Proteomic and functional analyses of protein-DNA complexes during gene transfer

Decoding cellular mechanism of recombinant adeno-associated virus (rAAV) and engineering host-cell factories toward intensified viral vector manufacturing

Recombinant adeno-associated virus (rAAV) is one of the prominent gene delivery vehicles that has opened promising opportunities for novel gene therapeutic approaches. However, the current major viral vector production platform, triple transfection in mammalian cells, may not meet the increasing demand. Thus, it is highly required to understand production bottlenecks from the host cell perspective and engineer the cells to be more favorable and tolerant to viral vector production, thereby effectively enhancing rAAV manufacturing. In this review, we provided a comprehensive exploration of the intricate cellular process involved in rAAV production, encompassing various stages such as plasmid entry to the cytoplasm, plasmid trafficking and nuclear delivery, rAAV structural/non-structural protein expression, viral capsid assembly, genome replication, genome packaging, and rAAV release/secretion. The knowledge in the fundamental biology of host cells supporting viral replication as manufacturing factories or exhibiting defending behaviors against viral production is summarized for each stage. The control strategies from the perspectives of host cell and materials (e.g., AAV plasmids) are proposed as our insights based on the characterization of molecular features and our existing knowledge of the AAV viral life cycle, rAAV and other viral vector production in the Human embryonic kidney (HEK) cells.

Nuclear-targeted carbon quantum dot mediated CRISPR/Cas9 delivery for fluorescence visualization and efficient editing

Nuclear targeted delivery has great potential in improving the efficiency of non-viral carrier mediated genome editing. However, direct and efficient delivery of CRISPR/Cas9 plasmid into the nucleus remains a challenge. In this study, a nuclear targeted gene delivery platform based on fluorescent carbon quantum dots (CQDs) was developed. Polyethylenimine (PEI) and polyethylene glycol (PEG) synergistically passivated the surface of CQDs, providing an excitation-independent green-emitting fluorescent CQDs-PEI-PEG conjugate (CQDs-PP) with an ultra-small size and positive surface charge. Here we show that CQDs-PP could bind CRISPR/Cas9 plasmid to form a nano-complex by electrostatic attraction, which can bypass lysosomes and enter the nucleus by passive diffusion, and thereby improve the transfection efficiency. Also, CQDs-PP could deliver CRISPR/Cas9 plasmid into HeLa cells, resulting in the insertion/deletion mutation of the target EFHD1 gene. More importantly, CQDs-PP exhibited a considerably higher gene editing efficiency as well as comparable or lower cytotoxicity relative to Lipo2000 and PEI-passivated CQDs-PEI (CQDs-P). Thus, the nuclear-targeted CQDs-PP is expected to constitute an efficient CRISPR/Cas9 delivery carrier in vitro with imaging-trackable ability.

Revisiting the role of pulsed electric fields in overcoming the barriers to in vivo gene electrotransfer

Gene therapies are revolutionizing medicine by providing a way to cure hitherto incurable diseases. The scientific and technological advances have enabled the first gene therapies to become clinically approved. In addition, with the ongoing COVID-19 pandemic, we are witnessing record speeds in the development and distribution of gene-based vaccines. For gene therapy to take effect, the therapeutic nucleic acids (RNA or DNA) need to overcome several barriers before they can execute their function of producing a protein or silencing a defective or overexpressing gene. This includes the barriers of the interstitium, the cell membrane, the cytoplasmic barriers and (in case of DNA) the nuclear envelope. Gene electrotransfer (GET), i.e., transfection by means of pulsed electric fields, is a non-viral technique that can overcome these barriers in a safe and effective manner. GET has reached the clinical stage of investigations where it is currently being evaluated for its therapeutic benefits across a wide variety of indications. In this review, we formalize our current understanding of GET from a biophysical perspective and critically discuss the mechanisms by which electric field can aid in overcoming the barriers. We also identify the gaps in knowledge that are hindering optimization of GET in vivo.

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

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.

The Benefits of Going Small: Nanostructures for Mammalian Cell Transfection

Nanostructures, with their localized interactions with mammalian cells, can offer better efficiency and lower cell perturbation than conventional viral, biochemical, and electroporation transfection techniques. In this Perspective, I describe the different stages of transfection and provide a comparison of transfection techniques based on their mechanisms. Focusing on specific aims of transfection, I also illustrate how recent developments in high-aspect-ratio nanostructures have endowed them with properties that are superior to existing viral, biochemical, and electroporation methods as a versatile technique to deliver a variety of cargoes and to interface with different mammalian cell types for biomedical applications. Finally, I describe the challenges associated with transfection that need to be overcome to enhance cargo delivery efficiency and clinical translation.

