Recent progress in gene therapy to deliver nucleic acids with multivalent cationic vectors

CFTR and dystrophin encoding plasmids carrying both luciferase reporter gene, nuclear import specific sequences and triple helix sites

Duchenne Muscular Dystrophy and Cystic Fibrosis are two major monogenetic diseases which could be treated by non-viral gene therapy. For this purpose, plasmid DNA (pDNA) coding for the functional genes requires its equipment with signal molecules favouring its intracellular trafficking and delivery in the nucleus of the target cells. Here, two novel constructions of large pDNAs encoding the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) and full-length dystrophin (DYS) genes are reported. The expression of CFTR and DYS genes are driven respectively by the hCEF1 airway epithelial cells and spc5-12 muscle cells specific promoter. Those pDNAs encode also the luciferase reporter gene driven by the CMV promoter to evaluate gene delivery in animals by bioluminescence. In addition, oligopurine • oligopyrimidine sequences are inserted to enable equipment of pDNAs with peptides conjugated with a triple helix forming oligonucleotide (TFO). Furthermore, specific κB sequences are also inserted to promote their NFκB-mediated nuclear import. pDNA constructions are reported; transfection efficiency, tissue specific expression of CFTR and dystrophin in target cells, and triple helix formation are demonstrated. These plasmids are tools of interest to develop non-viral gene therapy of Cystic Fibrosis and Duchenne Muscular Dystrophy.

An Overview of the Stability and Delivery Challenges of Commercial Nucleic Acid Therapeutics

Nucleic acid (NA)-based biopharmaceuticals have emerged as promising therapeutic modalities. NA therapeutics are a diverse class of RNA and DNA and include antisense oligonucleotides, siRNA, miRNA, mRNA, small activating RNA, and gene therapies. Meanwhile, NA therapeutics have posed significant stability and delivery challenges and are expensive. This article discusses the challenges and opportunities for achieving stable formulations of NAs with novel drug delivery systems (DDSs). Here we review the current progress in the stability issues and the significance of novel DDSs associated with NA-based biopharmaceuticals, as well as mRNA vaccines. We also highlight the European Medicines Agency (EMA) and US Food and Drug Administration (FDA)-approved NA-based therapeutics with their formulation profiles. NA therapeutics could impact future markets if the remaining challenges and requirements are addressed. Regardless of the limited information available for NA therapeutics, reviewing and collating the relevant facts and figures generates a precious resource for formulation experts familiar with the NA therapeutics' stability profile, their delivery challenges, and regulatory acceptance.

Nanosystems for gene therapy targeting brain damage caused by viral infections

Several human pathogens can cause long-lasting neurological damage. Despite the increasing clinical knowledge about these conditions, most still lack efficient therapeutic interventions. Gene therapy (GT) approaches comprise strategies to modify or adjust the expression or function of a gene, thus providing therapy for human diseases. Since recombinant nucleic acids used in GT have physicochemical limitations and can fail to reach the desired tissue, viral and non-viral vectors are applied to mediate gene delivery. Although viral vectors are associated to high levels of transfection, non-viral vectors are safer and have been further explored. Different types of nanosystems consisting of lipids, polymeric and inorganic materials are applied as non-viral vectors. In this review, we discuss potential targets for GT intervention in order to prevent neurological damage associated to infectious diseases as well as the role of nanosized non-viral vectors as agents to help the selective delivery of these gene-modifying molecules. Application of non-viral vectors for delivery of GT effectors comprise a promising alternative to treat brain inflammation induced by viral infections.

Hypoxia-sensitive miRNA regulation via CRISPR/dCas9 loaded in hybrid exosomes: A novel strategy to improve embryo implantation and prevent placental insufficiency during pregnancy

Assisted reproductive techniques as a new regenerative medicine approach have significantly contributed to solving infertility problems that affect approximately 15% of couples worldwide. However, the success rate of an in vitro fertilization (IVF) cycle remains only about 20%-30%, and 75% of these losses are due to implantation failure (the crucial rate-limiting step of gestation). Implantation failure and abnormal placenta formation are mainly caused by defective adhesion, invasion, and angiogenesis. Placental insufficiency endangers both the mother's and the fetus's health. Therefore, we suggested a novel treatment strategy to improve endometrial receptivity and implantation success rate. In this strategy, regulating mir-30d expression as an upstream transcriptomic modifier of the embryo implantation results in modified expression of the involved genes in embryonic adhesion, invasion, and angiogenesis and consequently impedes implantation failure. For this purpose, "scaffold/matrix attachment regions (S/MARs)" are employed as non-viral episomal vectors, transfecting into trophoblasts by exosome-liposome hybrid carriers. These vectors comprise CRISPR/dCas9 with a guide RNA to exclusively induce miR-30d gene expression in hypoxic stress conditions. In order to avoid concerns about the fetus's genetic manipulation, our vector would be transfected specifically into the trophoblast layer of the blastocyst via binding to trophoblast Erb-B4 receptors without entering the inner cell mass. Additionally, S/MAR episomal vectors do not integrate with the original cell DNA. As an on/off regulatory switch, a hypoxia-sensitive promoter (HRE) is localized upstream of dCas9. The miR-30d expression increases before and during the implantation and placental insufficiency conditions and is extinguished after hypoxia elimination. This hypothesis emphasizes that improving the adhesion, invasion, and angiogenesis in the uterine microenvironment during pregnancy will result in increased implantation success and reduced placental insufficiency, as a new insight in translational medicine.

miRNA-encapsulated abiotic materials and biovectors for cutaneous and oral wound healing: Biogenesis, mechanisms, and delivery nanocarriers

MicroRNAs (miRNAs) as therapeutic agents have attracted increasing interest in the past decade owing to their significant effectiveness in treating a wide array of ailments. These polymerases II-derived noncoding RNAs act through post-transcriptional controlling of different proteins and their allied pathways. Like other areas of medicine, researchers have utilized miRNAs for managing acute and chronic wounds. The increase in the number of patients suffering from either under-healing or over-healing wound demonstrates the limited efficacy of the current wound healing strategies and dictates the demands for simpler approaches with greater efficacy. Various miRNA can be designed to induce pathway beneficial for wound healing. However, the proper design of miRNA and its delivery system for wound healing applications are still challenging due to their limited stability and intracellular delivery. Therefore, new miRNAs are required to be identified and their delivery strategy needs to be optimized. In this review, we discuss the diverse roles of miRNAs in various stages of wound healing and provide an insight on the most recent findings in the nanotechnology and biomaterials field, which might offer opportunities for the development of new strategies for this chronic condition. We also highlight the advances in biomaterials and delivery systems, emphasizing their challenges and resolutions for miRNA-based wound healing. We further review various biovectors (e.g., adenovirus and lentivirus) and abiotic materials such as organic and inorganic nanomaterials, along with dendrimers and scaffolds, as the delivery systems for miRNA-based wound healing. Finally, challenges and opportunities for translation of miRNA-based strategies into clinical applications are discussed.

