Stefania Mura

FTIR nanobiosensors for Escherichia coli detection

Summary Infections due to enterohaemorrhagic E. coli (Escherichia coli) have a low incidence but can have severe and sometimes fatal health consequences, and thus represent some of the most serious diseases due to the contamination of water and food. New, fast and simple devices that monitor these pathogens are necessary to improve the safety of our food supply chain. In this work we report on mesoporous titania thin-film substrates as sensors to detect E. coli O157:H7. Titania films treated with APTES ((3-aminopropyl)triethoxysilane) and GA (glutaraldehyde) were functionalized with specific antibodies and the absorption properties monitored. The film-based biosensors showed a detection limit for E. coli of 1 × 102 CFU/mL, constituting a simple and selective method for the effective screening of water samples.

Modified graphene oxide sensors for ultra-sensitive detection of nitrate ions in water

Nitrate ions is a very common contaminant in drinking water and has a significant impact on the environment, necessitating routine monitoring. Due to its chemical and physical properties, it is hard to directly detect nitrate ions with high sensitivity in a simple and inexpensive manner. Herein with amino group modified graphene oxide (GO) as a sensing element, we show a direct and ultra-sensitive method to detect nitrate ions, at a lowest detected concentration of 5 nM in river water samples, much lower than the reported methods based on absorption spectroscopy. Furthermore, unlike the reported strategies based on absorption spectroscopy wherein the nitrate concentration is determined by monitoring an increase in aggregation of gold nanoparticles (GNPs), our method evaluates the concentration of nitrate ions based on reduction in aggregation of GNPs for monitoring in real samples. To improve sensitivity, several optimizations were performed, including the assessment of the amount of modified GO required, concentration of GNPs and incubation time. The detection methodology was characterized by zeta potential, TEM and SEM. Our results indicate that an enrichment of modified GO with nitrate ions contributed to excellent sensitivity and the entire detection procedure could be completed within 75 min with only 20 μl of sample. This simple and rapid methodology was applied to monitor nitrate ions in real samples with excellent sensitivity and minimum pretreatment. The proposed approach paves the way for a novel means to detect anions in real samples and highlights the potential of GO based detection strategy for water quality monitoring.

Multifunctionalization of wool fabrics through nanoparticles: A chemical route towards smart textiles

A new approach towards the design of smart nanotextiles with innovative properties is presented. Silica (SiO2), titania (TiO2), and silver (Ag) nanoparticles (NPs), were synthesized without the use of any toxic organic compound and then were used, alone and in combination, to functionalize wool fabrics. Electrostatic forces, influenced by a low pH of the solutions, allowed the interactions between wool fabrics and NPs, enabling a robust functionalization. This was verified by X-ray microfluorescence and visualized by scanning electron microscopy measurements. The antibacterial Ag NPs were embedded in a polymer, alginic acid, to reduce the possible side effect due to their direct contact with the skin. SiO2 NPs, instead, were used to change the hydrophilicity of wool while the functionalization with TiO2 NPs was chosen to provide self-cleaning properties. The antibacterial activity of the fabrics was studied against the bacteria Escherichia coli, while the hydrophilicity of wool was studied by contact angle measurements and the self-cleaning properties were tested by estimating the visible discoloring of a dye stain under sunlight irradiation. Interestingly the combination of three different types of NPs provided the best results. SiO2 and Ag made the wool superhydrophilic providing at the same time the best antibacterial properties, while fabrics with titania (alone or in combination) were hydrophobic and showed the best self-cleaning properties.

Innovative Composite Films of Chitosan, Methylcellulose, and Nanoparticles

Plastic is readily available and inexpensive, so it is becoming the main material for packaging. Unfortunately plastics do not biodegrade and, if reduced in small pieces, contaminate soil and waterways. In the present work, natural films composed of chitosan, methylcellulose, and silica (SiO(2)) nanoparticles (NPs) were developed as new packaging materials. The effect of the incorporation of NPs into the polymeric film matrix was evaluated. An excellent improvement of the mechanical properties was obtained for nanostructured films with a composition of CH:MC 50:50 and NPs 1% w/v that make these materials able to replace plastics and derivatives, reducing environmental pollution.

Ferrates for water remediation

The availability of safe drinking-water at the global level is one of the biggest challenges of our century. At present, toxins and pathogens in fresh waters are responsible for more than two million deaths per year. This scenario allows understanding how the development of effective and sustainable technologies for water treatment is of pivotal importance for future generations. A number of different agents and methods are used for water purification and environmental remediation, however they all show main drawbacks, revealing the need for a major technological advancement. Iron-based materials are earning a particular interest due to the effectiveness in water purification, the environmental friendly and earth-abundant nature. Moreover, some iron-containing materials are magnetic, allowing for an easy removal of the materials after water sanitizations. In the present review, the state of the art of iron based nanomaterials for water remediation is presented, with a special attention on ferrates, their synthesis, stability, mechanism of action and analytical determination. More in details, the review focuses on the following environmental applications of iron based nanomaterials: wastewater disinfection, organic matter removal, treatment of pharmaceuticals, inactivation of bacteria and viruses, removal of heavy metals and arsenic, degradation of fluoro-compounds and inactivation of cyanobacteria.

Latest Developments of Nanotoxicology in Plants

In the last years metal nanoparticles have been largely used for their unique physical, chemical, and biological properties, which differ from those of bulk materials. The wide number of applications has led to a significant diffusion of such particles in the environment and their absorption by plants. The aim of this chapter is to follow the metabolic pathway of nanoparticles (NPs) and nanomaterials inside the plant cells. In particular, the effects of different metal nanomaterials on seed germination, growth, chlorophyll concentration, biomass accumulation, root elongation, variation in the shoot/root ratio, photosynthetic characteristics, and antioxidant responses will be analyzed. Furthermore, the latest studies of phytotoxicity (including production of Reactive Oxygen Species (ROS), biomass reduction, stress levels, mitochondrial dysfunction, membrane damage, and release of toxic ions) will be presented. Along the chapter, the acute toxicity of nanomaterials in plants and the long-term effects to different generations will be investigated. Finally, the concentration of NPs in different parts of the plants and their uptake in plant foliar will be described with the choice of NPs that have less toxic and more useful effects in agriculture.