Multiple cytosolic DNA sensors bind plasmid DNA after transfection

Mammalian cells express a variety of nucleic acid sensors as one of the first lines of defense against infection. Despite extensive progress in the study of sensor signaling pathways during the last decade, the detailed mechanisms remain unclear. In our previous studies, we reported increased type I interferon expression and the upregulation of several proposed cytosolic DNA sensors after transfection of several tumor cell types with plasmid DNA (pDNA). In the present study, we sought to reveal the early events in the cytosolic sensing of this nucleic acid in a myoblast cell line. We demonstrated that DNA-dependent activator of interferon regulatory factors/Z-DNA binding protein 1 (DAI/ZBP1) bound plasmid DNA in the cytosol within 15 minutes of transfection and at consistent levels for 4 h. Interferon activated gene 204 protein (p204) and DEAH box helicase 9 (DHX9) also bound pDNA, peaking 15 and 30 min respectively. Plasmid DNA was not detectably bound by DEAD box helicase 60 (DDX60) protein, despite a similar level of mRNA upregulation to DAI/ZBP1, or by cyclic GMP-AMP synthase (cGAS), despite its presence in the cell cytosol. Taken together, these results indicate several DNA sensors may participate and cooperate in the complex process of cytosolic DNA sensing.

A Critical Review of Electroporation as A Plasmid Delivery System in Mouse Skeletal Muscle

The gene delivery to skeletal muscles is a promising strategy for the treatment of both muscular disorders (by silencing or overexpression of specific gene) and systemic secretion of therapeutic proteins. The use of a physical method like electroporation with plate or needle electrodes facilitates long-lasting gene silencing in situ. It has been reported that electroporation enhances the expression of the naked DNA gene in the skeletal muscle up to 100 times and decreases the changeability of the intramuscular expression. Coelectransfer of reporter genes such as green fluorescent protein (GFP), luciferase or beta-galactosidase allows the observation of correctly performed silencing in the muscles. Appropriate selection of plasmid injection volume and concentration, as well as electrotransfer parameters, such as the voltage, the length and the number of electrical pulses do not cause long-term damage to myocytes. In this review, we summarized the electroporation methodology as well as the procedure of electrotransfer to the gastrocnemius, tibialis, soleus and foot muscles and compare their advantages and disadvantages.

Nucleic acid delivery to mesenchymal stem cells: a review of nonviral methods and applications

Background

Mesenchymal stem cells (MSCs) are multipotent stem cells that can be isolated and expanded from many tissues, and are being investigated for use in cell therapies. Though MSC therapies have demonstrated some success, none have been FDA approved for clinical use. MSCs lose stemness ex vivo, decreasing therapeutic potential, and face additional barriers in vivo, decreasing therapeutic efficacy. Culture optimization and genetic modification of MSCs can overcome these barriers. Viral transduction is efficient, but limited by safety concerns related to mutagenicity of integrating viral vectors and potential immunogenicity of viral antigens. Nonviral delivery methods are safer, though limited by inefficiency and toxicity, and are flexible and scalable, making them attractive for engineering MSC therapies.

Main text

Transfection method and nucleic acid determine efficiency and expression profile in transfection of MSCs. Transfection methods include microinjection, electroporation, and nanocarrier delivery. Microinjection and electroporation are efficient, but are limited by throughput and toxicity. In contrast, a variety of nanocarriers have been demonstrated to transfer nucleic acids into cells, however nanocarrier delivery to MSCs has traditionally been inefficient. To improve efficiency, plasmid sequences can be optimized by choice of promoter, inclusion of DNA targeting sequences, and removal of bacterial elements. Instead of DNA, RNA can be delivered for rapid protein expression or regulation of endogenous gene expression. Beyond choice of nanocarrier and nucleic acid, transfection can be optimized by priming cells with media additives and cell culture surface modifications to modulate barriers of transfection. Media additives known to enhance MSC transfection include glucocorticoids and histone deacetylase inhibitors. Culture surface properties known to modulate MSC transfection include substrate stiffness and specific protein coating. If nonviral gene delivery to MSCs can be sufficiently improved, MSC therapies could be enhanced by transfection for guided differentiation and reprogramming, transplantation survival and directed homing, and secretion of therapeutics. We discuss utilized delivery methods and nucleic acids, and resulting efficiency and outcomes, in transfection of MSCs reported for such applications.