Selective attachment of a microtubule interacting peptide to plasmid DNA via a triplex forming oligonucleotide for transfection improvement

In nonviral gene therapy approaches, the linkage of signal molecules to plasmid DNA (pDNA) is of interest for guiding its delivery to the nucleus. Here, we report its linkage to a peptide (P_79-98) mediating migration on microtubules by using a triplex-forming oligonucleotide (TFO). pDNA of 5 kbp and 21 kbp containing 6 and 36 oligopurine • oligopyrimidine sites (TH), respectively, inserted outside the luciferase gene sequence were used. TFO with a dibenzocyclooctyl (DBCO) group in 3' end comprising some Bridged Nucleic Acid bases was conjugated by click chemistry with the peptide carrying an azide function in the C-terminal end. We found the formation of 6 and 18 triplex with pDNA of 5 kbp and 21 kbp, respectively. A twofold increase of the transfection efficiency was observed in the hind-limbs upon Hydrodynamic Limb Vein (HLV) injection in mice of naked P_79-98 -pDNA of 21 kbp. This work paves the way for the selective equipping of pDNA with intracellular targeting molecules while preserving the full expression of the encoded gene.

Optimization of DOTAP/chol Cationic Lipid Nanoparticles for mRNA, pDNA, and Oligonucleotide Delivery

Lipid nanoparticles (LNPs) can be used as delivery vehicles for nucleic acid biotherapeutics. In fact, LNPs are currently being used in the Pfizer/BioNTech and Moderna COVID-19 vaccines. Cationic LNPs composed of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP)/cholesterol (chol) LNPs have been classified as one of the most efficient gene delivery systems and are being tested in numerous clinical trials. The objective of this study was to examine the effect of the molar ratio of DOTAP/chol, PEGylation, and lipid to mRNA ratio on mRNA transfection, and explore the applications of DOTAP/chol LNPs in pDNA and oligonucleotide transfection. Here we showed that PEGylation significantly decreased mRNA transfection efficiency of DOTAP/chol LNPs. Among non-PEGylated LNP formulations, 1:3 molar ratio of DOTAP/chol in DOTAP/chol LNPs showed the highest mRNA transfection efficiency. Furthermore, the optimal ratio of DOTAP/chol LNPs to mRNA was tested to be 62.5 µM lipid to 1 μg mRNA. More importantly, these mRNA-loaded nanoparticles were stable for 60 days at 4 °C storage without showing reduction in transfection efficacy. We further found that DOTAP/chol LNPs were able to transfect pDNA and oligonucleotides, demonstrating the ability of these LNPs to transport the cargo into the cell nucleus. The influence of various factors in the formulation of DOTAP/chol cationic LNPs is thus described and will help improve drug delivery of nucleic acid-based vaccines and therapies.

Strategies for improving the safety and RNAi efficacy of noncovalent peptide/siRNA nanocomplexes

In the past decades, the striking development of cationic polypeptides and cell-penetrating peptides (CPPs) tailored for small interfering RNA (siRNA) delivery has been fuelled by the conception of nuclear acid therapy and precision medicine. Owing to their amino acid compositions, inherent secondary structures as well as diverse geometrical shapes, peptides or peptide-containing polymers exhibit good biodegradability, high flexibility, and bio-functional diversity as nonviral siRNA vectors. Also, a variety of noncovalent nanocomplexes could be built via self-assembling and electrostatic interactions between cationic peptides and siRNAs. Although the peptide/siRNA nanocomplex-based RNAi therapies, STP705 and MIR-19, are under clinical trials, a guideline addressing the current bottlenecks of peptide/siRNA nanocomplex delivery is in high demand for future research and development. In this review, we present strategies for improving the safety and RNAi efficacy of noncovalent peptide/siRNA nanocomplexes in the treatment of genetic disorders. Through thorough analysis of those RNAi formulations using different delivery strategies, we seek to shed light on the rationale of peptide design and modification in constructing robust siRNA delivery systems, including targeted and co-delivery systems. Based on this, we provide a timely and comprehensive understanding of how to engineer biocompatible and efficient peptide-based siRNA vectors.

Protein Delivery to Cytosol by Cell-Penetrating Peptide Bearing Tandem Repeat Penetration-Accelerating Sequence

Pas2r12 is comprised of a repeat of the penetration-accelerating sequence (Pas) (Pas2: FFLIG-FFLIG) and D-form dodeca-arginine (r12), a cell-penetrating peptide. Pas2r12 significantly enhances cytosolic delivery of cargo proteins, including enhanced green fluorescent protein and immunoglobulin G. Simply incubating Pas2r12 with cargo leads to their cytosolic tranlsocation. Cytosolic delivery of cargo by Pas2r12 involves caveolae-mediated endocytosis. In this chapter, we describe methods of cytosolic delivery of cargo using Pas2r12 and provide methods for investigating the cellular uptake pathway of cargo by Pas2r12.

Transgene expression in mice of the Opa1 mitochondrial transmembrane protein through bicontinuous cubic lipoplexes containing gemini imidazolium surfactants

BACKGROUND

Lipoplexes are non-viral vectors based on cationic lipids used to deliver DNA into cells, also known as lipofection. The positively charge of the hydrophilic head-group provides the cationic lipids the ability to condensate the negatively charged DNA into structured complexes. The polar head can carry a large variety of chemical groups including amines as well as guanidino or imidazole groups. In particular, gemini cationic lipids consist of two positive polar heads linked by a spacer with different length. As for the hydrophobic aliphatic chains, they can be unsaturated or saturated and are connected to the polar head-groups. Many other chemical components can be included in the formulation of lipoplexes to improve their transfection efficiency, which often relies on their structural features. Varying these components can drastically change the arrangement of DNA molecules within the lamellar, hexagonal or cubic phases that are provided by the lipid matrix. Lipofection is widely used to deliver genetic material in cell culture experiments but the simpler formulations exhibit major drawbacks related to low transfection, low specificity, low circulation half-life and toxicity when scaled up to in vivo experiments.

RESULTS

So far, we have explored in cell cultures the transfection ability of lipoplexes based on gemini cationic lipids that consist of two C16 alkyl chains and two imidazolium polar head-groups linked with a polyoxyethylene spacer, (C16Im)2(C4O). Here, PEGylated lipids have been introduced to the lipoplex formulation and the transgene expression of the Opa1 mitochondrial transmembrane protein in mice was assessed. The addition of PEG on the surface of the lipid mixed resulted in the formation of Ia3d bicontinuous cubic phases as determined by small angle X-ray scattering. After a single intramuscular administration, the cubic lipoplexes were accumulated in tissues with tight endothelial barriers such as brain, heart, and lungs for at least 48 h. The transgene expression of Opa1 in those organs was identified by western blotting or RNA expression analysis through quantitative polymerase chain reaction.

CONCLUSIONS

The expression reported here is sufficient in magnitude, duration and toxicity to consolidate the bicontinuous cubic structures formed by (C16Im)2(C4O)-based lipoplexes as valuable therapeutic agents in the field of gene delivery.

Gene therapy: A promising approach for breast cancer treatment

Breast cancer (BC) is the most prevalent malignancy and the second leading cause of death among women worldwide that is caused by numerous genetic and environmental factors. Hence, effective treatment for this type of cancer requires new therapeutic approaches. The traditional methods for treating this cancer have side effects, therefore so much research have been performed in last decade to find new methods to alleviate these problems. The study of the molecular basis of breast cancer has led to the introduction of gene therapy as an effective therapeutic approach for this cancer. Gene therapy involves sending genetic material through a vector into target cells, which is followed by a correction, addition, or suppression of the gene. In this technique, it is necessary to target tumour cells without affecting normal cells. In addition, clinical trial studies have shown that this approach is less toxic than traditional therapies. This study will review various aspects of breast cancer, gene therapy strategies, limitations, challenges and recent studies in this area.

