Magdalena Oćwieja

Bio: Magdalena Oćwieja is an academic researcher from Polish Academy of Sciences. The author has contributed to research in topics: Silver nanoparticle & Nanoparticle. The author has an hindex of 17, co-authored 59 publications receiving 833 citations.

Effects of exposure of callus cells of two wheat varieties to silver nanoparticles and silver salt (AgNO3)

Abstract: Metal nanoparticles significantly affect the physiological properties of plants, e.g., seed germination, growth and metabolism. In the present study, the toxic effects of silver nanoparticles (AgNPs) and silver ions were studied on callus cells of two varieties of wheat (Triticum aestivum L.): stress tolerant—Parabola; stress sensitive—Raweta. Stress induced by silver particles or ions (0, 20, 40, 60 ppm) was investigated using different parameters such as morphological characteristics, lipid peroxidation and mobilization of defense system which was determined by analyzing the activity of antioxidant enzymes, glutathione (GSH) and proline contents. Microscopic observations revealed deformation of cells after treatment by sol of higher silver concentrations. An increase in malondialdehyde content in both studied varieties was observed. Tested varieties showed an increased proline content in the silver-treated cells. There was no effect of silver on the superoxide dismutases activity, while the activity of catalase was significantly decreased. The changes in the activity of peroxidases in both varieties were opposite. The highest content of intracellular GSH was noticed at a concentration of 20 ppm of both AgNPs and silver ions. The presented results demonstrate a significant similarity of the effects caused by the studied stressors: silver nanoparticles and silver ions. The results characterized the mechanism of action of nanosilver on wheat callus: morphology disorder, damage to cell membranes, severe oxidative stress and in consequence intensification of production of non-enzymatic antioxidants.

Oxidative dissolution of silver nanoparticles: A new theoretical approach

Abstract: A general model of an oxidative dissolution of silver particle suspensions was developed that rigorously considers the bulk and surface solute transport. A two-step surface reaction scheme was proposed that comprises the formation of the silver oxide phase by direct oxidation and the acidic dissolution of this phase leading to silver ion release. By considering this, a complete set of equations is formulated describing oxygen and silver ion transport to and from particles' surfaces. These equations are solved in some limiting cases of nanoparticle dissolution in dilute suspensions. The obtained kinetic equations were used for the interpretation of experimental data pertinent to the dissolution kinetics of citrate-stabilized silver nanoparticles. In these kinetic measurements the role of pH and bulk suspension concentration was quantitatively evaluated by using the atomic absorption spectrometry (AAS). It was shown that the theoretical model adequately reflects the main features of the experimental results, especially the significant increase in the dissolution rate for lower pH. Also the presence of two kinetic regimes was quantitatively explained in terms of the decrease in the coverage of the fast dissolving oxide layer. The overall silver dissolution rate constants characterizing these two regimes were determined.

Tuning properties of silver particle monolayers via controlled adsorption-desorption processes.

Abstract: Using the well-defined silver particle suspension, systematic studies of adsorption kinetics on mica modified by poly(allylamine hydrochloride) (PAH) were carried out. The coverage of adsorbed particles was directly determined by AFM and SEM imaging. The dependence of the coverage on adsorption time, bulk suspension concentration, and ionic strength was systematically studied. It was confirmed that adsorption was diffusion controlled, with the initial rate proportional to the bulk concentration of particles. On the other hand, for long adsorption times, the saturation coverage was attained, which increased systematically with the ionic strength of the particle suspension. The adsorption kinetic runs were adequately reflected for the entire range of times and bulk concentration by the random sequential adsorption (RSA) model. Additionally, particle desorption kinetics from previously formed monolayers were studied. The decrease in the surface coverage of particles as a function of time was measured, which allowed one to determine the equilibrium adsorption constant K a . The binding energy of silver particles (energy minimum depth) derived form these measurements varied between −16.9 kT and −17.8 kT, which suggests that it is mainly controlled by electrostatic interactions. Knowing the equilibrium adsorption constant, a particle adsorption isotherm was theoretically derived using the RSA model. Experimental data obtained for various bulk concentration of particles were in agreement with these theoretical predictions. These measurements suggest that it is feasible to produce uniform silver particle monolayers of desired coverage in the self-assembly process of particles.

Methods in Enzymology.

