Manuel Ignacio Azocar | Universidad de Santiago de Chile (original) (raw)

Papers by Manuel Ignacio Azocar

Research paper thumbnail of 1.1.5. Synthesis and characterization of silver(I) complexes with ligands having anti-inflammatory properties

Communications in Inorganic Synthesis, 2013

Five water soluble silver(I) complex with Ibuprofen (AgIbu), Naproxen (AgNap), Mefenamic acid (... more Five water soluble silver(I) complex with Ibuprofen (AgIbu), Naproxen (AgNap), Mefenamic acid (AgMef), acetyl salicylic acid(AgAsp) and salicylic acid (AgSal) were synthesized and characterized by elemental analysis, FT-IR, 1 H and 13 C NMR. Data suggest coordination of the ligand to Ag(I) through the oxygen atom of the carboxylic group. AgAsp was obtained as a mixture of AgAsp and Ag(I)-2-hydroxybenzoate (AgSal) due to decomposition by thermal and hydrolysis of acetylsalicylic acid into salicylic acid. AgSal structure was confirmed by FT-IR, NMR and X-ray diffraction. Synthesized compounds were tested toward UV-radiation (258 nm, 30 W) and compared with AgCl in order to characterize their light sensibility.

Research paper thumbnail of Synthesis, characterization and 2,5-pyridinedicarboxylic acid interaction of Zinc(II) complexes with N-(4-X-phenyl)pyridine-2-yl-methanimine ligands (X= -Cl and -N(CH3)2)

Communications in Inorganic Synthesis, 2017

Abstract: Two new Zn(II) N-(4-X-phenyl)pyridine-2-yl-methanimine complexes, [Zn(NN´-Cl)Cl 2 ]( 1 ... more Abstract: Two new Zn(II) N-(4-X-phenyl)pyridine-2-yl-methanimine complexes, [Zn(NN´-Cl)Cl 2 ]( 1 ) and [Zn(NN´-N(CH 3 ) 2 )Cl 2 ]( 2 ), have been synthesized and characterized by elemental analysis, FT-IR and NMR- 1 H spectra. The crystal structure of complex 1 was determined by X-ray single crystal diffraction. Experiments performed by Benesi-Hilderbrand method indicate that zinc complexes interact with 2,5-pyridinedicarboxyc acid.

Research paper thumbnail of Electrochemical dynamic sensing of hydrogen peroxide in the presence of microorganisms

Electrochimica Acta, 2019

New experimental techniques and protocols are needed to study microbiologically influenced corros... more New experimental techniques and protocols are needed to study microbiologically influenced corrosion (MIC). In this work, we studied the capacity of microorganisms to modify their environment in vitro. The methodology involved cyclic voltammetry measurements using carbon electrodes modified with cobalt phthalocyanine, which is a known catalyst for the two-electron reduction of O 2 to give peroxide. Mueller-Hinton (21 g/l) was used as an electrolyte in a sterilized aqueous medium. The open circuit potential (OCP) and oxygen concentration behaved similarly over time, with generally similar growth curves. However, there were peculiarities that indicated the presence of peroxide and catalase. Catalase activity was demonstrated by comparing the voltammetric responses of the culture medium in the absence and presence of bacterial strains of Escherichia coli (Gram +) and Staphylococcus aureus (Gram-), both facultative and catalase positive. With this system, which is capable of discriminating O 2 and hydrogen peroxide, catalase activity is highly evident, and at its maximum at the end of the exponential stage of the growth curve.

Research paper thumbnail of Capping of silver nanoparticles by anti-inflammatory ligands: Antibacterial activity and superoxide anion generation

Journal of Photochemistry and Photobiology B: Biology, 2019

Silver nanoparticles (AgNPs) have been widely recognized as antibacterial agents. However, its st... more Silver nanoparticles (AgNPs) have been widely recognized as antibacterial agents. However, its stability and activity over time have been poorly studied. In this work, the properties and characteristics of differently stabilized AgNPs were evaluated during a span of time. The surface capping agents were diclofenac (d), and ketorolac (k), which currently are used as anti-inflammatory in human medicine. On evaluating the size variation over time, it was observed that the AgNPs-k are the most stable, unlike the non-capped nanoparticles agglomerate and precipitate. UV-Vis spectroscopy analysis showed that the absorbance during time decreases for the three types of nanoparticles, but the decrease is less marked for the two types of anti-inflammatory-capped AgNPs. The rapid loss of the optical properties of bare AgNPs, is mainly due to oxidation, agglomeration, and precipitation of this nanoparticles. The potential cytotoxicity of the AgNPs, evaluated through the formation of the superoxide anion using XXT, showed that both, AgNPs-k and AgNPs-d, generate the radical anion when the samples are irradiated with UV light at 365 nm. This effect appears associated with the capping agents, since the bare nanoparticles did not promote the formation of the superoxide anion. The antibacterial activity of the AgNPs throughout time, against two microorganisms (Escherichia coli and Staphylococcus aureus), was also evaluated. The results showed that capping agents played a decisive role in the antibacterial ability of AgNPs and also in enhancing the antibacterial activity over time. microorganisms has been reported successfully through the evaluation of bacterial susceptibility [4,5,9]. The pathways through which the AgNPs act against bacteria, are at least two: i) the generation of reactive oxygen species (ROS) [10,11] and ii) the release of silver ions (Ag +), both processes generating from the surface of the nanoparticles. Both Ag + ions and ROS can cause bacterial death by interacting with the macromolecules which are part of the bacterium [12,13]. Studies on the generation of ROS from AgNPs [14,15] have shown that the main radical species is the superoxide anion (O 2 .−). This species would be formed as a consequence of an electron transfer to molecular oxygen (O 2) present in the environment. [2,16] After irradiating the surface of the AgNPs with UV-Vis light, the absorption of energy that originates the passage of electrons from the valence band to the conduction band takes place. The excess electrons will participate in the reduction of molecular oxygen, forming super-oxide. [16] The O 2 .− and other reactive oxygen species can damage the cellular constituents

