Surfactant-mediated gene transfer for animal cells

Nanoemulsions and nanocapsules as carriers for the development of intranasal mRNA vaccines

The global emergency of coronavirus disease 2019 (COVID-19) has spurred extensive worldwide efforts to develop vaccines for protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Our contribution to this global endeavor involved the development of a diverse library of nanocarriers, as alternatives to lipid nanoparticles (LNPs), including nanoemulsions (NEs) and nanocapsules (NCs), with the aim of protecting and delivering messenger ribonucleic acid (mRNA) for nasal vaccination purposes. A wide range of prototypes underwent rigorous screening through a series of in vitro and in vivo experiments, encompassing assessments of cellular transfection, cytotoxicity, and intramuscular administration of a model mRNA for protein translation. As a result, two promising candidates were identified for nasal administration. One of them was a NE incorporating a combination of an ionizable lipid (C12-200) and cationic lipid (DOTAP), both intended to condense mRNA, along with DOPE, which is known to facilitate endosomal escape. This NE exhibited a size of 120 nm and a highly positive surface charge (+ 50 mV). Another candidate was an NC formulation comprising the same components and endowed with a dextran sulfate shell. This formulation showed a size of 130 nm and a moderate negative surface charge (-16 mV). Upon intranasal administration of mRNA encoding for ovalbumin (mOVA) associated with optimized versions of the said NE and NCs, a robust antigen-specific CD8 + T cell response was observed. These findings underscore the potential of NEs and polymeric NCs in advancing mRNA vaccine development for combating infectious diseases.

Compaction of Calf Thymus DNA by a Potential One-Head-Two-Tail Surfactant: Properties of Nanomaterials and Biological Testing for Gene Delivery

A one-head-two-tail cationic surfactant, Dilauryldimethylammonium bromide (DDAB) has shown a great extent of calf thymus DNA (ct-DNA) compaction being adsorbed on the surfaces of negatively charged SiO2 nanoparticles (NPs). DDAB molecules show high adsorption efficiency and induce many positive surface charges per-unit surface area of the SiO2 NPs compared to cationic Gemini (12-6-12) and conventional (DTAB) surfactants in an aqueous medium at pH 7.4, as evident from zeta potential and EDAX data. Transmission electron microscopy and field emission scanning electron microscopy images, along with ethidium bromide exclusion assay and DLS data support the compaction of ct-DNA. Fluorescence microscopic images show that in the presence of SiO2 NPs, DDAB can perform 50% compaction of ct-DNA at a concentration ∼58% and ∼99% lower than that of 12-6-12 and DTAB, respectively. Better ct-DNA compaction by DDAB is evident compared to other Gemini surfactants (12-4-12 and 12-8-12) as well reported before. Time-correlated single photon counting fluorescence intensity decay measurements of a probe DAPI in ct-DNA have revealed the average lifetime value that is decreased by ∼61% at 2.5 μM of DDAB in the presence of SiO2 NPs as compared to a decrease by only ∼29% in its absence, supporting NPs-induced stronger surfactant binding with ct-DNA. Fluorescence lifetime data have also demonstrated the crowding effect of NPs. At 2.5 μM of DDAB, both fast and slow rotational relaxation components of DAPI contribute almost equally to depolarization with the absence of NPs; however, with the presence of NPs, ∼96% weightage of the anisotropy decay is for the fast component. The present DDAB-SiO2 NPs combination has proved to be an excellent gene delivery system based on the cell viability in the mouse mammary gland adenocarcinoma cells (4T1) and human embryonic kidney (HEK) 293 cell lines, and in vitro and in vivo studies.

Role of Gemini Surfactants with Variable Spacers and SiO2 Nanoparticles in ct-DNA Compaction and Applications toward In Vitro/In Vivo Gene Delivery

