Nonviral siRNA delivery to the lung: investigation of PEG-PEI polyplexes and their in vivo performance

A facile and scalable method to synthesize PEGylated PDMAEMA for gene delivery

In recent years, cationic polymer vectors have been viewed as a promising method for delivering nucleic acids. With the advancement of synthetic polymer chemistry, we can control chemical structures and properties to enhance the efficacy of gene delivery. Herein, a facile, cost-effective, and scalable method was developed to synthesize PEGylated PDMAEMA polymers (PEO-PDMAEMA-PEO), where PEGylation could enable prolonged polyplexes circulation time in the blood stream. Two polymers of different molecular weights were synthesized, and polymer/eGFP polyplexes were prepared and characterized. The correlation between polymers' molecular weight and physicochemical properties (size and zeta potential) of polyplexes was investigated. Lipofectamine 2000, a commercial non-viral transfection reagent, was used as a standard control. PEO-PDMAEMA-PEO with higher molecular weight exhibited slightly better transfection efficiency than Lipofectamine 2000, and the cytotoxicity study proved that it could function as a safe gene vector. We believe that PEO-PDMAEMA-PEO could serve as a model to investigate more potential in the gene delivery area.

A new era of targeting cystic fibrosis with non-viral delivery of genomic medicines

Cystic fibrosis (CF) is a complex genetic respiratory disorder that necessitates innovative gene delivery strategies to address the mutations in the gene. This review delves into the promises and challenges of non-viral gene delivery for CF therapy and explores strategies to overcome these hurdles. Several emerging technologies and nucleic acid cargos for CF gene therapy are discussed. Novel formulation approaches including lipid and polymeric nanoparticles promise enhanced delivery through the CF mucus barrier, augmenting the potential of non-viral strategies. Additionally, safety considerations and regulatory perspectives play a crucial role in navigating the path toward clinical translation of gene therapy.

Closing the Gap between Experiment and Simulation─A Holistic Study on the Complexation of Small Interfering RNAs with Polyethylenimine

Rational design is pivotal in the modern development of nucleic acid nanocarrier systems. With the rising prominence of polymeric materials as alternatives to lipid-based carriers, understanding their structure-function relationships becomes paramount. Here, we introduce a newly developed coarse-grained model of polyethylenimine (PEI) based on the Martini 3 force field. This model facilitates molecular dynamics simulations of true-sized PEI molecules, exemplified by molecules with molecular weights of 1.3, 5, 10, and 25 kDa, with degrees of branching between 50.0 and 61.5%. We employed this model to investigate the thermodynamics of small interfering RNA (siRNA) complexation with PEI. Our simulations underscore the pivotal role of electrostatic interactions in the complexation process. Thermodynamic analyses revealed a stronger binding affinity with increased protonation, notably in acidic (endosomal) pH, compared to neutral conditions. Furthermore, the molecular weight of PEI was found to be a critical determinant of binding dynamics: smaller PEI molecules closely enveloped the siRNA, whereas larger ones extended outward, facilitating the formation of complexes with multiple RNA molecules. Experimental validations, encompassing isothermal titration calorimetry and single-molecule fluorescence spectroscopy, aligned well with our computational predictions. Our findings not only validate the fidelity of our PEI model but also accentuate the importance of in silico data in the rational design of polymeric drug carriers. The synergy between computational predictions and experimental validations, as showcased here, signals a refined and precise approach to drug carrier design.

Pulmonary siRNA Delivery with Sophisticated Amphiphilic Poly(Spermine Acrylamides) for the Treatment of Lung Fibrosis

RNA interference (RNAi) is an efficient strategy to post-transcriptionally silence gene expression. While all siRNA drugs on the market target the liver, the lung offers a variety of currently undruggable targets, which can potentially be treated with RNA therapeutics. To achieve this goal, the synthesis of poly(spermine acrylamides) (P(SpAA) is reported herein. Polymers are prepared via polymerization of N-acryloxysuccinimide (NAS) and afterward this active ester is converted into spermine-based pendant groups. Copolymerizations with decylacrylamide are employed to increase the hydrophobicity of the polymers. After deprotection, polymers show excellent siRNA encapsulation to obtain perfectly sized polyplexes at very low polymer/RNA ratios. In vitro 2D and 3D cell culture, ex vivo and in vivo experiments reveal superior properties of amphiphilic spermine-copolymers with respect to delivery of siRNA to lung cells in comparison to commonly used lipid-based transfection agents. In line with the in vitro results, siRNA delivery to human lung explants confirm more efficient gene silencing of protease-activated receptor 2 (PAR2), a G protein-coupled receptor involved in fibrosis. This study reveals the importance of the balance between efficient polyplex formation, cellular uptake, gene knockdown, and toxicity for efficient siRNA delivery in vitro, in vivo, and in fibrotic human lung tissue ex vivo.

Recent Advances in Engineering Carriers for siRNA Delivery

RNA interference (RNAi) technology has been a promising treatment strategy for combating intractable diseases. However, the applications of RNAi in clinical are hampered by extracellular and intracellular barriers. To overcome these barriers, various siRNA delivery systems have been developed in the past two decades. The first approved RNAi therapeutic, Patisiran (ONPATTRO) using lipids as the carrier, for the treatment of amyloidosis is one of the most important milestones. This has greatly encouraged researchers to work on creating new functional siRNA carriers. In this review, the recent advances in siRNA carriers consisting of lipids, polymers, and polymer-modified inorganic particles for cancer therapy are summarized. Representative examples are presented to show the structural design of the carriers in order to overcome the delivery hurdles associated with RNAi therapies. Finally, the existing challenges and future perspective for developing RNAi as a clinical modality will be discussed and proposed. It is believed that the addressed contributions in this review will promote the development of siRNA delivery systems for future clinical applications.

Exploring modified chitosan-based gene delivery technologies for therapeutic advancements

One of the critical steps in gene therapy is the successful delivery of the genes. Immunogenicity and toxicity are major issues for viral gene delivery systems. Thus, non-viral vectors are explored. A cationic polysaccharide like chitosan could be used as a nonviral gene delivery vector owing to its significant interaction with negatively charged nucleic acid and biomembrane, providing effective cellular uptake. However, the native chitosan has issues of targetability, unpacking ability, and solubility along with poor buffer capability, hence requiring modifications for effective use in gene delivery. Modified chitosan has shown that the "proton sponge effect" involved in buffering the endosomal pH results in osmotic swelling owing to the accumulation of a greater amount of proton and chloride along with water. The major challenges include limited exploration of chitosan as a gene carrier, the availability of high-purity chitosan for toxicity reduction, and its immunogenicity. The genetic drugs are in their infancy phase and require further exploration for effective delivery of nucleic acid molecules as FDA-approved marketed formulations soon.