Research paper thumbnail of Porous Nanogold/Polyurethane Scaffolds with Improved Antibiofilm, Mechanical, and Thermal Properties and with Reduced Effects on Cell Viability: A Suitable Material for Soft Tissue Applications

ACS applied materials & interfaces, Jan 25, 2018

The use of implants carries on a series of problems, among them infections, poor biocompatibility... more The use of implants carries on a series of problems, among them infections, poor biocompatibility, high levels of cytotoxicity, and significant mechanical differences between implants and host organs that promote stress shielding effects. These problems indicate that the materials used to make implants must meet essential requirements and high standards for implantations to be successful. In this work, we present the synthesis, characterization and evaluation of the antibiofilm, mechanical, and thermal properties, and cytotoxic effect of a nanocomposite-based scaffold on polyurethane (PU) and gold nanoparticles (AuNPs) for soft tissue applications. The effect of the quantity of AuNPs on the antibacterial activity of nanocomposite scaffolds was evaluated against Staphylococcus epidermidis and Klebsiella spp., with a resulting 99.99% inhibition of both bacteria using a small quantity of nanoparticles. Cytotoxicity was evaluated with the T10 1/2 test against fibroblast cells. The resul...

Research paper thumbnail of {"__content__"=>"Stability of Antibacterial Silver Carboxylate Complexes against and Their Cytotoxic Effects.", "i"=>{"__content__"=>"Staphylococcus epidermidis"}}

Molecules (Basel, Switzerland), Jan 4, 2018

The antibacterial effects against of five silver carboxylate complexes with anti-inflammatory lig... more The antibacterial effects against of five silver carboxylate complexes with anti-inflammatory ligands were studied in order to analyze and compare them in terms of stability (in solution and after exposure to UV light), and their antibacterial and morphological differences. Four effects of the Ag-complexes were evidenced by transmission electronic microscopy (TEM) and scanning electronic microscopy (SEM): DNA condensation, membrane disruption, shedding of cytoplasmic material and silver compound microcrystal penetration of bacteria. 5-Chlorosalicylic acid (5Cl) and sodium 4-aminosalicylate (4A) were the most effective ligands for synthesizing silver complexes with high levels of antibacterial activity. However, Ag-5Cl was the most stable against exposure UV light (365 nm). Cytotoxic effects were tested against two kinds of eukaryotic cells: murine fibroblast cells (T10 1/2) and human epithelial ovarian cancer cells (A2780). The main objective was to identify changes in their antibac...

Research paper thumbnail of Correlating light and thermal stability of silver carboxylate complexes by infrared and 13C NMR spectroscopy

Journal of Coordination Chemistry, 2016

Bond nature of carboxylic groups can play an important role in Ag(I)-carboxylate compounds becaus... more Bond nature of carboxylic groups can play an important role in Ag(I)-carboxylate compounds because light and thermal stability are important requirements for future applications such as antibacterial additives. A linear correlation between bond character and light stability of silver carboxylate complexes has been predicted by a direct relationship of infrared and 13 C NMR spectroscopic data. This correlation is in agreement with the thermogravimetric analysis and provides a new approach to explore the interaction and the physical properties of metalcarboxylate bonds.

Research paper thumbnail of Copper-polymer nanocomposites: An excellent and cost-effective biocide for use on antibacterial surfaces

Materials Science and Engineering: C, 2016

The development of polymer nanocomposites with antimicrobial properties has been a key factor for... more The development of polymer nanocomposites with antimicrobial properties has been a key factor for controlling or inhibiting the growth of microorganisms and preventing foodborne diseases and nosocomial infections. Commercially available antibacterial products based on silver-polymer are the most widely used despite the fact that copper is considerably less expensive. The incorporation of copper nanoparticles as antibacterial agents in polymeric matrices to generate copper-polymer nanocomposites have presented excellent results in inhibiting the growth of a broad spectrum of microorganisms. The potential applications in food packaging, medical devices, textiles and pharmaceuticals and water treatment have generated an increasing number of investigations on preparing copper based nanocomposites and alternative polymeric matrices, as potential hosts of nano-modifiers. This review presents a comprehensive compilation of previous published work on the subject, mainly related to the antimicrobial activity of copper polymer nanocomposites. Within all the phenomenology associated to antibacterial effects we highlight the possible mechanisms of action. We discuss the differences in the susceptibility of Gram negative and positive bacteria to the antibacterial activity of nanocomposites, and influencing factors. As well, the main applications of copper polymer-metal nanocomposites are described, considering their physical and chemical characteristics. Finally, some commercially available copper-polymer nanocomposites are described.

Research paper thumbnail of Polyethylene/silver-nanofiber composites: A material for antibacterial films

Materials Science and Engineering: C, 2016

Silver nanofibers (Ag-Nfbs)~80 nm in diameter were synthesized by hydrothermal treatment. The nan... more Silver nanofibers (Ag-Nfbs)~80 nm in diameter were synthesized by hydrothermal treatment. The nanofibers (3 and 5 wt%) were added in the initial feed together with the catalytic system. Polymerizations in an ethylene atmosphere were performed, yielding PE nanocomposites in situ with 3 and 5 wt% content of Ag-Nfbs. The antibacterial effect of the silver-nanofiber composites was evaluated after incubation of Escherichia coli ATCC 25923 for 8 h on their surface. Bacterial viability tests showed that the silver-nanofiber composites inhibited the growth of Escherichia coli ATCC 25923 by 88 and 56%. This behavior is attributed to increased silver ions release from the nanocomposite. TEM analysis showed that the antibacterial effect is associated with membrane disruption but not with changes in shape.

