Electroporation-mediated gene delivery

An Overview of Methods and Tools for Transfection of Eukaryotic Cells in vitro

Transfection is a powerful analytical tool enabling studies of gene products and functions in eukaryotic cells. Successful delivery of genetic material into cells depends on DNA quantity and quality, incubation time and ratio of transfection reagent to DNA, the origin, type and the passage of transfected cells, and the presence or absence of serum in the cell culture. So far a number of transfection methods that use viruses, non-viral particles or physical factors as the nucleic acids carriers have been developed. Among non-viral carriers, the cationic polymers are proposed as the most attractive ones due to the possibility of their chemical structure modification, low toxicity and immunogenicity. In this review the delivery systems as well as physical, biological and chemical methods used for eukaryotic cells transfection are described and discussed.

Population scale nucleic acid delivery to Caenorhabditis elegans via electroporation

The free-living nematode Caenorhabditis elegans remains one of the most robust and flexible genetic systems for interrogating the complexities of animal biology. Targeted genetic manipulations, such as RNA interference (RNAi), CRISPR/Cas9- or array-based transgenesis, all depend on initial delivery of nucleic acids. Delivery of dsRNA by feeding can be effective, but the expression in Escherichia coli is not conducive to experiments intended to remain sterile or with defined microbial communities. Soaking-based delivery requires prolonged exposure of animals to high-material concentrations without a food source and is of limited throughput. Last, microinjection of individual animals can precisely deliver materials to animals' germlines, but is limited by the need to target and inject each animal one-by-one. Thus, we sought to address some of these challenges in nucleic acid delivery by developing a population-scale delivery method. We demonstrate efficient electroporation-mediated delivery of dsRNA throughout the worm and effective RNAi-based silencing, including in the germline. Finally, we show that guide RNA delivered by electroporation can be utilized by transgenic Cas9 expressing worms for population-scale genetic targeting. Together, these methods expand the scale and scope of genetic methodologies that can be applied to the C. elegans system.

Molecular dynamics simulations of the effects of lipid oxidation on the permeability of cell membranes

The formation of transient pores in their membranes is a well-known mechanism of permeabilization of cells exposed to high-intensity electric pulses. However, the formation of such pores is not able to explain all aspects of the so-called electroporation phenomenon. In particular, the reasons for sustained permeability of cell membranes, persisting long after the pulses' application, remain elusive. The complete resealing of cell membranes takes indeed orders of magnitude longer than the time for electropore closure as reported from molecular dynamics (MD) investigations. Lipid peroxidation has been suggested as a possible mechanism to explain the sustainable permeability of cell membranes. However, theoretical investigations of membrane lesions containing excess amounts of hydroperoxides have shown that the conductivities of such lesions were not high enough to account for the experimental measurements. Here, expanding on these studies, we investigate quantitatively the permeability of cell membrane lesions that underwent secondary oxidation. MD simulations and free energy calculations of lipid bilayers show that such lesions provide a better model of post-pulse permeable and conductive electropermeabilized cells. These results are further discussed in the context of sonoporation and ferroptosis, respectively a procedure and a phenomenon, among others, in which, alike electroporation, substantial lipid oxidation might be triggered.

Repurposed drug against COVID-19: nanomedicine as an approach for finding new hope in old medicines

The coronavirus disease 2019 (COVID-19) has become a threat to global public health. It is caused by the novel severe acute respiratory syndrome coronavirus (SARS-CoV-2) and has triggered over 17 lakh causalities worldwide. Regrettably, no drug or vaccine has been validated for the treatment of COVID-19 and standard treatment for COVID-19 is currently unavailable. Most of the therapeutics moieties which were originally intended for the other disease are now being evaluated for the potential to be effective against COVID-19 (re-purpose). Nanomedicine has emerged as one of the most promising technologies in the field of drug delivery with the potential to deal with various diseases efficiently. It has addressed the limitations of traditional repurposed antiviral drugs including solubility and toxicity. It has also imparted enhanced potency and selectivity to antivirals towards viral cells. This review emphasizes the scope of repositioning of traditional therapeutic approaches, in addition to the fruitfulness of nanomedicine against COVID-19.

Gene electrotransfer of IL-2 and IL-12 plasmids effectively eradicated murine B16.F10 melanoma

Gene therapy has become an important approach for treating cancer, and electroporation represents a technology for introducing therapeutic genes into a cell. An example of cancer gene therapy relying on gene electrotransfer is the use of immunomodulatory cytokines, such as interleukin 2 (IL-2) and 12 (IL-12), which directly stimulate immune cells at the tumour site. The aim of our study was to determine the effects of gene electrotransfer with two plasmids encoding IL-2 and IL-12 in vitro and in vivo. Two different pulse protocols, known as EP1 (600 V/cm, 5 ms, 1 Hz, 8 pulses) and EP2 (1300 V/cm, 100 µs, 1 Hz, 8 pulses), were assessed in vitro for application in subsequent in vivo experiments. In the in vivo experiment, gene electrotransfer of pIL-2 and pIL-12 using the EP1 protocol was performed in B16.F10 murine melanoma. Combined treatment of tumours using pIL2 and pIL12 induced significant tumour growth delay and 71% complete tumour regression. Furthermore, in tumours coexpressing IL-2 and IL-12, increased accumulation of dendritic cells and M1 macrophages was obtained along with the activation of proinflammatory signals, resulting in CD4 + and CD8 + T-lymphocyte recruitment and immune memory development in the mice. In conclusion, we demonstrated high antitumour efficacy of combined IL-2 and IL-12 gene electrotransfer protocols in low-immunogenicity murine B16.F10 melanoma.

