Polyelectrolytes can be very efficiently deposited on charged surfaces. In that respect, according to the theory and molecular cellular morphology the surface of cells should be charged. In that respect, the biggest contribution to the negative charge of the cell surface is based on phosphate groups of the membrane phospholipids. Based on that assumption as well as on the assumption that cells are very similar to the nonliving micron sized particle, it was also demonstrated that polyelectrolytes can be deposited on cell surfaces. However, among all those assumptions two important facts has not been kept in mind: (i) cell surface is not composed only of cell membrane and (ii) cell is alive and it is therefore modifying it surface, is dividing and is responding to the environmental changes. In addition, especially bacterial cells are also very special in these two aspects. They are very metabolically diverse and they are very different in molecular composition and their molecular morphology. Here we demonstrated that this diversity extents also in electrostatic properties. We showed that surface charge is different for different bacterial species, strains as well as at different growth time points. This then affects the deposition of polyelectrolytes. In addition, bacterial cells are also electrostatically as well as mechanically very soft and the protocol for omitting aggregation has been needed to be developed, which enabled us to observe changes in whole population of bacterial cells as well as on the level of separate single cells by using time laps microscopy. As a result the deposition of polyelectrolytes on bacterial cells resulted in bacteria entrapment. However, during bacterial growth and division cells can escape. However, this deposition affects their physiology by increasing time for the first division, increasing protein expression and metabolic rate and can increase size of bacterial cells. By such use of polyelectrolyte deposition it can be controlled growth, it can increase production of bioactive substances and can enable regulation of population and interspecies interaction, which will be also shown by some examples.
B.04 Guest lecture
COBISS.SI-ID: 29586215This contribution is one of the many contribution that the consortium members contributed at the ECIS conference. The conference is one of the highly visible conferences among the colloid and surface scientists in Europe. Group of prof. Kristl was fully engaged in the organisation of the conference. dr. Lapanje was involved as the chair of the section. We also contributed 3 different oral presentations and more than 10 posters.
B.01 Organiser of a scientific meeting
COBISS.SI-ID: 4576625The lecture was presented at VU Amsterdam, AIMS research, which is one of the very famous institution in EU in the field of molecular cell physiology: Polyelectrolytes can be very efficiently deposited on charged surfaces. In that respect, according to the theory and molecular cellular morphology the surface of cells should be charged. In that respect, the biggest contribution to the negative charge of the cell surface is based on phosphate groups of the membrane phospholipids. Based on that assumption as well as on the assumption that cells are very similar to the nonliving micron sized particle, it was also demonstrated that polyelectrolytes can be deposited on cell surfaces. However, among all those assumptions two important facts has not been kept in mind: (i) cell surface is not composed only of cell membrane and (ii) cell is alive and it is therefore modifying it surface, is dividing and is responding to the environmental changes. In addition, especially bacterial cells are also very special in these two aspects. They are very metabolically diverse and they are very different in molecular composition and their molecular morphology. Here we demonstrated that this diversity extents also in electrostatic properties. We showed that surface charge is different for different bacterial species, strains as well as at different growth time points. This then affects the deposition of polyelectrolytes. In addition, bacterial cells are also electrostatically as well as mechanically very soft and the protocol for omitting aggregation has been needed to be developed, which enabled us to observe changes in whole population of bacterial cells as well as on the level of separate single cells by using time laps microscopy. As a result the deposition of polyelectrolytes on bacterial cells resulted in bacteria entrapment. However, during bacterial growth and division cells can escape. However, this deposition affects their physiology by increasing time for the first division, increasing protein expression and metabolic rate and can increase size of bacterial cells. By such use of polyelectrolyte deposition it can be controlled growth, it can increase production of bioactive substances and can enable regulation of population and interspecies interaction, which will be also shown by some examples.
B.05 Guest lecturer at an institute/university
COBISS.SI-ID: 32185639The procedure for impregnating porous cell carriers and the method of holding cells in the pores of impregnated carriers is described. The method is particularly suitable for porous carriers that have very low Young module, which can not be used with elasticity, so it is predefined in the procedure described in US Pat. No. 4,669,600. Immobilized cell biomass is used for the decomposition of undesirable substances fro purification of contamination present in the drinking water by microorganisms in biological treatment plants or in water containing sand filters. The immobilisatio is necessary to protect bacterial cells within carriers, cells must be protected against the loss of the number and their activities for as well as the contamination of the final product of the biotechnological process. According to this invention, the impregnation of the porous carrier with a solution of linear polymers is made that enables the replacement of the cells in the lumen of the pore of the porous carrier or the binding to the surface of the pores by the electrostatic binding of the cells to the previously prepared surface of the pore portions of the porous carrier. The solution is based on a change in pressure variation and the addition of solutions in the individual steps of the process. Porous carriers thus prepared can then be used in continuous as well as batch processes.
F.33 Slovenian patent
COBISS.SI-ID: 37774085The industrial production of biopharmaceutical product is based on the use of bacterial cells. For the purpose of preserving biological material, researchers have been developing techniques that would enable artificial immobilization of living cells at the laboratory and industrial level. The purpose of the master's thesis was to develop and evaluate two types of immobilization of living bacterial cells E. coli, as gram negative bacteria, and bacteria from the genus Bacillus sp. 25.2.M, as gram positive bacteria that are unlike E. coli capable of forming spores. Cell immobilization was carried out with polyelectrolyte coating (layer-by-layer deposition method) and electrospinning, according to the developed protocols. Cationic polyethylenimine and anionic alginate proved to be suitable for electrostatic coating of living cells. The charge of the cell surface and the loading of the polyelectrolyte layers were monitored by measuring zeta potential, the effect on growth was evaluated by measuring the optical density of the cell suspension in time and the metabolic activity by resazurin reduction assay. We used dispersions of polyethylene oxide, polyvinylpyrrolidone, and a combination of alginate and polyethylene oxide with and without bacterial cells for electrospinning of nanofibers, checked the level of cell incorporation in nanofibers and viability of the cellsafter incorporation. We connected the polyelectrolyte coating technique and electrospinning by incorporating coated cells into the nanofibres.The coating of cells with polyelectrolytes was successful on living bacteria E. coli and vegetative bacteria and spores of Bacillus sp.,according to the measurements of zeta potential. We found out that with increasing number of polyelectrolyte layers the exponential growth phase of the cells is delayed, and that the coated cells are metabolically active on longer term than uncoated.
D.10 Educational activities
COBISS.SI-ID: 4521329