Research paper thumbnail of Stripping voltammetry microprobe (SPV): Substantial improvements of the protocol

Journal of Electroanalytical Chemistry, 2015

The recently introduced new electroanalytical protocol of stripping voltammetry microprobe (SPV) ... more The recently introduced new electroanalytical protocol of stripping voltammetry microprobe (SPV) has been considerably improved with respect to analytical performance. The determination of the silver ions is shown to be possible by the precipitation of a solution of silver drops on an electrode surface, which is previously moistened with a solution of NaCl. The electrode thus modified, i.e., with the silver chloride precipitate on the surface, is introduced into a chloride electrolyte and is negatively polarized to reduce the silver salt to metallic silver. Whereas this reduction process produces only a broad signal, the following electrochemical oxidation of the silver metal back to AgCl provides a highly sensitive and narrow signal, which lends itself for analysis. The linear range for determination of silver ions following this protocol is 1.4 Â 10 À7 to 7.4 Â 10 À4 mol L À1 and the detection limit is 4.6 Â 10 À8 mol L À1 .

Research paper thumbnail of Antibiofouling Properties of Sol-Gel Type Polymers for Aluminium Alloys: Biocorrosion Protection Against Pseudomonas Aeruginosa

The antibiofouling ability of three hybrid sol-gel coatings against P. aeruginosa for the protect... more The antibiofouling ability of three hybrid sol-gel coatings against P. aeruginosa for the protection of AA2024-T3 aluminium alloy has been investigated. The polymers were synthesized by mixing tetraethoxysilane (TEOS) with three precursors: (a) triethoxypropylsilane (TEPRS), (b) triethoxypentylsilane (TEPES) and (c) triethoxyoctylsilane (TEOCS). The main difference between the three precursors is the length of the aliphatic chain of one of the substituents. The antibacterial properties of the polymers were examined using viability techniques. The morphology of the polymers was characterized using scanning electron microscopy (SEM). The resistance of the AA2024 alloy coated with the respective polymers to microbiologically influenced corrosion was evaluated by potentiodynamic polarization. The results showed that the polymers possess antibacterial ability against P. aeruginosa and that the length of the aliphatic chain of the precursors does not significantly affect this property. Further, the electrochemical measurements revealed that the coatings inhibited microbiologically influenced corrosion in the mixture of P. aeruginosa and 0.1 M NaCl, due to the antibacterial properties of the polymers. A correlation between the degree of protection and the length of the aliphatic chain was revealed. Thus, the longer the chain length, the greater the protective effect. The antibiofouling ability resides mainly on the hydrophobic characteristic of polymers and the pH change occurring at the polymer-electrolyte interface when the coated aluminium alloy was immersed in the electrolytes.

Research paper thumbnail of A systematic study of antibacterial silver nanoparticles: efficiency, enhanced permeability, and cytotoxic effects

Journal of Nanoparticle Research, 2014

We report here a systematic study of the antibacterial behavior of silver nanoparticles coated wi... more We report here a systematic study of the antibacterial behavior of silver nanoparticles coated with fatty acids (oleic: AgNP-O, linoleic: AgNP-L, and palmitic acids: AgNP-P) in water. We have found remarkable differences in their capability to penetrate bacteria cell over a broader range of particle size of *4-96 nm compared to previously reported work, and a variable toxicity depending on the particles size. Our results indicate that silver nanoparticles stabilized with oleic acid showed clear advantages in antibacterial activity, penetration inside the bacteria cells, cytotoxicity, time effectiveness, efficiency, and stability against light. Keywords Silver Á Nanoparticles Á Antibacterial Á Cytotoxicity Á Permeability Á Environmental and health effects Electronic supplementary material The online version of this article (

Research paper thumbnail of Biofilm formation on aluminum alloy 2024: A laboratory study

Journal of Electroanalytical Chemistry, 2015

Research paper thumbnail of Review: Antibacterial behavior of carboxylate silver(I) complexes

Journal of Coordination Chemistry, 2014

ABSTRACT Since ancient times, silver ions have been known to be effective against a broad range o... more ABSTRACT Since ancient times, silver ions have been known to be effective against a broad range of micro-organisms but in the last decade, this metal has been greatly studied because of their antimicrobial capability against a wide range of bacteria, viruses, and fungi. For the same reason, it is the most extensively studied metal with antibacterial applications in medicine. Besides applications, the antimicrobial activity is associated with high effectiveness, low toxicity, and virtually no resistance of micro-organisms to the presence of this metal. The appearance of new bacterial strains resistant to antibiotics is a serious health problem; so, there is a strong incentive to develop new bactericides. This makes current research in bactericidal silver complexes particularly important. This review summarizes the most important aspect related to coordination chemistry of Ag(I) carboxylate complexes and their influence as antibacterial agents.

Research paper thumbnail of Characterization of salmon gelatin based film on antimicrobial properties of chitosan against E. coli

Procedia Food Science, 2011

Salmon gelatin and chitosan are high potential biopolymer to obtain edible films with antimicrobi... more Salmon gelatin and chitosan are high potential biopolymer to obtain edible films with antimicrobial effect for fresh meat. Therefore, it is important to characterize the structural (glassy or rubbery) state of the gelatin film on antimicrobial properties of chitosan. Extracted salmon (Salmo Salar) gelatin (acid-basic extraction) and low molecular weight chitosan solutions (0; 0.25; 0.5 and 1% w/w) at pH 5.5 were prepared to obtain a final concentration to 7% w/w (gelatin + chitosan). Films were obtained by casting at 5ºC and equilibrated at 33% and 85% of relative humidity (RH) in order to obtain a glassy and rubbery state, respectively. Water content, specific volume and glass transition temperature (Tg) were measured and antimicrobial properties against Escherichia coli (E.c.) (105 ufc/ml) were obtained by agar plate diffusion and kinetic measurements at 37ºC. Chitosan diffusion in agar plate was determined using liquid solutions and films over agar plate. The results showed diminution of Tg (maintaining structural state) as increase chitosan concentration, increasing also specific volume and water content due their high capacity to adsorb water. Although inhibition by chitosan of bacteria growth kinetic was 100%, solutions and films samples could not diffuse in the agar. In conclusion, the chitosan could not diffuse on the films matrix and also in agar plate and therefore in food when is combined with salmon gelatin. The implication of this work have been investigate the use of edible films from marine sources with antimicrobial effects in an effort to growing demand from consumers for safer and better quality foods.

