Jan Paczesny

Bystander cell death and stress response is inhibited by the radical scavenger α(1)-microglobulin in irradiated cell cultures.

Abstract Alpha-particle irradiation of cells damages not only the irradiated cells but also nontargeted bystander cells. It has been proposed that the bystander effect is caused by oxidants and free radicals generated by the radiation. Recent studies have shown that &agr;1-microglobulin protects against cell damage caused by oxidants and free radicals. Using a novel experimental system that allows irradiation of 0.02% of a human hepatoma monolayer, leaving 99.98% as bystander cells, we investigated the influence of oxidative stress and the cell-protective effects of &agr;1-microglobulin during &agr;-particle irradiation. The results showed an increase in cell death in both irradiated cells and bystander cells. A significant increase in apoptosis, oxidation markers and expression of the stress response genes heme oxygenase 1, superoxide dismutase, catalase, glutathione peroxidase 1, p21 and p53 were observed. Addition of &agr;1-microglobulin reduced the amount of dead cells and inhibited apoptosis, formation of oxidation markers, and up-regulation of stress response genes. The results emphasize the role of oxidative stress in promoting bystander effects. Furthermore, the results suggest that &agr;1-microglobulin protects nonirradiated cells by eliminating oxidants and free radicals generated by radiation and imply that &agr;1-microglobulin can be used in radiation therapy of tumors to minimize damage to surrounding tissues.

Towards Organized Hybrid Nanomaterials at the Air/Water Interface Based on Liquid-Crystal/ZnO Nanocrystals

The ability to self-assemble nanosized ligand-stabilized metal oxide or semiconductor materials offers an intriguing route to engineer nanomaterials with new tailored properties from the disparate components. We describe a novel one-pot two-step organometallic approach to prepare ZnO nanocrystals (NCs) coated with deprotonated 4-(dodecyloxy)benzoic acid (i.e., an X-type liquid-crystalline ligand) as a model LC system (termed ZnO-LC1 NCs). Langmuir and Langmuir-Blodgett films of the resulting hybrids are investigated. The observed behavior of the ZnO NCs at the air/water interface is rationalized by invoking a ZnO-interdigitation process mediated by the anchored liquid-crystalline shell. The ordered superstructures form according to mechanism based on a ZnO-interdigitation process mediated by liquid crystals (termed ZIP-LC). The external and directed force applied upon compression at the air/water interface and the packing of the ligands that stabilize the ZnO cores drives the formation of nanorods of ordered internal structure. To study the process in detail, we follow a nontraditional protocol of thin-film investigation. We collect the films from the air/water interface in powder form (ZnO-LC1 LB), resuspend the powder in organic solvents and utilize otherwise unavailable experimental techniques. The structural and physical properties of the resulting superlattices were studied by using electron microscopy, atomic force microscopy, X-ray studies, dynamic light scattering, thermogravimetric analysis, UV/Vis absorption, and photoluminescence spectroscopy.

Aggregation and Layering Transitions in Thin Films of X-, T-, and Anchor-Shaped Bolaamphiphiles at the Air–Water Interface

Aggregation in Langmuir films is usually understood as being a disorderly grouping of molecules turning into chaotic three-dimensional aggregates and is considered an unwanted phenomenon causing irreversible changes. In this work we present the studies of 11 compounds from the group of specific surfactants, known as bolaamphiphiles, that exhibit reversible aggregation and, in many cases, transition to well-defined multilayers, which can be considered as a layering transition. These bolaamphiphiles incorporate rigid π-conjugated aromatics as hydrophobic cores, glycerol-based polar groups and hydrophobic lateral chains. Molecules of different shapes (X-, T-, and anchor) were studied and compared. The key property of these compounds is the partial fluorination of the lateral chains linked to the rigid cores of the molecules. The most interesting feature of the compounds is that, depending on their shape and degree of fluorination, they are able to resist aggregation and preserve a monolayer structure up to relatively high surface pressures (T-shaped and some X-shaped molecules), or create well-defined trilayers (X- and anchor-shaped molecules). Experimental studies were performed using Langmuir balance, surface potential and X-ray reflectivity measurements.