Optimization of Lung Surfactant Coating of siRNA Polyplexes for Pulmonary Delivery

PURPOSE

The aim of this study was to understand how coating with a pulmonary surfactant, namely Alveofact, affects the physicochemical parameters as well as in vitro behavior of polyethylenimine (PEI) polyplexes for pulmonary siRNA delivery.

METHODS

Alveofact-coated polyplexes were prepared at different Alveofact:PEI coating ratios and analyzed in terms of size, PDI and zeta potential as well as morphology by transmission electron microscopy. The biological behavior was evaluated in a lung epithelial cell line regarding cell viability, cellular uptake via flow cytometry and gene downregulation by qRT-PCR. Furthermore, a 3D ALI culture model was established to test the mucus diffusion and cellular uptake by confocal microscopy as well as gene silencing activity by qRT-PCR.

RESULTS

After optimizing the coating process by testing different Alveofact:PEI coating ratios, a formulation with suitable parameters for lung delivery was obtained. In lung epithelial cells, Alveofact-coated polyplexes were well tolerated and internalized. Furthermore, the coating improved the siRNA-mediated gene silencing efficiency. Alveofact-coated polyplexes were then tested on a 3D air-liquid interface (ALI) culture model that, by expressing tight junctions and secreting mucus, resembles important traits of the lung epithelium. Here, we identified the optimal Alveofact:PEI coating ratio to achieve diffusion through the mucus layer while retaining gene silencing activity. Interestingly, the latter underlined the importance of establishing appropriate in vitro models to achieve more consistent results that better predict the in vivo activity.

CONCLUSION

The addition of a coating with pulmonary surfactant to polymeric cationic polyplexes represents a valuable formulation strategy to improve local delivery of siRNA to the lungs.

Delivery of nucleic acids using nanomaterials

The increasing number of approved nucleic acid therapeutics demonstrates the potential for the prevention and treatment of a broad spectrum of diseases. This trend underscores the significant impact and promise of nucleic acid-based treatments in the field of medicine. Nevertheless, employing nucleic acids as therapeutics is challenging due to their susceptibility to degradation by nucleases and their unfavorable physicochemical characteristics that hinder delivery into cells. Appropriate vectors play a pivotal role in improving nucleic acid stability and delivering nucleic acids into specific cells. The maturation of delivery systems has led to breakthroughs in the development of therapeutics based on nucleic acids such as DNA, siRNA, and mRNA. Non-viral vectors have gained prominence among the myriad of nanomaterials due to low immunogenicity, ease of manufacturing, and simplicity of cost-effective, large-scale production. Here, we provide an overview of the recent advancements in nanomaterials for nucleic acid delivery. Specifically, we give a detailed introduction to the characteristics of polymers, lipids, and polymer-lipid hybrids, and provide comprehensive descriptions of their applications in nucleic acid delivery. Also, biological barriers, administration routes, and strategies for organ-selective delivery of nucleic acids are discussed. In summary, this review offers insights into the rational design of next-generation delivery vectors for nucleic acid delivery.

Modification of Branched Poly(ethylene imine) with d-Fructose for Selective Delivery of siRNA into Human Breast Cancer Cells

Branched poly(ethylene imine) (bPEI) is frequently used in RNA interference (RNAi) experiments as a cationic polymer for the delivery of small interfering RNA (siRNA) because of its ability to form stable polyplexes that facilitate siRNA uptake. However, the use of bPEI in gene delivery is limited by its cytotoxicity and a need for target specificity. In this work, bPEI is modified with d-fructose to improve biocompatibility and target breast cancer cells through the overexpressed GLUT5 transporter. Fructose-substituted bPEI (Fru-bPEI) is accessible in three steps starting from commercially available protected fructopyranosides and bPEI. Several polymers with varying molecular weights, degrees of substitution, and linker positions on d-fructose (C1 and C3) are synthesized and characterized with NMR spectroscopy, size exclusion chromatography, and elemental analysis. In vitro biological screenings show significantly reduced cytotoxicity of 10 kDa bPEI after fructose functionalization, specific uptake of siRNA polyplexes, and targeted knockdown of green fluorescent protein (GFP) in triple-negative breast cancer cells (MDA-MB-231) compared to noncancer cells (HEK293T).

Delivery systems of therapeutic nucleic acids for the treatment of acute lung injury/acute respiratory distress syndrome

Acute lung injury (ALI)/ acute respiratory distress syndrome (ARDS) is a devastating inflammatory lung disease with a high mortality rate. ALI/ARDS is induced by various causes, including sepsis, infections, thoracic trauma, and inhalation of toxic reagents. Corona virus infection disease-19 (COVID-19) is also a major cause of ALI/ARDS. ALI/ARDS is characterized by inflammatory injury and increased vascular permeability, resulting in lung edema and hypoxemia. Currently available treatments for ALI/ARDS are limited, but do include mechanical ventilation for gas exchange and treatments supportive of reduction of severe symptoms. Anti-inflammatory drugs such as corticosteroids have been suggested, but their clinical effects are controversial with possible side-effects. Therefore, novel treatment modalities have been developed for ALI/ARDS, including therapeutic nucleic acids. Two classes of therapeutic nucleic acids are in use. The first constitutes knock-in genes for encoding therapeutic proteins such as heme oxygenase-1 (HO-1) and adiponectin (APN) at the site of disease. The other is oligonucleotides such as small interfering RNAs and antisense oligonucleotides for knock-down expression of target genes. Carriers have been developed for efficient delivery for therapeutic nucleic acids into the lungs based on the characteristics of the nucleic acids, administration routes, and targeting cells. In this review, ALI/ARDS gene therapy is discussed mainly in terms of delivery systems. The pathophysiology of ALI/ARDS, therapeutic genes, and their delivery strategies are presented for development of ALI/ARDS gene therapy. The current progress suggests that selected and appropriate delivery systems of therapeutic nucleic acids into the lungs may be useful for the treatment of ALI/ARDS.

Comparison of tyrosine-modified low molecular weight branched and linear polyethylenimines for siRNA delivery

Polyethylenimines (PEIs) have been previously introduced for siRNA delivery. In particular, in the case of higher molecular weight PEIs, this is associated with toxicity, while low molecular weight PEIs are often insufficient for siRNA complexation. The tyrosine-modification of PEIs has been shown to enhance PEI efficacy and biocompatibility. This paper evaluates a set of tyrosine-modified low molecular weight linear or branched polyethylenimines as efficient carriers of siRNA. Complexation efficacies and biophysical complex properties were analyzed by zeta potential, dynamic light scattering and circular dichroism measurements as well as gel electrophoresis. Biological knockdown was studied in 2 D cell culture and 3 D ex vivo tissue slice air-liquid interface culture. The results demonstrate that siRNAs were able to form stable complexes with all tested polymers. Complexation was able to protect siRNA from degradation by RNase and to mediate target gene knockdown, as determined on the mRNA level and in PC3-Luc3/EGFP and HCT116-Luc3/EGFP expressing reporter cells on the protein level, using flow cytometry and confocal microscopy. The direct comparison of the studied polymers revealed differences in biological efficacies. Moreover, the tyrosine-modified PEIs showed high biocompatibility, as determined by LDH release and mitochondria integrity (J-aggregate assay) as well as caspase 3/7 (apoptosis) and H₂O₂ levels (ROS). In 3 D tissue slices, complexes based on LP10Y proved to be most efficient, by combining tissue penetration with efficient gene expression knockdown.

