Natalia Bellotti

The application of bioactive compounds from the food industry to control mold growth in indoor waterborne coatings

Microbial growth in indoor environments creates health problems, especially in people with asthma; approximately 80% of these patients are allergic to mold. Antimicrobial coatings are formulated to generate surfaces that are easy to clean and may also incorporate active agents, commonly called biocides, which inhibit microbial colonization, subsequent growth and bio-deterioration of the substrates. Some research lines seek to replace traditional organometallic and organochlorines biocides with environmentally acceptable ones. The aim of this research was, primarily, to explore the possible application of different compounds used in food industry like preservatives to be used as antimicrobial additives for antimicrobial coatings. Four biocides were tested against two different ambient molds isolated from an interior painted wall (Chaetomium globosum and Alternaria alternate). The selected biocides were zinc salicylate, zinc benzoate, calcium benzoate and potassium sorbate. The resulting paints were subjected to biological and physical tests (viscosity, hiding power, humidity absorption and biocides leaching rate). Bioassays revealed that zinc benzoate and zinc salicylate resulted active against both fungi.

Lanthanum-exchanged zeolite and clay as anticorrosive pigments for galvanized steel

Abstract A wide variety of inhibitive pigments is now being offered as possible alternatives to chromate and lead compounds for painted metals protection. Unfortunately, the most wide spread of these substitute pigments, zinc phosphate, has, at present, raised some environmental concern because phosphate causes the eutrophication of water courses and zinc itself is toxic. The aim of this research was to study the anticorrosive performance of a mixture consisting of zinc phosphate, modified zeolite and clay (bentonite) in order to diminish phosphate content in paints. The zeolite and the clay were exchanged with La(III) ions, as inorganic green inhibitor. In the first step, the anticorrosion protection by La(III) ions in solution was assessed by electrochemical tests. In the second step, an epoxy-polyamide paint formulated with the pigment mixture applied on galvanized panels was studied by salt spray test and electrochemical noise measurements (ENM). The results showed that it was possible to replace part of the zinc phosphate content in the paint with the exchanged zeolite and the clay.

''Quebracho'' tannin derivative and boosters biocides for new antifouling formulations

The growth of fouling communities on ships’ hulls causes economic losses due to increased fuel consumption and to the deterioration of the metallic substrate by corrosion. Antifouling paints are formulated to avoid the settlement of these organisms and may contain biocides as active compounds. The objective of this research was to evaluate the antifouling performance of paints formulated with a “quebracho” tannin derivative (zinc “tannate”) and “boosters” (secondary biocides). The “boosters” used in this study were bismuth lactate, a zeolite exchanged with silver cations, and the same zeolite modified with silver chloride. Bioassays with “boosters” solutions were carried out employing Artemia persimilis. Soluble matrix antifouling paints were formulated and their action was assessed in a natural sea water environment. Results showed that the bismuth lactate resulted in a coating with almost triple service life of the antifouling paints with zinc “tannate.” Paints formulated with the silver composites behaved slightly better than the control paint.

Improved antimicrobial activity of silica–Cu using a heteropolyacid and different precursors by sol–gel: synthesis and characterization

Antimicrobial coatings are used to avoid the proliferation of fungi and bacteria inside urban buildings by incorporating low concentrations of antimicrobial agents (biocides). This study is focused on evaluating the antifungal activity of copper (II) supported on a silica matrix, and as counter-cation of a heteropolyacid, obtained from the sol–gel method using various catalysts, against two fungal isolates. The fungi used in this evaluation were Alternaria alternata and Chaetomium globosum isolated by routine microbiological techniques from biodeteriorated paints films. In all cases, fungi were selected due to their ability to grow on the paint films and their negative impact on human health. First, silicas were prepared using tetraethylorthosilicate and methyl trimethoxysilane as precursors and acetic acid, hydrochloric acid as catalysts of the hydrolysis reaction of the alkoxide. The effect of addition of copper (II) in the form of copper nitrate was studied. With respect to the morphology of the silica, most of them are similar, between pure and modified silica, in all cases. Once the stage of the synthesis and characterization of the prepared materials was performed, six of them were selected to evaluate their antifungal activity by agar plate inhibition test against both fungi of interest (A. alternata and C. globosum), and the percent inhibition was determined in each case. Tested Cu-based solids were shown to have a higher antifungal activity because they completely inhibit the growth of both fungi with lower concentrations relative to its control. This work was performed as a preliminary study, in order to guide the selection of a suitable organic biocide from a list of possible antifungal agents.Graphical Abstract

Síntesis verde y caracterización de sólidos de matriz silícea con cobre y plata obtenidos a partir de dos precursores para su aplicación como aditivos antifúngicos

The synthesis of new environmentally friendly products with antimicrobial activity, applied to the formulation of coatings that prevent biofilm formation is an issue that has become important in recent years. Biofilms produce undesirable changes (biodeterioration) in material properties due to the vital activity of microorganisms. They reduce indoor air quality by contributing to the formation of bioaerosols and therefore affect human health. This paper aims to greensynthesis and characterization of solid silica matrix associated with copper and silver, as counter cations of a heteropolyacid for use as antimicrobial additives in paints. The solids were obtained from the sol-gel method using different acidic medium. The antifungal activity of the synthesized solids was evaluated against two fungal isolates, Alternaria alternata and Chaetomium globosum, obtained from biodeteriorated paints films. Different silicas were prepared using tetraethyl orthosilicate and methyltrimethoxysilane as precursors and acids as catalysts for the hydrolysis reaction of the alkoxide. Once the synthesis phase and the characterization of the samples were finished, the antifungal activity against the microorganisms selected was evaluated and the inhibition percent was determined in each case. Among the solids tested, most showed antifungal activity, because they inhibited the fungal growth at the lower concentrations compared to the sample without the solids, although the presence of copper and silver increases the inhibition in most cases.