On the mechanism of biological activation by tritium

The mechanism of biological activation by beta-emitting radionuclide tritium was studied. Luminous marine bacteria were used as a bioassay to monitor the biological effect of tritium with luminescence intensity as the physiological parameter tested. Two different types of tritium sources were used: HTO molecules distributed regularly in the surrounding aqueous medium, and a solid source with tritium atoms fixed on its surface (tritium-labeled films, 0.11, 0.28, 0.91, and 2.36 MBq/cm2). When using the tritium-labeled films, tritium penetration into the cells was prevented. The both types of tritium sources revealed similar changes in the bacterial luminescent kinetics: a delay period followed by bioluminescence activation. No monotonic dependences of bioluminescence activation efficiency on specific radioactivities of the films were found. A 15-day exposure to tritiated water (100 MBq/L) did not reveal mutations in bacterial DNA. The results obtained give preference to a “non-genomic” mechanism of bioluminescence activation by tritium. An activation of the intracellular bioluminescence process develops without penetration of tritium atoms into the cells and can be caused by intensification of trans-membrane cellular processes stimulated by ionization and radiolysis of aqueous media

Molecular targets of the hydrophobic block of pluronics in cells: a photo affinity labelling approach

PurposePluronics are known as inhibitors of multidrug resistance thus making tumor cells sensitive to therapeutic doses of drugs. The purpose of our study consists in revealing molecular targets of the hydrophobic poly(propylene oxide) block of pluronics in living cells and the dependence of the polymers chemosensitizing efficiency upon targeting.MethodsA photo sensitive tracer was attached to the hydrophobic poly(propylene oxide) block of H-3-labeled tert-Bu-EO-PO copolymer. The conjugate was used for treatment cells in culture. We searched for its complexes with cellular lipids or proteins using RP TLC and SDS-electrophoresis, respectively. The chemosensitizing efficiency of pluronics was evaluated by their least concentrations sufficient for MDR reversion (C-MDR).ResultsThe poly(propylene oxide) block inserts in the lipid core of plasma membrane. No preferential binding of the conjugate with any cellular protein, particularly P-gp, has been detected. FITC-labeled pluronic L61 bound to alcohol insoluble cellular targets did not participate in MDR reversion. C-MDR values of 13 block copolymers have been determined. These values inversely correlated with the polymers affinity toward lipids and the ability to accelerate flip-flop.ConclusionInsertion of the hydrophobic poly(propylene oxide) block of amphiphiles in the lipid core of plasma membrane and acceleration of flip-flop of lipids underlie the mechanism of MDR reversion

On the mechanism of biological activation by tritium

The mechanism of biological activation by beta-emitting radionuclide tritium was studied. Luminous marine bacteria were used as a bioassay to monitor the biological effect of tritium with luminescence intensity as the physiological parameter tested. Two different types of tritium sources were used: HTO molecules distributed regularly in the surrounding aqueous medium, and a solid source with tritium atoms fixed on its surface (tritium-labeled films, 0.11, 0.28, 0.91, and 2.36 MBq/cm2). When using the tritium-labeled films, tritium penetration into the cells was prevented. The both types of tritium sources revealed similar changes in the bacterial luminescent kinetics: a delay period followed by bioluminescence activation. No monotonic dependences of bioluminescence activation efficiency on specific radioactivities of the films were found. A 15-day exposure to tritiated water (100 MBq/L) did not reveal mutations in bacterial DNA. The results obtained give preference to a “non-genomic” mechanism of bioluminescence activation by tritium. An activation of the intracellular bioluminescence process develops without penetration of tritium atoms into the cells and can be caused by intensification of trans-membrane cellular processes stimulated by ionization and radiolysis of aqueous media

PHYSICAL-CHEMICAL PRINCIPLES OF THE PREPARATION OF HYBRID MATERIALS ON THE BASIS OF DETONATION NANODIAMONDS AS A NEW GENERATION DRUG DELIVERY SYSTEMS AND THEIR PROPERTIES

There were illustrated the main questions of development of new generation drug delivery systems as hybrid nanomaterials as follows: selection of nanocarrier, its standardization and the methods of immobilization of biologically active and medicinal substances. The basic organs of distribution and accumulation of advanced carbon nanocarrier - detonation nanodiamond were identified. It was shown that antihypoxic effect of the nanodiamond-glycine conjugate increased in comparison with a native Glycine and Mexidolum® as reference drugs

Tritium Labeling and Phase Distribution of 18-Crown-6 and Its Derivatives for Further Reprocessing of Radium Waste

To date, the world has accumulated a large amount of long-lived radioactive materials that need to be disposed of or reprocessed. Such materials include nuclear legacy objects containing 226Ra, which is an important material for obtaining a wide range of isotopes for nuclear medicine via irradiation in reactors, cyclotrons, and electron accelerators. For the selective recovery of 226Ra from waste materials, crown-ether (CE) 18-crown-6 (18C6) or its derivatives can be used, which, however, have not been widely studied for these purposes. In our work, the key property of 18C6 and its derivatives, the phase distribution, was studied using tritium labeling. The possibility of introducing a tritium label into CEs molecules using thermal activation of tritium has been demonstrated; a high specific activity of the obtained compounds was achieved (from 18 to 108 TBq/mol). Methods for chromatographic purification of the studied CEs were developed. The distribution of 18C6 and its derivatives between various organic solvents and water was studied in detail for the first time. Subsequently, the obtained data will allow us to choose conditions for the selective recovery of 226Ra from aged sources

Estimation of Uptake of Humic Substances from Different Sources by Escherichia coli Cells under Optimum and Salt Stress Conditions by Use of Tritium-Labeled Humic Materials▿

The primary goal of this paper is to demonstrate potential strengths of the use of tritium-labeled humic substances (HS) to quantify their interaction with living cells under various conditions. A novel approach was taken to study the interaction between a model microorganism and the labeled humic material. The bacterium Escherichia coli was used as a model microorganism. Salt stress was used to study interactions of HS with living cells under nonoptimum conditions. Six tritium-labeled samples of HS originating from coal, peat, and soil were examined. To quantify their interaction with E. coli cells, bioconcentration factors (BCF) were calculated and the amount of HS that penetrated into the cell interior was determined, and the liquid scintillation counting technique was used as well. The BCF values under optimum conditions varied from 0.9 to 13.1 liters kg−1 of cell biomass, whereas under salt stress conditions the range of corresponding values increased substantially and accounted for 0.2 to 130 liters kg−1. The measured amounts of HS that penetrated into the cells were 23 to 167 mg and 25 to 465 mg HS per kg of cell biomass under optimum and salt stress conditions, respectively. This finding indicated increased penetration of HS into E. coli cells under salt stress