Coacervate microdroplet protocell-mediated gene transfection for nitric oxide production and induction of cell apoptosis

Liquid coacervate microdroplets have been widely explored as membrane-free compartment protocells for cargo delivery in therapeutic applications. In this study, coacervate protocells were developed as gene carriers for transfection of nitric oxide synthase (NOS) and overproduction of nitric oxide (NO) for killing of cancer cells. The coacervate microdroplet protocells were formed via the liquid-liquid phase separation of oppositely charged diethylaminoethyl-dextran/polyacrylic acids. The coacervate microdroplet protocells were found to facilitate gene transfection, which was demonstrated by cell imaging of the internalized coacervate microdroplets containing plasmids of enhanced green fluorescent protein. Due to their high transfection capability, the coacervate protocells were subsequently utilized for the delivery of NOS plasmids (pNOS). The cellular internalization of pNOS-containing coacervate carriers was found to result in high NOS expression coupled with NO overproduction, which then induced cell apoptosis and decreased cell viability. The cell apoptosis is associated with NO-mediated mitochondrial damage. The enhanced gene transfection was attributed to coacervate microdroplets' unique high sequestration capability and liquid-like fluidity. Overall, the incorporation of genes in coacervate microdroplets was demonstrated as a viable and novel strategy for the development of cargo biocarriers for biomedical applications.

Increasing Transfection Efficiency of Lipoplexes by Modulating Complexation Solution for Transient Gene Expression

Transient gene expression is a suitable tool for the production of biopharmaceutical candidates in the early stage of development and provides a simple and rapid alternative to the generation of stable cell line. In this study, an efficient transient gene expression methodology using DC-Chol/DOPE cationic liposomes and pDNA in Chinese hamster ovary suspension cells was established through screening of diverse lipoplex formation conditions. We modulated properties of both the liposome formation and pDNA solution, together called complexation solutions. Protein expression and cellular cytotoxicity were evaluated following transfection over the cell cultivation period to select the optimal complexation solution. Changes in hydrodynamic size, polydispersity index, and ζ potential of the liposomes and lipoplexes were analyzed depending on the various pH ranges of the complexation solutions using dynamic light scattering. The transfer of lipoplexes to the cytosol and their conformation were traced using fluorescence analysis until the early period of transfection. As a result, up to 1785 mg/L and 191 mg/L of human Fc protein and immunoglobulin G (bevacizumab), respectively, were successfully produced using acidic liposome formation and alkaline pDNA solutions. We expect that this lipoplex formation in acidic and alkaline complexation solutions could be an effective methodology for a promising gene delivery strategy.

Liposomal nanoparticles based on steroids and isoprenoids for nonviral gene delivery

Natural lipid molecules are an essential part of life as they constitute the membrane of cells and organelle. In most of these cases, the hydrophobicity of natural lipids is contributed by alkyl chains. Although natural lipids with a nonfatty acid hydrophobic backbone are quite rare, steroids and isoprenoids have been strong candidates as part of a lipid. Over the years, these natural molecules (steroid and isoprenoids) have been used to make either lipid-based nanoparticle or functionalize in such a way that it could form nano assembly alone for therapeutic delivery. Here we mainly focus on the synthetic functionalized version of these natural molecules which forms cationic liposomal nanoparticles (LipoNPs). These cationic LipoNPs were further used to deliver various negatively charged genetic materials in the form of pDNA, siRNA, mRNA (nucleic acids), and so on. This article is categorized under: Biology-Inspired Nanomaterials > Lipid-Based Structures.

Correlation between Biophysical Properties of Niosomes Elaborated with Chloroquine and Different Tensioactives and Their Transfection Efficiency

Lipid nanocarriers, such as niosomes, are considered attractive candidates for non-viral gene delivery due to their suitable biocompatibility and high versatility. In this work, we studied the influence of incorporating chloroquine in niosomes biophysical performance, as well as the effect of non-ionic surfactant composition and protocol of incorporation in their biophysical performance. An exhaustive comparative evaluation of three niosome formulations differing in these parameters was performed, which included the analysis of their thermal stability, rheological behavior, mean particle size, dispersity, zeta potential, morphology, membrane packing capacity, affinity to bind DNA, ability to release and protect the genetic material, buffering capacity and ability to escape from artificially synthesized lysosomes. Finally, in vitro biological studies were, also, performed in order to determine the compatibility of the formulations with biological systems, their transfection efficiency and transgene expression. Results revealed that the incorporation of chloroquine in niosome formulations improved their biophysical properties and the transfection efficiency, while the substitution of one of the non-ionic surfactants and the phase of addition resulted in less biophysical variations. Of note, the present work provides several biophysical parameters and characterization strategies that could be used as gold standard for gene therapy nanosystems evaluation.

Lipophilic Polyamines as Promising Components of Liposomal Gene Delivery Systems

Gene therapy requires an effective and safe delivery vehicle for nucleic acids. In the case of non-viral vehicles, including cationic liposomes, the structure of compounds composing them determines the efficiency a lot. Currently, cationic amphiphiles are the most frequently used compounds in liposomal formulations. In their structure, which is a combination of hydrophobic and cationic domains and includes spacer groups, each component contributes to the resulting delivery efficiency. This review focuses on polycationic and disulfide amphiphiles as prospective cationic amphiphiles for gene therapy and includes a discussion of the mutual influence of structural components.

Controlled pDNA Release in Gemini Cationic Lipoplexes by Femtosecond Laser Irradiation of Gold Nanostars

The design of nanovectors able to overcome biological barriers is one of the main challenges in biomedicine. Gemini cationic lipids are considered potential candidates for gene therapy due to their high biocompatibility and capacity to condense nucleic acids safely in the form of lipoplexes. However, this approach presents difficulties regarding genetic unpacking and, therefore, control over this process becomes crucial to ensure successful transfection. In this work, gemini cationic lipoplexes were prepared in the presence of plasmonic gold nanostars (AuNSs) to afford a nanovector that efficiently releases plasmid DNA (pDNA) upon irradiation with near-infrared femtosecond laser pulses. A critical AuNSs concentration of 50 pM and optimized laser power density of 400 mW led to successful pDNA release, whose efficiency could be further improved by increasing the irradiation time. Agarose gel electrophoresis was used to confirm pDNA release. UV-Vis-NIR spectroscopy and transmission electron microscopy studies were performed to monitor changes in the morphology of the AuNSs and lipoplexes after irradiation. From a physicochemical point of view, this study demonstrates that the use of AuNSs combined with gemini cationic lipoplexes allows control over pDNA release under ultrafast laser irradiation.

