Oksana Velgosová

Background: This study evaluated the antibacterial, antibiofilm, and biofilm eradication activities of biogenically synthesized silver nanoparticles (AgNPs-L, AgNPs-R) mediated by extracts of Lavandula angustifolia and Salvia rosmarinus, individually and in combination with their respective essential oils (EOs) and ampicillin (AMP), against a multidrug-resistant biofilm-forming Staphylococcus equorum strain. Physicochemical characterization confirmed the successful biosynthesis of spherical AgNPs-L (10–25 nm) and AgNPs-R (5–15 nm). Individual treatments exhibited distinct antibacterial activity, with MIC values of 25 µg/mL for AgNPs-L, 12.5 µg/mL for AgNPs-R, and 0.1% (v/v) for both EOs; however, they showed no ability to eradicate preformed biofilms. Dual AgNPs/EO combinations at subinhibitory concentrations demonstrated borderline additive effects (FICI = 0.501) and significantly potentiated antibacterial and antibiofilm activity compared with individual treatments. Triple AgNPs/EO/AMP combinations exhibited the most pronounced biological effects, with predominantly additive interactions depending on AMP concentration. Lavender-based triple combinations achieved up to 63.9% inhibition of planktonic growth, 78.1% prevention of biofilm formation, and 37.3% eradication of mature biofilms, whereas rosemary-based combinations resulted in 57.1%, 69.4%, and 42.7% inhibition, respectively. These findings highlight the potential of multi-component systems integrating biogenic nanomaterials, phytochemicals, and conventional antibiotics as a promising strategy to enhance antimicrobial efficacy against persistent biofilm-forming non-aureus staphylococci.

Background: Multidrug-resistant and biofilm-forming staphylococci pose a threat to the sustainability of public health, livestock health and the ecosystem. Pathogenic potential with a worsening prognosis of therapy is mainly due to methicillin-resistant Staphylococcus aureus (MRSA) or multidrug-resistant Non-aureus staphylococci and mammaliicocci (NASM). Alternative approaches based on the use of biosynthesized nanoparticles or substances of natural origin appear to be promising solutions to the problem of ineffective suppression of infections caused by pathogenic microorganisms. Methods: The aim of this study was to monitor and compare the biological effects of silver nanoparticles prepared by green synthesis using Lavandula angustifolia and lavender essential oil. In particular, the antibacterial, antibiofilm, and biofilm-eradicating effects against biofilm-forming and multidrug-resistant reference strains and field isolates of staphylococci were monitored. Results: AgNPs inhibited the growth and formation of biofilms of S. aureus strains at a concentration of 0.05 μg/μL, but clinical NASM at 0.025 μg/μL. Sensitivity to Lavender essential oil (LEO) was the same against all tested staphylococcal strains, with an antibacterial MIC of 0.901 μg/μL. The essential oil also had an effect on biofilm formation against all tested strains, but its effect was recorded at a tenfold lower concentration (antibiofilm MIC = 0.0901 μg/μL). No eradication activity was recorded for either tested substance. Their activity against the formed biofilms was not recorded. Conclusions: The results demonstrate promising antibacterial and antibiofilm activities of biosynthesized AgNPs and lavender essential oil under in vitro conditions. These findings support further investigation of these materials as potential alternative antimicrobial approaches, particularly in combination with conventional antimicrobial agents.

This study investigates the influence of pH and extract concentration on the green synthesis of gold nanoparticles (AuNPs) using Camellia sinensis extract as a reducing and stabilizing agent. Synthesis was performed at pH 1–12 using undiluted and diluted extracts (2:5 and 1:5). The colloids were characterized by UV–Vis spectroscopy, TEM, SAED, and elemental mapping. Both parameters significantly affected nanoparticle formation, morphology, and optical properties. At extreme pH values and low extract concentrations, AuNP formation was suppressed. The pH range of 3–6 produced diverse morphologies: spherical (~18 nm), triangular (~21 nm), rod-shaped (~25 nm), and anisotropic flower-like structures (~53 nm). At higher pH values, smaller, more uniform spherical nanoparticles formed, including red (~18 nm) and yellow colloids (~6 nm). These changes were reflected in distinct UV–Vis spectra and color variations. Toxicity tests using Chlorella kessleri revealed no inhibition of algal growth. In contrast, selected AuNPs colloids reduced germination and root growth of Sinapis alba, with germination falling below 50% for spherical AuNPs smaller than 18 nm and root length decreasing by more than 60% compared to the positive control. Under the tested conditions, controlled adjustment of pH and extract concentration allows tuning of AuNP properties through a simple green synthesis approach.

