Influence of charge ratio of liposome/DNA complexes on their size after extrusion and transfection efficiency

Inclusion of TAT and NLS sequences in lipopeptide molecules generates homogenous nanoparticles for gene delivery applications

PURPOSES

The objective of this study is to develop a versatile gene carrier based on lipopeptides capable of delivering genetic material into target cells with minimal cytotoxicity.

METHODS

Two lipopeptide molecules, palmitoyl-CKKHH and palmitoyl-CKKHH-YGRKKRRQRRR-PKKKRKV, were synthesized using solid phase peptide synthesis and evaluated as transfection agents. Physicochemical characterization of the lipopeptides included a DNA shift mobility assay, particle size measurement, and transmission electron microscopy (TEM) analysis. Cytotoxicity was assessed in CHO-K1 and HepG2 cells using the MTT assay, while transfection efficiency was determined by evaluating the expression of the green fluorescent protein-encoding gene.

RESULTS

Our findings demonstrate that the lipopeptides can bind, condense, and shield DNA from DNase degradation. The inclusion of the YGRKKRRQRRR sequence, a transcription trans activator, and the PKKKRKV sequence, a nuclear localization signal, imparts desirable properties. Lipopeptide-based TAT-NLS/DNA nanoparticles exhibited stability for up to 20 days when stored at 6-8 °C, displaying uniformity with a compact size of approximately 120 nm. Furthermore, the lipopeptides exhibited lower cytotoxicity compared to the poly-L-lysine. Transfection experiments revealed that protein expression mediated by the lipopeptide occurred at a charge ratio ranging from 4.0 to 8.0.

CONCLUSION

These results indicate that the lipopeptide, composed of a palmitoyl alkyl chain and TAT and NLS sequences, can efficiently condense and protect DNA, form stable and uniform nanoparticles, and exhibit promising characteristics as a potential gene carrier with minimal cytotoxicity.

Lipid/polyelectrolyte complexes - effects of the polyelectrolyte architecture on the self-assembled structures

Self-assembly is a key process in forming biological materials. Especially the interaction between amphiphiles and polyelectrolytes has been widely investigated in recent years due to their potential application in industry and medicine, with a special focus on gene therapy. Accordingly, we investigated the formation of lipoplexes by mixing the cationic lipid DOTAP (1,2-dioleoyl-3-trimethylammonium-propane (chloride salt)) with different anionic polyelectrolytes (PE), such as NaPA (sodium polyacrylate), CMC (sodium carboxymethyl cellulose) with different degrees of substitution (DS, namely, different charge density), PSS (sodium polystyrenesulfonate) and DNA (deoxyribonucleic acid sodium salt). The goal of this project was to explore the influence of different system parameters, such as the charge ratio, CR = [+]/[-] = [DOTAP]/[PE], the charge density of the PE, or the type of PE on the morphology of the formed complexes. The investigation of these systems was performed by cryo-transmission electron microscopy (cryo-TEM), and with small-angle X-ray scattering (SAXS), to support our findings. In our experiments, we obtained a comprehensive picture of the formed lipoplexes, and how their structure depends on the different properties of the employed polyelectrolyte. Although the basic nanostructure of all complexes is lamellar, their detailed morphology depends strongly on parameters of the PE, e.g., the persistence length, charge density, or the polymer backbone. Understanding these specific interactions will allow the formation of more stable and optimized complexes as they are needed for drug or genetic material delivery.