Two-Photon Near-Infrared AIE Luminogens as Multifunctional Gene Carriers for Cancer Theranostics

Construction of multifunctional nonviral gene vectors to execute defined tasks holds great potential for the precise and effective treatment of gene-associated diseases. Herein, we have developed four large π-conjugation triphenylamine derivatives bearing two polar [12]aneN₃ heads and a lipophilic tail for applications in gene delivery, one/two-photon-triggered near-infrared (NIR) fluorescence bioimaging, and combined photodynamic therapy (PDT) and gene therapy of cancer. These compounds possess typical NIR aggregation-induced emission characteristics, mega Stokes shifts, strong two-photon excitation fluorescence, and excellent DNA condensation abilities. Among them, vector 4 with a tail of n-hexadecane realized a transfection efficiency as high as 6.7 times that of the commercial transfection agent Lipofectamine 2000 in HEK293T cell lines. Using vector 4 as an example, transfection process tracking and ex vivo/in vivo tumoral imaging and retention with high resolution, high brightness, deep tissue penetration, and good biosafety were demonstrated. In addition, efficient singlet oxygen (¹O₂) generation by the DNA complex formed by vector 4 (4/DNA) resulted in effective PDT. Combined with anticancer gene therapy, collaborative cancer treatment with a dramatically enhanced cancer cell-killing effect was achieved. The development of this "three birds, one stone" approach suggests a new and promising strategy for better cancer treatment and real-time tracking of gene delivery.

Gemini Cationic Lipid-Type Nanovectors Suitable for the Transfection of Therapeutic Plasmid DNA Encoding for Pro-Inflammatory Cytokine Interleukin-12

Ample evidence exists on the role of interleukin-12 (IL-12) in the response against many pathogens, as well as on its remarkable antitumor properties. However, the unexpected toxicity and disappointing results in some clinical trials are prompting the design of new strategies and/or vectors for IL-12 delivery. This study was conceived to further endorse the use of gemini cationic lipids (GCLs) in combination with zwitterionic helper lipid DOPE (1,2-dioleoyl-sn-glycero-3-phosphatidyl ethanol amine) as nanovectors for the insertion of plasmid DNA encoding for IL-12 (pCMV-IL12) into cells. Optimal GCL formulations previously reported by us were selected for IL-12-based biophysical experiments. In vitro studies demonstrated efficient pCMV-IL12 transfection by GCLs with comparable or superior cytokine levels than those obtained with commercial control Lipofectamine2000*. Furthermore, the nanovectors did not present significant toxicity, showing high cell viability values. The proteins adsorbed on the nanovector surface were found to be mostly lipoproteins and serum albumin, which are both beneficial to increase the blood circulation time. These outstanding results are accompanied by an initial physicochemical characterization to confirm DNA compaction and protection by the lipid mixture. Although further studies would be necessary, the present GCLs exhibit promising characteristics as candidates for pCMV-IL12 transfection in future in vivo applications.

CEBA: A new heterobifunctional reagent for plasmid DNA functionalization by click chemistry

Here, we report the synthesis of 3,6,9-trioxaundecan-1-{4-[(2-Chloroethyl)Ethylamino)]-Benzylamino},11-Azide (CEBA). CEBA alkylates the N7 of guanine of DNA thanks its chloroethyl group and can be coupled by a strain-promoted azide-alkyne cycloaddition to an alkynylated molecule. The optimization of the alkylation level of pDNA reveals that the expression of the encoded gene is preserved when it is randomly modified with at most 1 CEBA molecule per 150 bp. We show that the azido group of CEBA allows the linkage via click chemistry of CEBA-pDNA with a fluorophore or a peptide containing a dibenzocyclooctyne (DBCO) function. This new heterobifunctional reagent opens new ways to equip pDNA easily with signal molecules including peptides and nucleic acids without side products providing great interest for non-viral gene therapy.

Cationic Single-Chained Surfactants with a Functional Group at the End of the Hydrophobic Tail DNA Compacting Efficiency

The interaction between calf-thymus DNA, ctDNA, and various single-chained surfactants with different functional groups at the end of hydrophobic tail was studied with the goal of investigating the influence of the functional group nature on surfactant DNA compacting efficiency. The surfactants investigated were dodecyltriethylammonium bromide (DTEABr), triethyl(1-phenoxydodecyl)ammonium bromide (12PhBr), triethyl(2-naphthoxydodecyl)ammonium bromide (12NBr) and 11-(isonicotinoyloxy)-N,N,N-triethyl-1-undecanaminium bromide (11PyBr). Results made evident that the surfactants' tendencies to self-aggregation is the key factor determining their efficiency to compact the nucleic acid. Subsequently, DOPE/12NBr/pEGFP-C1 lipoplexes, with different cationic surfactant molar fractions (α) and mass ratios (L/D), were prepared and characterized. DOPE is a zwitterionic phospholipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine, and the plasmid pEGFP-C1 carries a GFP coding sequence with the necessary regulatory elements for constitutive expression of the gene in human cells. 12NBr was chosen because it was the most efficient DNA compacting agent among the surfactants investigated. Finally, the cytotoxicity and transfection efficiency (TE) of DOPE/12NBr/pDNA lipoplexes, with different compositions, were investigated.

Effective cytocompatible nanovectors based on serine-derived gemini surfactants and monoolein for small interfering RNA delivery

Non-viral gene therapy based on gene silencing with small interfering RNA (siRNA) has attracted great interest over recent years. Among various types of cationic complexation agents, amino acid-based surfactants have been recently explored for nucleic acid delivery due to their low toxicity and high biocompatibility. Monoolein (MO), in turn, has been used as helper lipid in liposomal systems due to its ability to form inverted nonbilayer structures that enhance fusogenicity, thus contributing to higher transfection efficiency. In this work, we focused on the development of nanovectors for siRNA delivery based on three gemini amino acid-based surfactants derived from serine - (12Ser)₂N12, amine derivative; (12Ser)₂COO12, ester derivative; and (12Ser)₂CON12, amide derivative - individually combined with MO as helper lipid. The inclusion of MO in the cationic surfactant system influences the morphology and size of the mixed aggregates. Furthermore, the gemini surfactant:MO systems showed the ability to efficiently complex siRNA, forming stable lipoplexes, in some cases clearly depending on the MO content, without inducing significant levels of cytotoxicity. High levels of gene silencing were achieved in comparison with a commercially available standard indicating that these gemini:MO systems are promising candidates as lipofection vectors for RNA interference (RNAi)-based therapies.

Kelvin probe force microscopy to study electrostatic interactions of DNA with lipid-gemini surfactant monolayers for gene delivery

In novel gene therapy mechanisms utilising gemini surfactants, electrostatic interactions of the surfactant molecules with the DNA strands is a primary mechanism by which the two components of the delivery vehicle bind. In this work, we show for the first time direct evidence of electrostatic interactions of these compounds visualised with Kelvin probe force microscopy (KPFM) and correlated to their topography from atomic force microscopy (AFM). We construct monolayers of lipids and gemini surfactant to simulate interactions on a cellular level, using lipids commonly found in cell membranes, and allow DNA to bind to the monolayer as it is formed on a Langmuir-Blodgett trough. The difference in topography and electrical surface potential between monolayers with and without DNA is striking. In fact, KPFM reveals a strongly positive relative electrical surface potential in between where we identify a background lipid and the DNA strands, evidenced by the height profiles of the domains. Such identification is not possible without KPFM. We conclude that it is likely we are seeing cationic surfactant molecules surrounding DNA strands within a sea of background lipid.