Research paper thumbnail of Influence of Glassy or Rubbery State on the Antimicrobial Activity of Chitosan-gelatin Films

Journal of Food Research, 2012

The aim was to study if the antimicrobial activity of chitosan incorporated into edible films bas... more The aim was to study if the antimicrobial activity of chitosan incorporated into edible films based on gelatin could be affected by the molecular mobility (glassy or rubbery state) of the matrix. Films were obtained from film-forming suspensions (FFS) of bovine and salmon gelatins (7% w/w) and chitosan (0; 0.25; 0.5; 1% w/w) equilibrated at 33% y 85% of relative humidities. Antimicrobial properties against <em>Escherichia coli, Listeria monocytogenes </em>and <em>Salmonella thyphimurium…

Research paper thumbnail of Electroreduction of CO2 Catalyzed by Metallomacrocyclics

N4-Macrocyclic Metal Complexes

Research paper thumbnail of Release of silver and copper nanoparticles from polyethylene nanocomposites and their penetration into Listeria monocytogenes

Materials Science and Engineering: C, 2014

Since infection is a major cause of death in a patient whose immune responses have been compromis... more Since infection is a major cause of death in a patient whose immune responses have been compromised (immunocompromised patient), considerable attention has been focused on developing materials for the prevention of infections. This has been directed primarily at suppressing or eliminating the host's endogenous microbial burden and decreasing the acquisition of new organisms. In this study, the antibacterial properties of two nanocomposites, polyethylene modified with silver nanoparticles (PE-AgNps) or copper nanoparticles (PE-CuNps), against Listeria monocytogenes have been investigated. In order to elucidate the antibacterial mechanism, specifically whether this mechanism corresponds to bactericidal or bacteriolytic activities, we have determined the extent of release of metal ions (Ag + and Cu 2+) and, also, the morphology of the bacteria. The metal ion release from nanocomposites was followed by inductively coupled plasma spectrometry and the morphology of the bacteria was revealed through examination of ultramicrotomed sections of bacteria in a transmission electron microscope. The study of metal ion release from the nanocomposites shows that for both nanocomposites the amount of ions released varies with time, which initially displays a linear behavior until an asymptotic behavior is reached. Further, TEM images show that silver nanoparticles (AgNps) and copper nanoparticles (CuNps), which are released from the nanocomposites, can penetrate to the cell wall and the plasma membrane of bacteria. Resulting morphological changes involve separation of the cytoplasmic membrane from the cell wall, which is known to be an effect of plasmolysis. It was revealed that the antibacterial abilities of the two nanocomposites against L. monocytogenes are associated with both bactericidal and bacteriolytic effects.

Research paper thumbnail of Antibacterial, kinetics and bacteriolytic properties of silver(I) pyridinedicarboxylate compounds

Materials Science and Engineering: C, 2014

Antibacterial properties of silver(I)-pyridinedicarboxylate compounds (with Pyridine-2,3-dicarbox... more Antibacterial properties of silver(I)-pyridinedicarboxylate compounds (with Pyridine-2,3-dicarboxylic(Lutidinic acid), pyridine-2,4-dicarboxylic (Quinolinic acid) and pyridine-2,5-dicarboxylic (Isocinchomeronic acid)) were studied against Escherichia coli, Listeria monocytogenes (ISP-65-08), Salmonella typhi and Staphylococcus aureus (ATCC 25923) using kinetics of grown inhibition, viability assays, minimum inhibitory concentration and optical microscopy. The 3 silver compounds were tested toward UV-radiation in order to characterize their light insensitivity for potential medical devices: UV-radiation curable polymers. Photophysical measurements show remarkable differences toward UV-radiation, which were explained based on their polymeric structures with multiple nature bonds between pyridinedicarboxylic ligands and Ag(I) centers. We found a bacteriolytic effect and differences in the antibacterial efficiency depending on the structure of the complexes and the nature of Ag\X (X = oxygen and nitrogen) bonds: AgQuinol N AgLutidin N AgIsocinchom.

Research paper thumbnail of Preparation and antibacterial properties of hybrid-zirconia films with silver nanoparticles

Materials Chemistry and Physics, 2012

The antimicrobial effect of incorporating silver nanoparticles (AgNps) into zirconia matrix-polye... more The antimicrobial effect of incorporating silver nanoparticles (AgNps) into zirconia matrix-polyether glycol was studied. AgNps of 4-6 nm in size were synthesized using the inverse micelles method, and different doses of metallic nanoparticles were incorporated into zirconia-polyether glycol mixtures during the ageing procedure. Atomic force microscopy (AFM) of the modified hybrid film showed a homogenous distribution of 20-80 nm diameter AgNps, indicating agglomeration of these structures during film modification; such agglomerations were greater when increasing the dosage of the colloidal system. The AgNps-hybrid films showed higher antimicrobial activity against Gram-positive bacteria than for Gram-negative bacteria. Hybrid films prepared with dioctyl sodium sulfosuccinate (AOT) stabilized AgNps presented enhanced antibacterial activity compared to that obtained through the addition of a high AgNO 3 concentration (0.3 wt%).