New Insights into the Therapeutic Applications of CRISPR/Cas9 Genome Editing in Breast Cancer

Breast cancer is one of the most prevalent forms of cancer globally and is among the leading causes of death in women. Its heterogenic nature is a result of the involvement of numerous aberrant genes that contribute to the multi-step pathway of tumorigenesis. Despite the fact that several disease-causing mutations have been identified, therapy is often aimed at alleviating symptoms rather than rectifying the mutation in the DNA sequence. The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 is a groundbreaking tool that is being utilized for the identification and validation of genomic targets bearing tumorigenic potential. CRISPR/Cas9 supersedes its gene-editing predecessors through its unparalleled simplicity, efficiency and affordability. In this review, we provide an overview of the CRISPR/Cas9 mechanism and discuss genes that were edited using this system for the treatment of breast cancer. In addition, we shed light on the delivery methods—both viral and non-viral—that may be used to deliver the system and the barriers associated with each. Overall, the present review provides new insights into the potential therapeutic applications of CRISPR/Cas9 for the advancement of breast cancer treatment.

N-[4-(N,N,N-Trimethylammonium)Benzyl]Chitosan Chloride as a Gene Carrier: The Influence of Polyplex Composition and Cell Type

Polyplex-based gene delivery systems are promising substitutes for viral vectors because of their high versatility and lack of disadvantages commonly encountered with viruses. In this work, we studied the DNA polyplexes with N-[4-(N,N,N-trimethylammonium)benzyl]chitosan chloride (TMAB-CS) of various compositions in different cell types. Investigations of the interaction of TMAB-CS with DNA by different physical methods revealed that the molecular weight and the degree of substitution do not dramatically influence the hydrodynamic properties of polyplexes. Highly substituted TMAB-CS samples had a high affinity for DNA. The transfection protocol was optimized in HEK293T cells and achieved the highest efficiency of 30-35%. TMAB-CS was dramatically less effective in nonadherent K562 cells (around 1% transfected cells), but it was more effective and less toxic than polyarginine.

Gene transfer by electroporation with high frequency bipolar pulses in vitro

High-frequency bipolar pulses (HF-BP) have been demonstrated to be efficient for membrane permeabilization and irreversible electroporation. Since membrane permeabilization has been achieved using HF-BP pulses we hypothesized that with these pulses we can also achieve successful gene electrotransfer (GET). Three variations of bursts of 2 µs bipolar pulses with 2 µs interphase delay were applied in HF-BP protocols. We compared transfection efficiency of monopolar micro and millisecond pulses and HF-BP protocols at various plasmid DNA (pDNA) concentrations on CHO - K1 cells. GET efficiency increased with increasing pDNA concentration. Overall GET obtained by HF-BP pulse protocols was comparable to overall GET obtained by longer monopolar pulse protocols. Our results, however, suggest that although we were able to achieve similar percent of transfected cells, the number of pDNA copies that were successfully transferred into cells seemed to be higher when longer monopolar pulses were used. Interestingly, we did not observe any direct correlation between fluorescence intensity of pDNA aggregates formed on cell membrane and transfection efficiency. The results of our study confirmed that we can achieve successful GET with bipolar microsecond i. e. HF-BP pulses, although at the expense of higher pDNA concentrations.

Creating cell lines for mimicking diseases

Cell lines can be good models for the disease they are derived from but can also be used to study general physiological and pathological processes. They can also be used to generate cell models of diseases when primary cultures are not available. Recent genome editing tools have been very promising tools toward creating cell models to mimic diseases in vitro. In this chapter, we highlight techniques used to obtain genome-edited cell lines, including cell line selection, transfection and gene editing tools available, together with methods of phenotype characterization and, lastly, a few examples of how in vitro disease models were created using CRISPR-Cas9.

Pulmonary gene delivery-Realities and possibilities

Delivery of genetic material to tissues in vivo is an important technique used in research settings and is the foundation upon which clinical gene therapy is built. The lung is a prime target for gene delivery due to a host of genetic, acquired, and infectious diseases that manifest themselves there, resulting in many pathologies. However, the in vivo delivery of genetic material to the lung remains a practical problem clinically and is considered the major obstacle needed to be overcome for gene therapy. Currently there are four main strategies for in vivo gene delivery to the lung: viral vectors, liposomes, nanoparticles, and electroporation. Viral delivery uses several different genetically modified viruses that enter the cell and express desired genes that have been inserted to the viral genome. Liposomes use combinations of charged and neutral lipids that can encapsulate genetic cargo and enter cells through endogenous mechanisms, thereby delivering their cargoes. Nanoparticles are defined by their size (typically less than 100 nm) and are made up of many different classes of building blocks, including biological and synthetic polymers, cell penetrant and other peptides, and dendrimers, that also enter cells through endogenous mechanisms. Electroporation uses mild to moderate electrical pulses to create pores in the cell membrane through which delivered genetic material can enter a cell. An emerging fifth category, exosomes and extracellular vesicles, may have advantages of both viral and non-viral approaches. These extracellular vesicles bud from cellular membranes containing receptors and ligands that may aid cell targeting and which can be loaded with genetic material for efficient transfer. Each of these vectors can be used for different gene delivery applications based on mechanisms of action, side-effects, and other factors, and their use in the lung and possible clinical considerations is the primary focus of this review.

Delivery technologies for in utero gene therapy

Advances in prenatal imaging, molecular diagnostic tools, and genetic screening have unlocked the possibility to treat congenital diseases in utero prior to the onset of clinical symptoms. While fetal surgery and in utero stem cell transplantation can be harnessed to treat specific structural birth defects and congenital hematological disorders, respectively, in utero gene therapy allows for phenotype correction of a wide range of genetic disorders within the womb. However, key challenges to realizing the broad potential of in utero gene therapy are biocompatibility and efficiency of intracellular delivery of transgenes. In this review, we outline the unique considerations to delivery of in utero gene therapy components and highlight advances in viral and non-viral delivery platforms that meet these challenges. We also discuss specialized delivery technologies for in utero gene editing and provide future directions to engineer novel delivery modalities for clinical translation of this promising therapeutic approach.