Compaction of calf thymus DNA (ct-DNA) by two cationic gemini surfactants, 12-4-12 and 12-8-12, in the absence and presence of negatively charged SiO₂ nanoparticles (NPs) (∼100 nm) has been explored using various techniques. 12-8-12 having a longer hydrophobic spacer induces a greater extent of ct-DNA compaction than 12-4-12, which becomes more efficient with SiO₂ NPs. While 50% ct-DNA compaction in the presence of SiO₂ NPs occurs at ∼77 nM of 12-8-12 and ∼130 nM of 12-4-12, but a conventional counterpart surfactant, DTAB, does it at its concentration as high as ∼7 μM. Time-resolved fluorescence anisotropy measurements show changes in the rotational dynamics of a fluorescent probe, DAPI, and helix segments in the condensed DNA. Fluorescence lifetime data and ethidium bromide exclusion assays reveal the binding sites of surfactants to ct-DNA. 12-8-12 with SiO₂ NPs has shown the highest cell viability (≥90%) and least cell death in the human embryonic kidney (HEK) 293 cell lines in contrast to the cell viability of ≤80% for DTAB. These results show that 12-8-12 with SiO₂ NPs has the highest time and dose-dependent cytotoxicity compared to 12-8-12 and 12-4-12 in the murine breast cancer 4T1 cell line. Fluorescence microscopy and flow cytometry are performed for in vitro cellular uptake of YOYO-1-labeled ct-DNA with surfactants and SiO₂ NPs using 4T1 cells after 3 and 6 h incubations. The in vivo tumor accumulation studies are carried out using a real-time in vivo imaging system after intravenous injection of the samples into 4T1 tumor-bearing mice. 12-8-12 with SiO₂ has delivered the highest amount of ct-DNA in cells and tumors in a time-dependent manner. Thus, the application of a gemini surfactant with a hydrophobic spacer and SiO₂ NPs in compacting and delivering ct-DNA to the tumor is proven, warranting its further exploration in nucleic acid therapy for cancer treatment.

A Surfactant Enables Efficient Membrane Spanning by Non-Aggregating DNA-Based Ion Channels

DNA nanotechnology makes use of hydrophobically modified constructs to create synthetic membrane protein mimics. However, nucleic acid structures exhibit poor insertion efficiency, leading to a low activity of membrane-spanning DNA protein mimics. It is suggested that non-ionic surfactants improve insertion efficiency, partly by disrupting hydrophobicity-mediated clusters. Here, we employed confocal microscopy and single-molecule transmembrane current measurements to assess the effects of the non-ionic surfactant octylpolyoxyethylene (oPOE) on the clustering behavior and membrane activity of cholesterol-modified DNA nanostructures. Our findings uncover the role of aggregation in preventing bilayer interactions of hydrophobically decorated constructs, and we highlight that premixing DNA structures with the surfactant does not disrupt the cholesterol-mediated aggregates. However, we observed the surfactant's strong insertion-facilitating effect, particularly when introduced to the sample separately from DNA. Critically, we report a highly efficient membrane-spanning DNA construct from combining a non-aggregating design with the addition of the oPOE surfactant.

Cationic lipids for gene delivery: many players, one goal

Lipid-based carriers represent the most widely used alternative to viral vectors for gene expression and gene silencing purposes. This class of non-viral vectors is particularly attractive for their ease of synthesis and chemical modifications to endow them with desirable properties. Despite combinatorial approaches have led to the generation of a large number of cationic lipids displaying different supramolecular structures and improved behavior, additional effort is needed towards the development of more and more effective cationic lipids for transfection purposes. With this review, we seek to highlight the great progress made in the design of each and every constituent domain of cationic lipids, that is, the chemical structure of the headgroup, linker and hydrophobic moieties, and on the specific effect on the assembly with nucleic acids. Since the complexity of such systems is known to affect their performances, the role of formulation, stability and phase behavior on the transfection efficiency of such assemblies will be thoroughly discussed. Our objective is to provide a conceptual framework for the development of ever more performing lipid gene delivery vectors.

Cationic lipid-nanoceria hybrids, a novel nonviral vector-mediated gene delivery into mammalian cells: investigation of the cellular uptake mechanism

Gene therapy is a promising technique for the treatment of various diseases. The development of minimally toxic and highly efficient non-viral gene delivery vectors is the most challenging undertaking in the field of gene therapy. Here, we developed dimethyldioctadecylammonium bromide (DODAB)-nanoceria (CeO2) hybrids as a new class of non-viral gene delivery vectors. These DODAB-modified CeO2 nanoparticles (CeO2/DODAB) could effectively compact the pDNA, allowing for highly efficient gene transfection into the selected cell lines. The CeO2/DODAB nanovectors were also found to be non-toxic and did not induce ROS formation as well as any stress responsive and pro-survival signaling pathways. The overall vector performance of CeO2/DODAB nanohybrids was comparable with lipofectamine and DOTAP, and higher than calcium phosphate and DEAE-dextran for transfecting small plasmids. The increased cellular uptake of the nanovector/DNA complexes through clathrin- and caveolae-mediated endocytosis and subsequent release from the endosomes further support the increased gene transfection efficiency of the CeO2/DODAB vectors. Besides, CeO2/DODAB nanovectors could transfect genes in vivo without any sign of toxicity. Taken together, this new nano-vector has the potential to be used for gene delivery in biomedical applications.

