Physicochemical characterization of anionic lipid-based ternary siRNA complexes

Dissolving microneedles-based programmed delivery system for enhanced chemo-immunotherapy of melanoma

Immune checkpoint blockade, especially the programmed cell death ligand 1 (PD-L1) blockade, has revolutionized the treatment of melanoma. However, PD-1/PD-L1 monotherapy leads to unsatisfactory therapeutic outcomes. The immunotherapy of melanoma could be improved by adding doxorubicin (DOX), which triggers immunogenic cell death (ICD) effect to activate anti-tumor immunity. Additionally, microneedles, especially dissolving microneedles (dMNs), can further enhance outcomes of chemo-immunotherapy due to the physical adjuvant effect of dMNs. Herein, we developed the dMNs-based programmed delivery system that incorporated pH-sensitive and melanoma-targeting liposomes to co-deliver DOX and siPD-L1, achieving enhanced chemo-immunotherapy of melanoma (si/DOX@LRGD dMNs). The incorporated si/DOX@LRGD LPs demonstrated uniform particle size, pH-sensitive drug release, high in vitro cytotoxicity and targeting ability. Besides, si/DOX@LRGD LPs effectively downregulated the expression of PD-L1, induced tumor cell apoptosis and triggered ICD effect. The si/DOX@LRGD LPs also showed deep penetration (approximately 80 μm) in 3D tumor spheroids. Moreover, si/DOX@LRGD dMNs dissolved rapidly into the skin and had sufficient mechanical strength to penetrate skin, reaching a depth of approximately 260 μm in mice skin. In mice model of melanoma tumor, si/DOX@LRGD dMNs exhibited better anti-tumor efficacy than monotherapy by dMNs and tail intravenous injection at the same dose. This was due to the higher cytotoxic CD8+ T cells and the secreted cytotoxic cytokine IFN-γ evoked by si/DOX@LRGD dMNs, thereby eliciting strong T-cell mediated immune response and resulted in enhanced anti-tumor effects. In conclusion, these findings suggested that si/DOX@LRGD dMNs provided a promising and effective strategy for enhanced chemo-immunotherapy of melanoma.

Emergence of Small Interfering RNA-Based Gene Drugs for Various Diseases

Small molecule, peptide, and protein-based drugs have been developed over decades to treat various diseases. The importance of gene therapy as an alternative to traditional drugs has increased after the discovery of gene-based drugs such as Gendicine for cancer and Neovasculgen for peripheral artery disease. Since then, the pharma sector is focusing on developing gene-based drugs for various diseases. After the discovery of the RNA interference (RNAi) mechanism, the development of siRNA-based gene therapy has been accelerated immensely. siRNA-based treatment for hereditary transthyretin-mediated amyloidosis (hATTR) using Onpattro and acute hepatic porphyria (AHP) by Givlaari and three more FDA-approved siRNA drugs has set up a milestone and further improved the confidence for the development of gene therapeutics for a spectrum of diseases. siRNA-based gene drugs have more advantages over other gene therapies and are under study to treat different types of diseases such as viral infections, cardiovascular diseases, cancer, and many more. However, there are a few bottlenecks to realizing the full potential of siRNA-based gene therapy. They include chemical instability, nontargeted biodistribution, undesirable innate immune responses, and off-target effects. This review provides a comprehensive view of siRNA-based gene drugs: challenges associated with siRNA delivery, their potential, and future prospects.

Anionic liposomes prepared without organic solvents for effective siRNA delivery

Currently, organic solvents are necessary for the preparation of anionic liposomes for siRNA delivery. The removal of organic solvent is time-consuming and the residual organic solvent is not only a hidden danger, but also affects the stability of anionic liposomes. Glycerol, which is physiologically compatible and does not need to be removed, is used to promote the dispersion of lipids and the formation of anionic liposomes. Additionally, the preparation process is simple and not time-consuming. The results showed that anionic liposomes, which were typically spherical with a particle size of 188.9 nm were successfully prepared with glycerol. And with the help of Ca²⁺ , siRNA was encapsulated in anionic liposomes. The highest encapsulation efficiency at 2.4 mM Ca²⁺ reached 91%. And the formation of calcium phosphate could promote the endosomal escape of siRNA effectively. The results from cell viability showed that the anionic liposomes had no obvious cytotoxicity. It was also verified that anionic liposomes could improve the resistance of siRNA against degradation. Additionally, siRNA delivered by anionic liposomes could play an effective role in knockout. Therefore, anionic liposomes prepared with glycerol will be a safe and effective delivery platform for siRNA and even other nucleic acid drugs.

