Biological activity of silver nanoparticles synthesized using viticultural waste.

This research paper presents a novel approach to the green synthesis of silver nanoparticles (AgNPs) using viticultural waste, allowing to obtain NP dispersions with distinct properties and morphologies (monodisperse and polydisperse AgNPs, referred to as mAgNPs and pAgNPs) and to compare their biological activities. Our synthesis method utilized the ethanolic extract of Vitis vinifera pruning residues, resulting in the production of mAgNPs and pAgNPs with average sizes of 12 ± 5 nm and 19 ± 14 nm, respectively. Both these AgNPs preparations demonstrated an exceptional stability in terms of size distribution, which was maintained for one year. Antimicrobial testing revealed that both types of AgNPs inhibited either the growth of planktonic cells or the metabolic activity of biofilm sessile cells in Gram-negative bacteria and yeasts. No comparable activity was found towards Gram-positives. Overall, pAgNPs exhibited a higher antimicrobial efficacy compared to their monodisperse counterparts, suggesting that their size and shape may provide a broader spectrum of interactions with target cells. Both AgNP preparations showed no cytotoxicity towards a human keratinocyte cell line. Furthermore, in vivo tests using a silkworm animal model indicated the biocompatibility of the phytosynthesized AgNPs, as they had no adverse effects on insect larvae viability. These findings emphasize the potential of targeted AgNPs synthesized from viticultural waste as environmentally friendly antimicrobial agents with minimal impact on higher organisms.

Antibiofilm activity of silver nanoparticles biosynthesized using viticultural waste.

Green methods have become vital for sustainable development of the scientific and commercial sphere; however, they can bring new challenges, including the need for detailed characterization and elucidation of efficacy of their products. In this study, green method of silver nanoparticles (AgNPs) production was employed using an extract from grapevine canes. The aim of the study was to contribute to the knowledge about biosynthesized AgNPs by focusing on elucidation of their antifungal efficiency based on their size and/or hypothesized synergy with bioactive substances from Vitis vinifera cane extract. The antifungal activity of AgNPs capped and stabilized with bioactive compounds was tested against the opportunistic pathogenic yeast Candida albicans. Two dispersions of nanoparticles with different morphology (characterized by SEM-in-STEM, DLS, UV-Vis, XRD, and AAS) were prepared by modification of reaction conditions suitable for economical production and their long-term stability monitored for six months was confirmed. The aims of the study included the comparison of the antifungal effect against suspension cells and biofilm of small monodisperse AgNPs with narrow size distribution and large polydisperse AgNPs. The hypothesis of synergistic interaction of biologically active molecules from V. vinifera extracts and AgNPs against both cell forms were tested. The interactions of all AgNPs dispersions with the cell surface and changes in cell morphology were imaged using SEM. All variants of AgNPs dispersions were found to be active against suspension and biofilm cells of C. albicans; nevertheless, surprisingly, larger polydisperse AgNPs were found to be more effective. Synergistic action of nanoparticles with biologically active extract compounds was proven for biofilm cells (MBIC80 20 mg/L of polydisperse AgNPs in extract), while isolated nanoparticles suspended in water were more active against suspension cells (MIC 20 mg/L of polydisperse AgNPs dispersed in water). Our results bring new insight into the economical production of AgNPs with defined characteristics, which were proven to target a specific mode of growth of significant pathogen C. albicans.

Antimicrobial properties and applications of metal nanoparticles biosynthesized by green methods.

There is a growing interest in the potential and application of metal nanoparticles across many fields. A vast array of techniques for metal nanoparticle synthesis has been discovered; however, sustainability, cost-effectiveness, and environmental concerns favor the green biological approach, using various plant and microbial sources. This review describes the diversity in green methods for nanoparticle biosynthesis, antimicrobial properties of metal nanoparticles and their potential applications. Metal nanoparticle biosynthesis by extracts and solutions obtained from plants, bacteria, fungi and templates such as viruses are discussed. As biosynthesized nanoparticles have been proven to possess antibacterial, antifungal, and even antiviral properties, these are discussed in detail, with silver and gold nanoparticles as the most studied and with the highest potential for medical application. The focus on prospective antimicrobial applications of nanoparticles stems from the arising resistance of many serious pathogens to traditional disinfectants and antibiotics. Other fields for the application of biosynthesized nanoparticles are also stated briefly, such as in agriculture as pesticides, in wastewater treatment and bioremediation. Finally, the limitations and safety issues connected with widespread use of nanoparticles are discussed.

Combination of non-thermal plasma and subsequent antibiotic treatment for biofilm re-development prevention.

The influence of non-thermal plasma (NTP) treatment on the prevention of antibiotic resistance of microbial biofilms was studied. Staphylococcus epidermidis and Escherichia coli bacteria and a yeast Candida albicans, grown on the surface of Ti-6Al-4V alloy used in the manufacture of prosthetic implants, were employed. Their biofilms were exposed to NTP produced by DC cometary discharge and subsequently treated with antibiotics commonly used for the treatment of infections caused by them: erythromycin (ERY), polymyxin B (PMB), or amphotericin B (AMB), respectively. All biofilms displayed significant reduction of their metabolic activity after NTP exposure, the most sensitive was S. epidermidis. The subsequent action of antibiotics caused significant decrease in the metabolic activity of S. epidermidis and E. coli, but not C. albicans, although the area covered by biofilm decreased in all cases. The combined effect of NTP with antibiotics was thus proved to be a promising strategy in bacterial pathogen treatment.

A novel approach for the production of green biosurfactant from Pseudomonas aeruginosa using renewable forest biomass.