siRNA-based nanotherapeutics as emerging modalities for immune-mediated diseases: A preliminary review

Immune‐mediated diseases (IMDs) are chronic conditions that have an immune‐mediated etiology. Clinically, these diseases appear to be unrelated, but pathogenic pathways have been shown to connect them. While inflammation is a common occurrence in the body, it may either stimulate a favorable immune response to protect against harmful signals or cause illness by damaging cells and tissues. Nanomedicine has tremendous promise for regulating inflammation and treating IMIDs. Various nanoparticles coated with nanotherapeutics have been recently fabricated for effective targeted delivery to inflammatory tissues. RNA interference (RNAi) offers a tremendous genetic approach, particularly if traditional treatments are ineffective against IMDs. In cells, several signaling pathways can be suppressed by using RNAi, which blocks the expression of particular messenger RNAs. Using this molecular approach, the undesirable effects of anti‐inflammatory medications can be reduced. Still, there are many problems with using short‐interfering RNAs (siRNAs) to treat IMDs, including poor localization of the siRNAs in target tissues, unstable gene expression, and quick removal from the blood. Nanotherapeutics have been widely used in designing siRNA‐based carriers because of the restricted therapy options for IMIDs. In this review, we have discussed recent trends in the fabrication of siRNA nanodelivery systems, including lipid‐based siRNA nanocarriers, liposomes, and cationic lipids, stable nucleic acid‐lipid particles, polymeric‐based siRNA nanocarriers, polyethylenimine (PEI)‐based nanosystems, chitosan‐based nanoformulations, inorganic material‐based siRNA nanocarriers, and hybrid‐based delivery systems. We have also introduced novel siRNA‐based nanocarriers to control IMIDs, such as pulmonary inflammation, psoriasis, inflammatory bowel disease, ulcerative colitis, rheumatoid arthritis, etc. This study will pave the way for new avenues of research into the diagnosis and treatment of IMDs.

Can pulmonary RNA delivery improve our pandemic preparedness?

The coronavirus pandemic has changed our perception of RNA medicines, and RNA vaccines have revolutionized our pandemic preparedness. But are we indeed prepared for the next variant or the next emerging virus? How can we prepare? And what does the role of inhaled antiviral RNA play in this regard? When the pandemic started, I rerouted much of the ongoing inhaled RNA delivery research in my group towards the inhibition and treatment of respiratory viral infections. Two years later, I have taken the literature, past and ongoing clinical trials into consideration and have gained new insights based on our collaborative research which I will discuss in this oration.

Inhibition of SARS-CoV-2 replication in the lung with siRNA/VIPER polyplexes

SARS-CoV-2 has been the cause of a global pandemic since 2019 and remains a medical urgency. siRNA-based therapies are a promising strategy to fight viral infections. By targeting a specific region of the viral genome, siRNAs can efficiently downregulate viral replication and suppress viral infection. However, to achieve the desired therapeutic activity, siRNA requires a suitable delivery system. The VIPER (virus-inspired polymer for endosomal release) block copolymer has been reported as promising delivery system for both plasmid DNA and siRNA in the past years. It is composed of a hydrophilic block for condensation of nucleic acids as well as a hydrophobic, pH-sensitive block that, at acidic pH, exposes the membrane lytic peptide melittin, which enhances endosomal escape. In this study, we aimed at developing a formulation for pulmonary administration of siRNA to suppress SARS-CoV-2 replication in lung epithelial cells. After characterizing siRNA/VIPER polyplexes, the activity and safety profile were confirmed in a lung epithelial cell line. To further investigate the activity of the polyplexes in a more sophisticated cell culture system, an air-liquid interface (ALI) culture was established. siRNA/VIPER polyplexes reached the cell monolayer and penetrated through the mucus layer secreted by the cells. Additionally, the activity against wild-type SARS-CoV-2 in the ALI model was confirmed by qRT-PCR. To investigate translatability of our findings, the activity against SARS-CoV-2 was tested ex vivo in human lung explants. Here, siRNA/VIPER polyplexes efficiently inhibited SARS-CoV-2 replication. Finally, we verified the delivery of siRNA/VIPER polyplexes to lung epithelial cells in vivo, which represent the main cellular target of viral infection in the lung. In conclusion, siRNA/VIPER polyplexes efficiently delivered siRNA to lung epithelial cells and mediated robust downregulation of viral replication both in vitro and ex vivo without toxic or immunogenic side effects in vivo, demonstrating the potential of local siRNA delivery as a promising antiviral therapy in the lung.

Modification of Lipid-Based Nanoparticles: An Efficient Delivery System for Nucleic Acid-Based Immunotherapy

Lipid-based nanoparticles (LBNPs) are biocompatible and biodegradable vesicles that are considered to be one of the most efficient drug delivery platforms. Due to the prominent advantages, such as long circulation time, slow drug release, reduced toxicity, high transfection efficiency, and endosomal escape capacity, such synthetic nanoparticles have been widely used for carrying genetic therapeutics, particularly nucleic acids that can be applied in the treatment for various diseases, including congenital diseases, cancers, virus infections, and chronic inflammations. Despite great merits and multiple successful applications, many extracellular and intracellular barriers remain and greatly impair delivery efficacy and therapeutic outcomes. As such, the current state of knowledge and pitfalls regarding the gene delivery and construction of LBNPs will be initially summarized. In order to develop a new generation of LBNPs for improved delivery profiles and therapeutic effects, the modification strategies of LBNPs will be reviewed. On the basis of these developed modifications, the performance of LBNPs as therapeutic nanoplatforms have been greatly improved and extensively applied in immunotherapies, including infectious diseases and cancers. However, the therapeutic applications of LBNPs systems are still limited due to the undesirable endosomal escape, potential aggregation, and the inefficient encapsulation of therapeutics. Herein, we will review and discuss recent advances and remaining challenges in the development of LBNPs for nucleic acid-based immunotherapy.

The quest for a better fight: How can nanomaterials address the current therapeutic and diagnostic obstacles in the fight against COVID-19?