Conclusion

Recent developments in transfection methods, including nanocarrier and nucleic acid technologies, combined with chemical and physical priming of MSCs, may sufficiently improve transfection efficiency, enabling scalable genetic engineering of MSCs, potentially bringing effective MSC therapies to patients.

Mechanisms of unprimed and dexamethasone-primed nonviral gene delivery to human mesenchymal stem cells

Human mesenchymal stem cells (hMSCs) are under intense study for applications of cell and gene therapeutics because of their unique immunomodulatory and regenerative properties. Safe and efficient genetic modification of hMSCs could increase their clinical potential by allowing functional expression of therapeutic transgenes or control over behavior and differentiation. Viral gene delivery is efficient, but suffers from safety issues, while nonviral methods are safe, but highly inefficient, especially in hMSCs. Our lab previously demonstrated that priming cells before delivery of DNA complexes with dexamethasone (DEX), an anti‐inflammatory glucocorticoid drug, significantly increases hMSC transfection success. This work systematically investigates the mechanisms of hMSC transfection and DEX‐mediated enhancement of transfection. Our results show that hMSC transfection and its enhancement by DEX are decreased by inhibiting classical intracellular transport and nuclear import pathways, but DEX transfection priming does not increase cellular or nuclear internalization of plasmid DNA (pDNA). We also show that hMSC transgene expression is largely affected by pDNA promoter and enhancer sequence changes, but DEX‐mediated enhancement of transfection is unaffected by any pDNA sequence changes. Furthermore, DEX‐mediated transfection enhancement is not the result of increased transgene messenger RNA transcription or stability. However, DEX‐priming increases total protein synthesis by preventing hMSC apoptosis induced by transfection, resulting in increased translation of transgenic protein. DEX may also promote further enhancement of transgenic reporter enzyme activity by other downstream mechanisms. Mechanistic studies of nonviral gene delivery will inform future rationally designed technologies for safe and efficient genetic modification of clinically relevant cell types.

Intracellular Delivery by Membrane Disruption: Mechanisms, Strategies, and Concepts

Intracellular delivery is a key step in biological research and has enabled decades of biomedical discoveries. It is also becoming increasingly important in industrial and medical applications ranging from biomanufacture to cell-based therapies. Here, we review techniques for membrane disruption-based intracellular delivery from 1911 until the present. These methods achieve rapid, direct, and universal delivery of almost any cargo molecule or material that can be dispersed in solution. We start by covering the motivations for intracellular delivery and the challenges associated with the different cargo types-small molecules, proteins/peptides, nucleic acids, synthetic nanomaterials, and large cargo. The review then presents a broad comparison of delivery strategies followed by an analysis of membrane disruption mechanisms and the biology of the cell response. We cover mechanical, electrical, thermal, optical, and chemical strategies of membrane disruption with a particular emphasis on their applications and challenges to implementation. Throughout, we highlight specific mechanisms of membrane disruption and suggest areas in need of further experimentation. We hope the concepts discussed in our review inspire scientists and engineers with further ideas to improve intracellular delivery.

Graphene oxide sensitizes cancer cells to chemotherapeutics by inducing early autophagy events, promoting nuclear trafficking and necrosis

Rationale: Cisplatin (CDDP) is a broad-spectrum anticancer drug but chemoresistance to CDDP impedes its wide use for cancer therapy. Autophagy is an event occurring in the cytoplasm and cytoplasmic LC3 puncta formation is a hallmark of autophagy. Graphene oxide (GO) is a nanomaterial that provokes autophagy in CT26 colon cancer cells and confers antitumor effects. Here we aimed to evaluate whether combined use of GO with CDDP (GO/CDDP) overcomes chemoresistance in different cancer cells and uncover the underlying mechanism.

Methods: We treated different cancer cells with GO/CDDP and evaluated the cytotoxicity, death mechanism, autophagy induction and nuclear entry of CDDP. We further knocked down genes essential for autophagic flux and deciphered which step is critical to nuclear import and cell death. Finally, we performed immunoprecipitation, mass spectrometry and immunofluorescence labeling to evaluate the association of LC3 and CDDP.