Systematic study of liposomes composition towards efficient delivery of plasmid DNA as potential application of dermal fibroblasts targeting

The use of non-viral DNA vectors to topically treat skin diseases has demonstrated a high potential. However, vectors applied on the skin face extracellular barriers including the stratum corneum and intracellular barriers such as the endosomal escape and the nuclear targeting of the plasmid DNA. The aim of this study was to develop a formulation suitable for dermal application and effective for delivering plasmid DNA into cells. Different formulations were prepared using different cationic lipids (DOTAP, DC-Chol, DOTMA) and co-lipids (DOPE, DSPE). Lipoplexes were produced by complexing liposomes with plasmid DNA at different pDNA/CL (w/w) ratios. Our results showed that appropriate pDNA/CL ratios allowing total complexation of plasmid DNA differed depending on the structure of the lipid used. The transfection rates showed that (i) higher rates were obtained with DOTMA lipoplexes, (ii) DC-Chol lipoplexes provided a transfection twice as important as DOTAP lipoplexes and (iii) when DSPE was added, the cytotoxicity decreased while transfection rates were similar. We found that formulations composed of DC-Chol:DOPE:DSPE or DOTMA:DOPE were appropriate to complex plasmid DNA and to transfect human primary dermal fibroblasts with efficacy and limited cytotoxicity. Therefore, these formulations are highly promising in the context of gene therapy to treat skin diseases.

Lipid-Nucleic Acid Complexes: Physicochemical Aspects and Prospects for Cancer Treatment

Cancer is an extremely complex disease, typically caused by mutations in cancer-critical genes. By delivering therapeutic nucleic acids (NAs) to patients, gene therapy offers the possibility to supplement, repair or silence such faulty genes or to stimulate their immune system to fight the disease. While the challenges of gene therapy for cancer are significant, the latter approach (a type of immunotherapy) starts showing promising results in early-stage clinical trials. One important advantage of NA-based cancer therapies over synthetic drugs and protein treatments is the prospect of a more universal approach to designing therapies. Designing NAs with different sequences, for different targets, can be achieved by using the same technologies. This versatility and scalability of NA drug design and production on demand open the way for more efficient, affordable and personalized cancer treatments in the future. However, the delivery of exogenous therapeutic NAs into the patients’ targeted cells is also challenging. Membrane-type lipids exhibiting permanent or transient cationic character have been shown to associate with NAs (anionic), forming nanosized lipid-NA complexes. These complexes form a wide variety of nanostructures, depending on the global formulation composition and properties of the lipids and NAs. Importantly, these different lipid-NA nanostructures interact with cells via different mechanisms and their therapeutic potential can be optimized to promising levels in vitro. The complexes are also highly customizable in terms of surface charge and functionalization to allow a wide range of targeting and smart-release properties. Most importantly, these synthetic particles offer possibilities for scaling-up and affordability for the population at large. Hence, the versatility and scalability of these particles seem ideal to accommodate the versatility that NA therapies offer. While in vivo efficiency of lipid-NA complexes is still poor in most cases, the advances achieved in the last three decades are significant and very recently a lipid-based gene therapy medicine was approved for the first time (for treatment of hereditary transthyretin amyloidosis). Although the path to achieve efficient NA-delivery in cancer therapy is still long and tenuous, these advances set a new hope for more treatments in the future. In this review, we attempt to cover the most important biophysical and physicochemical aspects of non-viral lipid-based gene therapy formulations, with a perspective on future cancer treatments in mind.

Protein Expression Knockdown in Cancer Cells Induced by a Gemini Cationic Lipid Nanovector with Histidine-Based Polar Heads

A histidine-based gemini cationic lipid, which had already demonstrated its efficiency as a plasmid DNA (pDNA) nanocarrier, has been used in this work to transfect a small interfering RNA (siRNA) into cancer cells. In combination with the helper lipid monoolein glycerol (MOG), the cationic lipid was used as an antiGFP-siRNA nanovector in a multidisciplinary study. Initially, a biophysical characterization by zeta potential (ζ) and agarose gel electrophoresis experiments was performed to determine the lipid effective charge and confirm siRNA compaction. The lipoplexes formed were arranged in Lα lamellar lyotropic liquid crystal phases with a cluster-type morphology, as cryo-transmission electron microscopy (cryo-TEM) and small-angle X-ray scattering (SAXS) studies revealed. Additionally, in vitro experiments confirmed the high gene knockdown efficiency of the lipid-based nanovehicle as detected by flow cytometry (FC) and epifluorescence microscopy, even better than that of Lipofectamine2000*, the transfecting reagent commonly used as a positive control. Cytotoxicity assays indicated that the nanovector is non-toxic to cells. Finally, using nano-liquid chromatography tandem mass spectrometry (nanoLC-MS/MS), apolipoprotein A-I and A-II followed by serum albumin were identified as the proteins with higher affinity for the surface of the lipoplexes. This fact could be beyond the remarkable silencing activity of the histidine-based lipid nanocarrier herein presented.

Biocompatible Nanovector of siRNA Consisting of Arginine-Based Cationic Lipid for Gene Knockdown in Cancer Cells

Despite the use of small interfering RNAs (siRNAs) as therapeutic agents through the knockdown expression of pathogenic proteins, transportation and delivery of such siRNAs into cells continue to be under investigation. Within nonviral vectors, cationic lipids that include amino acid residues in their structures, and that have already demonstrated their suitability as plasmid DNA nanocarriers, may be also considered as potential siRNA vehicles. A double-chain cationic lipid based on the amino acid arginine mixed with a helper lipid has been the object of this biophysical study. First, ζ-potential measurements and agarose gel electrophoresis experiments confirmed the siRNA compaction, while small-angle X-ray scattering analysis (SAXS) revealed the structural pattern of the lipoplexes. Two bicontinuous cubic phases were found to coexist: the double-gyroid phase (Q_II^G) and the double-diamond phase (Q_II^D), with Pn3m and Ia3d as crystallographic space groups, respectively; the siRNA is known to be located inside their bicontinuous aqueous channels. Second, in vitro studies in HeLa-green fluorescent protein (GFP) and T731-GFP cell lines (modified for GFP overexpression) showed moderate to high gene knockdown levels (determined by flow cytometry and epifluorescence microscopy) with remarkable cell viabilities (CCK-8 assay). Finally, nano-liquid chromatography/mass spectrometry (nanoLC-MS/MS) was used to identify the nature of the proteins adhered to the surface of the lipoplexes after incubation with human serum, simulating their behavior in biological fluids. The abundant presence of lipoproteins and serum albumin in such protein corona, together with the coexistence of the bicontinuous cubic phases, may be behind the remarkable silencing activity of these lipoplexes. The results reported herein show that the use of amino-acid-based cationic lipids mixed with a suitable helper lipid, which have already provided good results as DNA plasmid nanocarriers in cellular transfection processes, may also be a biocompatible option, and so far little investigated, in gene silencing in vitro strategies.

Synthesis of Glutathione (GSH)-Responsive Amphiphilic Duplexes and their Application in Gene Delivery

Oligoamide molecular strands with hydrogen-bonding sequences DADDAD and guanidine (O-1) or 1,5,9-triazacyclododecane ([12]aneN₃ ; O-2) side chains and oligoamides with hydrogen-bonding sequences ADAADA and octyl moieties (O-3), were synthesized. Two duplexes (D-1 and D-2) were prepared by conjugating the hydrophilic O-1 or O-2 and hydrophobic O-3 through sequence-specific hydrogen-bond association and cross-linked disulfide bonds. Electrophoresis measurements indicated that O-1, O-2, D-1, and D-2 were able to completely retard the DNA mobiliy at concentrations of 30, 30, 10, and 20 μM, respectively. Reversible DNA release in O-1 and O-2 complexes can be achieved in the presence of heparin sodium, whereas the presence of GSH greatly improved DNA release in D-1 and D-2 complexes. The particles formed were in a size range of 50-170 nm with positively charged surfaces. D-1 and D-2 transfected pEGFP-N1 into HeLa cells successfully.