Research paper thumbnail of 1.1.5. Synthesis and characterization of silver(I) complexes with ligands having anti-inflammatory properties

Communications in Inorganic Synthesis, 2013

Five water soluble silver(I) complex with Ibuprofen (AgIbu), Naproxen (AgNap), Mefenamic acid (... more Five water soluble silver(I) complex with Ibuprofen (AgIbu), Naproxen (AgNap), Mefenamic acid (AgMef), acetyl salicylic acid(AgAsp) and salicylic acid (AgSal) were synthesized and characterized by elemental analysis, FT-IR, 1 H and 13 C NMR. Data suggest coordination of the ligand to Ag(I) through the oxygen atom of the carboxylic group. AgAsp was obtained as a mixture of AgAsp and Ag(I)-2-hydroxybenzoate (AgSal) due to decomposition by thermal and hydrolysis of acetylsalicylic acid into salicylic acid. AgSal structure was confirmed by FT-IR, NMR and X-ray diffraction. Synthesized compounds were tested toward UV-radiation (258 nm, 30 W) and compared with AgCl in order to characterize their light sensibility.

Research paper thumbnail of Synthesis, characterization and 2,5-pyridinedicarboxylic acid interaction of Zinc(II) complexes with N-(4-X-phenyl)pyridine-2-yl-methanimine ligands (X= -Cl and -N(CH3)2)

Communications in Inorganic Synthesis, 2017

Abstract: Two new Zn(II) N-(4-X-phenyl)pyridine-2-yl-methanimine complexes, [Zn(NN´-Cl)Cl 2 ]( 1 ... more Abstract: Two new Zn(II) N-(4-X-phenyl)pyridine-2-yl-methanimine complexes, [Zn(NN´-Cl)Cl 2 ]( 1 ) and [Zn(NN´-N(CH 3 ) 2 )Cl 2 ]( 2 ), have been synthesized and characterized by elemental analysis, FT-IR and NMR- 1 H spectra. The crystal structure of complex 1 was determined by X-ray single crystal diffraction. Experiments performed by Benesi-Hilderbrand method indicate that zinc complexes interact with 2,5-pyridinedicarboxyc acid.

Research paper thumbnail of Electrochemical dynamic sensing of hydrogen peroxide in the presence of microorganisms

Electrochimica Acta, 2019

New experimental techniques and protocols are needed to study microbiologically influenced corros... more New experimental techniques and protocols are needed to study microbiologically influenced corrosion (MIC). In this work, we studied the capacity of microorganisms to modify their environment in vitro. The methodology involved cyclic voltammetry measurements using carbon electrodes modified with cobalt phthalocyanine, which is a known catalyst for the two-electron reduction of O 2 to give peroxide. Mueller-Hinton (21 g/l) was used as an electrolyte in a sterilized aqueous medium. The open circuit potential (OCP) and oxygen concentration behaved similarly over time, with generally similar growth curves. However, there were peculiarities that indicated the presence of peroxide and catalase. Catalase activity was demonstrated by comparing the voltammetric responses of the culture medium in the absence and presence of bacterial strains of Escherichia coli (Gram +) and Staphylococcus aureus (Gram-), both facultative and catalase positive. With this system, which is capable of discriminating O 2 and hydrogen peroxide, catalase activity is highly evident, and at its maximum at the end of the exponential stage of the growth curve.

Research paper thumbnail of Capping of silver nanoparticles by anti-inflammatory ligands: Antibacterial activity and superoxide anion generation

Journal of Photochemistry and Photobiology B: Biology, 2019

Silver nanoparticles (AgNPs) have been widely recognized as antibacterial agents. However, its st... more Silver nanoparticles (AgNPs) have been widely recognized as antibacterial agents. However, its stability and activity over time have been poorly studied. In this work, the properties and characteristics of differently stabilized AgNPs were evaluated during a span of time. The surface capping agents were diclofenac (d), and ketorolac (k), which currently are used as anti-inflammatory in human medicine. On evaluating the size variation over time, it was observed that the AgNPs-k are the most stable, unlike the non-capped nanoparticles agglomerate and precipitate. UV-Vis spectroscopy analysis showed that the absorbance during time decreases for the three types of nanoparticles, but the decrease is less marked for the two types of anti-inflammatory-capped AgNPs. The rapid loss of the optical properties of bare AgNPs, is mainly due to oxidation, agglomeration, and precipitation of this nanoparticles. The potential cytotoxicity of the AgNPs, evaluated through the formation of the superoxide anion using XXT, showed that both, AgNPs-k and AgNPs-d, generate the radical anion when the samples are irradiated with UV light at 365 nm. This effect appears associated with the capping agents, since the bare nanoparticles did not promote the formation of the superoxide anion. The antibacterial activity of the AgNPs throughout time, against two microorganisms (Escherichia coli and Staphylococcus aureus), was also evaluated. The results showed that capping agents played a decisive role in the antibacterial ability of AgNPs and also in enhancing the antibacterial activity over time. microorganisms has been reported successfully through the evaluation of bacterial susceptibility [4,5,9]. The pathways through which the AgNPs act against bacteria, are at least two: i) the generation of reactive oxygen species (ROS) [10,11] and ii) the release of silver ions (Ag +), both processes generating from the surface of the nanoparticles. Both Ag + ions and ROS can cause bacterial death by interacting with the macromolecules which are part of the bacterium [12,13]. Studies on the generation of ROS from AgNPs [14,15] have shown that the main radical species is the superoxide anion (O 2 .−). This species would be formed as a consequence of an electron transfer to molecular oxygen (O 2) present in the environment. [2,16] After irradiating the surface of the AgNPs with UV-Vis light, the absorption of energy that originates the passage of electrons from the valence band to the conduction band takes place. The excess electrons will participate in the reduction of molecular oxygen, forming super-oxide. [16] The O 2 .− and other reactive oxygen species can damage the cellular constituents