Intrabodies targeting human papillomavirus 16 E6 and E7 oncoproteins for therapy of established HPV-associated tumors

Background

The oncogenic activity of the high risk human papillomavirus type 16 (HPV16) is fully dependent on the E6 and E7 viral oncoproteins produced during viral infection. The oncoproteins interfere with cellular homeostasis by promoting proliferation, inhibiting apoptosis and blocking epithelial differentiation, driving the infected cells towards neoplastic progression. The causal relationship between expression of E6/E7 and cellular transformation allows inhibiting the oncogenic process by hindering the activity of the two oncoproteins. We previously developed and characterized some antibodies in single-chain format (scFvs) against the HPV16 E6 and E7 proteins, and demonstrated both in vitro and in vivo their antitumor activity consisting of protective efficacy against tumor progression of HPV16-positive cells.

Methods

Envisioning clinical application of the best characterized anti-HPV16 E6 and –HPV16 E7 scFvs, we verified their activity in the therapeutic setting, on already implanted tumors. Recombinant plasmids expressing the anti-HPV16 E6 scFvI7 with nuclear targeting sequence, or the anti-HPV16 E7 scFv43M2 with endoplasmic reticulum targeting sequence were delivered by injection followed by electroporation to three different preclinical models using C57/BL6 mice, and their effect on tumor growth was investigated. In the first model, the HPV16+ TC-1 Luc cells were used to implant tumors in mice, and tumor growth was measured by luciferase activity; in the second model, a fourfold number of TC-1 cells was used to obtain more aggressively growing tumors; in the third model, the HPV16+ C3 cells where used to rise tumors in mice. To highlight the scFv possible mechanism of action, H&E and caspase-3 staining of tumor section were performed.

Results

We showed that both the anti-HPV16 E6 and HPV16 E7 scFvs tested were efficacious in delaying tumor progression in the three experimental models and that their antitumor activity seems to rely on driving tumor cells towards the apoptotic pathway.

Conclusion

Based on our study, two scFvs have been identified that could represent a safe and effective treatment for the therapy of HPV16-associated lesions. The mechanism underlying the scFv effectiveness appears to be leading cells towards death by apoptosis. Furthermore, the validity of electroporation, a methodology allowed for human treatment, to deliver scFvs to tumors was confirmed.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-01841-w.

Changes in lung immune cell infiltrates after electric field treatment in mice

Exogenous electric fields are currently used in human therapy in a number of contexts. Interestingly, electric fields have also been shown to alter migration and function of immune cells, suggesting the potential for electric field-based immune therapy. Little is known as to the effect of electric field treatment (EFT) on the lung. To determine if EFT associates with changes in lung immune cell infiltration, we used a mouse model with varying methods of EFT application and measured cells and soluble mediators using flow cytometry and cytokine/chemokine multiplex. EFT was associated with a transient increase in lung neutrophils and decrease in eosinophils in naïve mice within 2 h of treatment, accompanied by an increase in IL-6 levels. In order to test whether EFT could alter eosinophil/neutrophil recruitment in a relevant disease model, a mouse model of allergic airway inflammation was used. Four EFT doses in allergen-sensitized mice resulted in increased neutrophil and reduced eosinophil infiltrates following allergen challenge, suggesting a durable change in inflammation by EFT. Mice with allergic inflammation were analyzed by flexiVent for measures of lung function. EFT-treated mice had increased inspiratory capacity and other measures of lung function were not diminished. These data suggest EFT may be used to manipulate immune cell infiltration in the lung without affecting lung function.

Controlled Delivery of Plasmid DNA to Melanoma Tumors by Gene Electrotransfer

Gene electrotransfer (GET) is a reliable and effective physical method for in vivo delivery of plasmid DNA (pDNA). Several preclinical and clinical studies have utilized GET to deliver plasmids encoding immune stimulating genes for treatment of melanoma and other tumor types. Intratumor delivery of plasmids encoding cytokines directly to tumors can induce not only a local immune response, but a systemic one as well. To obtain an effective immune response, it is critical to achieve the appropriate expression pattern of the delivered transgene. Expression pattern (levels and kinetics) can be modified by manipulating the electrotransfer parameters. These parameters include the tissue target and the electric pulse parameters of pulse width, electric field, and pulse number. We have found that to induce a robust immune response, we needed only low to moderately elevated expression levels compared to controls. When developing a therapeutic protocol, it is important to establish what expression profile will enable the appropriate response. In this chapter we describe how to determine the appropriate GET protocol to achieve the expression profile that can result in the desired clinical response.

Gene Expression Profile at the Motor Endplate of the Neuromuscular Junction of Fast-Twitch Muscle

