Cristina Rîmbu

Green synthesis of the silver nanoparticles mediated by pullulan and 6-carboxypullulan

Unoxidized and carboxylated pullulan (obtained by pullulan oxidation using TEMPO-sodium hypochlorite-sodium bromide system) have been used as mediators for the silver nanoparticles formation (AgNPs), under environment-friendly conditions: using aqueous solutions, room temperature and notably, by using both mediators as reducing and stabilizing agents. The formation of AgNPs was first screened by measuring the surface plasmon resonance peak in the range of 380-440 nm using UV-vis spectroscopy. The morphology of the synthesized silver nanoparticles was determined by TEM, which indicated that the AgNPs differ on shape and thickness of the polymer shell by varying the silver nitrate concentration, different size and shape of AgNPs was achieved. The presence of elemental silver and the crystalline structure of the AgNPs were confirmed by EDX and XRD analyses. Moreover, the possible functional groups of pullulan (oxidized pullulan) responsible for the reduction and stabilization of AgNPs were evaluated using FT-IR. The results showed that both, pullulan and 6-carboxypullulan could be successfully used as reducing as well as capping agents for the AgNPs synthesis which shows potential antimicrobial activity against Gram positive and Gram negative bacteria.

Zinc oxide application in the textile industry: surface tailoring and water barrier attributes as parameters with direct implication in comfort performance

The present study focuses on surface tailoring and water barrier attributes of zinc oxide (ZnO)-polyester composite textile materials. The surface properties, such as surface topography and roughness, composite compositions as well as thermal stability of ZnO-100% polyester textile composite materials treated through a padding process with different concentrations of ZnO dispersions as active agent in water and methanol were studied. The results show that 3% ZnO-textile composite material have enhanced water barrier properties compared with the other compositions; a fact which promises improved properties in terms of comfort. ZnO modification of polyester surfaces leads to a dramatic decrease in their thermal stability.

Research Regarding a Correlation Core–Shell Morphology–Thermal Stability of Silica–Silver Nanoparticles

Silica nanoparticles repeatedly inhaled lead to acute and chronic lung inflammation and finally to pulmonary fibrosis and lung cancer, people with chronic respiratory diseases like asthma or allergic rhinitis being even more susceptible to their toxic effects. In order to reduce these above-mentioned toxic effects, the aim of this study was to engineer the environmental silica nanoparticles with silver and subsequent thermal treatment. Nanometer-sized and spherical silica particles were synthesized in a homogeneous state, using a simple one-pot chemical method. An applicable approach resulted in silver particles forming over the surface of the silica. The outcome was materialized in extremely small silver particles attached to silica core particles. Playing their well-known decisive role, precursors and catalysts effectively controlled the size of silver and silica particles. The synchronized structure of the synthesized particles was revealed by the electrostatic repulsion among the silica spheres and the electrostatic attraction between silica spheres and silver particles. The morphological images are revealed by means of a scanning electron microscope. The formation of silver–silica composite particles was confirmed by using infrared spectroscopy and X-ray photoelectron spectroscopy analysis. Following thermal analysis, the results concerning the thermal stability of the prepared particles provided higher temperature applications.

Antimicrobial controlled release systems for the knitted cotton fabrics based on natural substances

Materials with antibacterial properties, that can be used as barrier materials, hygiene products, plasters or bandages, have been obtained by applying some systems consisting of essential oils incorporated in beeswax and beeswax/chitosan. The influence of oil, wax and chitosan amounts on emultion stability has been analyzed by optical microscopy. The controlled release of essential oils of Eucalyptus (EEO), Tea Tree (TTEO) and Sage (SEO) incorporated in beeswax and beeswax/chitosan from the treated material was estimated through UV/Visible spectrophotometric analyses. The antibacterial effect of the emulsions and of the materials obtained by treating them with these emulsions have been investigated against the Staphylococcus aureus ATCC 29213 and Escherichia Coli ATCC 25922 bacteria. Comfort performances (air and vapor permeability and hygroscopicity) for the treated materials have also been evaluated. The best antimicrobial activity and the highest amount of essential oil released in vitro were obtained for the treatment variants that contain 7.14 % beeswax and 26.67 % essential oil, and respectively 26.67 % essential oil, 3.33 % beeswax and 3.33 % chitosan.

Characterisation of the Resistance Patterns to Non Beta-Lactam Antimicrobials in Esbl-Producing Enterobacteriaceae Isolated from Dogs and Their Owners

Enterobacteriaceae producing extended-spectrum beta-lactamase (ESBL) enzymes are resistant to betalactam agents and are also commonly multidrug resistant being associated with the resistance to other classes of antibiotics. The aim of our study was to characterise resistance patterns in non-beta-lactam antibiotics of ESBL-producing Enterobacteriaceae strains isolated from faecal matter of pets and owners. The study was carried out on 63 samples of faecal matter (42 from pets and 21 from owners). The ESBL screening was carried out using the Brilliance ESBL Oxoid chromogenic medium. The isolated strains that generated characteristic presumptive ESBL-producing colonies were cultivated on 5% sheep blood medium for the extraction of bacterial DNA using the boiled preps technique. The confirmation of E. coli species was performed molecularly based on the detection of blauidA and blauspA genes. Other Enterobacteriaceae species were identified based on the minimum biochemical characteristics using the MIU and TSI medium. The phenotypical confirmation of presumptive ESBL-producing strains was carried out using the Double Disc Synergy Test (DDST) using a combination of 3rd generation cephalosporins and beta-lactamase inhibitor agents. The determination of the resistance degree in other classes of antibiotics was carried out through the Kirby-Bauer diffusimetric method, and the results were interpreted according to the CLSI standard. Following the species investigation of isolates, 60/63 (95.28%) belonged to the E. coli species and 3/63 (4.72%) to the K. pneumoniae species. Animal isolates were resistant to sulphonamides (54.76% resistance to SXT), fluoroquinolones (45.23% resistance to ENR) and tetracyclines (54.75% resistance to TE). In addition to strains of animal origin for isolates of human origin, an increased resistance has been noticed to phenicols and aminoglycosides. This study has identified a high prevalence of ESBL-producing Enterobacteriaceae strains and associated with multidrug resistance for pets and their owners.