Research paper thumbnail of Porous Nanogold/Polyurethane Scaffolds with Improved Antibiofilm, Mechanical, and Thermal Properties and with Reduced Effects on Cell Viability: A Suitable Material for Soft Tissue Applications

ACS applied materials & interfaces, Jan 25, 2018

The use of implants carries on a series of problems, among them infections, poor biocompatibility... more The use of implants carries on a series of problems, among them infections, poor biocompatibility, high levels of cytotoxicity, and significant mechanical differences between implants and host organs that promote stress shielding effects. These problems indicate that the materials used to make implants must meet essential requirements and high standards for implantations to be successful. In this work, we present the synthesis, characterization and evaluation of the antibiofilm, mechanical, and thermal properties, and cytotoxic effect of a nanocomposite-based scaffold on polyurethane (PU) and gold nanoparticles (AuNPs) for soft tissue applications. The effect of the quantity of AuNPs on the antibacterial activity of nanocomposite scaffolds was evaluated against Staphylococcus epidermidis and Klebsiella spp., with a resulting 99.99% inhibition of both bacteria using a small quantity of nanoparticles. Cytotoxicity was evaluated with the T10 1/2 test against fibroblast cells. The resul...

Research paper thumbnail of {"__content__"=>"Stability of Antibacterial Silver Carboxylate Complexes against and Their Cytotoxic Effects.", "i"=>{"__content__"=>"Staphylococcus epidermidis"}}

Molecules (Basel, Switzerland), Jan 4, 2018

The antibacterial effects against of five silver carboxylate complexes with anti-inflammatory lig... more The antibacterial effects against of five silver carboxylate complexes with anti-inflammatory ligands were studied in order to analyze and compare them in terms of stability (in solution and after exposure to UV light), and their antibacterial and morphological differences. Four effects of the Ag-complexes were evidenced by transmission electronic microscopy (TEM) and scanning electronic microscopy (SEM): DNA condensation, membrane disruption, shedding of cytoplasmic material and silver compound microcrystal penetration of bacteria. 5-Chlorosalicylic acid (5Cl) and sodium 4-aminosalicylate (4A) were the most effective ligands for synthesizing silver complexes with high levels of antibacterial activity. However, Ag-5Cl was the most stable against exposure UV light (365 nm). Cytotoxic effects were tested against two kinds of eukaryotic cells: murine fibroblast cells (T10 1/2) and human epithelial ovarian cancer cells (A2780). The main objective was to identify changes in their antibac...

Research paper thumbnail of Correlating light and thermal stability of silver carboxylate complexes by infrared and 13C NMR spectroscopy

Journal of Coordination Chemistry, 2016

Bond nature of carboxylic groups can play an important role in Ag(I)-carboxylate compounds becaus... more Bond nature of carboxylic groups can play an important role in Ag(I)-carboxylate compounds because light and thermal stability are important requirements for future applications such as antibacterial additives. A linear correlation between bond character and light stability of silver carboxylate complexes has been predicted by a direct relationship of infrared and 13 C NMR spectroscopic data. This correlation is in agreement with the thermogravimetric analysis and provides a new approach to explore the interaction and the physical properties of metalcarboxylate bonds.

Research paper thumbnail of Copper-polymer nanocomposites: An excellent and cost-effective biocide for use on antibacterial surfaces

Materials Science and Engineering: C, 2016

The development of polymer nanocomposites with antimicrobial properties has been a key factor for... more The development of polymer nanocomposites with antimicrobial properties has been a key factor for controlling or inhibiting the growth of microorganisms and preventing foodborne diseases and nosocomial infections. Commercially available antibacterial products based on silver-polymer are the most widely used despite the fact that copper is considerably less expensive. The incorporation of copper nanoparticles as antibacterial agents in polymeric matrices to generate copper-polymer nanocomposites have presented excellent results in inhibiting the growth of a broad spectrum of microorganisms. The potential applications in food packaging, medical devices, textiles and pharmaceuticals and water treatment have generated an increasing number of investigations on preparing copper based nanocomposites and alternative polymeric matrices, as potential hosts of nano-modifiers. This review presents a comprehensive compilation of previous published work on the subject, mainly related to the antimicrobial activity of copper polymer nanocomposites. Within all the phenomenology associated to antibacterial effects we highlight the possible mechanisms of action. We discuss the differences in the susceptibility of Gram negative and positive bacteria to the antibacterial activity of nanocomposites, and influencing factors. As well, the main applications of copper polymer-metal nanocomposites are described, considering their physical and chemical characteristics. Finally, some commercially available copper-polymer nanocomposites are described.

Research paper thumbnail of Polyethylene/silver-nanofiber composites: A material for antibacterial films

Materials Science and Engineering: C, 2016

Silver nanofibers (Ag-Nfbs)~80 nm in diameter were synthesized by hydrothermal treatment. The nan... more Silver nanofibers (Ag-Nfbs)~80 nm in diameter were synthesized by hydrothermal treatment. The nanofibers (3 and 5 wt%) were added in the initial feed together with the catalytic system. Polymerizations in an ethylene atmosphere were performed, yielding PE nanocomposites in situ with 3 and 5 wt% content of Ag-Nfbs. The antibacterial effect of the silver-nanofiber composites was evaluated after incubation of Escherichia coli ATCC 25923 for 8 h on their surface. Bacterial viability tests showed that the silver-nanofiber composites inhibited the growth of Escherichia coli ATCC 25923 by 88 and 56%. This behavior is attributed to increased silver ions release from the nanocomposite. TEM analysis showed that the antibacterial effect is associated with membrane disruption but not with changes in shape.