Dextran-based coacervate nanodroplets as potential gene carriers for efficient cancer therapy

The intractable toxicity of cationic polymers limits their applicability in gene transport and controlled release. In consideration of the good biocompatibility and biofunctionality of dextran, herein we design and synthesize two types of amino group-containing cationic copolymers based on dextran by the copolymerization of cationic monomers from dextran backbones. Additionally, allyl crosslinkers containing disulfide bonds were introduced into polymerization, that made the copolymer crosslinked by disulfide. The resultant coacervates were formed from the self-assembly of cationic coplymers and anionic genes, and redox-responsive disulfide branch points endow coacervates with reducing environment responsiveness. The in vitro experiments showed that the dextran-based coacervates were sensitive to the reducing environment and underwent cleavage, which resulted in an effective release, uptake, and transfection of the genes by 293T cells. In addition, dextran-based coacervates can be used to carry siRNA into cancer cells with a high transfection efficiency, demonstrating their potential applicability in treatment against cancer.

Sphingomyelin-Based Nanosystems (SNs) for the Development of Anticancer miRNA Therapeutics

Gene replacement therapy with oncosuppressor microRNAs (miRNAs) is a promising alternative to interfere with cancer progression. However, miRNAs are highly inefficient in a biological environment, hampering a successful translation to clinics. Nanotechnology can tackle this drawback by providing delivery systems able to efficiently deliver them to cancer cells. Thus, the objective of this work was to develop biocompatible nanosystems based on sphingomyelin (SM) for the intracellular delivery of miRNAs to colorectal cancer cells. We pursued two different approaches to select the most appropriate composition for miRNA delivery. On the one hand, we prepared sphingomyelin-based nanosystems (SNs) that incorporate the cationic lipid stearylamine (ST) to support the association of miRNA by the establishment of electrostatic interactions (SNs–ST). On the other hand, the cationic surfactant (DOTAP) was used to preform lipidic complexes with miRNA (Lpx), which were further encapsulated into SNs (SNs-Lpx). Restitution of miRNA145 levels after transfection with SNs-Lpx was related to the strongest anticancer effect in terms of tumor proliferation, colony forming, and migration capacity assays. Altogether, our results suggest that SNs have the potential for miRNA delivery to develop innovative anticancer therapies.

Lipid Nanoparticles Potentiate CpG-Oligodeoxynucleotide-Based Vaccine for Influenza Virus

Current influenza vaccines are generally effective against highly similar (homologous) strains, but their effectiveness decreases markedly against antigenically mismatched (heterologous) strains. One way of developing a universal influenza vaccine with a broader spectrum of protection is to use appropriate vaccine adjuvants to improve a vaccine's effectiveness and change its immune properties. Oligodeoxynucleotides (ODNs) with unmethylated cytosine-phosphate-guanine (CpG) motifs (CpG ODNs), which are Toll-like-receptor 9 (TLR9) agonists, are among the most promising adjuvants and are already being used in humans. However, the development of novel delivery vehicles to improve adjuvant effects in vivo is highly desirable. Here, we assessed the potential of lipid nanoparticles (LNPs) as CpG ODN delivery vehicles in mice to augment the vaccine adjuvant effects of CpG ODN and enhance the protective spectrum of conventional influenza split vaccine (SV). In vitro, compared with CpG ODN, LNPs containing CpG ODNs (LNP-CpGs) induced significantly greater production of cytokines such as IL-12 p40 and IFN-α by mouse dendritic cells (DCs) and significantly greater expression of the co-stimulatory molecules CD80 and CD86 on DCs. In addition, after subcutaneous administration in mice, compared with CpG ODN, LNP-CpGs enhanced the expression of CD80 and CD86 on plasmacytoid DCs in draining lymph nodes. LNP-CpGs given with SV from H1N1 influenza A virus improved T-cell responses and gave a stronger not only SV-specific but also heterologous-virus-strain-specific IgG2c response than CpG ODN. Furthermore, immunization with SV plus LNP-CpGs protected against not only homologous strain challenge but also heterologous and heterosubtypic strain challenge, whereas immunization with SV plus CpG ODNs protected against homologous strain challenge only. We therefore demonstrated that LNP-CpGs improved the adjuvant effects of CpG ODN and broadened the protective spectrum of SV against influenza virus. We expect that this strategy will be useful in developing adjuvant delivery vehicles and universal influenza vaccines.

Correlation of mRNA delivery timing and protein expression in lipid-based transfection

Non-viral gene delivery is constrained by the dwell time that most synthetic nucleic acid nanocarriers spend inside endosomal compartments. In order to overcome this endosomal-release bottleneck, methods are required that measure nanocarrier uptake kinetics and transfection efficiency simultaneously. Here, we employ live-cell imaging on single-cell arrays (LISCA) to study the delivery-time distribution of lipid-based mRNA complexes under varied serum conditions. By fitting a translation-maturation model to hundreds of individual eGFP reporter fluorescence time courses, the protein expression onset times and the expression rates after transfection are determined. Using this approach, we find that delivery timing and protein expression rates are not intrinsically correlated at the single-cell level, even though population-averaged values of both parameters conjointly change as a function of increasing external serum protein fraction. Lipofectamine-mediated delivery showed decreased transfection efficiency and longer delivery times with increasing serum protein concentration. This is in contrast to ionizable lipid nanoparticle (i-LNP)-mediated transfer, which showed increased efficiency and faster uptake in the presence of serum. In conclusion, the interdependences of single-cell expression rates and onset timing provide additional clues on uptake and release mechanisms, which are useful for improving nucleic acid delivery.

A mechanistic explanation of the inhibitory role of the protein corona on liposomal gene expression

The past three decades have witnessed fast advances in the use of cationic liposome-DNA complexes (lipoplexes) for gene delivery applications. However, no lipoplex formulation has reached into the clinical practice so far. The primary drawback limiting clinical use of lipoplexes is the lack of mechanistic understanding of their low transfection efficiency (TE) in vivo. In physiological environments, lipoplexes are coated by a protein corona (PC) that mediates the interactions with the cell machinery. Here we show that the formation of PC can change the interactions of multicomponent (MC) lipoplexes with our cell model (i.e., HeLa). At the highest lipoplex concentration, the formation of PC can reduce the TE of MC lipoplexes from 60% to <5%. Combining dynamic light scattering and synchrotron small-angle X-ray scattering (SAXS), we clarify that the formation of PC modifies physical-chemical properties of MC lipoplexes so as to affect their TE. Moreover, we examined single transfection barriers by a combination of fluorescence-activated cell sorting, single-cell real-time fluorescence confocal microscopy, and synchrotron SAXS. We demonstrate that PC formation has the ability to modify the relative contribution of caveolae-mediated endocytosis and macropinocytosis in lipoplexes uptake, in favor of the latter, increasing accumulation of PC-decorated lipoplexes into degradative lysosomal compartments. Finally, we report evidences that PC reduces the structural stability of lipoplexes against solubilization by cellular lipids, likely favoring premature DNA release and cytosolic digestion by DNAase. These combined effects revealed here offer a comprehensive mechanistic explanation on the reason behind reduction in gene expression of MC lipoplexes.