Abstract: I read this book the same weekend that the Packers took on the Rams, and the experience of the latter event, obviously, colored my judgment. Although I abhor anything that smacks of being a handbook (like, \"How to Earn a Merit Badge in Neurosurgery\") because too many volumes in biomedical science already evince a boyscout-like approach, I must confess that parts of this volume are fast, scholarly, and significant, with certain reservations. I like parts of this well-illustrated book because Dr. Sj6strand, without so stating, develops certain subjects on technique in relation to the acquisition of judgment and sophistication. And this is important! So, given that the author (like all of us) is somewhat deficient in some areas, and biased in others, the book is still valuable if the uninitiated reader swallows it in a general fashion, realizing full well that what will be required from the reader is a modulation to fit his vision, propreception, adaptation and response, and the kind of problem he is undertaking. A major deficiency of this book is revealed by comparison of its use of physics and of chemistry to provide understanding and background for the application of high resolution electron microscopy to problems in biology. Since the volume is keyed to high resolution electron microscopy, which is a sophisticated form of structural analysis, but really morphology in a modern guise, the physical and mechanical background of The instrument and its ancillary tools are simply and well presented. The potential use of chemical or cytochemical information as it relates to biological fine structure , however, is quite deficient. I wonder when even sophisticated morphol-ogists will consider fixation a reaction and not a technique; only then will the fundamentals become self-evident and predictable and this sine qua flon will become less mystical. Staining reactions (the most inadequate chapter) ought to be something more than a technique to selectively enhance contrast of morphological elements; it ought to give the structural addresses of some of the chemical residents of cell components. Is it pertinent that auto-radiography gets singled out for more complete coverage than other significant aspects of cytochemistry by a high resolution microscopist, when it has a built-in minimal error of 1,000 A in standard practice? I don't mean to blind-side (in strict football terminology) Dr. Sj6strand's efforts for what is \"routinely used in our laboratory\"; what is done is usually well done. It's just that …

Microplastics and Nanoplastics in Aquatic Environments: Aggregation, Deposition, and Enhanced Contaminant Transport

Abstract: Plastic litter is widely acknowledged as a global environmental threat, and poor management and disposal lead to increasing levels in the environment. Of recent concern is the degradation of plastics from macro- to micro- and even to nanosized particles smaller than 100 nm in size. At the nanoscale, plastics are difficult to detect and can be transported in air, soil, and water compartments. While the impact of plastic debris on marine and fresh waters and organisms has been studied, the loads, transformations, transport, and fate of plastics in terrestrial and subsurface environments are largely overlooked. In this Critical Review, we first present estimated loads of plastics in different environmental compartments. We also provide a critical review of the current knowledge vis-a-vis nanoplastic (NP) and microplastic (MP) aggregation, deposition, and contaminant cotransport in the environment. Important factors that affect aggregation and deposition in natural subsurface environments are identified and c...

Characterization techniques for nanoparticles: comparison and complementarity upon studying nanoparticle properties

Abstract: Nanostructures have attracted huge interest as a rapidly growing class of materials for many applications. Several techniques have been used to characterize the size, crystal structure, elemental composition and a variety of other physical properties of nanoparticles. In several cases, there are physical properties that can be evaluated by more than one technique. Different strengths and limitations of each technique complicate the choice of the most suitable method, while often a combinatorial characterization approach is needed. In addition, given that the significance of nanoparticles in basic research and applications is constantly increasing, it is necessary that researchers from separate fields overcome the challenges in the reproducible and reliable characterization of nanomaterials, after their synthesis and further process (e.g. annealing) stages. The principal objective of this review is to summarize the present knowledge on the use, advances, advantages and weaknesses of a large number of experimental techniques that are available for the characterization of nanoparticles. Different characterization techniques are classified according to the concept/group of the technique used, the information they can provide, or the materials that they are destined for. We describe the main characteristics of the techniques and their operation principles and we give various examples of their use, presenting them in a comparative mode, when possible, in relation to the property studied in each case.

Facile Synthesis of Silver Nanoparticles Stabilized by Cationic Polynorbornenes and Their Catalytic Activity in 4-Nitrophenol Reduction

Abstract: We report the facile one-pot single-phase syntheses of silver nanoparticles stabilized by norbornene type cationic polymers. Silver nanoparticles (AgNPs) stabilized by polyguanidino oxanorbornenes (PG) at 5 and 25 kDa and polyamino oxanorbornenes (PA) at 3 and 15 kDa have been synthesized by the reduction of silver ions with NaBH4 in aqueous solutions at ambient temperature. The four different silver nanoparticles have been characterized by UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and transmission electron microscopy (TEM) for their particle size distributions. Interestingly, PG stabilizes the silver nanoparticles better than PA as evident from our spectroscopic data. Furthermore, the AgNP-PG-5K (5K = 5 kDa) was found to serve as an effective catalyst for the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4. The reduction has a pseudo-first-order rate constant of 5.50 × 10–3 s–1 and an activity parameter of 1375 s–1 g–1, which...