Membrane-Fusing Vehicles for Re-Sensitizing Transporter-Mediated Multiple-Drug Resistance in Cancer

Reversing the multiple drug resistance (MDR) arising from the overexpression of the efflux transporters often fails mainly due to the high toxicity or the poor water solubility of the inhibitors of these transporters. Here, we demonstrate the delivery of an inhibitor targeting three ABC transporters (ABCB1, ABCC1 and ABCG2) directly to the cell membrane using membrane-fusing vehicles (MFVs). Three different transfected MDCK II cell lines, along with parental cells, were used to investigate the inhibitory effect of cyclosporine A (CsA) in solution versus direct delivery to the cell membrane. CsA-loaded MFVs successfully reversed MDR for all three investigated efflux transporters at significantly lower concentrations compared with CsA in solution. Results showed a 15-fold decrease in the IC50 value for ABCB1, a 7-fold decrease for ABCC1 and an 11-fold decrease for ABCG2. We observed binding site specificity for ABCB1 and ABCG2 transporters. Lower concentrations of empty MFVs along with CsA contribute to the inhibition of Hoechst 33342 efflux. However, higher concentrations of CsA along with the high amount of MFVs activated transport via the H-binding site. This supports the conclusion that MFVs can be useful beyond their role as delivery systems and also help to elucidate differences between these transporters and their binding sites.

Influence of the Charge Ratio of Guanine-Quadruplex Structure-Based CpG Oligodeoxynucleotides and Cationic DOTAP Liposomes on Cytokine Induction Profiles

Cationic liposomes, specifically 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) liposomes, serve as successful carriers for guanine-quadruplex (G4) structure-based cytosine-guanine oligodeoxynucleotides (CpG ODNs). The combined benefits of CpG ODNs forming a G4 structure and a non-viral vector carrier endow the ensuing complex with promising adjuvant properties. Although G4-CpG ODN-DOTAP complexes show a higher immunostimulatory effect than naked G4-CpG ODNs, the effects of the complex composition, especially charge ratios, on the production of the pro-inflammatory cytokines interleukin (IL)-6 and interferon (IFN)-α remain unclear. Here, we examined whether charge ratios drive the bifurcation of cytokine inductions in human peripheral blood mononuclear cells. Linear CpG ODN-DOTAP liposome complexes formed micrometer-sized positively charged agglomerates; G4-CpG ODN-DOTAP liposome complexes with low charge ratios (0.5 and 1.5) formed ~250 nm-sized negatively charged complexes. Notably, low-charge-ratio (0.5 and 1.5) complexes induced significantly higher IL-6 and IFN-α levels simultaneously than high-charge-ratio (2 and 2.5) complexes. Moreover, confocal microscopy indicated a positive correlation between the cellular uptake of the complex and amount of cytokine induced. The observed effects of charge ratios on complex size, surface charge, and affinity for factors that modify cellular-uptake, intracellular-activity, and cytokine-production efficiency highlight the importance of a rational complex design for delivering and controlling G4-CpG ODN activity.

The potential application of branch-PCR assembled PTEN gene nanovector in lung cancer gene therapy

Gene therapy offers an alternative and promising avenue to lung cancer treatment. Here, we used dibenzocyclooctyne (DBCO)-branched primers to construct a kind of PTEN gene nanovector (NP-PTEN) through branch-PCR. NP-PTEN showed the nanoscale structure with the biocompatible size (84.7 ± 11.2 nm) and retained the improved serum stability compared to linear DNA. When transfected into NCI-H1299 cancer cells, NP-PTEN could overexpress PTEN protein to restore PTEN function through the deactivation of PI3K-AKT-mTOR signaling pathway to inhibit cell proliferation and induce cell apoptosis. The apoptosis rate of NCI-H1299 cancer cells could reach up to 54.5% ± 4.6% when the transfection concentration of NP-PTEN was 4.0 μg/mL. In mice bearing NCI-H1299 tumor xenograft intratumorally administrated with NP-PTEN, the average tumor volume and tumor weight was separately reduced by 61.7% and 63.9% compared with the PBS group on the 18 th day of administration. The anticancer efficacy of NP-PTEN in NCI-H1299 tumor xenograft suggested the promising therapeutic potential of this branch-PCR assembled PTEN gene nanovectors in lung cancer gene therapy and also provided more opportunities to introduce two or more tumor suppressor genes as the all-in-one gene nanovectors for multiple gene-based cancer gene therapy.

