Enhanced electro-mediated gene delivery using carrier genes

Effect of Experimental Electrical and Biological Parameters on Gene Transfer by Electroporation: A Systematic Review and Meta-Analysis

The exact mechanisms of nucleic acid (NA) delivery with gene electrotransfer (GET) are still unknown, which represents a limitation for its broader use. Further, not knowing the effects that different experimental electrical and biological parameters have on GET additionally hinders GET optimization, resulting in the majority of research being performed using a trial-and-error approach. To explore the current state of knowledge, we conducted a systematic literature review of GET papers in in vitro conditions and performed meta-analyses of the reported GET efficiency. For now, there is no universal GET strategy that would be appropriate for all experimental aims. Apart from the availability of the required electroporation device and electrodes, the choice of an optimal GET approach depends on parameters such as the electroporation medium; type and origin of cells; and the size, concentration, promoter, and type of the NA to be transfected. Equally important are appropriate controls and the measurement or evaluation of the output pulses to allow a fair and unbiased evaluation of the experimental results. Since many experimental electrical and biological parameters can affect GET, it is important that all used parameters are adequately reported to enable the comparison of results, as well as potentially faster and more efficient experiment planning and optimization.

The impact of impaired DNA mobility on gene electrotransfer efficiency: analysis in 3D model

Background

Gene electrotransfer is an established method that enables transfer of DNA into cells with electric pulses. Several studies analyzed and optimized different parameters of gene electrotransfer, however, one of main obstacles toward efficient electrotransfection in vivo is relatively poor DNA mobility in tissues. Our aim was to analyze the effect of impaired mobility on gene electrotransfer efficiency experimentally and theoretically. We applied electric pulses with different durations on plated cells, cells grown on collagen layer and cells embedded in collagen gel (3D model) and analyzed gene electrotransfer efficiency. In order to analyze the effect of impaired mobility on gene electrotransfer efficiency, we applied electric pulses with different durations on plated cells, cells grown on collagen layer and cells embedded in collagen gel (3D model) and analyzed gene electrotransfer efficiency.

Results

We obtained the highest transfection in plated cells, while transfection efficiency of embedded cells in 3D model was lowest, similarly as in in vivo. To further analyze DNA diffusion in 3D model, we applied DNA on top or injected it into 3D model and showed, that for the former gene electrotransfer efficiency was similarly as in in vivo. The experimental results are explained with theoretical analysis of DNA diffusion and electromobility.

Conclusion

We show, empirically and theoretically that DNA has impaired electromobility and especially diffusion in collagen environment, where the latter crucially limits electrotransfection. Our model enables optimization of gene electrotransfer in in vitro conditions.

A switching role of hard-uptake nanoparticles in microalgae cell electroporation

The microalgal cell wall is a natural barrier that limits the efficiency of gene delivery in algae genetic engineering. Here, we report the role of hard-uptake nanoparticles (huNPs) in microalgae cell electroporation to enhance the delivery of genes in Chlamydomonas reinhardtii. This role can be divided into two categories: (i) a 'transient state' for short-term behavior under confocal visualization and (ii) a 'steady state' for long-term behavior in cell culture. First, the 'transient' role of gene-huNP complexes was investigated after washing for clear confocal imaging to observe the location of huNPs after electroporation. Second, the 'steady-state' role of the gene-huNP complexes was examined after electroporation by transferring cells to a fresh, medium-rich culture environment without washing to obtain a stable cell culture. For selection of the huNPs, we used two types of nanoparticles (NPs, 250 nm and 530 nm) larger than the threshold size of electroporation uptake to avoid unwanted endocytic uptake of NPs. In the transient state, the visualization results indicate that gene-NP (250 nm) complexes were positioned on the cells and helped to deliver more genes than did the 530 nm NPs. In the steady state, the gene-NP (530 nm) complexes helped stably deliver more genes to the cells by precipitation of NPs due to gravity. We believe that these findings illustrate how gene-NP complexes function in microalgae cell electroporation and could help set up a protocol for enhanced microalgae applications associated with NPs such as environmental waste removal and biofuel production.

Calibration of on-chip cell electroporation by a pseudo-volumetric uptake model

Most conventional methods for assessing uptake of exogenous molecules and nanomaterials into cells use the projected two-dimensional (2D) area of uptake intensity into individual cells. However, since most cells have a three-dimensional (3D) spherical shape, volumetric uptake cannot be quantified accurately using 2D area analysis. Here, we present a method for calibrating the electroporative uptake intensity of small molecules by using a novel predictable spherical volume (PSV) model, which is more accurate and quantitative than previous methods. As a proof-of-concept, we visualized the electroporative uptake of propidium iodide (PI) into mammalian cells in a single rectangular polydimethylsiloxane (PDMS) microfluidic channel, often used for direct observation of on-chip cell electroporation. Our PSV method yielded more accurate results than conventional methods and faithfully reflected volumetric changes in uptake intensity, even those due to microflow. We believe that this approach can be potentially beneficial for screening the electroporative uptake efficiency of cell-membrane impermeable nanodrugs, such as functional nanoparticles incorporated with a small drug capable of slowly diffusing inside cells.

Electroporation for nanomedicine: a review

Here, we present a review of recent advances in electroporation for the delivery of nanomedicine as intracellular carriers by electroporation (NICE) in a drug format with functional nanoparticles.

Seeing the electroporative uptake of cell-membrane impermeable fluorescent molecules and nanoparticles

This paper presents direct visualization of uptake directionality for cell-membrane impermeant fluorescent molecules and fluorescence-doped nanoparticles at a single-cell level during electroporation. To observe directly the uptake direction, we used microchannel-type electroporation that can generate a relatively symmetric and uniform electric field. For all the image frames during electroporation, fluorescence intensities that occurred at cell membranes in both uptake directions toward the electrodes have been sequentially recorded and quantitatively analyzed pixel by pixel. In our experiments, we found that fluorescent molecules, even not labeled to target biomolecules, had their own uptake direction with different intensities. It is also observed that the uptake intensity toward the cell membrane had a maximal value at a certain electric voltage, not at the highest value of voltages applied. The results also imply that the uptake direction of fluorescence-doped nanoparticles can be determined by a net surface charge of uptake materials and sizes in the electroporative environments. In summary, we performed a quantitative screening and direct visualization of uptake directionality for a set of fluorescent molecules and fluorescence-doped nanoparticles using electric-pulsation. Taking a closer look at the uptake direction of exogenous materials will help researchers to understand an unknown uptake phenomenon in which way foreign materials are inclined to move, and furthermore to design functional nanoparticles for electroporative gene delivery.

Role of weakly polarized nanoparticles in electroporation

In this study, we present a role for weakly polarized nanoparticles as engineered gene transporters that can enhance electromediated gene delivery. To validate this proof-of-concept, fluorescent poly(ethylene glycol) (PEG)-coated silica nanoparticles (SiNPs) with opposite polarities, SiNPs(RITC)-PEG/PTMA(+) and SiNPs(RITC)-PEG/PMP(-), are used. To investigate the electroporative uptake direction of the nanoparticles-gene complex, we employ microscale electroporation to generate more symmetric and uniform electric fields. The effect of the polarity of the nanoparticles on EGFP gene transfection efficiency in HeLa cells is measured by flow cytometry analysis. The results show that, compared to cationic nanoparticles, anionic nanoparticles have potential as electromediated gene transporters at a low gene concentration. Furthermore, we believe that this finding can be useful for developing a platform that enables electroporation-based gene/drug delivery associated with functional nanoparticles.