Suzana Dimitrijević

Influence of size scale and morphology on antibacterial properties of ZnO powders hydrothemally synthesized using different surface stabilizing agents

Metal oxide nanoparticles represent a new class of important materials that are increasingly being developed for use in research and health-related applications. Although the antibacterial activity and efficiency of bulk zinc oxide were investigated in vitro, the knowledge about the antibacterial activity of ZnO nanoparticles remains deficient. In this study, we have synthesized ZnO particles of different sizes and morphologies with the assistance of different types of surface stabilizing agents - polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA) and poly (α,γ, l-glutamic acid) (PGA) - through a low-temperature hydrothermal procedure. The characterization of the prepared powders was preformed using X-ray diffraction (XRD) method and field emission scanning electron microscopy (FE SEM), as well as Malverns Mastersizer instrument for particle size distribution. The specific surface area (SSA) of the ZnO powders was measured by standard Brunauer-Emmett-Teller (BET) technique. The antibacterial behavior of the synthesized ZnO particles was tested against gram-negative and gram-positive bacterial cultures, namely Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), respectively. We compared the results of the antibacterial properties of the synthesized ZnO samples with those of the commercial ZnO powder. According to the obtained results, the highest microbial cell reduction rate was recorded for the synthesized ZnO powder consisting of nanospherical particles. In all of the examined samples, ZnO particles demonstrated a significant bacteriostatic activity.

Nanomaterial with High Antimicrobial Efficacy—Copper/Polyaniline Nanocomposite

This study explores different mechanisms of antimicrobial action by designing hybrid nanomaterials that provide a new approach in the fight against resistant microbes. Here, we present a cheap copper-polyaniline (Cu-PANI) nanocomposite material with enhanced antimicrobial properties, prepared by simple in situ polymerization method, when polymer and metal nanoparticles are produced simultaneously. The copper nanoparticles (CuNPs) are uniformly dispersed in the polymer and have a narrow size distribution (dav = 6 nm). We found that CuNPs and PANI act synergistically against three strains, Escherichia coli, Staphylococcus aureus, and Candida albicans, and resulting nanocomposite exhibits higher antimicrobial activity than any component acting alone. Before using the colony counting method to quantify its time and concentration antimicrobial activity, different techniques (UV-visible spectroscopy, transmission electron microscopy, scanning electron microscope, field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectrophotometry, and inductively coupled plasma optical emission spectrometry) were used to identify the optical, structural, and chemical aspects of the formed Cu-PANI nanocomposite. The antimicrobial activity of this nanocomposite shows that the microbial growth has been fully inhibited; moreover, some of the tested microbes were killed. Atomic force microscopy revealed dramatic changes in morphology of tested cells due to disruption of their cell wall integrity after incubation with Cu-PANI nanocomposite.

Impregnation of cotton fabric with silver nanoparticles synthesized by dextran isolated from bacterial species Leuconostoc mesenteroides T3.

This study was aimed to highlight the possibility of cotton fabric impregnation with silver nanoparticles synthesized by dextran isolated from Leuconostoc mesenteroides T3 in order to obtain antimicrobial properties. The fabrication of dextran was proved by FTIR spectroscopy. Particle sizes of synthesized dextran and silver nanoparticles were measured by dynamic light scattering method. The presence of silver nanoparticles on the surface of cotton fabric was confirmed by scanning electron microscopy, X-ray diffraction measurements and reflectance spectrophotometry. Antimicrobial activity of cotton fabric impregnated with silver nanoparticles was tested against bacteria Escherichia coli and Staphylococcus aureus, and fungus Candida albicans. The results indicated that synthesized silver nanoparticles can provide satisfactory antimicrobial activity. However, maximum reduction (99.9%) of all tested microorganisms can be obtained only when 1.0mmolL(-1) colloid consisting of silver nanoparticles is applied.

Design of pectin-sodium alginate based films for potential healthcare application: Study of chemico-physical interactions between the components of films and assessment of their antimicrobial activity

In this study, pectin based films including different amounts of sodium alginate were prepared by casting method. All the films, with and without polyglycerol as plasticizer, were crosslinked with zinc ions in order to extend their potential functionality. The development of junction points, occurring during the crosslinking process with zinc ions, induced the increasing of free volume with following changing in chemico-physical properties of films. The inclusion of alginate in pectin based formulations improved the strength of zinc ions crosslinking network, whereas the addition of polyglycerol significantly improved mechanical performance. Finally, zinc-crosslinked films evidenced antimicrobial activity against the most common exploited pathogens: Staphylococcus Aureus, Escherichia Coli and Candida Albicans. These results suggest that zinc-crosslinked based films can be exploitable as novel bio-active biomaterials for protection and disinfection of medical devices.

Negative influence of Ag and TiO2 nanoparticles on biodegradation of cotton fabrics

Abstract Recently, many efforts have been made to efficiently impregnate different textile materials with metal and metal oxide nanoparticles in order to provide antimicrobial, UV protective or self-cleaning properties. Evidence of their environmental risks is limited at this point. The aim of this study was to explore the influence of Ag and TiO2 nanoparticles on biodegradation of cotton fabrics. Biodegradation behavior of cotton fabrics impregnated with Ag and TiO2 NPs from colloidal solutions of different concentrations was assessed according to standard test method ASTM 5988-03 and soil burial test. Degradation of cotton fabrics was also evaluated by enzymatic hydrolysis with cellulase. The morphology of fibers affected by biodegradation was analyzed by scanning electron microscopy (SEM). In order to get better insight into biodegradation process, dehydrogenase activity of soil has been determined. Ag and particularly TiO2 nanoparticles suppressed the biodegradation of cotton fabrics. The dehydrogenase activity of soil with cotton fabrics impregnated with TiO2 nanoparticles was the weakest. Severe damage of cotton fibers during the biodegradation process was confirmed by SEM.Graphical Abstract