Gemini-Based Lipoplexes Complement the Mitochondrial Phenotype in MFN1-Knockout Mouse Embryonic Fibroblasts

Mitochondria form a dynamic network of constantly dividing and fusing organelles. The balance between these antagonistic processes is crucial for normal cellular function and requires the action of specialized proteins. The mitochondrial membrane proteins mitofusin 1 (Mfn1) and mitofusin 2 (Mfn2) are responsible for the fusion of the outer membrane of adjacent mitochondria. Mutations within Mfn1 or Mfn2 impair mitochondrial fusion and lead to some severe mitochondrial dysfunctions and mitochondrial diseases (MDs). A characteristic phenotype of cells carrying defective Mfn1 or Mfn2 is the presence of a highly fragmented mitochondrial network. Here, we use a biocompatible mixture of lipids, consisting on synthetic gemini cationic lipids (GCLs) and the zwitterionic phospholipid (DOPE), to complex, transport, and deliver intact copies of MFN1 gene into MFN1-Knockout mouse embryonic fibroblasts (MFN1-KO MEFs). We demonstrate that the GCL/DOPE-DNA lipoplexes are able to introduce the intact MFN1 gene into the cells and ectopically produce functional Mfn1. A four-fold increase of the Mfn1 levels is necessary to revert the MFN1-KO phenotype and to partially restore a mitochondrial network. This phenotype complementation was correlated with the transfection of GCL/DOPE-MFN1 lipoplexes that exhibited a high proportion of highly packaged hexagonal phase. GCL/DOPE-DNA lipoplexes are formulated as efficient therapeutic agents against MDs.

A Non-Viral Plasmid DNA Delivery System Consisting on a Lysine-Derived Cationic Lipid Mixed with a Fusogenic Lipid

The insertion of biocompatible amino acid moieties in non-viral gene nanocarriers is an attractive approach that has been recently gaining interest. In this work, a cationic lipid, consisting of a lysine-derived moiety linked to a C12 chain (LYCl) was combined with a common fusogenic helper lipid (DOPE) and evaluated as a potential vehicle to transfect two plasmid DNAs (encoding green fluorescent protein GFP and luciferase) into COS-7 cells. A multidisciplinary approach has been followed: (i) biophysical characterization based on zeta potential, gel electrophoresis, small-angle X-ray scattering (SAXS), and cryo-transmission electronic microscopy (cryo-TEM); (ii) biological studies by fluorescence assisted cell sorting (FACS), luminometry, and cytotoxicity experiments; and (iii) a computational study of the formation of lipid bilayers and their subsequent stabilization with DNA. The results indicate that LYCl/DOPE nanocarriers are capable of compacting the pDNAs and protecting them efficiently against DNase I degradation, by forming Lα lyotropic liquid crystal phases, with an average size of ~200 nm and low polydispersity that facilitate the cellular uptake process. The computational results confirmed that the LYCl/DOPE lipid bilayers are stable and also capable of stabilizing DNA fragments via lipoplex formation, with dimensions consistent with experimental values. The optimum formulations (found at 20% of LYCl content) were able to complete the transfection process efficiently and with high cell viabilities, even improving the outcomes of the positive control Lipo2000*.

Interplay of protein corona and immune cells controls blood residency of liposomes

In vivo liposomes, like other types of nanoparticles, acquire a totally new 'biological identity' due to the formation of a biomolecular coating known as the protein corona that depends on and modifies the liposomes' synthetic identity. The liposome-protein corona is a dynamic interface that regulates the interaction of liposomes with the physiological environment. Here we show that the biological identity of liposomes is clearly linked to their sequestration from peripheral blood mononuclear cells (PBMCs) of healthy donors that ultimately leads to removal from the bloodstream. Pre-coating liposomes with an artificial corona made of human plasma proteins drastically reduces capture by circulating leukocytes in whole blood and may be an effective strategy to enable prolonged circulation in vivo. We conclude with a critical assessment of the key concepts of liposome technology that need to be reviewed for its definitive clinical translation.

Endocytic Profiling of Cancer Cell Models Reveals Critical Factors Influencing LNP-Mediated mRNA Delivery and Protein Expression

Lipid nanoparticles have great potential for delivering nucleic-acid-based therapeutics, but low efficiency limits their broad clinical translation. Differences in transfection capacity between in vitro models used for nanoparticle pre-clinical testing are poorly understood. To address this, using a clinically relevant lipid nanoparticle (LNP) delivering mRNA, we highlight specific endosomal characteristics in in vitro tumor models that impact protein expression. A 30-cell line LNP-mRNA transfection screen identified three cell lines having low, medium, and high transfection that correlated with protein expression when they were analyzed in tumor models. Endocytic profiling of these cell lines identified major differences in endolysosomal morphology, localization, endocytic uptake, trafficking, recycling, and endolysosomal pH, identified using a novel pH probe. High-transfecting cells showed rapid LNP uptake and trafficking through an organized endocytic pathway to lysosomes or rapid exocytosis. Low-transfecting cells demonstrated slower endosomal LNP trafficking to lysosomes and defective endocytic organization and acidification. Our data establish that efficient LNP-mRNA transfection relies on an early and narrow endosomal escape window prior to lysosomal sequestration and/or exocytosis. Endocytic profiling should form an important pre-clinical evaluation step for nucleic acid delivery systems to inform model selection and guide delivery-system design for improved clinical translation.

Influence of the degree of oligomerization of surfactants on the DNA/surfactant interaction

The interaction between calf thymus DNA, ctDNA, and a series of oligomeric surfactants derived from N-benzyl-N,N-dimethyl-N-(1-dodecyl)ammonium chloride is investigated. The influence of the surfactants' degree of oligomerization (2, 3 and 4) on the ctDNA/surfactant interaction is studied, as well as the effect of the structure of the spacer group linking the individual surfactant fragments. In particular, the effect of the distance between the positive charges and the hydrophobic chains within the oligomers on these interactions was examined, by using the three positional isomers (i.e., ortho-, meta-, and para-) with the rigid xylidene moiety as spacer. Results show that the dimeric ("gemini") surfactants are much more efficient in the inversion of the nucleic acid charge than the single-chained (monomeric) surfactant. Whereas the ortho - isomer causes a partial condensation, the meta - and para - isomers can completely condense ctDNA. The meta - and para - isomers of the trimeric surfactants can also completely condense the polynucleotide. In contrast, the tetrameric surfactant investigated does not change the morphology of the nucleic acid from an elongated coil into a compacted form, in spite of effectively inverting the nucleic acid's charge in their complex. Accordingly, the capacity for ctDNA compaction of oligomeric surfactants is not simply correlated to their degree of oligomerization, but depends on a complex balance of the number and relative distance of cationic charges and/or hydrophobic tails in the surfactants for effectively interacting with the nucleic acid to form the appropriate complex. This information will help to design more effective cationic surfactants as non-viral vectors for gene therapy.