Lipid nanoparticles produce chimeric antigen receptor T cells with interleukin-6 knockdown in vivo

Chimeric receptor T cells (CAR-T) can effectively cure leukemia; however, there are two limitations: a complicated preparation process ex vivo and cytokine release syndrome (CRS). In this study, we constructed a lipid nanoparticle system modified by CD3 antibody on the surface, loading with the plasmid containing the combination gene of interleukin 6 short hairpin RNA (IL-6 shRNA) and CD19-CAR (AntiCD3-LNP/CAR19 + shIL6). The system targeted T cells by the mediation of CD3 antibody and stably transfected T cells to transform them into CAR-T cells with IL-6 knockdown, thus killing CD19-highly expressed leukemia tumor cells and reducing CRS caused by IL-6. In vivo experiments showed that AntiCD3-LNP/CAR19 + shIL6 could stably transfect T cells and produce CAR-T within 90 days to kill the tumor. This significantly prolonged the survival time of leukemia model mice and demonstrated the prepared LNP exhibited the same anti-tumor effect as the traditional CAR-T cells prepared ex vivo. In this study, CAR-T cells were directly produced in vivo after intravenous injection of the lipid nanoparticles, without the need of using the current complex process ex vivo. Additionally, IL-6 expression was silenced, which would be helpful to reduce the CRS and improve the safety of CAR-T therapy. This method improves the convenience of using CAR-T technology and is helpful in further promoting the clinical application of CAR-T.

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.

A novel method for the development of plasmid DNA-loaded nanoliposomes for cancer gene therapy

We aimed to develop a simple yet novel method to prepare plasmid DNA-loaded nanoliposomes for cancer gene therapy. Murine interleukin-12 (mIL-12) pDNA-loaded nanoliposomes were prepared via novel freeze-drying of a monophase solution method. The physicochemical characteristics, cytotoxicity, and transfection efficiency of the prepared nanoliposomes in murine CT-26 colon carcinoma cells were evaluated. Furthermore, tumor progression and survival rate in CT-26 colon carcinoma-bearing BALB/c mice subsequent to direct intratumoral injections were investigated over a period of 40 days. Using this preparation method, nanoliposomes with particle size of around 300 nm and zeta potential of 96.5 mV were obtained. The transmission electron microscope results showed that the liposomes were nano-sized and almost spherical. The agarose gel retardation assay revealed the pDNA encapsulation in the nanoliposomes. The nanoliposomes with 72.4% encapsulation efficiency and low cell toxicity could significantly improve mIL-12 expression by approximately 25-fold relative to the naked mIL-12 pDNA. There was a significant tumor growth inhibition after repeated injections of mIL-12 pDNA-loaded nanoliposomes. This is the first study on the freeze-drying of a monophase solution method as a simple yet novel technique for the preparation of pDNA-loaded nanoliposomes. Given the ease of preparation method and promising in vitro and in vivo characteristics, this investigation demonstrates advances in pDNA lipid formulation for cancer gene therapy.

Complexation design of cationized gelatin and molecular beacon to visualize intracellular mRNA

The objective of this study is to prepare cationized gelatin-molecular beacon (MB) complexes for the visualization of intracellular messenger RNA (mRNA). The complexes were prepared from cationized gelatins with different extents of cationization and different mixing ratios of MB to cationized gelatin. The apparent size of complexes was almost similar, while the zeta potential was different among the complexes. Irrespective of the preparation conditions, the complexes had a sequence specificity against the target oligonucleotides in hybridization. The cytotoxicity and the amount of complexes internalized into cells increased with an increase in the cationization extent and the concentration of cationized gelatin. After the incubation with complexes prepared from cationized gelatin with the highest extent of cationization and at mixing ratios of 10 and 20 pmole MB/μg cationized gelatin, a high fluorescent intensity was detected. On the other hand, the complex prepared with the mixing ratio at 20 pmole/μg did not show any cytotoxicity. The complex was the most effective to visualize the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA endogenously present. In addition, even for enhanced green fluorescent protein (EGFP) mRNA exogenously transfected, the complex permitted to effectively detect it as well. It is concluded that both the endogenous and exogenous mRNA can be visualized in living cells by use of cationized gelatin-MB complexes designed.