Results: We uncovered that combination of GO and CDDP (GO/CDDP) promoted the killing of not only CT26 cells, but also ovarian, cervical and prostate cancer cells. In the highly chemosensitized Skov-3 cells, GO/CDDP significantly enhanced concurrent nuclear import of CDDP and autophagy marker LC3 and elevated cell necrosis, which required autophagy initiation and progression but did not necessitate late autophagy events (e.g., autophagosome completion and autolysosome formation). The GO/CDDP-elicited nuclear trafficking and cell death also required importin α/β, and LC3 also co-migrated with CDDP and histone H1/H4 into the nucleus. In particular, GO/CDDP triggered histone H4 acetylation in the nucleus, which could decondense the chromosome and enable CDDP to more effectively access chromosomal DNA to trigger cell death.

Conclusion: These findings shed light on the mechanisms of GO/CDDP-induced chemosensitization and implicate the potential applications of GO/CDDP to treat multiple cancers.

Cytoplasmic transport and nuclear import of plasmid DNA

Productive transfection and gene transfer require not simply the entry of DNA into cells and subsequent transcription from an appropriate promoter, but also a number of intracellular events that allow the DNA to move from the extracellular surface of the cell into and through the cytoplasm, and ultimately across the nuclear envelope and into the nucleus before any transcription can initiate. Immediately upon entry into the cytoplasm, naked DNA, either delivered through physical techniques or after disassembly of DNA-carrier complexes, associates with a large number of cellular proteins that mediate subsequent interactions with the microtubule network for movement toward the microtubule organizing center and the nuclear envelope. Plasmids then enter the nucleus either upon the mitotic disassembly of the nuclear envelope or through nuclear pore complexes in the absence of cell division, using a different set of proteins. This review will discuss our current understanding of these pathways used by naked DNA during the transfection process. While much has been elucidated on these processes, much remains to be discerned, but with the development of a number of model systems and approaches, great progress is being made.

Immunogenicity of DNA Vaccine against H5N1 Containing Extended Kappa B Site: In Vivo Study in Mice and Chickens

Influenza is one of the most important illnesses in the modern world, causing great public health losses each year due to the lack of medication and broadly protective, long-lasting vaccines. The development of highly immunogenic and safe vaccines is currently one of the major problems encountered in efficient influenza prevention. DNA vaccines represent a novel and powerful alternative to the conventional vaccine approaches. To improve the efficacy of the DNA vaccine against influenza H5N1, we inserted three repeated kappa B (κB) motifs, separated by a 5-bp nucleotide spacer, upstream of the cytomegalovirus promoter and downstream of the SV40 late polyadenylation signal. The κB motif is a specific DNA element (10pb-long) recognized by one of the most important transcription factors NFκB. NFκB is present in almost all animal cell types and upon cell stimulation under a variety of pathogenic conditions. NFκB is released from IκB and translocates to the nucleus and binds to κB sites, thereby leading to enhanced transcription and expression of downstream genes. We tested the variants of DNA vaccine with κB sites flanking the antigen expression cassette and without such sites in two animal models: chickens (broilers and layers) and mice (BALB/c). In chickens, the variant with κB sites stimulated stronger humoral response against the target antigen. In mice, the differences in humoral response were less apparent. Instead, it was possible to spot several gene expression differences in the spleens isolated from mice immunized with both variants. The results of our study indicate that modification of the sequence outside of the sequence encoding the antigen might enhance the immune response to the target but understanding the mechanisms responsible for this process requires further analysis.

Gene Electrotransfer: A Mechanistic Perspective

Gene electrotransfer is a powerful method of DNA delivery offering several medical applications, among the most promising of which are DNA vaccination and gene therapy for cancer treatment. Electroporation entails the application of electric fields to cells which then experience a local and transient change of membrane permeability. Although gene electrotransfer has been extensively studied in in vitro and in vivo environments, the mechanisms by which DNA enters and navigates through cells are not fully understood. Here we present a comprehensive review of the body of knowledge concerning gene electrotransfer that has been accumulated over the last three decades. For that purpose, after briefly reviewing the medical applications that gene electrotransfer can provide, we outline membrane electropermeabilization, a key process for the delivery of DNA and smaller molecules. Since gene electrotransfer is a multipart process, we proceed our review in describing step by step our current understanding, with particular emphasis on DNA internalization and intracellular trafficking. Finally, we turn our attention to in vivo testing and methodology for gene electrotransfer.