This study focuses on the development of antibacterial polymer nanocomposites based on biologically synthesized silver nanoparticles (AgNPs) and polyvinyl alcohol (PVA) as the polymer matrix. Silver nanoparticles were produced using an aqueous extract from dried Lavandula angustifolia (lavender) leaves, which proved to be highly effective in reducing silver ions and stabilizing the resulting nanoparticles. The synthesized AgNPs were characterized by FTIR, UV-Vis, TEM, SEM, and DLS analyses. The nanoparticles were predominantly spherical, with more than 70% having diameters below 20 nm. Subsequently, AgNPs were incorporated into the PVA matrix via an ex situ approach to fabricate nanocomposite fibers and thin films. SEM analysis confirmed successful incorporation and uniform distribution of AgNPs within the polymer structures. The nanocomposites exhibited pronounced antibacterial activity against both Gram-positive (Staphylococcus aureus, Staphylococcus haemolyticus, Streptococcus uberis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria, with nanofibers demonstrating superior performance compared to thin films. These findings highlight the potential of lavender-extract-mediated AgNPs as sustainable functional fillers for the fabrication of eco-friendly antibacterial materials applicable in biomedical and food packaging fields.

The synthesis of silver nanoparticles (AgNPs) using sustainable and non-toxic methods has become an important research focus due to the limitations of conventional chemical approaches, which often involve hazardous reagents and produce unstable products. In particular, the effects of reaction conditions on the quality and stability of AgNPs obtained via green synthesis remain insufficiently understood. This study addresses this gap by examining the influence of pH and temperature on the synthesis of AgNPs using Rosmarinus officinalis extract as both reducing and stabilizing agents. UV-vis spectroscopy and TEM analysis revealed that optimal conditions for producing uniform, stable, and spherical AgNPs were achieved at pH 8, with a narrow size distribution (~17.5 nm). At extreme pH values (≤3 or ≥13), nanoparticle formation was hindered by aggregation or precipitation, while elevated temperatures mainly accelerated reaction without altering particle morphology. HRTEM and SAED confirmed the crystalline face-centered cubic structure, and colloids synthesized at pH 8 showed excellent stability over 30 days. Overall, the results demonstrate that precise pH control is critical for obtaining high-quality AgNPs via a simple, scalable, and environmentally friendly approach. Their stability and homogeneous size highlight potential applications in biomedicine, food packaging, and sensing, where reproducibility and long-term functionality are essential.

The mineral chalcopyrite (CuFeS₂) is inherently resistant to conventional leaching techniques, necessitating the intensification of the leaching process to achieve efficient metal recovery. Microwave-assisted leaching, combined with the application of a suitable oxidizing agent, presents a viable approach to enhancing the dissolution rate of metals in solutions. The objective of this study is to investigate the effect of microwave irradiation on the leaching behavior of chalcopyrite concentrate in a hydrochloric acid (HCl) medium, employing deep-sea polymetallic nodules (DSP) as the oxidizing agent. The influence of acid concentration and microwave power on copper extraction efficiency was examined. Optimal copper extraction was observed at an HCl concentration of 5 M and a microwave power of 750 W. The results indicate that DSP nodules serve as a more effective oxidizing agent than pyrolusite in acidic oxidative microwave-assisted leaching of chalcopyrite, particularly in terms of copper recovery. Analytical techniques employed for the characterization of leach residues and solutions included Atomic Absorption Spectroscopy (AAS) and Scanning Electron Microscopy (SEM) coupled with Energy-Dispersive X-ray Spectroscopy (EDS).