The inexorable coronavirus disease 2019 (COVID-19) pandemic with around 226 million people diagnosed and approximately 4.6 million deaths, is still moving toward more frightening statistics, calling for the urgent need to explore solutions for the current challenges in therapeutic and diagnostic approaches. The challenges associated with existing therapeutics in COVID-19 include lack of in vivo stability, efficacy, and safety. Nanoparticles (NPs) can offer a handful of tools to tackle these problems by enabling efficacious and safe delivery of both virus- and host-directed therapeutics. Furthermore, they can enable maximized clinical outcome while eliminating the chance of resistance to therapy by tissue-targeting and concomitant delivery of multiple therapeutics. The promising application of NPs as vaccine platforms is reflected by the major advances in developing novel COVID-19 vaccines. Two of the most critical COVID-19 vaccines are mRNA-based vaccines delivered via NPs, making them the first FDA-approved mRNA vaccines. Besides, NPs have been deployed as simple, rapid, and precise tools for point of care disease diagnosis. Not enough said NPs can also be exploited in novel ways to expedite the drug discovery process. In light of the above, this review discusses how NPs can overcome the hurdles associated with therapeutic and diagnostic approaches against COVID-19.

Targeting genomic SARS-CoV-2 RNA with siRNAs allows efficient inhibition of viral replication and spread

A promising approach to tackle the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) could be small interfering (si)RNAs. So far it is unclear, which viral replication steps can be efficiently inhibited with siRNAs. Here, we report that siRNAs can target genomic RNA (gRNA) of SARS-CoV-2 after cell entry, and thereby terminate replication before start of transcription and prevent virus-induced cell death. Coronaviruses replicate via negative sense RNA intermediates using a unique discontinuous transcription process. As a result, each viral RNA contains identical sequences at the 5′ and 3′ end. Surprisingly, siRNAs were not active against intermediate negative sense transcripts. Targeting common sequences shared by all viral transcripts allowed simultaneous suppression of gRNA and subgenomic (sg)RNAs by a single siRNA. The most effective suppression of viral replication and spread, however, was achieved by siRNAs that targeted open reading frame 1 (ORF1) which only exists in gRNA. In contrast, siRNAs that targeted the common regions of transcripts were outcompeted by the highly abundant sgRNAs leading to an impaired antiviral efficacy. Verifying the translational relevance of these findings, we show that a chemically modified siRNA that targets a highly conserved region of ORF1, inhibited SARS-CoV-2 replication ex vivo in explants of the human lung. Our work encourages the development of siRNA-based therapies for COVID-19 and suggests that early therapy start, or prophylactic application, together with specifically targeting gRNA, might be key for high antiviral efficacy.

The mixture of siRNAs targeted to IL-4 and IL-13 genes effectively reduces the airway hyperreactivity and allergic inflammation in a mouse model of asthma

Bronchial asthma (BA) is one of the most common chronic inflammatory disease of airways. There are huge experimental data indicating that Th2-cytokines IL-4 and IL-13 play a key role in BA pathogenesis. They are implicated in the IgE synthesis, eosinophil infiltration to the lungs and in the development of airway hyperreactivity (AHR), that makes these cytokines the promising targets. Neutralization of IL-4 and IL-13 or its common receptor chain (IL-4Rα) by monoclonal antibodies substantially reduce asthma symptoms. RNA interference provides a novel method for regulation of gene expression by siRNA molecules. In this study we evaluated whether the siRNA targeted to IL-4 and IL-13 reduce BA symptoms in mice model. Experimental BA was induced in BALB/c mice by sensitization to ovalbumin allergen followed by intranasal challenge. The intranasal delivery of siRNAs targeted to IL-4 and IL-13 inhibited the lung expression of these cytokines by more than 50% that led to the attenuation of AHR and pulmonary inflammation; the quantity of eosinophils in lungs which are one of the major inflammatory cells involved in allergic asthma pathogenesis decreased by more than 50% after siRNA treatment. These data support the possibility of a dual IL-4 and IL-13 inhibition by locally delivered siRNAs which in turn leads to the suppression of allergen-induced pulmonary inflammation and AHR.

Targeting Inflammasome Activation in COVID-19: Delivery of RNA Interference-Based Therapeutic Molecules

Mortality and morbidity associated with COVID-19 continue to be significantly high worldwide, owing to the absence of effective treatment strategies. The emergence of different variants of SARS-CoV-2 is also a considerable source of concern and has led to challenges in the development of better prevention and treatment strategies, including vaccines. Immune dysregulation due to pro-inflammatory mediators has worsened the situation in COVID-19 patients. Inflammasomes play a critical role in modulating pro-inflammatory cytokines in the pathogenesis of COVID-19 and their activation is associated with poor clinical outcomes. Numerous preclinical and clinical trials for COVID-19 treatment using different approaches are currently underway. Targeting different inflammasomes to reduce the cytokine storm, and its associated complications, in COVID-19 patients is a new area of research. Non-coding RNAs, targeting inflammasome activation, may serve as an effective treatment strategy. However, the efficacy of these therapeutic agents is highly dependent on the delivery system. MicroRNAs and long non-coding RNAs, in conjunction with an efficient delivery vehicle, present a potential strategy for regulating NLRP3 activity through various RNA interference (RNAi) mechanisms. In this regard, the use of nanomaterials and other vehicle types for the delivery of RNAi-based therapeutic molecules for COVID-19 may serve as a novel approach for enhancing drug efficacy. The present review briefly summarizes immune dysregulation and its consequences, the roles of different non-coding RNAs in regulating the NLRP3 inflammasome, distinct types of vectors for their delivery, and potential therapeutic targets of microRNA for treatment of COVID-19.

Nanoparticles for local delivery of siRNA in lung therapy

An overview of the application of natural and synthetic, non-viral vectors for oligonucleotide delivery into the lung is presented in this review, with a special focus on lung cancer. Due to the specificity of the respiratory tract, its structure and natural barriers, the administration of drugs (especially those based on nucleic acids) is a particular challenge. Among widely tested non-viral drug and oligonucleotides carriers, synthetic polymers seem to be most promising. Unique properties of these nanoparticles allow for essentially unlimited possibilities regarding their design and modification. This gives hope that optimal nanoparticles with ideal nucleic acid carrier properties for lung cancer therapy will eventually emanate.

Chitosan oligosaccharide modified liposomes enhance lung cancer delivery of paclitaxel

Lung cancer is one of the leading causes of cancer-related death worldwide. Various therapeutic failed in the effective treatment of the lung cancer due to their limited accumulation and exposure in tumors. In order to promote the chemotherapeutics delivery to lung tumor, we introduced chitosan oligosaccharide (CSO) modification on the liposomes. CSO conjugated Pluronic P123 polymers with different CSO grafting amounts, called as CP50 and CP20, were synthesized and used to prepare CSO modified liposomes (CP50-LSs and CP20-LSs). CP50-LSs and CP20-LSs displayed significantly enhanced cellular uptake in A549 cells in vitro as well as superior tumor accumulation in vivo compared with non-CSO modified liposomes (P-LSs). This phenomenon was related to the increased affinity between CSO modified liposomes and tumor cells following massive adsorption of collagen, which was highly expressed in lung tumors. In the A549 tumor-bearing mouse model, intravenous injection of paclitaxel (PTX)-loaded CP50-LSs every 3 days for 21 days resulted in optimal antitumor therapeutic performance with an inhibition rate of 86.4%. These results reveal that CSO modification provides promising applicability for nanomedicine design in the lung cancer treatment.