Polyethylenimine coated plasmid DNA-surfactant complexes as potential gene delivery systems

Nanometer scaled particles have been prepared from strong association between plasmid DNA (pcDNA3-FLAG-p53) and oppositely charged surfactants. Although these particles present suitable properties for gene delivery purposes, their cytotoxicity could compromise their use in gene therapy applications. To ensure biocompatibility of this potential gene delivery system, the nanoparticles were coated with polyethylenimine (PEI) with various molar ratios of PEI nitrogen to plasmid DNA phosphate groups. This led to a drastic increase in the cell viability of the particles, and in addition particle characteristics such as size, surface charge and loading efficiency, have also been enhanced as a result of the PEI coating process. The dissolution or swelling/deswelling behaviour displayed by these particulate vehicles could be tailored and monitored in time, to promote the controlled and sustained release of plasmid DNA. Moreover, we show that both the surfactant alkyl chain length and the ratio of nitrogen to phosphate groups are important parameters for controlling the plasmid DNA release. Overall, the developed plasmid DNA carriers have the potential as a new nanoplatform to be further explored for advances in the gene therapy field.

Mesoscale nanoparticles selectively target the renal proximal tubule epithelium

We synthesized "mesoscale" nanoparticles, approximately 400 nm in diameter, which unexpectedly localized selectively in renal proximal tubules and up to 7 times more efficiently in the kidney than other organs. Although nanoparticles typically localize in the liver and spleen, modulating their size and opsonization potential allowed for stable targeting of the kidneys through a new proposed uptake mechanism. Applying this kidney targeting strategy, we anticipate use in the treatment of renal disease and the study of renal physiology.

Enhancement of DNA compaction by negatively charged nanoparticles: effect of nanoparticle size and surfactant chain length

We study the compaction of genomic DNA by a series of alkyltrimethylammonium bromide surfactants having different hydrocarbon chain lengths n: dodecyl-(DTAB, n=12), tetradecyl-(TTAB, n=14) and hexadecyl-(CTAB, n=16), in the absence and in the presence of negatively charged silica nanoparticles (NPs) with a diameter in the range 15-100 nm. We show that NPs greatly enhance the ability of all cationic surfactants to induce DNA compaction and that this enhancement increases with an increase in NP diameter. In the absence of NP, the ability of cationic surfactants to induce DNA compaction increases with an increase in n. Conversely, in the presence of NPs, the enhancement of DNA compaction increases with a decrease in n. Therefore, although CTAB is the most efficient surfactant to compact DNA, maximal enhancement by NPs is obtained for the largest NP diameter (here, 100 nm) and the smallest surfactant chain length (here, DTAB). We suggest a mechanism where the preaggregation of surfactants on NP surface mediated by electrostatic interactions promotes cooperative binding to DNA and thus enhances the ability of surfactants to compact DNA. We show that the amplitude of enhancement is correlated with the difference between the surfactant concentration corresponding to aggregation on DNA alone and that corresponding to the onset of adsorption on nanoparticles.

Cationic lipid bilayer coated gold nanoparticles-mediated transfection of mammalian cells

Here, we demonstrated dimethyldioctadecylammonium bromide (DODAB), a cationic lipid, bilayer coated Au nanoparticles (AuNPs) could efficiently deliver two types of plasmid DNA into human embryonic kidney cells (HEK 293) in the presence of serum. The transfection efficiency of AuNPs was about five times higher than that of DODAB. The interaction of AuNPs with DNA was characterized with dye intercalation assay and agarose gel electrophoresis. The morphology of the complex of AuNPs with DNA was observed with scanning electron microscope (SEM). The intracellular trafficking of the complex was monitored with transmission electron microscope (TEM). Based on experimental results, the possible mechanism was proposed and the barriers in the process of transfection were discussed. This work demonstrates a simple way to increase the transfection efficiency of cationic lipid through changing the stability of the complex of cationic lipid with DNA. It may provide some insights into understanding and controlling the interaction of cationic lipid with DNA. It also provides a novel way to construct gold nanoparticles-based gene vectors and some insights into learning the process of nanomaterials-mediated transfection.