Photoactive Langmuir–Blodgett, Freely Suspended and Free Standing Films of Carboxylate Ligand-Coated ZnO Nanocrystals

A new possibility for the formation of macroscopic and photoactive structures from zinc oxide nanocrystals is described. Photoactive freely suspended and free-standing films of macroscopic area (up to few square millimeters) and submicrometer thickness (up to several hundreds of nanometers) composed of carboxylate ligand-coated zinc oxide nanocrystallites (RCO2-ZnO NCs) of diameter less than 5 nm are prepared according to a modified Langmuir-Schaefer method. First, the suspension of RCO2-ZnO NCs is applied onto the air/water interface. Upon compression, the films become turbid and elastic. The integrity of such structures is ensured by interdigitation of ligands stabilizing ZnO NCs. Great elasticity allows transfer of the films onto a metal frame as a freely suspended film. Such membranes are afterward extracted from the supporting frame to form free-standing films of macroscopic area. Because the integrity of the films is maintained by ligands, no abolishment of quantum confinement occurs, and films retain spectroscopic properties of initial RCO2-ZnO NCs. The mechanism of formation of thin films of RCO2-ZnO NCs at the air/water interface is discussed in detail.

Gold–Oxoborate Nanocomposites and Their Biomedical Applications

A novel inorganic nanocomposite material, called BOA, which has the form of small building blocks composed of gold nanoparticles embedded in a polyoxoborate matrix, is presented. It is demonstrated that cotton wool decorated with the BOA nanocomposite displays strong antibacterial activity toward both Gram-positive and -negative bacteria strains. Importantly, the modified cotton does not release any toxic substances, and the bacteria are killed upon contact with the fibers coated with the BOA. Toxicity tests show that the nanocomposite--in spite of its antiseptic properties--is harmless for mammalian cells. The presented method of surface modification utilizes mild, environmentally friendly fabrication conditions. Thus, it offers a facile approach to obtain durable nontoxic antiseptic coatings for biomedical applications.

Recent advances in bacteriophage-based methods for bacteria detection

Fast and reliable bacteria detection is crucial for lowering the socioeconomic burden related to bacterial infections (e.g., in healthcare, industry or security). Bacteriophages (i.e., viruses with bacterial hosts) pose advantages such as great specificity, robustness, toughness and cheap preparation, making them popular biorecognition elements in biosensors and other assays for bacteria detection. There are several possible designs of bacteriophage-based biosensors. Here, we focus on developments based on whole virions as recognition agents. We divide the review into sections dealing with phage lysis as an analytical signal, phages as capturing elements in assays and phage-based sensing layers, putting the main focus on development reported within the past three years but without omitting the fundamentals.

Stable, ordered multilayers of partially fluorinated bolaamphiphiles at the air–water interface

The article presents systematic research on Langmuir films of partially fluorinated bolaamphiphiles of different shapes. Such films exhibit a layering transition from a monolayer to a trilayer during compression on the air–water interface. Further compression gives different results depending on the shape and degree of fluorination of the molecules. Partially fluorinated compounds form well defined multilayers in a reversible process. The balance between rigidity and flexibility of the molecules, adjusted by the fluorination and shape of the molecules, seems to be the key factor in avoiding irreversible aggregation of the molecules and creating ordered multilayer structures. Anchor-shaped bolaamphiphiles form a trilayer and, subsequently, a 9-layer film due to a double roll-over mechanism. In contrast, when trilayer films of X-shaped bolaamphiphiles are compressed, 5- and 7-layer films are created according to a different mechanism. Films of thickness of up to nine layers were transferred from the water surface to solid substrates in a single step procedure without any distortion in the structure of the layers. X-ray reflectometry (XRR) was used to measure the thickness of the layers. Perfect fits of the XRR data to theoretical equations allowed for a conclusion that the multilayers are well-ordered lamellar structures. These investigations lead to an improvement in the general understanding of trilayer and multilayer formation and indicate that only in exceptional cases it happens due to a roll-over process.

