Ivana Vinković Vrček

Toxicity of silver ions and differently coated silver nanoparticles in Allium cepa roots

Silver nanoparticles (AgNPs) are the dominating nanomaterial in consumer products due to their well-known antibacterial and antifungal properties. To enhance their properties, different surface coatings may be used, which affect physico-chemical properties of AgNPs. Due to their wide application, there has been concern about possible environmental and health consequences. Since plants play a significant role in accumulation and biodistribution of many environmentally released substances, they are also very likely to be influenced by AgNPs. In this study we investigated the toxicity of AgNO3 and three types of laboratory-synthesized AgNPs with different surface coatings [citrate, polyvinylpyrrolidone (PVP) and cetyltrimethylammonium bromide (CTAB)] on Allium cepa roots. Ionic form of Ag was confirmed to be more toxic than any of the AgNPs applied. All tested AgNPs caused oxidative stress and exhibited toxicity only when applied in higher concentrations. The highest toxicity was recorded for AgNPs-CTAB, which resulted with increased Ag uptake in the roots, consequently leading to strong reduction of the root growth and oxidative damage. The weakest impact was found for AgNPs-citrate, much bigger, negatively charged NPs, which also aggregated to larger particles. Therefore, we can conclude that the toxicity of AgNPs is directly correlated with their size, overall surface charge and/or surface coating.

Fatliquoring agent and drying temperature effects on leather properties

Leather, a collagen structure material, usually requires the addition of fatliquoring agents that have been recently found to cause instability during heating in critical manufacturing processes. The effect of fatliquoring agent concentration and drying temperature on the leather properties was investigated. Leather shrinkage, leather absorption of water and water vapour, and water vapour permeability were measured under defined conditions. The samples of bovine leather obtained after commercial liming and chrome tanning processes were used. The samples were fatliquored with 3, 6, 9 and 12% solutions of anionic synthetic fatliquoring agent and dried at different temperatures. The results of the investigation are corroborated by scanning electron microscope (SEM) study. It was shown how the concentration of fatliquoring agent and drying temperatures influence the leather properties.