Lipoplexes formed by DNA and ferrocenyl lipids: effect of lipid oxidation state on size, internal dynamics, and zeta-potential

The effect of lipid oxidation state on the physical properties of complexes formed by plasmid DNA and the redox-active lipid bis-(11-ferrocenylundecyl)dimethylammonium bromide (BFDMA) is reported. With increasing concentration of BFDMA, the hydrodynamic sizes of complexes formed by BFDMA and DNA (in the presence of 1 mM Li(2)SO(4)) pass through a maximum and the zeta-potential changes monotonically from -40 mV to +40 mV. In contrast, complexes formed by oxidized BFDMA and DNA exhibit a minimum in size and maintain a negative zeta-potential with increasing concentration of BFDMA. Angle-dependent dynamic light scattering measurements also reveal the presence of relaxation processes within complexes formed by DNA and oxidized BFDMA that are absent for complexes formed by DNA and reduced BFDMA. These results, when combined, reveal that the amphiphilic nature of reduced BFDMA leads to lipoplexes with physical properties resembling those formed by classical cationic lipids, whereas the interaction of oxidized BFDMA with DNA is similar to that of nonamphiphilic cationic molecules bearing multiple charges (e.g., spermidine). In particular, the negative zeta-potential and measurable presence of DNA chain dynamics within complexes formed by oxidized BFDMA and DNA indicate that these complexes are loosely packed with excess charge due to DNA in their outer regions. These results, when combined with additional measurements performed in OptiMEM reduced-serum cell culture medium, lead to the proposition that the strong dependence of transfection efficiency on the oxidation state of BFDMA, as reported previously, is largely a reflection of the substantial change in the zeta-potentials of these complexes with changes in the oxidation state of BFDMA.

Modified Paclitaxel-loaded Nanoparticles for Inhibition of Hyperplasia in a Rabbit Arterial Balloon Injury Model

PURPOSE

This study tested the possibility of localized intravascular infusion of positive charged paclitaxel-loaded nanoparticles (NPs) to better prevent neointimal formation in a rabbit carotid artery injury model.

MATERIALS AND METHODS

NPs were prepared by oil-water emulsion/solvent evaporation technique using biodegradable poly (lactide-co-glycolide) (PLGA). A cationic surfactant, didodecyldimethylammonium bromide (DMAB), was absorbed on the NP surface by electrostatic attraction between positive and negative charges. NPs were characterized in such aspects as size, surface morphology, surface charges as well as in vitro drug release profile. Balloon injured rabbit carotid arteries were treated with single infusion of paclitaxel-loaded NP suspension and observed for 28 days. The inhibitory effects of NPs on neointima formation were evaluated as end-point.

RESULTS

NPs showed spherical shape with a diameter ranging from 200 to 500 nm. Negatively charged PLGA NPs shifted to positive after the DMAB modification. The in vitro drug release profile showed a biphasic release pattern. Morphometric analyses on the retrieved artery samples revealed that the inhibitory effect of intima proliferation was dose-dependent. At a concentration of 30 mg ml(-1), NP infusion completely inhibited intima proliferation in a rabbit vascular injury model.

CONCLUSIONS

Paclitaxel-loaded NPs with DMAB modification were proven an effective means of inhibiting proliferative response to vascular injury in a rabbit model.

Novel block copolymer (PPDO/PLLA-b-PEG): enhancement of DNA uptake and cell transfection

The cationic lipid mediated uptake of plasmid DNA by cells in monolayer culture was significantly enhanced with an aqueous solution of the block copolymer poly(p-dioxanone-co-L-lactide)-b-poly(ethylene glycol) (PPDO/PLLA-b-PEG). Plasmid uptake studies with DNA encoding the beta-galactosidase gene and cytotoxicity evaluations were performed on MCF-7, NIH 3T3 and CT-26 cell lines. Transfection yields and time courses for maximum release of FITC labeled DNA in MCF-7 cells were observed and quantified by beta-galactosidase assay and spectrofluorometry, respectively. The reported results suggest that the studied block copolymer might be useful for the enhancement of polycation mediated transfection and could find application in gene therapy.

Integrase-mediated nonviral gene transfection with enhanced integration efficiency

Retroviruses efficiently integrate their genome into the host chromosome. Two elements of the retrovirus genome are needed for the integration: long terminal repeats (LTRs) and integrase protein. We attempted to incorporate the retrovirus integration machinery in lipid vesicle-mediated gene transfection with the aim of achieving efficient stable transfection in a nonviral gene transfection system. A DNA fragment, in which a neomycin-resistant gene was flanked between partial LTR sequences derived from the Rous sarcoma virus (RSV), was constructed. This DNA fragment was transfected together with purified recombinant RSV integrase or integrase expression vectors by means of lipid vesicle-mediated gene transfection. The integrase-mediated transfection enhanced the stable transfection efficiency. The length and the end structure of the LTR sequences were important in achieving high efficiency. Under optimal conditions, the stable transfection efficiency showed a 16-fold improvement over that without integrase.