Non-viral vectors for RNA delivery

RNA-based therapy is a promising and potential strategy for disease treatment by introducing exogenous nucleic acids such as messenger RNA (mRNA), small interfering RNA (siRNA), microRNA (miRNA) or antisense oligonucleotides (ASO) to modulate gene expression in specific cells. It is exciting that mRNA encoding the spike protein of COVID-19 (coronavirus disease 2019) delivered by lipid nanoparticles (LNPs) exhibits the efficient protection of lungs infection against the virus. In this review, we introduce the biological barriers to RNA delivery in vivo and discuss recent advances in non-viral delivery systems, such as lipid-based nanoparticles, polymeric nanoparticles, N-acetylgalactosamine (GalNAc)-siRNA conjugate, and biomimetic nanovectors, which can protect RNAs against degradation by ribonucleases, accumulate in specific tissue, facilitate cell internalization, and allow for the controlled release of the encapsulated therapeutics.

Calcium mediated DNA binding in non-lamellar structures formed by DOPG/glycerol monooleate

In order to test an encapsulation method of short fragmented DNA (∼ 20-300 bp), we study the solubilisation in 150 mM solution of NaCl of a cubic phase formed by glycerol monooleate (GMO) with negatively charged dioleoylphosphatidylglycerol (DOPG) up to the level of unilamellar vesicles and, subsequently, the restoration of the cubic phase using Ca²⁺ cations. We performed small angle X-ray and neutron scattering (SAXS and SANS) to follow structural changes in DOPG/GMO mixtures induced by increasing DOPG content. The cubic phase (Pn3m space group) is preserved up to ∼ 11 mol% of DOPG in DOPG/GMO. Above 20 mol%, the SANS curves are typical of unilamellar vesicles. The thickness of the DOPG/GMO lipid bilayer (d_L) decreases slightly with increasing fraction of DOPG. The addition of 15 mM of CaCl₂ solution shields the electrostatic repulsions of DOPG molecules, increases slightly d_L and restores the cubic structures in the mixtures up to ∼ 37 mol% of DOPG. Zeta potential shows negative surface charge. The analysis of the data provides the radius of the water nano-channels of the formed non-lamellar structures. We discuss their dimensions with respect to DNA binding. In addition, Ca²⁺ mediates DNA - DOPG/GMO binding. The formed hexagonal phase, H_II, binds less of DNA in comparison with cubic phases (∼ 6 wt% and ∼ 20 wt% of the total amount, respectively). The studied system can be utilized as anionic Q_II delivery vector for genetic material.

Innovations in Biomaterial Design toward Successful RNA Interference Therapy for Cancer Treatment

Gene regulation using RNA interference (RNAi) therapy has been developed as one of the frontiers in cancer treatment. The ability to tailor the expression of genes by delivering synthetic oligonucleotides to tumor cells has transformed the way scientists think about treating cancer. However, its clinical application has been limited due to the need to deliver synthetic RNAi oligonucleotides efficiently and effectively to target cells. Advances in nanotechnology and biomaterials have begun to address the limitations to RNAi therapeutic delivery, increasing the likelihood of RNAi therapeutics for cancer treatment in clinical settings. Herein, innovations in the design of nanocarriers for the delivery of oligonucleotides for successful RNAi therapy are discussed.

Improved delivery of miR-1296 loaded cationic nanoliposomes for effective suppression of triple negative breast cancer

Nowadays, microRNA is considered an attractive strategy for the effective treatment of cancer. A significant delivery of microRNA for cancer therapy remains a significant obstacle to target cancer cells. The restoring microRNA-1296 (miR-1296) has immense therapeutic efficacy in triple-negative breast cancer (TNBC). TNBC is an aggressive subtype of breast tumors with the progression of malignant transformation. This study aimed to develop a cationic nanoliposome that can serve as a miR-1296 carrier and studied its efficiency in TNBC. The efficacy of miR-1296 liposomes was evaluated on its apoptotic effect, cellular uptake, and potential chemotherapy sensitization in the TNBC cell line (MDA-MB-231). For in vitro viability study, the apoptotic effect was performed to validate protein expression using Alamar blue kit and western blot. The transfection of miR-1296 into TNBC cells was also investigated using cisplatin as a TNBC resistance drug. The fluorescent miR-1296-cy3 liposome was used for cellular uptake study. The miR-liposome was successfully prepared with a particle size of 123.6 ± 1.3 nm and encapsulation efficiency of 94.33%. A dose of 0.5 uM has significantly reduced the viability of MDA-MB-231 to be 33.45%±5.29 (P < 0.001). This result was validated by down-expression of CCND1, and PARP1, the miR-1296 receptor, and apoptosis marker. The image of the miR-1296-cy3 liposome showed cytoplasmic intracellular localization. It was found high sensitization of TNBC cell line for miR-1296 liposome compared to cisplatin (P < 0.001). Future in vivo research may answer questions concerning safety and stability. This study demonstrates that miR-191 liposomes may have promising clinical applications for TNBC therapy.