The neuromuscular junction (NMJ) is a prototypic chemical synapse between the spinal motor neuron and the motor endplate. Gene expression profiles of the motor endplate are not fully elucidated. Collagen Q (ColQ) is a collagenic tail subunit of asymmetric forms of acetylcholinesterase and is driven by two distinct promoters. pColQ1 is active throughout the slow-twitch muscle, whereas pColQ1a is active at the motor endplate of fast-twitch muscle. We made a transgenic mouse line that expresses nuclear localization signal (NLS)-attached Cre recombinase under the control of pColQ1a (pColQ1a-Cre mouse). RiboTag mouse expresses an HA-tagged ribosomal subunit, RPL22, in cells expressing Cre recombinase. We generated pColQ1a-Cre:RiboTag mouse, and confirmed that HA-tagged RPL22 was enriched at the NMJ of tibialis anterior (TA) muscle. Next, we confirmed that Chrne and Musk that are specifically expressed at the NMJ were indeed enriched in HA-immunoprecipitated (IP) RNA, whereas Sox10 and S100b, markers for Schwann cells, and Icam1, a marker for vascular endothelial cells, and Pax3, a marker for muscle satellite cells, were scarcely detected. Gene set enrichment analysis (GSEA) of RNA-seq data showed that “phosphatidylinositol signaling system” and “extracellular matrix receptor interaction” were enriched at the motor endplate. Subsequent analysis revealed that genes encoding diacylglycerol kinases, phosphatidylinositol kinases, phospholipases, integrins, and laminins were enriched at the motor endplate. We first characterized the gene expression profile under translation at the motor endplate of TA muscle using the RiboTag technique. We expect that our gene expression profiling will help elucidate molecular mechanisms of the development, maintenance, and pathology of the NMJ.

Induction of a local muscular dystrophy using electroporation in vivo: an easy tool for screening therapeutics

Intramuscular injection and electroporation of naked plasmid DNA (IMEP) has emerged as a potential alternative to viral vector injection for transgene expression into skeletal muscles. In this study, IMEP was used to express the DUX4 gene into mouse tibialis anterior muscle. DUX4 is normally expressed in germ cells and early embryo, and silenced in adult muscle cells where its pathological reactivation leads to Facioscapulohumeral muscular dystrophy. DUX4 encodes a potent transcription factor causing a large deregulation cascade. Its high toxicity but sporadic expression constitutes major issues for testing emerging therapeutics. The IMEP method appeared as a convenient technique to locally express DUX4 in mouse muscles. Histological analyses revealed well delineated muscle lesions 1-week after DUX4 IMEP. We have therefore developed a convenient outcome measure by quantification of the damaged muscle area using color thresholding. This method was used to characterize lesion distribution and to assess plasmid recirculation and dose–response. DUX4 expression and activity were confirmed at the mRNA and protein levels and through a quantification of target gene expression. Finally, this study gives a proof of concept of IMEP model usefulness for the rapid screening of therapeutic strategies, as demonstrated using antisense oligonucleotides against DUX4 mRNA.

Short microsecond pulses achieve homogeneous electroporation of elongated biological cells irrespective of their orientation in electric field

In gene electrotransfer and cardiac ablation with irreversible electroporation, treated muscle cells are typically of elongated shape and their orientation may vary. Orientation of cells in electric field has been reported to affect electroporation, and hence electrodes placement and pulse parameters choice in treatments for achieving homogeneous effect in tissue is important. We investigated how cell orientation influences electroporation with respect to different pulse durations (ns to ms range), both experimentally and numerically. Experimentally detected electroporation (evaluated separately for cells parallel and perpendicular to electric field) via Ca²⁺ uptake in H9c2 and AC16 cardiomyocytes was numerically modeled using the asymptotic pore equation. Results showed that cell orientation affects electroporation extent: using short, nanosecond pulses, cells perpendicular to electric field are significantly more electroporated than parallel (up to 100-times more pores formed), and with long, millisecond pulses, cells parallel to electric field are more electroporated than perpendicular (up to 1000-times more pores formed). In the range of a few microseconds, cells of both orientations were electroporated to the same extent. Using pulses of a few microseconds lends itself as a new possible strategy in achieving homogeneous electroporation in tissue with elongated cells of different orientation (e.g. electroporation-based cardiac ablation).

Nucleic-Acid Structures as Intracellular Probes for Live Cells

The chemical composition of cells at the molecular level determines their growth, differentiation, structure, and function. Probing this composition is powerful because it provides invaluable insight into chemical processes inside cells and in certain cases allows disease diagnosis based on molecular profiles. However, many techniques analyze fixed cells or lysates of bulk populations, in which information about dynamics and cellular heterogeneity is lost. Recently, nucleic-acid-based probes have emerged as a promising platform for the detection of a wide variety of intracellular analytes in live cells with single-cell resolution. Recent advances in this field are described and common strategies for probe design, types of targets that can be identified, current limitations, and future directions are discussed.

Design of an Epitope-Based Vaccine Ensemble for Animal Trypanosomiasis by Computational Methods

African animal trypanosomiasis is caused by vector-transmitted parasites of the genus Trypanosoma. T. congolense and T. brucei brucei are predominant in Africa; T. evansi and T. vivax in America and Asia. They have in common an extracellular lifestyle and livestock tropism, which provokes huge economic losses in regions where vectors are endemic. There are licensed drugs to treat the infections, but adherence to treatment is poor and appearance of resistances common. Therefore, the availability of a prophylactic vaccine would represent a major breakthrough towards the management and control of the disease. Selection of the most appropriate antigens for its development is a bottleneck step, especially considering the limited resources allocated. Herein we propose a vaccine strategy based on multiple epitopes from multiple antigens to counteract the parasites´ biological complexity. Epitopes were identified by computer-assisted genome-wide screenings, considering sequence conservation criteria, antigens annotation and sub-cellular localization, high binding affinity to antigen presenting molecules, and lack of cross-reactivity to proteins in cattle and other breeding species. We ultimately provide 31 B-cell, 8 CD4 T-cell, and 15 CD8 T-cell epitope sequences from 30 distinct antigens for the prospective design of a genetic ensemble vaccine against the four trypanosome species responsible for African animal trypanosomiasis.