Structure-activity relationship of serotonin derived tocopherol lipids

Tocopherol-based lipids are widely used for nucleic acid delivery. Using tocopherol molecules, we designed and synthesized 5-HT functionalized lipids by tethering 5-hydroxytryptamine (5-HT), a small molecule ligand as the head group to a natural amphiphilic molecule namely α-tocopherol (Vitamin E). This is with the aim of delivering nucleic acids specifically into cells expressing the serotonin receptors (5-hydroxytryptamine[5-HT]) which are abundant in the central nervous system. In order to achieve target recognition, we adopted an approach wherein two structurally different lipid molecules having serotonin as the head group was conjugated to tocopherol via different linkers thus generating lipids with either free -NH₂ or -OH moiety. The corresponding lipids designated as Lipid A (Tocopheryl carbonate serotonin-NH₂) and Lipid B (Tocopheryl 2-hydroxy propyl ammonium serotonin-OH), were formulated with co-lipids 1,2-dioleoyl-sn-glycero-3-phosphatidyl-ethanolamine (DOPE) and 1,2-dioleoyl-sn-glycero-sn-3-phosphatidylcholine (DOPC) and evaluated for their ability to deliver plasmid DNA through reporter gene expression assays in vitro. Furthermore, the physicochemical characteristics and cellular interactions of the formulations were examined using serotonin-receptor enriched cells in order to distinguish the structural and functional attributes of both lipids. Cell-based gene expression studies reveal that in comparison to Lipid A, a formulation of Lipid B prepared with DOPE as the co-lipid, contributes to efficient uptake leading to significant enhancement in transfection. Specific interactions explored by molecular docking studies suggests the role of the hydroxyl moiety and the enantiospecific significance of serotonin- conjugated tocopherol lipids in recognizing these receptors thus signifying a promising lipid-based approach to target the serotonin receptors in the central nervous system.

Interaction of DNA with Cationic Lipid Mixtures-Investigation at Langmuir Lipid Monolayers

Four different binary lipid mixtures composed of a cationic lipid and the zwitterionic colipids DOPE or DPPC, which show different DNA transfer activities in cell culture models, were investigated at the soft air/water interface to identify transfection efficiency determining characteristics. Langmuir films are useful models to investigate the interaction between DNA and lipid mixtures in a two-dimensional model system by using different surface sensitive techniques, namely, epifluorescence microscopy and infrared reflection-absorption spectroscopy. Especially, the effect of adsorbed DNA on the properties of the lipid mixtures has been examined. Distinct differences between the lipid composites were found which are caused by the different colipids of the mixtures. DOPE containing lipid mixtures form fluid monolayers with a uniform distribution of the fluorescent probe in the presence and absence of DNA at physiologically relevant surface pressures. Only at high nonphysiological pressures, the lipid monolayer collapses and phase separation was observed if DNA was present in the subphase. In contrast, DPPC containing lipid mixtures show domains in the liquid condensed phase state in the presence and absence of DNA in the subphase. The adsorption of DNA at the positively charged mixed lipid monolayer induces phase separation which is expressed in the morphology and the point of appearance of these domains.

Impact of the Charge Ratio on the In Vivo Immunogenicity of Lipoplexes

PURPOSE

The present study investigated the immunogenic potential of different cationic liposome formulations with a DNA plasmid encoding Pfs25, a malaria transmission-blocking vaccine candidate.

METHODS

Pfs25 plasmid DNA was complexed with cationic liposomes to produce lipoplexes at different charge ratios of the cationic lipid head group to the nucleotide phosphate (N:P). The formation of lipoplexes was visualized by Cryogenic-TEM. Confocal microscopy of lipoplexes formed with GFP encoding plasmid DNA, and flow cytometry was used to determine their in vitro transfection capability. Two different lipoplex formulations using plasmid DNA encoding Pfs25 were evaluated for in vivo immunogenicity after intramuscular administration in Balb/c mice. Immune sera were analyzed by ELISA.

