Effect of electroporation in a continuous flow system on bioaccumulation of magnesium, zinc and calcium ions in Lactobacillus rhamnosus B 442 cells.

Biomass of Lactobacillus rhamnosus B 442 was subjected to the continuous electroporation using an electroporator with a flow chamber (length of 10 cm, distance between electrodes 0.25 cm, stream width 0.25 cm, flow speed 10 mL/min) to improve accumulation of calcium, magnesium and zinc in the cells. For all tested ions, the following parameters were applied: voltage of 250 V (E = 1 kV/cm), 570 V (E = 2.28 kV/cm), 950 V (E = 3.8 kV/cm), and 1400 V (E = 5.6 kV/cm, the positive control), a frequency of 10 Hz, a pulse width of 100 µs and 30 electrical pulses. The use of PEF increased the accumulation of magnesium, zinc and calcium by 39, 73 and 162%, respectively, compared to the control. Positive correlation was found between ion accumulation and membrane permeability for zinc and magnesium. For calcium, the initial increase in permeability resulted in higher ion accumulation, but with a further increase of this parameter at 3.8 kV/cm, its decrease was observed caused by a drop in cell viability. Total number of bacteria ranged from 1.67 × 108 (for the cultures supplemented with calcium) to 1.34 × 1012 cfu/mL (for the cultures supplemented with magnesium).

Contactless electroporation induced by high intensity pulsed electromagnetic fields via distributed nanoelectrodes.

Pulsed electric fields (PEFs) can be used to transiently increase cell membrane permeability in procedures ranging from gene therapy to tumor eradication. Although very efficient, PEF-based therapies generally require the use of invasive electrodes, which cause pain and tissue damage. An emerging noninvasive, contactless alternative to PEFs are High Intensity Pulsed Electromagnetic Fields (HI-PEMF), whereby the electric field inside the tissue is induced remotely by external pulsed magnetic field. However, one of the current major drawbacks of HI-PEMFs is their inferior efficiency compared to PEFs. In this study we present the proof-of-concept that by adding highly conductive 5 and 20 nm gold nanoparticles (Au NPs), we can significantly potentiate the permeabilizing effect of HI-PEMFs, making it possible to permeabilize up to 80% of the cells with minimal or no effect on cell survival, compared to negligible percentage of permeabilized cells using HI-PEMF alone. Experiments, conducted on Chinese Hamster Ovary cells and Escherichia coli, suggest that Au NPs act as distributed nanoelectrodes, locally enhancing the electric field induced at the plasma membrane. Our findings open up an avenue of possibilities for combining naked as well as functionalized Au NPs with HI-PEMFs for noninvasive, remotely controlled smart drug delivery applications.