This study investigates the effect of precursor pH (1.3, 2, 4, 6, 8, and 10) on the synthesis of gold nanoparticles (AuNPs) via a green synthesis approach using an aqueous extract of green tea (Camellia sinensis) leaves. The formation of AuNPs was monitored using UV-vis spectrophotometry and confirmed using transmission electron microscopy (TEM). The results confirmed that the morphology and size of the AuNPs are strongly dependent on the pH of the reaction medium. Based on spectral features, the color of the colloids, and TEM analysis, the synthesized samples were classified into three groups. The first (pH 8 and 10) contained predominantly spherical nanoparticles with an average diameter of ~18 nm, the second (pH 1.3 and 2) contained different shaped nanoparticles (20–250 nm in diameter), and the third (pH 4 and 6) contained flower-like nanostructures with a mean diameter of ~60 nm. UV-vis analysis revealed good stability of all AuNP colloids, except at pH 1.3, where a significant decrease in absorbance intensity over time was observed. These findings confirm that tuning the precursor pH allows for controlled manipulation of nanoparticle morphology and stability in green synthesis systems.

In Slovakia, around 200 environmental burdens that contain a significant amount of usable raw materials were created by the extraction of ores or the dumping of industrial waste. In this research, the hydrometallurgical metal recovery method from a metal-bearing environmental landfill in Sereď was investigated. The analysis of a representative sample of waste obtained from this landfill proved the presence of significant amounts of metals (43.45% Fe; 1.3% Cr; 0.09% Co, and 0.23% Ni). A thermodynamic study of the metals’ (Fe, Cr, Ni, and Co) leaching probability confirmed the possibility of metal extraction in an acidic environment. Subsequently, the effect of the most important factors on the leaching process (stirring intensity, temperature, liquid-to-solid phase ratio, and acid concentration) was experimentally tested. The analysis of the results determined the optimal leaching conditions. The extraction of 90.35% Fe and 59.62% Cr was ensured at a stirring intensity of 400 rpm, a leaching temperature of 80 °C, a liquid-to-solid phase ratio of 40, and a H₂SO₄ concentration of 3 mol/dm³. Various techniques, including SEM, EDX, XRD, Eh-pH diagrams, and AAS analysis, were used to analyze samples and products after leaching. The possibility of precipitating metals/compounds from the leachate to obtain a marketable product was theoretically proposed and proven.

This article focuses on the eco-friendly (green) synthesis of silver nanoparticles (AgNPs) and their incorporation into a polymer matrix. For AgNPs synthesis, Lavandula angustifolia (lavender) leaf extract was used as a reducing and stabilizing agent, and as a silver precursor, AgNO₃ solution with different concentrations of silver (50, 100, 250, and 500 mg/L) was used. Prepared AgNPs colloids were characterized using UV–vis spectrophotometry, transmission electron microscopy (TEM), and X-ray diffraction (XRD). The spherical morphology of AgNPs with an average size of 20 nm was confirmed across all samples. Further, the antimicrobial properties of the AgNPs were evaluated using the disk diffusion method on algae (Chlorella kessleri) and the well diffusion method on bacteria (Staphylococcus chromogenes, Staphylococcus aureus, and Streptococcus uberis), along with root growth inhibition tests on white mustard (Sinapis alba). Polymer composite (PVA–AgNPs) was prepared by incorporation of AgNPs into the polymer matrix. Subsequently, non-woven textiles and thin foils were prepared. The distribution of AgNPs within the nanocomposites was observed by scanning electron microscopy (SEM). Antibacterial properties of PVA–AgNPs composites were analyzed on bacteria Streptococcus uberis. It was found that not only AgNPs showed good antimicrobial properties, but toxic properties were also transferred to the PVA–AgNPs nanocomposite.

This work aims to analyze the influence of selected plants on the synthesis of silver nanoparticles (AgNPs). Six plants were chosen for the experiment, from which extracts were prepared: maclura fruit, spruce and ginkgo needles, green algae (Ch. kessleri), and mushrooms, namely Collybia nuda, and Macrolepiota procera. The composition of the extracts and colloids after preparation of the nanoparticles was analyzed using FTIR analysis. The composition of the extracts affected not only the rate of the synthesis but also the shape of the nanoparticles. TEM analysis confirmed the synthesis of mainly spherical nanoparticles (size range: 10–25 nm). However, triangular prisms and polyhedral nanoparticles synthesized by the extracts containing mainly flavonoids, terpenes, and phenols (the main compounds of resins) were also confirmed. EDS analysis was used to analyze the composition of the nanoparticles. It was proven that by choosing the right plant extract and using the appropriate technology with extract treatment, it is possible to prepare nanoparticles of different shapes.