RESULTS

The results demonstrated that the cationic liposome-mediated DNA immunization with an N:P charge ratio of 1:3 (anionic lipoplexes) is more effective than the use of naked plasmid DNA alone. No antibody response was observed when lipoplexes with a higher N:P charge ratio of 10:3 (cationic lipoplexes) were used. Trehalose was added to some lipoplex formulations as a cryoprotectant and adjuvant, but it did not yield any further improvement of immunogenicity in vivo.

CONCLUSIONS

The results suggest that Pfs25 plasmid DNA delivered as lipoplexes at a charge ratio of 1:3 elicited strong immunogenicity in mice and may be improved further to match the immune responses of DNA vaccines administered by in vivo electroporation.

Delivery methods to increase cellular uptake and immunogenicity of DNA vaccines

DNA vaccines are ideal candidates for global vaccination purposes because they are inexpensive and easy to manufacture on a large scale such that even people living in low-income countries can benefit from vaccination. However, the potential of DNA vaccines has not been realized owing mainly to the poor cellular uptake of DNA in vivo resulting in the poor immunogenicity of DNA vaccines. In this review, we discuss the benefits and shortcomings of several promising and innovative non-biological methods of DNA delivery that can be used to increase cellular delivery and efficacy of DNA vaccines.

Di-Peptide-Modified Gemini Surfactants as Gene Delivery Vectors: Exploring the Role of the Alkyl Tail in Their Physicochemical Behavior and Biological Activity

The aim of this work was to elucidate the structure-activity relationship of new peptide-modified gemini surfactant-based carriers. Glycyl-lysine modified gemini surfactants that differ in the length and degree of unsaturation of their alkyl tail were used to engineer DNA nano-assemblies. To probe the optimal nitrogen to phosphate (N/P) ratio in the presence of helper lipid, in vitro gene expression and cell toxicity measurements were carried out. Characterization of the nano-assemblies was accomplished by measuring the particle size and surface charge. Morphological characteristics and lipid organization were studied by small angle X-ray scattering technique. Lipid monolayers were studied using a Langmuir-Blodgett trough. The highest activity of glycyl-lysine modified gemini surfactants was observed with the 16-carbon tail compound at 2.5 N/P ratio, showing a 5- to 10-fold increase in the level of reporter protein compared to the 12 and 18:1 carbon tail compounds. This ratio is significantly lower compared to the previously studied gemini surfactants with alkyl or amino- spacers. In addition, the 16-carbon tail compound exhibited the highest cell viability (85%). This high efficiency is attributed to the lowest critical micelle concentration of the 16-tail gemini surfactant and a balanced packing of the nanoparticles by mixing a saturated and unsaturated lipid together. At the optimal N/P ratio, all nanoparticles exhibited an inverted hexagonal lipid assembly. The results show that the length and nature of the tail of the gemini surfactants play an important role in determining the transgene efficiency of the delivery system. We demonstrated here that the interplay between the headgroup and the nature of tail is specific to each series, thus in the process of rational design, the contribution of the latter should be assessed in the appropriate context.

Influence of cationic lipid concentration on properties of lipid-polymer hybrid nanospheres for gene delivery

Nanoparticles have been widely used for nonviral gene delivery. Recently, cationic hybrid nanoparticles consisting of two different materials were suggested as a promising delivery vehicle. In this study, nanospheres with a poly(D,L-lactic-co-glycolic acid) (PLGA) core and cationic lipid shell were prepared, and the effect of cationic lipid concentrations on the properties of lipid polymer hybrid nanocarriers investigated. Lipid-polymer hybrid nanospheres (LPHNSs) were fabricated by the emulsion-solvent evaporation method using different concentrations of cationic lipids and characterized for size, surface charge, stability, plasmid DNA-binding capacity, cytotoxicity, and transfection efficiency. All LPHNSs had narrow size distribution with positive surface charges (ζ-potential 52-60 mV), and showed excellent plasmid DNA-binding capacity. In vitro cytotoxicity measurements with HEK293T, HeLa, HaCaT, and HepG2 cells also showed that LPHNSs exhibited less cytotoxicity than conventional transfection agents, such as Lipofectamine and polyethyleneimine-PLGA. As cationic lipid concentrations increased, the particle size of LPHNSs decreased while their ζ-potential increased. In addition, the in vitro transfection efficiency of LPHNSs increased as lipid concentration increased.