Bacteriophage-Based Bioconjugates as a Flow Cytometry Probe for Fast Bacteria Detection

Robust detection of bacteria can significantly reduce risks of nosocomial infections, which are a serious problem even in developed countries (4.1 million cases each year in Europe). Here we demonstrate utilization of novel multifunctional bioconjugates as specific probes for bacteria detection. Bifunctional magnetic-fluorescent microparticles are coupled with bacteriophages. The T4 bacteriophage, due to its natural affinity to bacterial receptors, namely, OmpC and LPS, enables specific and efficient detection of Escherichia coli bacteria. Prepared probes are cheap, accessible (even in nonbiological laboratories), as well as versatile and easily tunable for different bacteria species. The magnetic properties of the bioconjugates facilitate the separation of captured target bacteria from other components of complex samples and other bacteria strains. Fluorescence enables simple analysis. We chose flow cytometry as the detection method as it is fast and widely used for biotests. The capture efficiency of the prepared bioconjugates is close to 100% in the range of bacteria concentrations from tens to around 105 CFU/mL. The limit of detection is restricted by flow cytometry capabilities and in our case was around 104 CFU/mL.

Influence of nanomechanical stress induced by ZnO nanoparticles of different shapes on the viability of cells

There is growing interest in nanostructures interacting with living organisms. However, there are still no general rules for the design of biocompatible nanodevices. Here, we present a step towards understanding the interactions between nanostructures and living cells. We study the influence of nanomechanical stress induced by zinc oxide (ZnO) nanostructures of different shapes on the viability of both prokaryotic (Gram-negative bacteria: Escherichia coli and Enterobacter aerogenes, and Gram-positive bacteria: Staphylococcus epidermidis and Corynebacterium glutamicum) and eukaryotic cells (yeast Saccharomyces cerevisiae and liver cancer cell line HepG2). Nanoparticles (NPs) and nanorods (NRs) of matching crystallographic structure (P63mc) and active surface area (in the order of 5 × 10(-2)μm(2)) are almost non-toxic for cells under static conditions. However, under conditions that enable collisions between ZnO nanostructures and cells, NRs appear to be more damaging compared to NPs. This is due to the increased probability of mechanical damage caused by nanorods upon puncturing of the cell wall and membranes. Gram-positive bacteria, which have thicker cell walls, are more resistant to nanomechanical stress induced by NRs compared to Gram-negative strains and eukaryotic cells. The presented results may be exploited to improve the properties of nanotechnology based products such as implants, drug delivery systems, antibacterial emulsions and cosmetics.

Dense Layer of Bacteriophages Ordered in Alternating Electric Field and Immobilized by Surface Chemical Modification as Sensing Element for Bacteria Detection

Faster and more sensitive environmental monitoring should be developed to face the worldwide problem of bacterial infections. To remedy this issue, we demonstrate a bacteria-sensing element that utilizes dense and ordered layers of bacteriophages specific to the given bacteria strain. We combine (1) the chemical modification of a surface to increase the surface coverage of bacteriophages (2) with an alternating electric field to greatly increase the number of properly oriented bacteriophages at the surface. Usually, in sensing elements, a random orientation of bacteriophages results in steric hindrance, which results in no more than a few percent of all receptors being available. An increased number of properly ordered phages results in the optimal performance of phage receptors, manifesting in up to a 64-fold increase in sensitivity and a limit of detection as low as 100 CFU mL-1. Our sensing elements can be applied for selective, sensitive, and fast (15 min) bacterial detection. A well-studied pair T4 bacteriophage-bacteria Escherichia coli, was used as a model; however, the method could be adapted to prepare bacteriophage-based sensors for detection of a variety of bacterial strains.