Recent Advances in the Delivery Carriers and Chemical Conjugation Strategies for Nucleic Acid Drugs

With the development of new anticancer medicines, novel modalities are being explored for cancer treatment. For many years, conventional modalities, such as small chemical drugs and antibody drugs, have worked by "inhibiting the function" of target proteins. In recent years, however, nucleic acid drugs, such as ASOs and siRNAs, have attracted attention as a new modality for cancer treatment because nucleic acid drugs can directly promote the "loss of function" of target genes. Recently, nucleic acid drugs for use in cancer therapy have been extensively developed and some of them have currently been under investigation in clinical trials. To develop novel nucleic acid drugs for cancer treatment, it is imperative that cancer researchers, including ourselves, cover and understand those latest findings. In this review, we introduce and provide an overview of various DDSs and ligand modification technologies that are being employed to improve the success and development of nucleic acid drugs, then we also discuss the future of nucleic acid drug developments for cancer therapy. It is our belief this review will increase the awareness of nucleic acid drugs worldwide and build momentum for the future development of new cancer-targeted versions of these drugs.

Optimization of PEGylated KL4 Peptide for siRNA Delivery with Improved Pulmonary Tolerance

Pulmonary delivery of small interfering RNA (siRNA) is a promising therapeutic strategy for treating various respiratory diseases but an effective carrier for the delivery of siRNA into the cells of the lungs and a robust gene-silencing effect is still lacking. Previously, we reported that the KL4 peptide, a synthetic cationic peptide with a repeating KLLLL sequence, can mediate effective siRNA transfection in lung epithelial cells but its high hydrophobic leucine content, and hence poor water solubility, limits its application as a delivery vector. Here, we show that the covalent attachment of monodisperse poly(ethylene glycol) (PEG) improves the solubility of KL4 and the uptake of its complex with siRNA into lung epithelial cells, such that very robust silencing is produced. All PEGylated KL4 peptides, with PEG length varying between 6 and 24 monomers, could bind and form nanosized complexes with siRNA, but the interaction between siRNA and peptides became weaker as the PEG chain length increased. All PEGylated KL4 peptides exhibited satisfactory siRNA transfection efficiency on three human lung epithelial cell lines, including A549 cells, Calu-3 cells, and BEAS-2B cells. The PEG₁₂KL4 peptide, which contains 12 monomers of PEG, was optimal for siRNA delivery and also demonstrated a low risk of inflammatory response and toxicity in vivo following pulmonary administration.

Polymeric Delivery of Therapeutic Nucleic Acids

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

siRNA Therapeutics against Respiratory Viral Infections-What Have We Learned for Potential COVID-19 Therapies?

Acute viral respiratory tract infections (AVRIs) are a major burden on human health and global economy and amongst the top five causes of death worldwide resulting in an estimated 3.9 million lives lost every year. In addition, new emerging respiratory viruses regularly cause outbreaks such as SARS-CoV-1 in 2003, the "Swine flu" in 2009, or most importantly the ongoing SARS-CoV-2 pandemic, which intensely impact global health, social life, and economy. Despite the prevalence of AVRIs and an urgent need, no vaccines-except for influenza-or effective treatments were available at the beginning of the COVID-19 pandemic. However, the innate RNAi pathway offers the ability to develop nucleic acid-based antiviral drugs. siRNA sequences against conserved, essential regions of the viral genome can prevent viral replication. In addition, viral infection can be averted prophylactically by silencing host genes essential for host-viral interactions. Unfortunately, delivering siRNAs to their target cells and intracellular site of action remains the principle hurdle toward their therapeutic use. Currently, siRNA formulations and chemical modifications are evaluated for their delivery. This progress report discusses the selection of antiviral siRNA sequences, delivery techniques to the infection sites, and provides an overview of antiviral siRNAs against respiratory viruses.

Pulmonary siRNA delivery for lung disease: Review of recent progress and challenges

Lung diseases are a leading cause of mortality worldwide and there exists urgent need for new therapies. Approval of the first siRNA treatments in humans has opened the door for further exploration of this therapeutic strategy for other disease states. Pulmonary delivery of siRNA-based biopharmaceuticals offers the potential to address multiple unmet medical needs in lung-related diseases because of the specific physiology of the lung and characteristic properties of siRNA. Inhalation-based siRNA delivery designed for efficient, targeted delivery to specific cells within the lung holds great promise. Efficient delivery of siRNA directly to the lung, however, is relatively complex. This review focuses on the barriers that impact pulmonary siRNA delivery and successful recent approaches to advance this field forward. We focus on the pulmonary barriers that affect siRNA delivery, the disease-dependent pathological changes and their role in pulmonary disease and impact on siRNA delivery, as well as the recent development on the pulmonary siRNA delivery systems.

Poly(lactide-co-glycolide) Nanoparticles Mediate Sustained Gene Silencing and Improved Biocompatibility of siRNA Delivery Systems in Mouse Lungs after Pulmonary Administration

Pulmonary delivery of small interfering RNA (siRNA)-based drugs is promising in treating severe lung disorders characterized by the upregulated expression of disease-causing genes. Previous studies have shown that the sustained siRNA release in vitro can be achieved from polymeric matrix nanoparticles based on poly(lactide-co-glycolide) (PLGA) loaded with lipoplexes (LPXs) composed of cationic lipid and anionic siRNA (lipid-polymer hybrid nanoparticles, LPNs). Yet, the in vivo efficacy, potential for prolonging the pharmacological effect, disposition, and safety of LPNs after pulmonary administration have not been investigated. In this study, siRNA against enhanced green fluorescent protein (EGFP-siRNA) was either assembled with 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) to form LPX or co-entrapped with DOTAP in PLGA nanoparticles to form LPNs. The disposition and clearance of LPXs and LPNs in mouse lungs were studied after intratracheal administration by using single-photon emission computed tomography/computed tomography (SPECT/CT) and gamma counting. Fluorescence spectroscopy, Western blot, and confocal laser scanning microscopy were used to evaluate the silencing of the EGFP expression mediated by the LPXs and LPNs after intratracheal administration to transgenic mice expressing the EGFP gene. The in vivo biocompatibility of LPXs and LPNs was investigated by measuring the cytokine level, total cell counts in bronchoalveolar lavage fluid, and observing the lung tissue histology section. The results showed that the silencing of the EGFP expression mediated by LPNs after pulmonary administration was both prolonged and enhanced as compared to LPXs. This may be attributed to the sustained release characteristics of PLGA, and the prolonged retention in the lung tissue of the colloidally more stable LPNs in comparison to LPXs, as indicated by SPECT/CT. The presence of PLGA effectively alleviated the acute inflammatory effect of cationic lipids to the lungs. This study suggests that PLGA-based LPNs may present an effective formulation strategy to mediate sustained gene silencing effects in the lung via pulmonary administration.

