Algimantas Paškevičius

High-frequency submicrosecond electroporator

ABSTRACT In this work, we present a novel electroporator which is capable of generating single and bursts of high power (3 kV, 60 A) square wave pulses of variable duration (100 ns to 1 ms) with predefined repetition frequency (1 Hz to 3.5 MHz). The proposed synchronized crowbar implementation ensures a constant pulse rise and fall times, which are independent from the load, thus highly relevant in electroporation. The electroporator was successfully tested for the inactivation of the human pathogen Candida albicans. The device is compatible with standard commercial electroporation cuvettes.

Microsecond pulsed magnetic field improves efficacy of antifungal agents on pathogenic microorganisms

Control and treatment of the emerging filamentous and yeast fungal diseases are of high priority in the biomedical field. This study investigated the influence of the pulsed magnetic field combined with common antifungal agents on the viability of various pathogenic fungi such as Aspergillus fumigatus, Candida albicans, and Trychophyton rubrum. Repetitive microsecond pulsed magnetic fields up to 6.1 T were applied in the study. The synergistic effect of co-applying drugs and magnetic treatment to different fungi species causing various human mycoses showed the potential for more effective and less toxic therapy.

Controlled inactivation of Trichophyton rubrum using shaped electrical pulse bursts: Parametric analysis.

The dermatophytes infect the skin by adherence to the epidermis followed by germination, growth, and penetration of the fungal hyphae within the cells. The aim of this study was to investigate the efficacy of the pulsed electric fields (PEF) of controlled inactivation of Trichophyton rubrum (ATCC 28188). In this work, we have used bursts of the square wave PEF pulses of different intensity (10–30 kV/cm) to induce the irreversible inactivation in vitro. The electric field pulses of 50 µs and 100 µs have been generated in bursts of 5, 10, and 20 pulses with repetition frequency of 1 Hz. The dynamics of the inactivation using different treatment parameters were studied and the inactivation map for the T. rubrum has been defined. Further, the combined effect of PEF with the antifungal agents itraconazole, terbinafine, and naftifine HCl was investigated. It has been demonstrated that the combined effect results in the full inactivation of T. rubrum colony.

Measurement of Transient Permeability of Sp2/0 Myeloma Cells: Flow Cytometric Study

Abstract Electroporation is an electric field induced phenomenon occurring when the permeability of the cell membrane is increased due to the excess of critical transmembrane potential. Fluorescent dye assays are frequently used for evaluation of the permeabilization rate, however, the protocols vary, which negatively affects the repeatability of the results. In this work we have designed experiments to investigate the protocols and threshold concentrations of the Propidium Iodide (PI) and YO-PRO-1 (YP) fluorescent dyes for evaluation of mammalian cell permeabilization induced by electroporation. The Sp2/0 mouse myeloma cells were used and the bursts of 100 μs × 8 electrical pulses of 0.8-2 kV/cm were applied. It has been shown that the dye concentration has an influence on the detectable permeabilization, and the concentrations below 30 μM for PI and 1 μM for YP should be avoided for measurement of electropermeabilization efficacy due to unreliable fluorescence signals. Further, based on the experimental data, the permeabilization curve for the Sp2/0 myeloma cells in the 0.8-2 kV/cm range has been presented.

Reversible Permeabilization of Cancer Cells by High Sub-Microsecond Magnetic Field

Exposure of cells to pulsed electric fields (PEFs) induces a phenomenon known as electroporation, which leads to increase of membrane permeability. Electroporation is applied in biotechnology, food processing, and medicine, including cancer treatment. Recently, a contactless method based on pulsed magnetic fields (PMFs) for the permeabilization of biological cells has been proposed; however, the permeabilization mechanism of the PMF method is still hypothetical. In this paper, we have shown that it is possible to reversibly permeabilize Sp2/0 myeloma cells by sub-microsecond (450 ns) PMF in the range of 0–3.3 T. The PMF methodology was also combined with PEF treatment to evaluate additive effects. The 1.35 kV/cm

Antifungal properties of hypericin, hypericin tetrasulphonic acid and fagopyrin on pathogenic fungi and spoilage yeasts.