Polymer-Coated Hydroxyapatite Nanocarrier for Double-Stranded RNA Delivery

Conventional synthetic insecticides have limited success due to insect resistance and negative effects on off-target biota and the environment. Although RNA interference (RNAi) is a tool that is becoming more widely utilized in pest control products, naked dsRNA has limited success in most taxa. Nanocarriers have shown promising results in enhancing the efficacy of this tool. In this study, we used a layer-by-layer electrostatic assembly where we synthesized poly(acrylic acid) (PAA)-coated hydroxyapatite (HA) nanoparticles (PAA-HA NPs) as inorganic nanocarriers, which were then coated with a layer of a cationic poly(amino acid), 10 kDa poly-l-arginine (PLR₁₀), to allow for binding of a layer of negatively charged dsRNA. Binding of PLR₁₀-PAA-HA NPs to dsRNA was found to increase as the mass ratio of NPs to dsRNA increased. In vitro studies with transgenic SF9 cells (from Spodoptera frugiperda) expressing the firefly luciferase gene showed a significant gene silencing (35% decrease) at a 5:1 NP-to-dsRNA ratio, while naked dsRNA was ineffective at gene silencing. There was a significant concentration-response relationship in knockdown; however, cytotoxicity was observed at higher concentrations. Confocal microscopy studies showed that dsRNA from PLR₁₀-PAA-HA NPs was not localized within endosomes, while naked dsRNA appeared to be entrapped within the endosomes. Overall, polymer-functionalized HA nanocarriers enabled dsRNA to elicit gene knockdown in cells, whereas naked dsRNA was not effective in causing gene knockdown.

Interaction of DNA with likely-charged lipid monolayers: An experimental study

Anionic lipids are increasingly being used in lipoplexes for synthetic gene vectors as an alternative to cationic lipids. This is primarily due to their lower toxicity, which makes them biocompatible and adaptable to be tissue specific. However, anionic lipoplexes require the presence of multivalent cations to promote the electrostatic attraction between DNA and anionic lipid mono- and bilayers. In this work we provide for the first time experimental results of the adsorption of linear DNA onto anionic/zwitterionic lipid monolayers without any addition of cations. This is demonstrated experimentally by means of Langmuir monolayers of DOPE/DOPG (1:1) lipids spread on a water subphase that contains calf thymus DNA. The adsorption of DNA onto anionic/zwitterionic lipid monolayers is discussed in terms of the surface pressure-molecular area isotherms recorded in the absence and in the presence of different electrolytes. Measurements of the surface potential provide additional evidence of the different interaction of DNA anionic/zwitterionic lipid monolayers depending on the presence and nature of electrolyte. These experimental results are further analysed in terms of the overall dipole moment normal to the monolayers providing new insight into the behaviour of anionic lipoplexes and the role of zwitterionic lipids.

EpCAM-targeted liposomal si-RNA delivery for treatment of epithelial cancer

BACKGROUND

RNA interference (RNAi) technology using short interfering RNA (si-RNA) has shown immense potential in the treatment of cancers through silencing of specific genes. Cationic non-viral vectors employed for gene delivery exhibit toxic effects in normal cells limiting their widespread use, therefore, site-specific delivery using benign carriers could address this issue.

OBJECTIVE

Design of a non-toxic carrier that enables site-specific delivery of si-RNA into the cancer cells is of prime importance to realize the promise of gene silencing.

METHODS

In the present study, non-cationic liposomes encapsulating si-RNA against epithelial cell adhesion molecule (EpCAM) were developed and characterized for encapsulation efficiency, colloidal stability, in vitro and in vivo gene silencing efficacy.