Development and characterization of a cationic lipid nanocarrier as non-viral vector for gene therapy

The aim of the present work was to produce a cationic solid lipid nanoparticle (SLN) as non-viral vector for protein delivery. Cationic SLN were produced by double emulsion method, composed of softisan(®) 100, cetyltrimethylammonium bromide (CTAB), Tween(®) 80, Span(®) 80, glycerol and lipoid(®) S75 loading insulin as model protein. The formulation was characterized in terms of mean hydrodynamic diameter (z-ave), polydispersity index (PI), zeta potential (ZP), stability during storage time, stability after lyophilization, effect of toxicity and transfection ability in HeLa cells, in vitro release profile and morphology. SLN were stable for 30days and showed minimal changes in their physicochemical properties after lyophilization. The particles exhibited a relatively slow release, spherical morphology and were able to transfect HeLa cells, but toxicity remained an obstacle. Results suggest that SLN are nevertheless promising for delivery of proteins or nucleic acids for gene therapy.

Gene delivery to Her-2+ breast cancer cells using a two-component delivery system to achieve specificity

Current liposomal gene delivery systems predominately utilize cationic lipids, which efficiently bind and deliver DNA plasmid, but also result in nonspecific gene expression in lung and liver tissue. To improve specificity, a two-component delivery strategy employing neutral liposomes was used to target breast cancers positive for the human epidermal growth factor receptor 2 (Her-2). The first component consisted of plasmid DNA condensed with cationic polyethylene glycol (PEG) modified polylysine (PL/DNA). The second component was a neutral Her-2 targeting liposome conjugated to the pore-forming protein, Listeriolysin O (LLO). Independently, PL/DNA delivery resulted in low expression of plasmid DNA. However, when PL/DNA and LLO/liposomes co-localized within an endosome, LLO disrupted endosome integrity, leading to cytoplasmic delivery and expression of the plasmid. When used to deliver a plasmid encoding the luciferase gene, this two-component system resulted in gene expression that was 268-fold greater in Her-2 positive cells than in Her-2 negative cells.

FROM THE CLINICAL EDITOR

In this paper a novel two-component gene delivery method is presented using PL/DNA and LLO liposomes, demonstrating strongly significant results in a model system.

Alkylimidazolium end-modified poly(ethylene glycol) to form the mono-ion complex with plasmid DNA for in vivo gene delivery

In this study, we consider that the decrease in the transfection activity of polycations in vivo, compared with that in vitro, results from their polyion complex formation. Namely, owing to cross-linking between polycations and plasmid DNAs (pDNAs), the disadvantage of in vivo gene delivery mainly stems from the difficulty in controlling the properties of the resulting polyion complex at the nanoscale size. To avoid the cross-linking by polycations, we have establish the concept of "mono-ion complex" formation between pDNA and a monocationic biocompatible polymer. Here we have synthesized alkylimidazolium end-modified poly(ethylene glycol), that is, R-Im-PEG, and have tuned the electrostatic interaction between the resulting alkylimidazolium group and the phosphate group of pDNA by the length of the alkyl chain to achieve "mono-ion complex" formation with pDNA for in vivo gene delivery. Instead of a polyion complex, our original concept of the "mono-ion complex" consisting of the Bu-Im-PEG and pDNA is expected to offer unique tools to break through the barriers of in vivo gene delivery. As well as the field of gene delivery, this study is considered to have exploded the common sense that it is impossible to form not a polyion complex but a "mono-ion complex" under aqueous conditions for all fields of the modification of biomacromolecules.