1 \times 100~\mu \text{s}

Growth Inhibition and Membrane Permeabilization of Candida lusitaniae Using Varied Pulse Shape Electroporation

(PEF) and 3.3 T, 50 pulses, 0.25 Hz (PMF) protocols were applied. The cells were treated in the presence of fluorescence dye YO-PRO-1 and influx into the cells was evaluated by cytometry. Cell viability after the treatment was evaluated by CellEvent Caspase-3/7 assays. A significant (P < 0.05) additive effect of the two pulsed power methodologies was detected, resulting in up to 12% increase of membrane permeabilization. The PMF method is an emerging technique and the results of the study can be used for the development of new effective protocols, while the determined additive effects with PEF are promising in the field of electrochemotherapy.

Effectiveness research on a wavy lamellar plate-type biofilter with a capillary system for the humidification of the packing material applying introinduced microorganisms

Abstract Context: The role of hypericin-mediated photodynamic antimicrobial properties on pathogenic fungi and photodynamic therapy for human cancer cells is known. Antifungal properties of Hypericum perforatum L. (Hypericaceae) and Fagopyrum esculentum Moench. (Polygonaceae) extracts were also studied. The different polarities of solvents can cause complication in the identification of antifungal effects of separate biologically active compounds. In recent experimental work, we compared antifungal properties of purified hypericin, hypericin tetrasulphonic acid (hypericin + S) and fagopyrin, which is analogue of hypericin. Objective: The antifungal properties of aromatic polyketide derivatives such as hypericin, hypericin + S and fagopyrin on the selected pathogenic fungi and spoilage yeasts have been studied. Materials and methods: The antifungal properties of hypericin, hypericin + S and fagopyrin were determined using the broth microdilution method against a set of pathogenic fungi and spoilage yeasts including: Microsporum canis, Trichophyton rubrum, Fusarium oxysporum, Exophiala dermatitidis, Candida albicans, Kluyveromyces marxianus, Pichia fermentans and Saccharomyces cerevisiae. The tested concentrations of hypericin, hypericin + S and fagopyrin ranged from 750 to 0.011 μg/mL and MIC values were evaluated after 48 h incubation at 30 °C. Results: The results confirm different antifungal properties of hypericin, hypericin + S and fagopyrin on the selected pathogenic fungi and spoilage yeasts. For pathogenic fungi, the minimum inhibitory concentrations of hypericin ranged 0.18–46.9 μg/mL, hypericin + S 0.18–750 μg/mL and fagopyrin 11.7–46.9 μg/mL. For spoilage yeasts, the MICs of hypericin and hypericin + S ranged 0.18–46.9 and 0.011–0.73 μg/mL, respectively. Discussion and conclusion: The results obtained herein indicate that various chemical structures of hypericin, hypericin + S and fagopyrin can develop different antifungal properties.

Cellulose degradation in rye straw by micromycetes and their complexes@@@Celiuliozės degradacija rugių šiauduose pavieniais mikromicetais ir jų kompleksais

Candida lusitaniae is an opportunistic yeast pathogen, which can readily develop resistance to antifungal compounds and result in a complex long-term treatment. The efficient treatment is difficult since structure and metabolic properties of the fungal cells are similar to those of eukaryotic host. One of the potential methods to improve the inhibition rate or the cell permeability to inhibitors is the application of electroporation. In this work we investigated the dynamics of the growth inhibition and membrane permeabilization of C. lusitaniae by utilizing the various pulse shape and duration electric field pulses. Our results indicated that single electroporation procedure using 8 kV/cm electric field may result in up to 51 ± 5% inhibition rate. Also it has been experimentally shown that the electroporation pulse shape may influence the inhibitory effect; however, the amplitude of the electric field and the pulse energy remain the most important parameters for definition of the treatment outcome. The dynamics of the cell membrane permeabilization in the 2–8 kV/cm electric field were overviewed.

Succession of microorganisms in a plate-type air treatment biofilter during filtration of various volatile compounds

AbstractTo conduct research, a new generation plate-type air treatment biofilter for removing gaseous pollutants from air has been applied under laboratory conditions. A distinguishing feature of the packing material of the biofilter includes wavy lamellar polymer plates placed to each other and producing a capillary effect of humidification. While having such an arrangement, wavy lamellar plates also have rather wide spacing (6 mm), and therefore the employment of the structure of the plate-type packing material decreases the aerodynamic resistance of the device. A wavy porous plate is made of a polymer plate that ensures stiffness. Both sides of the wavy lamellar polymer plate have attached steam exploded birch fiber pellets under which, to increase plate capillarity, not-woven caulking material is put. This technological decision allows effectively enhancing the durability of the biopacking material. The work presents the results of research on the efficiency of the biodestruction process of acetone, x...