Combined Chemisorption and Complexation Generate siRNA Nanocarriers with Biophysics Optimized for Efficient Gene Knockdown and Air-Blood Barrier Crossing

Current nucleic acid (NA) nanotherapeutic approaches face challenges because of shortcomings such as limited control on loading efficiency, complex formulation procedure involving purification steps, low load of NA cargo per nanoparticle, endosomal trapping, and hampered release inside the cell. When combined, these factors significantly limit the amount of biologically active NA delivered per cell in vitro, delivered dosages in vivo for a prolonged biological effect, and the upscalability potential, thereby warranting early consideration in the design and developmental phase. Here, we report a versatile nanotherapeutic platform, termed auropolyplexes, for improved and efficient delivery of small interfering RNA (siRNA). Semitelechelic, thiolated linear polyethylenimine (PEI) was chemisorbed onto gold nanoparticles to endow them with positive charge. A simple two-step complexation method offers tunable loading of siRNA at concentrations relevant for in vivo studies and the flexibility for inclusion of multiple functionalities without any purification steps. SiRNA was electrostatically complexed with these cationic gold nanoparticles and further condensed with polycation or polyethyleneglycol-polycation conjugates. The resulting auropolyplexes ensured complete complexation of siRNA into nanoparticles with a high load of ∼15,500 siRNA molecules/nanoparticle. After efficient internalization into the tumor cell, an 80% knockdown of the luciferase reporter gene was achieved. Auropolyplexes were applied intratracheally in Balb/c mice for pulmonary delivery, and their biodistribution were studied spatio-temporally and quantitatively by optical tomography. Auropolyplexes were well tolerated with ∼25% of the siRNA dose remaining in the lungs after 24 h. Importantly, siRNA was released from auropolyplexes in vivo and a fraction also crossed the air-blood barrier, which was then excreted via kidneys, whereas >97% of gold nanoparticles were retained in the lung. Linear PEI-based auropolyplexes offer a combination of successful endosomal escape and better biocompatibility profile in vivo. Taken together, combined chemisorption and complexation endow auropolyplexes with crucial biophysical attributes, enabling a versatile and upscalable nanogold-based platform for siRNA delivery in vitro and in vivo.

Nanocarriers in effective pulmonary delivery of siRNA: current approaches and challenges

Research on siRNA is increasing due to its wide applicability as a therapeutic agent in irreversible medical conditions. siRNA inhibits expression of the specific gene after its delivery from formulation to cytosol region of a cell. RNAi (RNA interference) is a mechanism by which siRNA is silencing gene expression for a particular disease. Numerous studies revealed that naked siRNA delivery is not preferred due to instability and poor pharmacokinetic performance. Nanocarriers based delivery of siRNA has the advantage to overcome physiological barriers and protect the integrity of siRNA from degradation by RNAase. Various diseases like lung cancer, cystic fibrosis, asthma, etc can be treated effectively by local lung delivery. The selective targeted therapeutic action in diseased organ and least off targeted cytotoxicity are the key benefits of pulmonary delivery. The current review highlights recent developments in pulmonary delivery of siRNA with novel nanosized formulation approach with the proven in vitro/in vivo applications.

In Vitro and In Vivo Assessment of PEGylated PEI for Anti-IL-8/CxCL-1 siRNA Delivery to the Lungs

Inhalation offers a means of rapid, local delivery of siRNA to treat a range of autoimmune or inflammatory respiratory conditions. This work investigated the potential of a linear 10 kDa Poly(ethylene glycol) (PEG)-modified 25 kDa branched polyethyleneimine (PEI) (PEI-LPEG) to effectively deliver siRNA to airway epithelial cells. Following optimization with anti- glyceraldehyde 3-phosphate dehydrogenase (GAPDH) siRNA, PEI and PEI-LPEG anti-IL8 siRNA nanoparticles were assessed for efficacy using polarised Calu-3 human airway epithelial cells and a twin stage impinger (TSI) in vitro lung model. Studies were then advanced to an in vivo lipopolysaccharide (LPS)-stimulated rodent model of inflammation. In parallel, the suitability of the siRNA-loaded nanoparticles for nebulization using a vibrating mesh nebuliser was assessed. The siRNA nanoparticles were nebulised using an Aerogen^® Pro vibrating mesh nebuliser and characterised for aerosol output, droplet size and fine particle fraction. Only PEI anti-IL8 siRNA nanoparticles were capable of significant levels of IL-8 knockdown in vitro in non-nebulised samples. However, on nebulization through a TSI, only PEI-PEG siRNA nanoparticles demonstrated significant decreases in gene and protein expression in polarised Calu-3 cells. In vivo, both anti-CXCL-1 (rat IL-8 homologue) nanoparticles demonstrated a decreased CXCL-1 gene expression in lung tissue, but this was non-significant. However, PEI anti-CXCL-1 siRNA-treated rats were found to have significantly less infiltrating macrophages in their bronchoalveolar lavage (BAL) fluid. Overall, the in vivo gene and protein inhibition findings indicated a result more reminiscent of the in vitro bolus delivery rather than the in vitro nebulization data. This work demonstrates the potential of nebulised PEI-PEG siRNA nanoparticles in modulating pulmonary inflammation and highlights the need to move towards more relevant in vitro and in vivo models for respiratory drug development.

Nanoparticle-Mediated Gene Silencing for Sensitization of Lung Cancer to Cisplatin Therapy

Platinum-based chemotherapy remains a mainstay treatment for the management of advanced non-small cell lung cancer. A key cellular factor that contributes to sensitivity to platinums is the 5'-3' structure-specific endonuclease excision repair cross-complementation group 1 (ERCC1)/ xeroderma pigmentosum group F (XPF). ERCC1/XPF is critical for the repair of platinum-induced DNA damage and has been the subject of intense research efforts to identify small molecule inhibitors of its nuclease activity for the purpose of enhancing patient response to platinum-based chemotherapy. As an alternative to small molecule inhibitors, small interfering RNA (siRNA) has often been described to be more efficient in interrupting protein-protein interactions. The goal of this study was therefore to determine whether biocompatible nanoparticles consisting of an amphiphilic triblock copolymer (polyethylenimine-polycaprolactone-polyethylene glycol (PEI-PCL-PEG)) and carrying siRNA targeted to ERCC1 and XPF made by microfluidic assembly are capable of efficient gene silencing and able to sensitize lung cancer cells to cisplatin. First, we show that our PEI-PCL-PEG micelleplexes carrying ERCC1 and XPF siRNA efficiently knocked down ERCC1/XPF protein expression to the same extent as the standard siRNA transfection reagent, Lipofectamine. Second, we show that our siRNA-carrying nanoparticles enhanced platinum sensitivity in a p53 wildtype model of non-small cell lung cancer in vitro. Our results suggest that nanoparticle-mediated targeting of ERCC1/XPF is feasible and could represent a novel therapeutic strategy for targeting ERCC1/XPF in vivo.

