ABSTRACT
Classical wet chemical synthesis was used to fabricate a hybrid composite that contained copper nanoparticles (average size â¼1â¯nm), which were embedded into a silicon oxide carrier. The structural and chemical alternations in the copper-functionalized silica were investigated in systems that were sintered at 573â¯K, 873â¯K, 1173â¯K, and 1473â¯K. A general trend, which was associated with the transformation of metallic copper with a cubic structure into copper(II) oxide with a monoclinic structure in the heat-treated systems, was found. XPS and FTIR spectroscopies also revealed the presence of copper(I) oxide, which formed a shell around the CuO. SEM and TEM showed gradual densification of the hybrid system at ever higher sintering temperatures, which corresponded with the gradual copper agglomeration. A temperature of 873â¯K was determined to be the temperature at which amorphous silica was transformed into cristoballite and tridymite, as well as the formation of a bulk-like copper structure. In relation to the physicochemical and structural data, high antimicrobial features that had a relatively low toxicity effect on the normal human fibroblasts (NHDF) below 250â¯mg/L was found for the initial copper-silica composite and the samples that were sintered at 573â¯K. In turn, a significant decrease in the biological impact was observed in the samples that were sintered at temperatures above 573â¯K. As a result, the paper discusses the model of structural modifications in copper-silica nanocomposite concerning their biological impact that was developed.
Subject(s)
Copper , Nanocomposites , Silicon Dioxide , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/toxicity , Bacteria/drug effects , Cell Survival/drug effects , Cells, Cultured , Copper/chemistry , Copper/toxicity , Hot Temperature , Humans , Nanocomposites/chemistry , Nanocomposites/toxicity , Particle Size , Silicon Dioxide/chemistry , Silicon Dioxide/toxicityABSTRACT
In the last few decades, many nanostructures with varying properties and possible applications have been developed. These materials have been intended to work in various environmental temperature conditions. In this context, the main challenge has been to comprehend the impact of synergic interaction between individual elements included in non-annealed materials in relation to systems subjected to temperature impact. Another problem has corresponded to the impact of thermal modification on organisms such as bacteria and human cells. Such problems can be solved by the fabrication of a nanocomposite with mono-dispersed 8â¯nm silver (Ag0 or Ag+) embedded into a silica carrier, followed by the analysis of the impact of heat treatment under various temperature conditions on its physicochemical features. Therefore, methodical studies reported in this text have shown an increase of silver particle size up to 170â¯nm, a decrease of its concentration, as well as the formation of sub-nanometer Ag+ and/or Ag2+ clusters as the temperature rises to 1173â¯K. In turn, the structurally disordered silica carrier had been entirely transformed to cristobalite and tridymite only at 1473â¯K as well as partial reduction of Ag2+ to Ag+. Simultaneously, inhibition of growth of Gram-positive and Gram-negative bacteria, as well as an increase in cytotoxicity towards human cells was observed as the temperature rose. As a final point, for the first time, a "pseudo" phase diagram of the structural alterations in the Ag/SiO2 nanocomposite has been created, as well as a model of silver-silica transformation to biological systems has been developed.
Subject(s)
Nanocomposites/chemistry , Silicon Dioxide/chemistry , Silver/chemistry , Cell Line , Cell Survival/drug effects , Gram-Negative Bacteria/drug effects , Gram-Positive Bacteria/drug effects , Hot Temperature , Humans , Microbial Sensitivity Tests , Nanocomposites/toxicityABSTRACT
Opportunistic fungi are the most important pathogens in modern world. They are responsible for severe infections in majority of immunocompromised patients. These microorganisms are commonly present in our environment which is natural reservoir of new, resistant species. For this reason mycoses are mainly chronic or long-lasting diseases. Our arsenal of antifungal drugs is growing but still insufficient for emerging resistant pathogens. An alternative for novel chemical entity drugs is the multidrug approach. This exploiting the drugs being currently on market applying simultaneously for better efficacy or to eradicate resistance. Synergy is the term that describes the phenomenon of increased potency of two or more drugs administered in combination. In the last decades it gains more interest and numbers of synergy claimed reports is growing exponentially. However these have rather low impact on clinical trials or practical use of antimycotics. In present review we wish to discuss current status of synergy between antifungal drugs. Both theoretical point of view and practical applicability in clinical terms are covered. There are serious differences between the assumptions, methods and interpretations of the results and sometimes even obvious mistakes in the procedure that was applied or in the outcomes discussed. On the other hands the specificity of fungal infections introduce dozens of factors affecting the observed results. Shift form in vitro studies to clinical trials reveals further difficulties. Hopefully multi-drug approach seems to be effective even if no strong synergy is displayed.