Ret finger protein-like 3 promotes tumor cell growth by activating telomerase reverse transcriptase expression in human lung cancer cells

In this study, we identified ret finger protein-like 3 (RFPL3) as a hTERT promoter binding protein in lung cancer cells. The high hTERT promoter-binding activity of RFPL3 was detected in lung cancer cells compared to normal cells. Chromatin immunoprecipitation confirmed RFPL3 as a tumor-specific hTERT promoter binding protein. Overexpression of RFPL3 activated hTERT promoter and up-regulated hTERT expression and telomerase activity. Inhibition of RFPL3 expression by siRNA suppressed hTERT promoter activation and telomerase activity. Inhibition of RFPL3 by siRNA or shRNA also significantly inhibited tumor cell growth in vitro and in a xenograft mouse model in vivo. Immunohistochemical analysis of 181 human lung adenocarcinomas specimens showed a significant correlation between RFPL3 and hTERT expression. The overexpression of RFPL3 was also associated significantly with lymph node metastasis. Univariate and multivariate Cox model analyses of NSCLC clinical specimens revealed a strong correlation between RFPL3 expression and overall survival. These results demonstrate that RFPL3 is an important cellular factor which promotes lung cancer growth by activating hTERT expression and may be a potential novel therapeutic target for lung cancer.

A KALA-modified lipid nanoparticle containing CpG-free plasmid DNA as a potential DNA vaccine carrier for antigen presentation and as an immune-stimulative adjuvant

Technologies that delivery antigen-encoded plasmid DNA (pDNA) to antigen presenting cell and their immune-activation are required for the success of DNA vaccines. Here we report on an artificial nanoparticle that can achieve these; a multifunctional envelope-type nanodevice modified with KALA, a peptide that forms α-helical structure at physiological pH (KALA-MEND). KALA modification and the removal of the CpG-motifs from the pDNA synergistically boosted transfection efficacy. In parallel, transfection with the KALA-MEND enhances the production of multiple cytokines and chemokines and co-stimulatory molecules via the Toll-like receptor 9-independent manner. Endosome-fusogenic lipid envelops and a long length of pDNA are essential for this immune stimulation. Furthermore, cytoplasmic dsDNA sensors that are related to the STING/TBK1 pathway and inflammasome are involved in IFN-β and IL-1β production, respectively. Consequently, the robust induction of antigen-specific cytotoxic T-lymphoma activity and the resulting prophylactic and therapeutic anti-tumor effect was observed in mice that had been immunized with bone marrow-derived dendritic cells ex vivo transfected with antigen-encoding pDNA. Collectively, the KALA-MEND possesses dual functions; gene transfection system and immune-stimulative adjuvant, those are both necessary for the successful DNA vaccine.

Electroporation-mediated gene delivery

Electroporation has been used extensively to transfer DNA to bacteria, yeast, and mammalian cells in culture for the past 30 years. Over this time, numerous advances have been made, from using fields to facilitate cell fusion, delivery of chemotherapeutic drugs to cells and tissues, and most importantly, gene and drug delivery in living tissues from rodents to man. Electroporation uses electrical fields to transiently destabilize the membrane allowing the entry of normally impermeable macromolecules into the cytoplasm. Surprisingly, at the appropriate field strengths, the application of these fields to tissues results in little, if any, damage or trauma. Indeed, electroporation has even been used successfully in human trials for gene delivery for the treatment of tumors and for vaccine development. Electroporation can lead to between 100 and 1000-fold increases in gene delivery and expression and can also increase both the distribution of cells taking up and expressing the DNA as well as the absolute amount of gene product per cell (likely due to increased delivery of plasmids into each cell). Effective electroporation depends on electric field parameters, electrode design, the tissues and cells being targeted, and the plasmids that are being transferred themselves. Most importantly, there is no single combination of these variables that leads to greatest efficacy in every situation; optimization is required in every new setting. Electroporation-mediated in vivo gene delivery has proven highly effective in vaccine production, transgene expression, enzyme replacement, and control of a variety of cancers. Almost any tissue can be targeted with electroporation, including muscle, skin, heart, liver, lung, and vasculature. This chapter will provide an overview of the theory of electroporation for the delivery of DNA both in individual cells and in tissues and its application for in vivo gene delivery in a number of animal models.