Development of Tumor Cell-Based Vaccine with IL-12 Gene Electrotransfer as Adjuvant

Tumor cell-based vaccines use tumor cells as a source of tumor-associated antigens. In our study, we aimed to develop and test a tumor vaccine composed of tumor cells killed by irradiation combined with in vivo interleukin-12 gene electrotransfer as an adjuvant. Vaccination was performed in the skin of B16-F10 malignant melanoma or CT26 colorectal carcinoma tumor-bearing mice, distant from the tumor site and combined with concurrent tumor irradiation. Vaccination was also performed before tumor inoculation in both tumor models and tumor outgrowth was followed. The antitumor efficacy of vaccination in combination with tumor irradiation or preventative vaccination varied between the tumor models. A synergistic effect between vaccination and irradiation was observed in the B16-F10, but not in the CT26 tumor model. In contrast, up to 56% of mice were protected from tumor outgrowth in the CT26 tumor model and none were protected in the B16-F10 tumor model. The results suggest a greater contribution of the therapeutic vaccination to tumor irradiation in a less immunogenic B16-F10 tumor model, in contrast to preventative vaccination, which has shown greater efficacy in a more immunogenic CT26 tumor model. Upon further optimization of the vaccination and irradiation regimen, our vaccine could present an alternative tumor cell-based vaccine.

Cytolytic Perforin as an Adjuvant to Enhance the Immunogenicity of DNA Vaccines

DNA vaccines present one of the most cost-effective platforms to develop global vaccines, which have been tested for nearly three decades in preclinical and clinical settings with some success in the clinic. However, one of the major challenges for the development of DNA vaccines is their poor immunogenicity in humans, which has led to refinements in DNA delivery, dosage in prime/boost regimens and the inclusion of adjuvants to enhance their immunogenicity. In this review, we focus on adjuvants that can enhance the immunogenicity of DNA encoded antigens and highlight the development of a novel cytolytic DNA platform encoding a truncated mouse perforin. The application of this innovative DNA technology has considerable potential in the development of effective vaccines.

Improving Magnetofection of Magnetic Polyethylenimine Nanoparticles into MG-63 Osteoblasts Using a Novel Uniform Magnetic Field

This study aimed to improve the magnetofection of MG-63 osteoblasts by integrating the use of a novel uniform magnetic field with low molecular weight polyethylenimine modified superparamagnetic iron oxide nanoparticles (PEI-SPIO-NPs). The excellent characteristics of PEI-SPIO-NPs such as size, zeta potential, the pDNA binding and protective ability were determined to be suitable for gene delivery. The novel uniform magnetic field enabled polyethylenimine-modified superparamagnetic iron oxide nanoparticles/pDNA complexes (PEI-SPIO-NPs/pDNA complexes) to rapidly and uniformly distribute on the surface of MG-63 cells, averting local transfection and decreasing disruption of the membrane caused by the centralization of positively charged PEI-SPIO-NPs, thereby increasing the effective coverage of magnetic gene carriers during transfection, and improving magnetofection efficiency. This innovative uniform magnetic field can be used to determine the optimal amount between PEI-SPIO-NPs and pDNA, as well as screen for the optimal formulation design of magnetic gene carrier under the homogenous conditions. Most importantly, the novel uniform magnetic field facilitates the transfection of PEI-SPIO-NPs/pDNA into osteoblasts, thereby providing a novel approach for the targeted delivery of therapeutic genes to osteosarcoma tissues as well as a reference for the treatment of other tumors.

Photoacoustic transfection of DNA encoding GFP

Photoacoustic transfection consists in the use of photoacoustic waves, generated in the thermoelastic expansion of a confined material absorbing a short pulse of a laser, to produce temporary mechanical deformations of the cell membrane and facilitate the delivery of plasmid DNA into cells. We show that high stress gradients, produced when picosecond laser pulses with a fluence of 100 mJ/cm² are absorbed by piezophotonic materials, enable transfection of a plasmid DNA encoding Green Fluorescent Protein (gWizGFP, 3.74 MDa) in COS-7 monkey fibroblast cells with an efficiency of 5% at 20 °C, in 10 minutes. We did not observe significant cytotoxicity under these conditions. Photoacoustic transfection is scalable, affordable, enables nuclear localization and the dosage is easily controlled by the laser parameters.

Advanced physical techniques for gene delivery based on membrane perforation

Gene delivery as a promising and valid tool has been used for treating many serious diseases that conventional drug therapies cannot cure. Due to the advancement of physical technology and nanotechnology, advanced physical gene delivery methods such as electroporation, magnetoporation, sonoporation and optoporation have been extensively developed and are receiving increasing attention, which have the advantages of briefness and nontoxicity. This review introduces the technique detail of membrane perforation, with a brief discussion for future development, with special emphasis on nanoparticles mediated optoporation that have developed as an new alternative transfection technique in the last two decades. In particular, the advanced physical approaches development and new technology are highlighted, which intends to stimulate rapid advancement of perforation techniques, develop new delivery strategies and accelerate application of these techniques in clinic.

Safe and efficient novel approach for non-invasive gene electrotransfer to skin

Gene transfer into cells or tissue by application of electric pulses (i.e. gene electrotransfer (GET)) is a non-viral gene delivery method that is becoming increasingly attractive for clinical applications. In order to make GET progress to wide clinical usage its efficacy needs to be improved and the safety of the method has to be confirmed. Therefore, the aim of our study was to increase GET efficacy in skin, by optimizing electric pulse parameters and the design of electrodes. We evaluated the safety of our novel approach by assaying the thermal stress effect of GET conditions and the biodistribution of a cytokine expressing plasmid. Transfection efficacy of different pulse parameters was determined using two reporter genes encoding for the green fluorescent protein (GFP) and the tdTomato fluorescent protein, respectively. GET was performed using non-invasive contact electrodes immediately after intradermal injection of plasmid DNA into mouse skin. Fluorescence imaging of transfected skin showed that a sophistication in the pulse parameters could be selected to get greater transfection efficacy in comparison to the standard ones. Delivery of electric pulses only mildly induced expression of the heat shock protein Hsp70 in a luminescent reporting transgenic mouse model, demonstrating that there were no drastic stress effects. The plasmid was not detected in other organs and was found only at the site of treatment for a limited period of time. In conclusion, we set up a novel approach for GET combining new electric field parameters with high voltage short pulses and medium voltage long pulses using contact electrodes, to obtain a high expression of both fluorescent reporter and therapeutic genes while showing full safety in living animals.