Oligoarginine-Bearing Tandem Repeat Penetration-Accelerating Sequence Delivers Protein to Cytosol via Caveolae-Mediated Endocytosis

To facilitate the cytosolic delivery of larger molecules such as proteins, we developed a new cell-penetrating peptide sequence, named Pas2r12, consisting of a repeated Pas sequence (FFLIG-FFLIG) and d-dodeca-arginine (r12). This peptide significantly enhanced the cellular uptake and cytosolic release of enhanced green fluorescent protein and immunoglobulin G as cargos. We found that simply mixing Pas2r12 with cargos could generate cytosolic introducible forms. The cytosolic delivery of cargos by Pas2r12 was found to be an energy-requiring process, to rely on actin polymerization, and to be suppressed by caveolae-mediated endocytosis inhibitors (genistein and methyl-β-cyclodextrin) and small interfering RNA against caveolin-1. These results suggest that Pas2r12 enhances membrane penetration of cargos without the need for cross-linking and that caveolae-mediated endocytosis may be the route by which cytosolic delivery is enhanced.

Trehalose-based Siamese twin amphiphiles with tunable self-assembling, DNA nanocomplexing and gene delivery properties

Trehalose Siamese twin vectors, encompassing gemini and facial amphiphilicity, promote pDNA compaction into core–shell nanocomplexes and selective delivery in the lungs.

MRI-visible liposome-polyethylenimine complexes for DNA delivery: preparation and evaluation

To noninvasively monitor the effect of gene therapy and achieve an optimal therapeutic effect, liposomes encapsulated polyethylenimine (PEI)-coated superparamagnetic iron oxide nanoparticles (SPION) with dual functions of MRI diagnosis and gene therapy were prepared. SPION was synthesized via co-precipitation, and then modified with PEI via thiourea reaction. The liposomes encapsulating PEI-SPION (LP-PEI-SPION) were prepared by ethanol injection. Fourier transform infrared spectra confirmed that PEI was successfully modified onto SPION, and thermogravimetric analysis indicated that the PEI content was about 17.1%. The LP-PEI-SPION/DNA had a small particle size of 253.07 ± 0.90 nm. LP-PEI-SPION/DNA had low cytotoxicity with more than 80% of the cell survival rates and high transfection efficiency compared with Lipofectamine® 2000/DNA. Additionally, it also showed good MRI effect on three cell lines. The liposomes encapsulating PEI-SPION (lipopolyplexes) have been successfully prepared as MRI contrast agents and gene delivery vectors, which may have great theoretical research significance and clinical potentials. Abbreviations: PEI, polyethylenimine; SPION, superparamagnetic iron oxide nanoparticles; LP-PEI-SPION, liposomes encapsulating PEI-SPION; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide; ICP-MS, inductively coupled plasma mass spectrometry; XRD, X-ray diffraction; TEM, transmission electron microscope; TGA, thermogravimetric analysis; DOTAP, 1,2-dioleoyl-3-trimethylammonium-propane; DOPE, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine; Chol, cholesterol.

A Gemini Cationic Lipid with Histidine Residues as a Novel Lipid-Based Gene Nanocarrier: A Biophysical and Biochemical Study

This work reports the synthesis of a novel gemini cationic lipid that incorporates two histidine-type head groups (C₃(C16His)₂). Mixed with a helper lipid 1,2-dioleoyl-sn-glycero-3-phosphatidyl ethanol amine (DOPE), it was used to transfect three different types of plasmid DNA: one encoding the green fluorescence protein (pEGFP-C3), one encoding a luciferase (pCMV-Luc), and a therapeutic anti-tumoral agent encoding interleukin-12 (pCMV-IL12). Complementary biophysical experiments (zeta potential, gel electrophoresis, small-angle X-ray scattering (SAXS), and fluorescence anisotropy) and biological studies (FACS, luminometry, and cytotoxicity) of these C₃(C16His)₂/DOPE-pDNA lipoplexes provided vast insight into their outcomes as gene carriers. They were found to efficiently compact and protect pDNA against DNase I degradation by forming nanoaggregates of 120⁻290 nm in size, which were further characterized as very fluidic lamellar structures based in a sandwich-type phase, with alternating layers of mixed lipids and an aqueous monolayer where the pDNA and counterions are located. The optimum formulations of these nanoaggregates were able to transfect the pDNAs into COS-7 and HeLa cells with high cell viability, comparable or superior to that of the standard Lipo2000*. The vast amount of information collected from the in vitro studies points to this histidine-based lipid nanocarrier as a potentially interesting candidate for future in vivo studies investigating specific gene therapies.

High-Throughput DNA Plasmid Transfection Using Acoustic Droplet Ejection Technology

The Labcyte Echo acoustic liquid handler allows accurate droplet ejection at high speed from a source well plate to a destination plate. It has already been used in various miniaturized biological assays, such as quantitative PCR (q-PCR), quantitative real-time PCR (q-RT-PCR), protein crystallization, drug screening, cell dispensing, and siRNA transfection. However, no plasmid DNA transfection assay has been published so far using this dispensing technology. In this study, we evaluated the ability of the Echo 550 device to perform plasmid DNA transfection in 384-well plates. Due to the high throughput of this device, we simultaneously optimized the three main parameters of a transfection process: dilution of the transfection reagent, DNA amount, and starting DNA concentration. We defined a four-step protocol whose optimal settings allowed us to transfect HeLa cells with up to 90% efficiency and reach a co-expression of nearly 100% within transfected cells in co-transfection experiments. This fast, reliable, and automated protocol opens new ways to easily and rapidly identify optimal transfection settings for a given cell type. Furthermore, it permits easy software-based transfection control and multiplexing of plasmids distributed on wells of a source plate. This new development could lead to new array applications, such as human ORFeome protein expression or CRISPR-Cas9-based gene function validation in nonpooled screening strategies.

Transfection by cationic gemini lipids and surfactants

Diseases that are linked to defective genes or mutations can in principle be cured by gene therapy, in which damaged or absent genes are either repaired or replaced by new DNA in the nucleus of the cell. Related to this, disorders associated with elevated protein expression levels can be treated by RNA interference via the delivery of siRNA to the cytoplasm of cells. Polynucleotides can be brought into cells by viruses, but this is not without risk for the patient. Alternatively, DNA and RNA can be delivered by transfection, i.e. by non-viral vector systems such as cationic surfactants, which are also referred to as cationic lipids. In this review, recent progress on cationic lipids as transfection vectors will be discussed, with special emphasis on geminis, surfactants with 2 head groups and 2 tails connected by a spacer.

Cationic lipid/DNA complexes manufactured by microfluidics and bulk self-assembly exhibit different transfection behavior

Recent advances in biochemical and biophysical research have been achieved through the employment of microfluidic devices. Microfluidic mixing of therapeutic agents with biomaterials yields systems with finely tuned physical-chemical properties for applications in drug and gene delivery. Here, we investigate the role of preparation technology (microfluidic mixing vs. bulk self-assembly) on the transfection efficiency (TE) and cytotoxicity of multicomponent cationic liposome/DNA complexes (lipoplexes) in live Chinese hamster ovarian (CHO) cells. Decoupling TE and cytotoxicity allowed us to combine them in a unique coherent vision. While bulk self-assembly produces highly efficient and highly toxic MC lipoplexes, microfluidics manufacture leads to less efficient, but less cytotoxic complexes. This discrepancy is ascribed to two main factors controlling lipid-mediated cell transfection, i.e. the lipoplex concentration at the cell surface and the lipoplex arrangement at the nanoscale. Further research is required to optimize microfluidic manufacturing of lipoplexes to obtain highly efficient and not cytotoxic gene delivery systems.