Intrapulmonary Cellular-Level Distribution of Inhaled Nanoparticles with Defined Functional Groups and Its Correlations with Protein Corona and Inflammatory Response

Concerns over the health risks associated with airborne exposure to ultrafine particles [PM0.1, or nanoparticles (NPs)] call for a comprehensive understanding in the interactions of inhaled NPs along their respiratory journey. We prepare a collection of polyethylene glycol-coated gold nanoparticles that bear defined functional groups commonly identified in atmospheric particulates (Au@PEG-X NPs, where X = OCH₃, COOH, NH₂, OH, or C₁₂H₂₅). Regardless of the functional group, these ∼50 nm NPs remain colloidally stable following aerosolization and incubation in bronchoalveolar lavage fluid (BALF), without pronouncedly crossing the air-blood barrier. The type of BALF proteins adhered onto the NPs is similar, but the composition of protein corona depends on functional group. By subjecting Balb/c mice to inhalation of Au@PEG-X NPs for 6 h, we demonstrate that the intrapulmonary distribution of NPs among the various types of cells (both found in BALF and isolated from the lavaged lung) and the acute inflammatory responses induced by inhalation are sensitive to the functional group of NPs and postinhalation period (0, 24, or 48 h). By evaluating the pairwise correlations between the three variables of "lung-nano" interactions (protein corona, intrapulmonary cellular-level distribution, and inflammatory response), we reveal strong statistical correlations between the (1) fractions of albumin or carbonyl reductase bound to NPs, (2) associations of inhaled NPs to neutrophils in BALF or macrophages in the lavaged lung, and (3) level of total protein in BALF. Our results provide insights into the effect of functional group on lung-nano interactions and health risks associated with inhalation of PM0.1.

Polymeric siRNA gene delivery - transfection efficiency versus cytotoxicity

Within the field of gene therapy, there is a considerable need for the development of non-viral vectors that are able to compete with the efficiency obtained by viral vectors, while maintaining a good toxicity profile and not inducing an immune response within the body. While there have been many reports of possible polymeric delivery systems, few of these systems have been successful in the clinical setting due to toxicity, systemic instability or gene regulation inefficiency, predominantly due to poor endosomal escape and cytoplasmic release. The objective of this review is to provide an overview of previously published polymeric non-coding RNA and, to a lesser degree, oligo-DNA delivery systems with emphasis on their positive and negative attributes, in order to provide insight in the numerous hurdles that still limit the success of gene therapy.

Coming in and Finding Out: Blending Receptor-Targeted Delivery and Efficient Endosomal Escape in a Novel Bio-Responsive siRNA Delivery System for Gene Knockdown in Pulmonary T Cells

RNA interference (RNAi) offers the potential to selectively silence disease-related genes in defined cell subsets. Translation into the clinical routine is, however, still hampered by the lack of efficient carrier systems for therapeutic siRNA, endosomal entrapment presenting a major hurdle. A promising siRNA delivery system has previously been developed on the base of polyethylenimine (PEI) and the targeting ligand transferrin (Tf) to specifically reach activated T cells in the lung. In the present work, the focus is on optimizing Tf-PEI polyplexes for gene knockdown in primary activated T cells by improving their endosomal escape properties. Blending of the conjugate with membrane lytic melittin significantly enhanced endosomal release and thereby cytoplasmic delivery, while maintaining selective T cell targeting abilities and overall cell tolerability. The gathered data furthermore demonstrate that melittin addition also distinctly improves several other essential particle characteristics, such as siRNA encapsulation efficiency and stability in lung lining fluids. In conclusion, this results in a novel upgraded siRNA delivery system that is not only able to specifically deliver its payload to the desired target cells via receptor-mediated endocytosis, but also shows enhanced release from endosomal vesicles in order to initiate RNAi in the cytoplasm.

Formulation of RNA interference-based drugs for pulmonary delivery: challenges and opportunities

With recent advances in the field of RNAi-based therapeutics, it is possible to make any target gene 'druggable', at least in principle. The present review focuses on aspects critical for pulmonary delivery of formulations of nucleic acid-based drugs. The first part introduces the therapeutic potential of RNAi-based drugs for the treatment of lung diseases. Subsequently, we discuss opportunities for formulation-enabled pulmonary delivery of RNAi drugs in light of key physicochemical properties and physiological barriers. In the following section, an overview is included of methodologies for imparting inhalable characteristics to nucleic acid formulations. Finally, we review one of the bottlenecks in the early preclinical testing of inhalable nucleic acid-based formulations, in other words, devices suitable for pulmonary administration of powder-based formulations in rodents.

Current Transport Systems and Clinical Applications for Small Interfering RNA (siRNA) Drugs

Small interfering RNAs (siRNAs) are an attractive new agent with potential as a therapeutic tool because of its ability to inhibit specific genes for many conditions, including viral infections and cancers. However, despite this potential, many challenges remain, including off-target effects, difficulties with delivery, immune responses, and toxicity. Traditional genetic vectors do not guarantee that siRNAs will silence genes in vivo. Rational design strategies, such as chemical modification, viral vectors, and non-viral vectors, including cationic liposomes, polymers, nanocarriers, and bioconjugated siRNAs, provide important opportunities to overcome these challenges. We summarize the results of research into vector delivery of siRNAs as a therapeutic agent from their design to clinical trials in ophthalmic diseases, cancers, respiratory diseases, and liver virus infections. Finally, we discuss the current state of siRNA delivery methods and the need for greater understanding of the requirements.

Biodegradable Polymers as a Noncoding miRNA Nanocarrier for Multiple Targeting Therapy of Human Hepatocellular Carcinoma

Therapeutic strategy based on the restoration of tumor suppressor-microRNAs (miRNAs) is a promising approach for cancer therapy, but the low delivery efficiency of miRNA remains a huge hurdle due to the lack of safe and efficient nonviral carriers. In this work, with the use of newly developed PEGylated biodegradable charged polyester-based vectors (PEG-BCPVs) as the carrier, the miR26a and miR122 codelivering therapeutic strategy (PEG-BCPVs/miR26a/miR122 as the delivery formulation) is successfully developed for efficient treatment of human hepatocellular carcinoma (HCC). In vitro study results show that PEG-BCPVs are capable of effectively facilitating miRNA cellular uptake via a cell endocytosis pathway. Consequently, the restoration of miR26a and miR122 remarkably inhibit the cell growth, migration, invasion, colony formation, and induced apoptosis of HepG2 cells. More importantly, the chemosensitivity of HepG2 to anticancer drug is also considerably enhanced. After treatment with the PEG-BCPV-based miRNA delivery system, the expression of the multiple targeted genes corresponding to miR26a and miR122 in HepG2 cells is greatly downregulated. Accordingly, the newly developed miRNA restoration therapeutic strategy via biodegradable PEG-BCPVs as the carrier should be a promising modality for combating HCC.