Current Progress in Electrotransfection as a Nonviral Method for Gene Delivery

Electrotransfection (ET) is a nonviral method for delivery of various types of molecules into cells both in vitro and in vivo. Close to 90 clinical trials that involve the use of ET have been performed, and approximately half of them are related to cancer treatment. Particularly, ET is an attractive technique for cancer immunogene therapy because treatment of cells with electric pulses alone can induce immune responses to solid tumors, and the responses can be further enhanced by ET of plasmid DNA (pDNA) encoding therapeutic genes. Compared to other gene delivery methods, ET has several unique advantages. It is relatively inexpensive, flexible, and safe in clinical applications, and introduces only naked pDNA into cells without the use of additional chemicals or viruses. However, the efficiency of ET is still low, partly because biological mechanisms of ET in cells remain elusive. In previous studies, it was believed that pDNA entered the cells through transient pores created by electric pulses. As a result, the technique is commonly referred to as electroporation. However, recent discoveries have suggested that endocytosis plays an important role in cellular uptake and intracellular transport of electrotransfected pDNA. This review will discuss current progresses in the study of biological mechanisms underlying ET and future directions of research in this area. Understanding the mechanisms of pDNA transport in cells is critical for the development of new strategies for improving the efficiency of gene delivery in tumors.

Monoclonal Cell Line Generation and CRISPR/Cas9 Manipulation via Single-Cell Electroporation

Stably transfected cell lines are widely used in drug discovery and biological research to produce recombinant proteins. Generation of these cell lines requires the isolation of multiple clones, using time-consuming dilution methods, to evaluate the expression levels of the gene of interest. A new and efficient method is described for the generation of monoclonal cell lines, without the need for dilution cloning. In this new method, arrays of patterned cell colonies and single cell transfection are employed to deliver a plasmid coding for a reporter gene and conferring resistance to an antibiotic. Using a nanofountain probe electroporation system, probe positioning is achieved through a micromanipulator with sub-micron resolution and resistance-based feedback control. The array of patterned cell colonies allows for rapid selection of numerous stably transfected clonal cell lines located on the same culture well, conferring a significant advantage over slower and labor-intensive traditional methods. In addition to plasmid integration, this methodology can be seamlessly combined with CRISPR/Cas9 gene editing, paving the way for advanced cell engineering.

Ferritin Nanocages with Biologically Orthogonal Conjugation for Vascular Targeting and Imaging

Genetic incorporation of biologically orthogonal functional groups into macromolecules has the potential to yield efficient, controlled, reproducible, site-specific conjugation of affinity ligands, contrast agents, or therapeutic cargoes. Here, we applied this approach to ferritin, a ubiquitous iron-storage protein that self-assembles into multimeric nanocages with remarkable stability, size uniformity (12 nm), and endogenous capacity for loading and transport of a variety of inorganic and organic cargoes. The unnatural amino acid, 4-azidophenylalanine (4-AzF), was incorporated at different sites in the human ferritin light chain (hFTL) to allow site-specific conjugation of alkyne-containing small molecules or affinity ligands to the exterior surface of the nanocage. The optimal positioning of the 4-AzF residue was evaluated by screening a library of variants for the efficiency of copper-free click conjugation. One of the engineered ferritins, hFTL-5X, was found to accommodate ∼14 small-molecule fluorophores (AlexaFluor 488) and 3-4 IgG molecules per nanocage. Intravascular injection in mice of radiolabeled hFTL-5X carrying antibody to cell adhesion molecule ICAM-1, but not control IgG, enabled specific targeting to the lung due to high basal expression of ICAM-1 (43.3 ± 6.99 vs 3.48 ± 0.14%ID/g for Ab vs IgG). Treatment of mice with endotoxin known to stimulate inflammatory ICAM-1 overexpression resulted in 2-fold enhancement of pulmonary targeting (84.4 ± 12.89 vs 43.3 ± 6.99%ID/g). Likewise, injection of fluorescent, ICAM-targeted hFTL-5X nanocages revealed the effect of endotoxin by enhancement of near-infrared signal, indicating potential utility of this approach for both vascular targeting and imaging.

Technology of irreversible electroporation and review of its clinical data on liver cancers

INTRODUCTION

Irreversible electroporation (IRE) has developed as a novel percutaneous ablative technique over the past decade and its utility in the treatment of primary and metastatic liver disease has progressed rapidly.

AREAS COVERED

After discussing the principles behind the technology and the practical steps in its use, this article offers a detailed analysis of the recent published work that evaluates its safety and efficacy. The strengths and weaknesses of other ablative techniques, including radiofrequency ablation, microwave ablation and cryoablation, are discussed in detail. Other aspects of IRE, including post-treatment clinical follow-up, expected imaging findings, and the most frequently encountered complications, are covered. Finally, the future of IRE is examined as it pertains to advancements in the treatment of hepatic malignancy.

EXPERT COMMENTARY

The characteristics of IRE that make this technology uniquely suited for the treatment of liver tumors have allowed it to gain a significant foothold in interventional oncology. Continued development of IRE will lead to further advances in the management of previously untreatable liver cancers.