Research paper thumbnail of Stripping voltammetry microprobe (SPV): Substantial improvements of the protocol

Journal of Electroanalytical Chemistry, 2015

The recently introduced new electroanalytical protocol of stripping voltammetry microprobe (SPV) ... more The recently introduced new electroanalytical protocol of stripping voltammetry microprobe (SPV) has been considerably improved with respect to analytical performance. The determination of the silver ions is shown to be possible by the precipitation of a solution of silver drops on an electrode surface, which is previously moistened with a solution of NaCl. The electrode thus modified, i.e., with the silver chloride precipitate on the surface, is introduced into a chloride electrolyte and is negatively polarized to reduce the silver salt to metallic silver. Whereas this reduction process produces only a broad signal, the following electrochemical oxidation of the silver metal back to AgCl provides a highly sensitive and narrow signal, which lends itself for analysis. The linear range for determination of silver ions following this protocol is 1.4 Â 10 À7 to 7.4 Â 10 À4 mol L À1 and the detection limit is 4.6 Â 10 À8 mol L À1 .

Research paper thumbnail of Antibiofouling Properties of Sol-Gel Type Polymers for Aluminium Alloys: Biocorrosion Protection Against Pseudomonas Aeruginosa

The antibiofouling ability of three hybrid sol-gel coatings against P. aeruginosa for the protect... more The antibiofouling ability of three hybrid sol-gel coatings against P. aeruginosa for the protection of AA2024-T3 aluminium alloy has been investigated. The polymers were synthesized by mixing tetraethoxysilane (TEOS) with three precursors: (a) triethoxypropylsilane (TEPRS), (b) triethoxypentylsilane (TEPES) and (c) triethoxyoctylsilane (TEOCS). The main difference between the three precursors is the length of the aliphatic chain of one of the substituents. The antibacterial properties of the polymers were examined using viability techniques. The morphology of the polymers was characterized using scanning electron microscopy (SEM). The resistance of the AA2024 alloy coated with the respective polymers to microbiologically influenced corrosion was evaluated by potentiodynamic polarization. The results showed that the polymers possess antibacterial ability against P. aeruginosa and that the length of the aliphatic chain of the precursors does not significantly affect this property. Further, the electrochemical measurements revealed that the coatings inhibited microbiologically influenced corrosion in the mixture of P. aeruginosa and 0.1 M NaCl, due to the antibacterial properties of the polymers. A correlation between the degree of protection and the length of the aliphatic chain was revealed. Thus, the longer the chain length, the greater the protective effect. The antibiofouling ability resides mainly on the hydrophobic characteristic of polymers and the pH change occurring at the polymer-electrolyte interface when the coated aluminium alloy was immersed in the electrolytes.

Research paper thumbnail of A systematic study of antibacterial silver nanoparticles: efficiency, enhanced permeability, and cytotoxic effects

Journal of Nanoparticle Research, 2014

We report here a systematic study of the antibacterial behavior of silver nanoparticles coated wi... more We report here a systematic study of the antibacterial behavior of silver nanoparticles coated with fatty acids (oleic: AgNP-O, linoleic: AgNP-L, and palmitic acids: AgNP-P) in water. We have found remarkable differences in their capability to penetrate bacteria cell over a broader range of particle size of *4-96 nm compared to previously reported work, and a variable toxicity depending on the particles size. Our results indicate that silver nanoparticles stabilized with oleic acid showed clear advantages in antibacterial activity, penetration inside the bacteria cells, cytotoxicity, time effectiveness, efficiency, and stability against light. Keywords Silver Á Nanoparticles Á Antibacterial Á Cytotoxicity Á Permeability Á Environmental and health effects Electronic supplementary material The online version of this article (

Research paper thumbnail of Biofilm formation on aluminum alloy 2024: A laboratory study

Journal of Electroanalytical Chemistry, 2015

Research paper thumbnail of Review: Antibacterial behavior of carboxylate silver(I) complexes

Journal of Coordination Chemistry, 2014

ABSTRACT Since ancient times, silver ions have been known to be effective against a broad range o... more ABSTRACT Since ancient times, silver ions have been known to be effective against a broad range of micro-organisms but in the last decade, this metal has been greatly studied because of their antimicrobial capability against a wide range of bacteria, viruses, and fungi. For the same reason, it is the most extensively studied metal with antibacterial applications in medicine. Besides applications, the antimicrobial activity is associated with high effectiveness, low toxicity, and virtually no resistance of micro-organisms to the presence of this metal. The appearance of new bacterial strains resistant to antibiotics is a serious health problem; so, there is a strong incentive to develop new bactericides. This makes current research in bactericidal silver complexes particularly important. This review summarizes the most important aspect related to coordination chemistry of Ag(I) carboxylate complexes and their influence as antibacterial agents.

Research paper thumbnail of Characterization of salmon gelatin based film on antimicrobial properties of chitosan against E. coli

Procedia Food Science, 2011

Salmon gelatin and chitosan are high potential biopolymer to obtain edible films with antimicrobi... more Salmon gelatin and chitosan are high potential biopolymer to obtain edible films with antimicrobial effect for fresh meat. Therefore, it is important to characterize the structural (glassy or rubbery) state of the gelatin film on antimicrobial properties of chitosan. Extracted salmon (Salmo Salar) gelatin (acid-basic extraction) and low molecular weight chitosan solutions (0; 0.25; 0.5 and 1% w/w) at pH 5.5 were prepared to obtain a final concentration to 7% w/w (gelatin + chitosan). Films were obtained by casting at 5ºC and equilibrated at 33% and 85% of relative humidity (RH) in order to obtain a glassy and rubbery state, respectively. Water content, specific volume and glass transition temperature (Tg) were measured and antimicrobial properties against Escherichia coli (E.c.) (105 ufc/ml) were obtained by agar plate diffusion and kinetic measurements at 37ºC. Chitosan diffusion in agar plate was determined using liquid solutions and films over agar plate. The results showed diminution of Tg (maintaining structural state) as increase chitosan concentration, increasing also specific volume and water content due their high capacity to adsorb water. Although inhibition by chitosan of bacteria growth kinetic was 100%, solutions and films samples could not diffuse in the agar. In conclusion, the chitosan could not diffuse on the films matrix and also in agar plate and therefore in food when is combined with salmon gelatin. The implication of this work have been investigate the use of edible films from marine sources with antimicrobial effects in an effort to growing demand from consumers for safer and better quality foods.

