobial agent exposure and the emergence and spread of resistant microorganisms: issues associated with study desing. Eur. J. Clin. Microbiol., 2013, 32, 581-595. [02] Pelgrift, R.Y.; Friedman, A.J. Nanotechnology as a therapeutic tool to combat microbial resistance. Adv. Drug. Deliv. Rev., 2013, 65, 1803-1815. [03] Seil, J.T.; Webster, T.J. Antimicrobial applications of nanotechnology: Methods and literature. Int. J. Nanomedicine., 2012, 7, 2767-2781. [04] Rodríguez-Argüelles, M.C.; Tourón-Touceda, P.; Cao, R.; García-Deibe, A.M.; Pelagatti, P.; Pelizzi, C.; Zani, F. Complexes of 2-acetyl-γ-butyrolactone and 2-furancarbaldehyde thiosemicarbazones: Antibacterial and antifungal activity. J. Inorg. Biochem., 2012, 103, 35-42. [05] Nair, L.S.; Laurencin, C.T. Silver Nanoparticles: Synthesis and Therapeutic Applications. J. Biomed. Nanotechnol., 2007, 3, 301-316. [06] Rai, M.; Yadav, A.; Gade, A. Silver nanoparticles as a new generation of antimicrobial. Biotechnol. Adv., 2009, 27, 76-83. [07] Panacek, A.; Kvítek, L.; Prucek, R.; Kolar, M.; Vecerova, R.; Pizúrova, N.; Sharma, V.K.; Nevecna, T.; Zboril, R. Silver colloid nanoparticles: synthesis, characterization, and their antibacterial activity. J. Phys. Chem. B., 2006, 110, 16248-53. [08] Ip, M.; Lui, S.L.; Poon, V.K.M.; Lung, I.; Burd, A. Antimicrobial activities of silver dressings: an in vitro comparison. J. Med. Microbiol., 2006, 55, 59-63. [09] De Simone, S.; Gallo, A. L.; Paladini, F.; Sannino, A.; Pollini, M. Development of silver nano-coatings on silk sutures as a novel approach against surgical infections. J. Mater. Sci: Mater. Med., 2014, 25, 2205-2214. [10] Hebeish, A.; El-Rafie, M.H.; El-Sheikh, M.A.; Seleem, A.A.; El-Naggar, M.E. Antimicrobial wound dressing and anti-inflamatory efficacy of silver nanoparticles. Int. J. Biol. Macromol., 2014, 65, 509-515. [11] Rodriguez-Argüelles, M.C.; Sieiro, C.; Cao, R.; Nasi, L. Chitosan and silver nanoparticles as pudding with raisins with antimicrobial properties. J. Colloid. Interf. Sci., 2011, 364, 80-84. [12] Shukla, S.K.; Mishra, A.K.; Arotiba, O.; Mamba, B. Chitosan-based nanomaterials: a state-of-the-art review. Int. J. Biol. Macromol., 2013, 59, 46-58. [13] Dhillon, G.S.; Kaur, S.; Sarma, S.J.; Brar, S.K. Recent Development in Applications of Important Biopolymer Chitosan in Biomedicine, Pharmaceuticals and Personal Care Products. Current Tissue Eng., 2013, 2, 20-40. [14] Croisier, F.; Jérome, C. Chitosan-based biomaterials for tissue engineering. Eur. Polym. J., 2013, 49, 780-792. [15] Elsabee, M.Z.; Abdou, E.S. Chitosan based edible films and coatings: a review. Mat. Sci. Eng. C., 2013, 33, 1819-1841. [16] Cota-Arriola, O.; Cortez-Rocha, M.; Burgos-Hernandez, A.; Ezquerra-Brauer, J.; Plascencia-Jatomea, M. Controlled release matrices and micro/nanoparticles of chitosan with antimicrobial potential: development of new strategies for microbial control in agriculture. J. Sci. Food Agric., 2013, 93, 1525-36. [17] Ahamed, M.I.N.; Sastry, T.P. Wound dressing application of chitosan based bioactive compounds. Int. J. Pharm. Life Sci., 2011, 2, 991-996. [18] Zamani, A.; Taherzadeh, M. Production of low molecular weight chitosan by hot diluted sulfuric acid. Bioresources., 2010, 5, 1554-1564. [19] Xie, H.; Jia, Z. Preparation of low molecular weight chitosan by complex enzymes hydrolysis. Int. J. Chem., 2011, 3, 180-186. [20] Nwe, N.; Furuike, T.; Tamura, H. Production of Fungal Chitosan by Enzymatic Method and Applications in Plant Tissue Culture and Tissue Engineering: 11 Years of Our Progress, Present Situation and Future Prospects. Biopolymers, MagdyElnashard, 2010; pp. 50-57. [21] Kingkaew, J.; Kirdponpattara, S.; Sanchavanakit, N.; Pavasant, P.; Phisalaphong, M. Effect of molecular weight of chitosan on antimicrobial properties and tissue compatibility of chitosan-impregnated bacterial cellulose films. Biotechnol. Bioprocess. Eng., 2014, 19, 534-544. [22] Liu, N.; Chen, X.G.; Park, H.J.; Liu, C.G.; Liu, C.S.; Meng, X.H.; Yu, L.J. Effect of MW and concentration of chitosan on antibacterial activity of Escherichia coli. Carbohyd. Polym., 2006, 64, 60-65. [23] Tomida, H.; Fujii, T.; Furutani, N.; Michihara, A.; Yasufuku, T.; Akasaki, K.; Maruyama, T.; Otagiri, M.; Gebicki, J.M.; Anraku, M. Antioxidant properties of some different molecular weight chitosans. Carbohyd. Res., 2009, 344, 1690-1696. [24] Weng, X.; Lin, S.; Zhong, Y.; Chen, Z. Chitosan stabilized bimetallic Fe/Ni nanoparticles used to remove mixed contaminants-amoxicillin and Cd (II) from aqueous solutions. Chem. Eng. J., 2013, 229, 27-34. [25] Wei, D.; Qian, W. Facile synthesis of Ag and Au nanoparticles utilizing chitosan as a mediator agent. Colloids surf. B., 2008, 62, 136-42. [26] Egger, S.; Lehmann, R.P.; Height, M.J.; Loessner, M.J.; Schuppler, M. Antimicrobial properties of a novel silver-silica nanocomposite material. Appl. Environ. Microbiol., 2009, 75, 2973-6. [27] Morones, J.R.; Elechiguerra, J.L.; Camacho, A.; Holt, K.; Kouri, J.B.; Ram, J.T.; Yacaman, M.J. The bactericidal effect of silver nanoparticles. Nanotechnology, 2005, 16, 2346-2353. [28] Sarkar, S.; Jana, A.D.; Samanta, S.K.; Mostafa, G. Facile synthesis of silver nanoparticles with highly efficient anti-microbial property. Polyhedron, 2007, 26, 4419-4426. [29] Potara, M.; Jakab, E.; Damert, A.; Popescu, O.; Canpean, V.; Astilean, S. Synergistic antibacterial activity of chitosan-silver nanocomposites on Staphylococcus aureus. Nanotechnology, 2011, 22, 135101-135110.