The Antibiotic-free pFAR4 Vector Paired with the Sleeping Beauty Transposon System Mediates Efficient Transgene Delivery in Human Cells

The anti-angiogenic and neurogenic pigment epithelium-derived factor (PEDF) demonstrated a potency to control choroidal neovascularization in age-related macular degeneration (AMD) patients. The goal of the present study was the development of an efficient and safe technique to integrate, ex vivo, the PEDF gene into retinal pigment epithelial (RPE) cells for later transplantation to the subretinal space of AMD patients to allow continuous PEDF secretion in the vicinity of the affected macula. Because successful gene therapy approaches require efficient gene delivery and stable gene expression, we used the antibiotic-free pFAR4 mini-plasmid vector to deliver the hyperactive Sleeping Beauty transposon system, which mediates transgene integration into the genome of host cells. In an initial study, lipofection-mediated co-transfection of HeLa cells with the SB100X transposase gene and a reporter marker delivered by pFAR4 showed a 2-fold higher level of genetically modified cells than when using the pT2 vectors. Similarly, with the pFAR4 constructs, electroporation-mediated transfection of primary human RPE cells led to 2.4-fold higher secretion of recombinant PEDF protein, which was still maintained 8 months after transfection. Thus, our results show that the pFAR4 plasmid is a superior vector for the delivery and integration of transgenes into eukaryotic cells.

Generation of gene-edited rats by delivery of CRISPR/Cas9 protein and donor DNA into intact zygotes using electroporation

The generation of gene-edited animals using the CRISPRs/Cas9 system is based on microinjection into zygotes which is inefficient, time consuming and demands high technical skills. We report the optimization of an electroporation method for intact rat zygotes using sgRNAs and Cas9 protein in combination or not with ssODNs (~100 nt). This resulted in high frequency of knockouts, between 15 and 50% of analyzed animals. Importantly, using ssODNs as donor template resulted in precise knock-in mutations in 25–100% of analyzed animals, comparable to microinjection. Electroporation of long ssDNA or dsDNA donors successfully used in microinjection in the past did not allow generation of genome-edited animals despite dsDNA visualization within zygotes. Thus, simultaneous electroporation of a large number of intact rat zygotes is a rapid, simple, and efficient method for the generation of a variety of genome-edited rats.

Biomaterials for polynucleotide delivery to anchorage-independent cells

Comparison of various chemical vectors used for polynucleotide delivery to mammalian anchorage-independent cells.

Journey to the Center of the Cell: Current Nanocarrier Design Strategies Targeting Biopharmaceuticals to the Cytoplasm and Nucleus

New biopharmaceutical molecules, potentially able to provide more personalized and effective treatments, are being identified through the advent of advanced synthetic biology strategies, sophisticated chemical synthesis approaches, and new analytical methods to assess biological potency. However, translation of many of these structures has been significantly limited due to the need for more efficient strategies to deliver macromolecular therapeutics to desirable intracellular sites of action. Engineered nanocarriers that encapsulate peptides, proteins, or nucleic acids are generally internalized into target cells via one of several endocytic pathways. These nanostructures, entrapped within endosomes, must navigate the intracellular milieu to orchestrate delivery to the intended destination, typically the cytoplasm or nucleus. For therapeutics active in the cytoplasm, endosomal escape continues to represent a limiting step to effective treatment, since a majority of nanocarriers trapped within endosomes are ultimately marked for enzymatic degradation in lysosomes. Therapeutics active in the nucleus have the added challenges of reaching and penetrating the nuclear envelope, and nuclear delivery remains a preeminent challenge preventing clinical translation of gene therapy applications. Herein, we review cutting-edge peptide- and polymer-based design strategies with the potential to enable significant improvements in biopharmaceutical efficacy through improved intracellular targeting. These strategies often mimic the activities of pathogens, which have developed innate and highly effective mechanisms to penetrate plasma membranes and enter the nucleus of host cells. Understanding these mechanisms has enabled advances in synthetic peptide and polymer design that may ultimately improve intracellular trafficking and bioavailability, leading to increased access to new classes of biotherapeutics.

Electroporation-mediated delivery of the FER gene in the resolution of trauma-related fatal pneumonia

Injured patients with lung contusion (LC) are at risk of developing bacterial pneumonia (PNA) followed by sepsis and death. A recent genome-wide association study (GWAS) showed FER gene expression positively correlating with survival rates among individuals with above conditions. We sought to determine whether electroporation (EP)-mediated delivery of FER gene could indeed improve survival, in a lethal model of combined LC and PNA. C57BL/6 mice sustained unilateral LC, which preceded a 500 Klebsiella colony forming unit (CFU) inoculation by 6 h. In-between these insults, human FER plasmid (pFER) was introduced into the lungs followed by eight EP pulses applied externally (10 ms at 200 V cm^-1). Control groups included EP of empty vector (pcDNA3) or Na⁺/K⁺-ATPase genes (pPump) and no treatment (LC+PNA). We recorded survival, histology, lung mechanics, bronchial alveolar lavage (BAL) fluid, FER and inflammatory gene expression and bacteriology. The data show that 7-day survival was significantly improved by pFER compared with control groups. pFER increased BAL monocytes and activated antibacterial response genes (nitric oxide synthase (NOS), Fizz). pFER treatment showed decreased lung and blood Klebsiella counts reaching, in some cases, complete sterilization. In conclusion, FER gene delivery promoted survival in LC+PNA mice via recruitment of activated immune cells, improving efficiency of bacterial clearance within contused lung.

Irreversible electroporation enhances delivery of gemcitabine to pancreatic adenocarcinoma

INTRODUCTION

Irreversible electroporation (IRE) utilizes short, high-voltage pulses to irreversibly permeabilize the cell membrane, resulting in apoptotic cell death. In addition to the irreversible zone, IRE creates a reversible zone that could be utilized for enhanced drug delivery. The hypothesis of this study is that a zone of reversible electroporation exists and allows for increased chemotherapy delivery.