The rising demand for surfactants by the pharmaceuticals and cosmetic industries has generated vast amounts of petroleum-based synthetic surfactants, which are often toxic and non-degradable. Owing to their low toxicity, stability in extreme conditions, and biodegradability, biosurfactants could represent a sustainable alternative. The present study aimed to maximize the production of rhamnolipids (RL) from Pseudomonas aeruginosa by optimizing glucose concentration, temperature, and C/N and C/P ratios. After 96 h of cultivation at 37 °C, the final RL concentration was 4.18 ± 0.19 g/L with a final yield of 0.214 ± 0.010 g/gglucose when pure glucose was used as a carbon source. At present, the main obstacle towards commercialization of RL production is economic sustainability, due to the high cost of downstream processes and media components. For this reason, a renewable source such as wood hydrolysates (from birch and spruce woodchips) was examined here as a possible source of glucose for RL production. Both hydrolysates proved to be adequate, resulting in 2.34 ± 0.17 and 2.31 ± 0.10 g/L of RL, respectively, and corresponding yields of 0.081 ± 0.006 and 0.089 ± 0.004 g/gsugar after 96 h. These results demonstrate the potential of using renewable biomass for the production of biosurfactants and, to the best of our knowledge, they constitute the first report on the use of wood hydrolysates for RL production.

Effect of resveratrol and Regrapex-R-forte on Trichosporon cutaneum biofilm.

Microorganisms that cause chronic infections exist predominantly as surface-attached stable communities known as biofilms. Microbial cells in biofilms are highly resistant to conventional antibiotics and other forms of antimicrobial treatment; therefore, modern medicine tries to develop new drugs that exhibit anti-biofilm activity. We investigated the influence of a plant polyphenolic compound resveratrol (representative of the stilbene family) on the opportunistic pathogen Trichosporon cutaneum. Besides the influence on the planktonic cells of T. cutaneum, the ability to inhibit biofilm formation and to eradicate mature biofilm was studied. We have tested resveratrol as pure compound, as well as resveratrol in complex plant extract-the commercially available dietary supplement Regrapex-R-forte, which contains the extract of Vitis vinifera grape and extract of Polygonum cuspidatum root. Regrapex-R-forte is rich in stilbenes and other biologically active substances. Light microscopy imaging, confocal microscopy, and crystal violet staining were used to quantify and visualize the biofilm. The metabolic activity of biofilm-forming cells was studied by the tetrazolium salt assay. Amphotericin B had higher activity against planktonic cells; however, resveratrol and Regrapex-R-forte showed anti-biofilm effects, both in inhibition of biofilm formation and in the eradication of mature biofilm. The minimum biofilm eradicating concentration (MBEC80) for Regrapex-R-forte was found to be 2222 mg/L (in which resveratrol concentration is 200 mg/L). These methods demonstrated that Regrapex-R-forte can be employed as an anti-biofilm agent, as it has similar effect as amphotericin B (MBEC80 = 700 mg/L), which is routinely used in clinical practice.

Resveratrol, pterostilbene, and baicalein: plant-derived anti-biofilm agents.

Microbial adhesion to surfaces and the subsequent biofilm formation may result in contamination in food industry and in healthcare-associated infections and may significantly affect postoperative care. Some plants produce substances with antioxidant and antimicrobial properties that are able to inhibit the growth of food-borne pathogens. The aim of our study was to evaluate antimicrobial and anti-biofilm effect of baicalein, resveratrol, and pterostilbene on Candida albicans, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Escherichia coli. We determined the minimum inhibitory concentrations (MIC), the minimum adhesion inhibitory concentration (MAIC), and the minimum biofilm eradication concentration (MBEC) by crystal violet and XTT determination. Resveratrol and pterostilbene have been shown to inhibit the formation of biofilms as well as to disrupt preformed biofilms. Our results suggest that resveratrol and pterostilbene appear potentially very useful to control and inhibit biofilm contaminations by Candida albicans, Staphylococcus epidermidis, and Escherichia coli in the food industry.

Characterization of rhamnolipids produced by non-pathogenic Acinetobacter and Enterobacter bacteria.

Rhamnolipid production by two non-pathogenic bacterial strains Acinetobacter calcoaceticus and Enterobacter asburiae, and established rhamnolipid producer Pseudomonas aeruginosa was investigated. Rhamnolipids were separated from supernatant and further purified by thin-layer chromatography. Mass spectrometry with negative electrospray ionization revealed rhamnolipid homologues varying in chain length and unsaturation. Tandem mass spectrometry identified mono-rhamnolipid and di-rhamnolipid homologues containing one or two 3-hydroxy fatty acids. Several media differing in carbon (sunflower oil, glycerol and sodium citrate), nitrogen (ammonium ions, nitrate) and phosphorus (total content) source, respectively, were tested to obtain enhanced rhamnolipid production. The best production (0.56g/l) was obtained when nitrate was used as a nitrogen source. Both strains produced rhamnolipids that exhibited excellent emulsification activity with aromatic and aliphatic hydrocarbons and several plant oils. Unlike P. aeruginosa the two strains, i.e. Acinetobacter and Enterobacter, are not pathogenic to humans.

Capacity of the bioremediation technology for clean-up of soil and groundwater contaminated with petroleum hydrocarbons.

A column reactor was designed and used to simulate conditions affecting the bioremediations of petroleum hydrocarbons. The work illustratively describes the aerobic (model) clean-up of soil samples enabling to predict the efficiency of a technology installed in parallel on contaminated former airport. The data showing the performance of thus precharacterized technology are presented.