Research paper thumbnail of Influence of Glassy or Rubbery State on the Antimicrobial Activity of Chitosan-gelatin Films

Journal of Food Research, 2012

The aim was to study if the antimicrobial activity of chitosan incorporated into edible films bas... more The aim was to study if the antimicrobial activity of chitosan incorporated into edible films based on gelatin could be affected by the molecular mobility (glassy or rubbery state) of the matrix. Films were obtained from film-forming suspensions (FFS) of bovine and salmon gelatins (7% w/w) and chitosan (0; 0.25; 0.5; 1% w/w) equilibrated at 33% y 85% of relative humidities. Antimicrobial properties against <em>Escherichia coli, Listeria monocytogenes </em>and <em>Salmonella thyphimurium…

Research paper thumbnail of Electroreduction of CO2 Catalyzed by Metallomacrocyclics

N4-Macrocyclic Metal Complexes

Research paper thumbnail of Release of silver and copper nanoparticles from polyethylene nanocomposites and their penetration into Listeria monocytogenes

Materials Science and Engineering: C, 2014

Since infection is a major cause of death in a patient whose immune responses have been compromis... more Since infection is a major cause of death in a patient whose immune responses have been compromised (immunocompromised patient), considerable attention has been focused on developing materials for the prevention of infections. This has been directed primarily at suppressing or eliminating the host's endogenous microbial burden and decreasing the acquisition of new organisms. In this study, the antibacterial properties of two nanocomposites, polyethylene modified with silver nanoparticles (PE-AgNps) or copper nanoparticles (PE-CuNps), against Listeria monocytogenes have been investigated. In order to elucidate the antibacterial mechanism, specifically whether this mechanism corresponds to bactericidal or bacteriolytic activities, we have determined the extent of release of metal ions (Ag + and Cu 2+) and, also, the morphology of the bacteria. The metal ion release from nanocomposites was followed by inductively coupled plasma spectrometry and the morphology of the bacteria was revealed through examination of ultramicrotomed sections of bacteria in a transmission electron microscope. The study of metal ion release from the nanocomposites shows that for both nanocomposites the amount of ions released varies with time, which initially displays a linear behavior until an asymptotic behavior is reached. Further, TEM images show that silver nanoparticles (AgNps) and copper nanoparticles (CuNps), which are released from the nanocomposites, can penetrate to the cell wall and the plasma membrane of bacteria. Resulting morphological changes involve separation of the cytoplasmic membrane from the cell wall, which is known to be an effect of plasmolysis. It was revealed that the antibacterial abilities of the two nanocomposites against L. monocytogenes are associated with both bactericidal and bacteriolytic effects.

Research paper thumbnail of Antibacterial, kinetics and bacteriolytic properties of silver(I) pyridinedicarboxylate compounds

Materials Science and Engineering: C, 2014

Antibacterial properties of silver(I)-pyridinedicarboxylate compounds (with Pyridine-2,3-dicarbox... more Antibacterial properties of silver(I)-pyridinedicarboxylate compounds (with Pyridine-2,3-dicarboxylic(Lutidinic acid), pyridine-2,4-dicarboxylic (Quinolinic acid) and pyridine-2,5-dicarboxylic (Isocinchomeronic acid)) were studied against Escherichia coli, Listeria monocytogenes (ISP-65-08), Salmonella typhi and Staphylococcus aureus (ATCC 25923) using kinetics of grown inhibition, viability assays, minimum inhibitory concentration and optical microscopy. The 3 silver compounds were tested toward UV-radiation in order to characterize their light insensitivity for potential medical devices: UV-radiation curable polymers. Photophysical measurements show remarkable differences toward UV-radiation, which were explained based on their polymeric structures with multiple nature bonds between pyridinedicarboxylic ligands and Ag(I) centers. We found a bacteriolytic effect and differences in the antibacterial efficiency depending on the structure of the complexes and the nature of Ag\X (X = oxygen and nitrogen) bonds: AgQuinol N AgLutidin N AgIsocinchom.

Research paper thumbnail of Preparation and antibacterial properties of hybrid-zirconia films with silver nanoparticles

Materials Chemistry and Physics, 2012

The antimicrobial effect of incorporating silver nanoparticles (AgNps) into zirconia matrix-polye... more The antimicrobial effect of incorporating silver nanoparticles (AgNps) into zirconia matrix-polyether glycol was studied. AgNps of 4-6 nm in size were synthesized using the inverse micelles method, and different doses of metallic nanoparticles were incorporated into zirconia-polyether glycol mixtures during the ageing procedure. Atomic force microscopy (AFM) of the modified hybrid film showed a homogenous distribution of 20-80 nm diameter AgNps, indicating agglomeration of these structures during film modification; such agglomerations were greater when increasing the dosage of the colloidal system. The AgNps-hybrid films showed higher antimicrobial activity against Gram-positive bacteria than for Gram-negative bacteria. Hybrid films prepared with dioctyl sodium sulfosuccinate (AOT) stabilized AgNps presented enhanced antibacterial activity compared to that obtained through the addition of a high AgNO 3 concentration (0.3 wt%).