RESULTS

PEGylated liposomes containing phosphatidyl choline and phosphatidyl ethanolamine exhibited maximum si-RNA encapsulation efficiency of 47%, zeta potential of -21 mV, phase transition temperature of 51 °C and good colloidal stability in phosphate-buffered saline (PBS) containing bovine serum albumin (BSA) and plasma protein (PP) at 37 °C. Conjugation of epithelial cell adhesion molecule (EpCAM) antibody to the liposomes resulted in enhanced cell internalization and superior down-regulation of EpCAM gene in MCF-7 cell lines when compared with free si-RNA and the non-targeted liposomes. In vivo evaluation of immunoliposomes for their efficacy in regressing the tumor volume in Balb/c SCID mice showed about 35% reduction of tumor volume in comparison with the positive control when administered with an extremely low dose of 0.15 mg/kg twice a week for 4 weeks.

CONCLUSION

Our results exhibit that the nanocarrier-mediated silencing of EpCAM gene is a promising strategy to treat epithelial cancers.

Non-viral nanocarriers for siRNA delivery in breast cancer

Breast cancer is the most frequently diagnosed malignancy in American women. While significant progress has been made in the development of modern diagnostic tools and surgical treatments, only marginal improvements have been achieved with relapsed metastatic breast cancer. Small interfering RNAs (siRNAs) mediate gene silencing of a target protein by disrupting messenger RNAs in an efficient and sequence-specific manner. One application of this technology is the knockdown of genes responsible for tumorigenesis, including those driving oncogenesis, survival, proliferation and death of cells, angiogenesis, invasion and metastasis, and resistance to treatment. Non-viral nanocarriers have attracted attention based on their potential for targeted delivery of siRNA and efficient gene silencing without toxicity. Here, we review promising, non-viral delivery strategies employing liposomes, nanoparticles and inorganic materials in breast cancer.

PEGylation improves the receptor-mediated transfection efficiency of peptide-targeted, self-assembling, anionic nanocomplexes

Non-viral vector formulations comprise typically complexes of nucleic acids with cationic polymers or lipids. However, for in vivo applications cationic formulations suffer from problems of poor tissue penetration, non-specific binding to cells, interaction with serum proteins and cell adhesion molecules and can lead to inflammatory responses. Anionic formulations may provide a solution to these problems but they have not been developed to the same extent as cationic formulations due to difficulties of nucleic acid packaging and poor transfection efficiency. We have developed novel PEGylated, anionic nanocomplexes containing cationic targeting peptides that act as a bridge between PEGylated anionic liposomes and plasmid DNA. At optimized ratios, the components self-assemble into anionic nanocomplexes with a high packaging efficiency of plasmid DNA. Anionic PEGylated nanocomplexes were resistant to aggregation in serum and transfected cells with a far higher degree of receptor-targeted specificity than their homologous non-PEGylated anionic and cationic counterparts. Gadolinium-labeled, anionic nanoparticles, administered directly to the brain by convection-enhanced delivery displayed improved tissue penetration and dispersal as well as more widespread cellular transfection than cationic formulations. Anionic PEGylated nanocomplexes have widespread potential for in vivo gene therapy due to their targeted transfection efficiency and ability to penetrate tissues.

Cellular uptake mechanisms of novel anionic siRNA lipoplexes

PURPOSE

To investigate cellular uptake pathways of novel anionic siRNA-lipoplexes as a function of formulation composition.

METHODS

Anionic formulations with anionic lipid/Ca(2+)/siRNA ratio of 1.3/2.5/1 (AF1) and 1.3/0.3/1 (AF2) were utilized. Uptake mechanisms were investigated using uptake inhibition and co-localization approaches in breast cancer cells. Actin-mediated uptake was investigated using actin polymerization and rearrangement assays. Silencing efficiency and endosomal escaping capability of lipoplexes were evaluated. The cationic formulation Lipofectamine-2000 was used as a control.

RESULTS

Anionic lipoplexes entered the breast cancer cells via endocytosis specifically via macropinocytosis or via both macropinocytosis and HSPG (heparin sulfate proteoglycans) pathways, depending on the Ca(2+)/siRNA ratio. Additionally, uptake of these lipoplexes was both microtubule and actin dependent. The control cationic lipid-siRNA complexes (Lipofectamine-2000) were internalized via both endocytic (phagocytosis, HSPG) and non-endocytic (membrane fusion) pathways. Their uptake was microtubule independent but actin dependent. Silencing efficiency of the AF2 formulation was negligible mainly due to poor endosomal release (rate-limiting step).

CONCLUSIONS

Formulation composition significantly influences the internalization mechanism of anionic lipoplexes. Uptake mechanism together with formulation bioactivity helped in identification of the rate-limiting steps to efficient siRNA delivery. Such studies are extremely useful for formulation optimization to achieve enhanced intracellular delivery of nucleic acids.