Technological and Theoretical Aspects for Testing Electroporation on Liposomes

Abstract

Recently, the use of nanometer liposomes as nanocarriers in drug delivery systems mediated by nanoelectroporation has been proposed. This technique takes advantage of the possibility of simultaneously electroporating liposomes and cell membrane with 10-nanosecond pulsed electric fields (nsPEF) facilitating the release of the drug from the liposomes and at the same time its uptake by the cells. In this paper the design and characterization of a 10 nsPEF exposure system is presented, for liposomes electroporation purposes. The design and the characterization of the applicator have been carried out choosing an electroporation cuvette with 1 mm gap between the electrodes. The structure efficiency has been evaluated at different experimental conditions by changing the solution conductivity from 0.25 to 1.6 S/m. With the aim to analyze the influence of device performances on the liposomes electroporation, microdosimetric simulations have been performed considering liposomes of 200 and 400 nm of dimension with different inner and outer conductivity (from 0.05 to 1.6 S/m) in order to identify the voltage needed for their poration.

Proof-of-Concept of Electrical Activation of Liposome Nanocarriers: From Dry to Wet Experiments

“…As a whole the significance of this work findings is related to the experimental validation of the possibility to on demand trigger the release from nanosized liposomes applying pulsed electric fields as such used for cells treatment. These outcomes open the way to the experimental application of liposomal drug delivery systems remotely activated by nsPEFs, previously studied only from a numerical point of view ( Retelj et al, 2013 ; Denzi et al, 2017a , b ). As a result of the lipid membrane destabilization, the fluorescent dye release of about 15–20% after a single treatment, is in line with literature on stimuli-sensitive drug delivery system activated by light or magnetic fields ( Spera et al, 2015 ; Senapati et al, 2018 ; Liu and An, 2019 ).…”

“…Another approach could be to electroporate such lipid vesicles when they are in close proximity of the target cells, simultaneously electroporating both the cell and liposomes population, without compromising the cell viability. In fact, since nsPEFs are able to electroporate the cell membrane, the content released from the liposomes could be taken by the electroporated cells (Denzi et al, 2017b). However, the possibility of triggering the release of liposome content with nsPEFs remains up to now at the theoretical level, and the experimental feasibility of this approach has not been confirmed yet.…”

“…Any trace of solvent was further removed keeping the flask under reduced pressure for 2 h. The dry lipid film was then hydrated with 5 mL of the 5-(6) CF dye solution, 50 mM in HEPES buffer (σ = 0.0304 ± 0.0041 S/m, 10 mM, pH = 7.4). The buffer properties have been chosen in accordance with the literature on electroporation (Silve et al, 2016;Denzi et al, 2017b). Five consecutive freezing/thawing cycles in a dry ice-ethanol bath were performed to increase the trapped volume of multilamellar preparations.…”

“…The system used to perform the nsPEFs exposure was composed by a standard electroporation cuvette (1002561E, BioGenerica, Italy), hosting a fixed volume of the prepared liposomal suspension, placed in the 11 mm-gap between the two brass electrodes of the cuvette holder, that are suitable connected to a HN coaxial cable, as first designed and developed in Denzi et al (2017b). To mechanically stabilize the structure, avoiding any air gaps between the holder and the standard cuvette, they were attached with a clamp.…”

“…Thanks to the similarity between cellular and liposomal membranes ( Breton et al, 2012 , 2015 ; Portet et al, 2012 ) and considering the second-order model of induced transmembrane voltage ( Postow and Polk, 1996 ; Kotnik and Miklavčič, 2000 ; Merla et al, 2012 ), such pulsed electric fields with high frequency content could be used as a promising external trigger to obtain simultaneous and reversible electropermeabilization of both cell and liposome membranes, thus overcoming the limitation of the well-known transmembrane dependence on the radius of the microscopic structures for pulses with a lower frequency spectral content. Authors have already shown through a theoretical study the possibility of nsPEFs to induce a simultaneous electroporation of cell and liposomes using small unilamellar lipid vesicles of the order of hundreds of nm ( Denzi et al, 2017a , b ).…”