Dextran coated silver nanoparticles — Chemical sensor for selective cysteine detection

A simple, fast and non-costly method for selective cysteine (Cys) detection, based on optical changes of silver colloids, is developed. For that purpose, stable colloids consisting of silver nanoparticles (Ag NPs) coated with polysaccharide dextran (Dex), isolated from bacterium species Leuconostoc mesenteroides T3, were prepared. The synthesized samples were thoroughly characterized including absorption and FTIR spectroscopy, as well as transmission electron microscopy and X-ray diffraction analysis. The silver colloids display high sensitivity and selectivity towards Cys detection in aqueous solutions. The Ag NPs coated with Dex provide possibility to detect Cys among a dozen amino acids and its detection limit was found to be 12.0μM. The sensing mechanism - red shift of optical absorption - is discussed in terms of the agglomeration of Ag NPs due to formation of hydrogen bonds between Cys molecules attached to different Ag NPs.

Antimicrobial Bioactive Band-Aids with Prolonged and Controlled Action

ABSTRACT The paper discusses the antimicrobial bioactive band-aids, a modem means of wound management and healing, which are effective against a wide spectrum of microorganisms. Ion-exchange fibres and nonwoven textile materials composed of PP/viscose blend were used as a textile basis. Antimicrobial bioactive band-aids were manufactured in two routs: - by chemisorption of gentamicin sulfate by ion-exchange fibres; and - by adhesion of gentamicin sulfate on nonwoven material with the aid of a polymer carrier (chitosan). For assessment of antimicrobial activity, the diffusion method on an agar medium has been used. Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella, Escherichia coli and Candida albicans have been utilised. The kinetics of active substance desorption has been examined through dissolving rate of medical substance from transdermal band-aid in vitro. Physical-chemical foundations and kinetics of desorption of gentamicin sulfate in vitro are described by a mathematical model which can be used for prognosis of prolonged release of medical substance from band-aid as a transdermal system.

Investigation of Antimicrobial Activity of Encapsulated Essential Oils

Antimicrobial activity of essential oils obtained from many plants has been known for a long time. However, the use of essential oils as active components of biomedical textile have recently gained popularity and aroused scientific interest. The antimicrobial activity of two essential oils, Rosmarinus officinalis and Abies sibirica, respectively, was detected using two indicator strains: Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922, respectively. To achieve a controlled release of antimicrobial activity and to enable utilization of higher concentrations of active ingredient, the essential oils were first encapsulated in beads based on alginate, gelatin and yeast cells, and then bounded to medical textile. The maximum oil content (85.4%) was achieved in alginate capsules. The release of essential oils was followed by determination of viable bacterial cells during a seven-day incubation of beads in saline. Rosmarinus officinalis and Abies sibirica immobilized in the beads showed a significantly prolonged activity, with some gel-dependent variation.

Response surface methodology for optimisation of edible coatings based on dextran from Leuconostoc mesenteroides T3

The aim of this study was to develop dextran-based edible films plasticized by sorbitol. In order to optimise the film-forming formulation, response surface methodology was used. The influence of dextran and sorbitol concentration on the mechanical and water vapour barrier properties of obtained films was investigated. The results showed that both parameters exhibited significant effect on the water vapour permeability of a film. Both dextran and sorbitol concentration had significant influence on tensile strength and elongation at break, whereas only sorbitol concentration had significant effect on Youngs modulus. After optimisation by desirability approach, it was found that a film made of 3.40 wt% of dextran and 20.43 wt% of sorbitol showed the lowest water vapour permeability and the highest tensile strength and elasticity.

Natural sorbents modified by divalent Cu2+- and Zn2+- ions and their corresponding antimicrobial activity

The objective of this study was to investigate the modification of materials used in wastewater treatment for possible antimicrobial application(s). Granulated activated carbon (GAC) and natural clinoptilolite (CLI) were activated using Cu2+- and Zn2+- ions and the disinfection ability of the resulting materials was tested. Studies of the sorption and desorption kinetics were performed in order to determine and clarify the antimicrobial activity of the metal-activated sorbents. The exact sorption capacities of the selected sorbents, GAC and CLI, activated through use of Cu2+- ions, were 15.90 and 3.60mg/g, respectively, while for the materials activated by Zn2+- ions, the corresponding capacities were 14.00 and 4.72mg/g,. The desorption rates were 2 and 3 orders of magnitude lower than their sorption efficacy for the Cu2+-, and Zn2+-activated sorbents, respectively. The intermediate sorption capacity and low desorption rate indicated that the overall antimicrobial activity of the metal-modified sorbents was a result of metal ions immobilized onto surface sites. The effect of antimicrobial activity of free ions desorbed from the metal-activated surface may thus be disregarded. The antimicrobial activities of Cu/GAC, Zn/GAC, Cu/CLI and Zn/CLI were also tested against Escherichia coli, Staphylococcus aureus, and Candida albicans. After 15min exposure, the highest levels of cell inactivation were obtained through the Cu/CLI and the Cu/GAC against E. coli, 100.0 and 98.24%, respectively. However, for S. aureus and yeast cell inactivation, all Cu2+- and Zn2+-activated sorbents proved to be unsatisfactory. A characterization of the sorbents was performed by X-ray diffraction (XRD), X-ray photo electron spectroscopy (XPS), and field emission scanning electron microscopy (FE-SEM). A concentration of the adsorbed and released ions was determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES) and mass spectrometry (ICP-MS). The results showed that the antimicrobial performance of the activated sorbents depended on the surface characteristics of the material, which itself designates the distribution and the bioavailability of the activating agent.