METHODS

Ten immunocompromised mice with orthotopic human pancreatic adenocarcinoma tumors (Panc1) were treated with either IRE between two doses of gemcitabine (15 mg/kg) (ECT) (N = 5) or gemcitabine alone (N = 5). Gemcitabine levels in the serum, liver, and pancreas were analyzed with liquid chromatography/mass spectrometry (LC/MS).

RESULTS

Concentration of gemcitabine within reversibly electroporated pancreatic tissue was higher in mice receiving ECT compared to those receiving gemcitabine alone (13,567 ng/ml vs.4,126 ng/ml; P = 0.0009). Pancreatic gemcitabine levels were 5.52 and 5.96 times higher than liver and serum levels, respectively, in the ECT group compared to 2.85 and 2.53 times higher (P = 0.117, P = 0.058), respectively, in mice receiving gemcitabine alone.

CONCLUSION

IRE can potentially reduce local recurrence by allowing increased drug delivery to the tissue in the reversible electroporation zone. This holds significant potential in augmenting efficacy of gemcitabine in treatment of locally advanced and borderline resectable pancreatic adenocarcinoma. J. Surg. Oncol. 2016;114:181-186. © 2016 Wiley Periodicals, Inc.

Electroporation-delivered transdermal neostigmine in rats: equivalent action to intravenous administration

Purpose

Transdermal electroporation has become one of the most promising noninvasive methods for drug administration, with greatly increased transport of macromolecules through the skin. The cecal-contracting effects of repeated transdermal electroporation delivery and intravenous administration of neostigmine were compared in anesthetized rats.

Methods

The cecal contractions were detected with implantable strain gauge sensors, and the plasma levels of neostigmine were followed by high-performance liquid chromatography.

Results

Both intravenously and EP-administered neostigmine (0.2–66.7 μg/kg) increased the cecal contractions in a dose-dependent manner. For both the low doses and the highest dose, the neostigmine plasma concentrations were the same after the two modes of administration, while an insignificantly higher level was observed at a dose of 20 μg/kg after intravenous administration as compared with the electroporation route. The contractile responses did not differ significantly after the two administration routes.

Conclusion

The results suggest that electroporation-delivered neostigmine elicits action equivalent to that observed after intravenous administration as concerning both time and intensity. Electroporation permits the delivery of even lower doses of water-soluble compounds through the skin, which is very promising for clinical practice.

Gene-based vaccines and immunotherapeutic strategies against neurodegenerative diseases: Potential utility and limitations

There has been a recent expansion of vaccination and immunotherapeutic strategies from controlling infectious diseases to the targeting of non-infectious conditions including neurodegenerative disorders. In addition to conventional vaccine and immunotherapeutic modalities, gene-based methods that express antigens for presentation to the immune system by either live viral vectors or non-viral naked DNA plasmids have been developed and evaluated. This mini-review/commentary summarizes the advantages and disadvantages, as well as the research findings to date, of both of these gene-based vaccination approaches in terms of how they can be targeted against appropriate antigens within the Alzheimer and Parkinson disease pathogenesis processes as well as potentially against targets in other neurodegenerative diseases. Most recently, the novel utilization of these viral vector and naked DNA gene-based technologies includes the delivery of immunoglobulin genes from established biologically active monoclonal antibodies. This modified passive immunotherapeutic strategy has recently been applied to deliver passive antibody immunotherapy against the pathologically relevant amyloid β protein in Alzheimer disease. The advantages and disadvantages of this technological application of gene-based immune interventions, as well as research findings to date are also summarized. In sum, it is suggested that further evaluation of gene based vaccines and immunotherapies against neurodegenerative diseases are warranted to determine their potential clinical utility.

Analysis of Alternative Pre-RNA Splicing in the Mouse Retina Using a Fluorescent Reporter

In vivo alternative splicing is controlled in a tissue and cell type specific manner. Often individual cellular components of complex tissues will express different splicing programs. Thus, when studying splicing in multicellular organisms it is critical to determine the exon inclusion levels in individual cells positioned in the context of their native tissue or organ. Here we describe how a fluorescent splicing reporter in combination with in vivo electroporation can be used to visualize alternative splicing in individual cells within mature tissues. In a test case we show how the splicing of a photoreceptor specific exon can be visualized within the mouse retina. The retina was chosen as an example of a complex tissue that is fragile and whose cells cannot be studied in culture. With minor modifications to the injection and electroporation procedure, the protocol we outline can be applied to other tissues and organs.

Endocytosis and Endosomal Trafficking of DNA After Gene Electrotransfer In Vitro

DNA electrotransfer is a successful technique for gene delivery into cells and represents an attractive alternative to virus-based methods for clinical applications including gene therapy and DNA vaccination. However, little is currently known about the mechanisms governing DNA internalization and its fate inside cells. The objectives of this work were to investigate the role of endocytosis and to quantify the contribution of different routes of cellular trafficking during DNA electrotransfer. To pursue these objectives, we performed flow cytometry and single-particle fluorescence microscopy experiments using inhibitors of endocytosis and endosomal markers. Our results show that ~50% of DNA is internalized by caveolin/raft-mediated endocytosis, 25% by clathrin-mediated endocytosis, and 25% by macropinocytosis. During active transport, DNA is routed through multiple endosomal compartments with, in the hour following electrotransfer, 70% found in Rab5 structures, 50% in Rab11-containing organelles and 30% in Rab9 compartments. Later, 60% of DNA colocalizes with Lamp1 vesicles. Because these molecular markers can overlap while following organelles through several steps of trafficking, the percentages do not sum up to 100%. We conclude that electrotransferred DNA uses the classical endosomal trafficking pathways. Our results are important for a generalized understanding of gene electrotransfer, which is crucial for its safe use in clinics.