Graphene oxide as a chemosensitizer: diverted autophagic flux, enhanced nuclear import, elevated necrosis and improved antitumor effects

Graphene oxide (GO) is a nanomaterial that provokes autophagy in CT26 colon cancer cells and confers antitumor effects. Here we demonstrated that both GO and the chemotherapy drug cisplatin (CDDP) induced autophagy but elicited low degrees of CT26 cell death. Strikingly, GO combined with CDDP (GO/CDDP) potentiated the CT26 cell killing via necrosis. GO/CDDP not only elicited autophagy, but induced the nuclear import of CDDP and the autophagy marker LC3. The nuclear LC3 did not co-localize with p62 or Lamp-2, neither did blocking autolysosome formation significantly hinder the nuclear import of LC3/CDDP and necrosis, indicating that autophagosome and autolysosome formation was dispensable. Conversely, suppressing phagophore formation and importin-α/β significantly alleviated the nuclear import of LC3/CDDP and necrosis. These data suggested that GO/CDDP diverted the LC3 flux in the early phase of autophagy, resulting in LC3 trafficking towards the nucleus in an importin-α/β-dependent manner, which concurred with the CDDP nuclear import and necrosis. Intratumoral injection of GO/CDDP into mice bearing CT26 colon tumors potentiated immune cell infiltration and promoted cell death, autophagy and HMGB1 release, thereby synergistically augmenting the antitumor effects. Altogether, we unveiled a mechanism concerning how nanomaterials chemosensitize cancer cells and demonstrated the potentials of GO as a chemosensitizer.

A double-pulse approach for electrotransfection

Gene transfer and expression can be obtained by delivering calibrated electric pulses on cells in the presence of plasmids coding for the activity of interest. The electric treatment affects the plasma membrane and induces the formation of a transient complex between nucleic acids and the plasma membrane. It results in a delivery of the plasmid in the cytoplasm. Expression is only obtained if the plasmid is translocated inside the nucleus. This is a key limit in the process. We previously showed that delivery of a high-field short-duration electric pulse was inducing a structural alteration of the nuclear envelope. This study investigates if the double-pulse approach (first pulse to transfer the plasmid to the cytoplasm, and second pulse to induce the structural alteration of the envelope) was a way to enhance the protein expression using the green fluorescent protein as a reporter. We observed that not only the double-pulse approach induced the transfection of a lower number of cells but moreover, these transfected cells were less fluorescent than the cells treated only with the first pulse.

Electropermeabilization of the cell membrane

Membrane electropermeabilization is the observation that the permeability of a cell membrane can be transiently increased when a micro-millisecond external electric field pulse is applied on a cell suspension or on a tissue. Applicative aspects for the transfer of foreign molecules (macromolecules) into the cytoplasm are routinely used. But only a limited knowledge about what is really occurring in the cell and its membranes at the molecular levels is available. This chapter is a critical attempt to report the present state of the art and to point out some of the still open problems. The experimental facts associated to membrane electropermeabilization are firstly reported. They are valid on biological and model systems. Secondly, soft matter approaches give access to the bioelectrochemical description of the thermodynamical constraints supporting the destabilization of simplified models of the biological membrane. It is indeed described as a thin dielectric leaflet, where a molecular transport takes place by electrophoresis and then diffusion. This naïve approach is due to the lack of details on the structural aspects affecting the living systems as shown in a third part. Membranes are part of the cell machinery. The critical property of cells as being an open system from the thermodynamical point of view is almost never present. Computer simulations are now contributing to our knowledge on electropermeabilization. The last part of this chapter is a (very) critical report of all the efforts that have been performed. The final conclusion remains that we still do not know all the details on the reversible structural and dynamical alterations of the cell membrane (and cytoplasm) supporting its electropermeabilization. We have a long way in basic and translational researches to reach a pertinent description.

Intracellular tracking of single-plasmid DNA particles after delivery by electroporation

Electroporation is a physical method of transferring molecules into cells and tissues. It takes advantage of the transient permeabilization of the cell membrane induced by electric field pulses, which gives hydrophilic molecules access to the cytoplasm. This method offers high transfer efficiency for small molecules that freely diffuse through electrically permeabilized membranes. Larger molecules, such as plasmid DNA, face several barriers (plasma membrane, cytoplasmic crowding, and nuclear envelope), which reduce transfection efficiency and engender a complex mechanism of transfer. Our work provides insight into the way electrotransferred DNA crosses the cytoplasm to reach the nucleus. For this purpose, single-particle tracking experiments of fluorescently labeled DNA were performed. Investigations were focused on the involvement of the cytoskeleton using drugs disrupting or stabilizing actin and tubulin filaments as the two relevant cellular networks for particle transport. The analysis of 315 movies (~4,000 trajectories) reveals that DNA is actively transported through the cytoskeleton. The large number of events allows a statistical quantification of the DNA motion kinetics inside the cell. Disruption of both filament types reduces occurrence and velocities of active transport and displacements of DNA particles. Interestingly, stabilization of both networks does not enhance DNA transport.