Nanomaterials-Based siRNA Delivery: Routes of Administration, Hurdles and Role of Nanocarriers

Ribonucleic acid interference (RNAi) is a potential alternative therapeutic approach to knock down the overexpression of genes in several disorders especially cancers with underlying genetic dysfunctions. For silencing of specific genes involved in cell cycle, small/short interfering ribonucleic acids (siRNAs) are being used clinically. The siRNA-based RNAi is more efficient, specific and safe antisense technology than other RNAi approaches. The route of siRNA administration for siRNA therapy depends on the targeted site. However, certain hurdles like poor stability of siRNA, saturation, off-target effect, immunogenicity, anatomical barriers and non-targeted delivery restrict the successful siRNA therapy. Thus, advancement of an effective, secure, and long-term delivery system is prerequisite to the medical utilization of siRNA. Polycationic nanocarriers mediated targeted delivery system is an ideal system to remove these hurdles and to increase the blood retention time and rate of intracellular permeability. In this chapter, we will mainly discuss the different biocompatible, biodegradable, non-toxic (organic, inorganic and hybrid) nanocarriers that encapsulate and shield the siRNA from the different harsh environment and provides the increased systemic siRNA delivery.

Corneal chemical burn treatment through a delivery system consisting of TGF-β1 siRNA: in vitro and in vivo

Chemical burns are major causes of corneal blindness. Transforming growth factor beta-1 (TGFβ₁) plays an important role in induction of corneal inflammation-related-fibrosis leading to the blindness. Here, a topical delivery system consisting anti-fibrotic TGF-β₁ siRNA, an inflammatory suppressing gene, was designed for treatment of corneal injuries. TGF-β₁ siRNA loaded in nanoparticles (NPs) made up of polyethyleneimine polymer demonstrated high fibroblast transfection efficiency. Moreover, TGF-β₁ and PDGF genes and ECM deposition were suppressed in isolated human corneal fibroblasts. NPs inhibited proliferation and transformation of fibroblasts to myofibroblasts by S-phase arrest and α-SMA suppression in vitro, respectively. The mentioned finding was also confirmed in vivo, addressing high wound-healing potential of prepared gene delivery system which was superior to conventional betamethasone treatment. Besides, CD4⁺ and α-SMA antibody staining showed inhibited angiogenesis and myofibroblast accumulation in treated corneas. This study opens a new way for treating corneal fibrosis through topical siRNA delivery.

RNAi-based therapeutics for lung cancer: biomarkers, microRNAs, and nanocarriers

INTRODUCTION

Despite the current advances in the discovery of the lung cancer biomarkers and, consequently, in the diagnosis, this pathology continues to be the primary cause of cancer-related death worldwide. In most cases, the illness is diagnosed in an advanced stage, which limits the current treatment options available and reduces the survival rate. Therefore, RNAi-based therapy arises as a promising option to treat lung cancer.

AREAS COVERED

This review provides an overview on the exploitation of lung cancer biology to develop RNAi-based therapeutics to be applied in the treatment of lung cancer. Furthermore, the review analyzes the main nanocarriers designed to deliver RNAi molecules and induce antitumoral effects in lung cancer, and provides updated information about current RNAi-based therapeutics for lung cancer in clinical trials.

EXPERT OPINION

RNAi-based therapy uses nanocarriers to perform a targeted and efficient delivery of therapeutic genes into lung cancer cells, by taking advantage of the known biomarkers in lung cancer. These therapeutic genes are key regulatory molecules of crucial cellular pathways involved in cell proliferation, migration, and apoptosis. Thereby, the characteristics and functionalization of the nanocarrier and the knowledge of lung cancer biology have direct influence in improving the therapeutic effect of this therapy.

Correlating quantitative tumor accumulation and gene knockdown using SPECT/CT and bioluminescence imaging within an orthotopic ovarian cancer model

Using an orthotopic model of ovarian cancer, we studied the delivery of siRNA in nanoparticles of tri-block copolymers consisting of hyperbranched polyethylenimine-graft-polycaprolactone-block-poly(ethylene glycol) (hyPEI-g-PCL-b-PEG) with and without a folic acid targeting ligand. A SKOV-3/LUC FRα overexpressing cell line was employed to mimic the clinical manifestations of ovarian cancer. Both targeted and non-targeted micelleplexes were able to effectively deliver siRNA to the primary tumor and its metastases, as measured by gamma scintillation counting and confocal microscopy. Stability of the micelleplexes was demonstrated with a serum albumin binding study. Regarding biodistribution, intravenous (I.V.) administration showed a slight advantage of FRα targeted over non-targeted micelleplex accumulation within the tumor. However, both formulations displayed significant liver uptake. On the other hand, intraperitoneally (I.P.) injected mice showed a modest 6% of the injected dose per gram (ID/g) uptake within the primary and most interestingly also in the metastatic lesions which subsequently resulted in a 62% knockdown of firefly luciferase expression in the tumor after a single injection. While this is, to the best of our knowledge, the first paper that correlates quantitative tumor accumulation in an orthotopic tumor model with in vivo gene silencing, these data demonstrate that PEI-g-PCL-b-PEG-Fol conjugates are a promising option for gene knockdown in ovarian cancer.

Chitosan in Non-Viral Gene Delivery: Role of Structure, Characterization Methods, and Insights in Cancer and Rare Diseases Therapies

Non-viral gene delivery vectors have lagged far behind viral ones in the current pipeline of clinical trials of gene therapy nanomedicines. Even when non-viral nanovectors pose less safety risks than do viruses, their efficacy is much lower. Since the early studies to deliver pDNA, chitosan has been regarded as a highly attractive biopolymer to deliver nucleic acids intracellularly and induce a transgenic response resulting in either upregulation of protein expression (for pDNA, mRNA) or its downregulation (for siRNA or microRNA). This is explained as the consequence of a multi-step process involving condensation of nucleic acids, protection against degradation, stabilization in physiological conditions, cellular internalization, release from the endolysosome ("proton sponge" effect), unpacking and enabling the trafficking of pDNA to the nucleus or the siRNA to the RNA interference silencing complex (RISC). Given the multiple steps and complexity involved in the gene transfection process, there is a dearth of understanding of the role of chitosan's structural features (Mw and degree of acetylation, DA%) on each step that dictates the net transfection efficiency and its kinetics. The use of fully characterized chitosan samples along with the utilization of complementary biophysical and biological techniques is key to bridging this gap of knowledge and identifying the optimal chitosans for delivering a specific gene. Other aspects such as cell type and administration route are also at play. At the same time, the role of chitosan structural features on the morphology, size and surface composition of synthetic virus-like particles has barely been addressed. The ongoing revolution brought about by the recent discovery of CRISPR-Cas9 technology will undoubtedly be a game changer in this field in the short term. In the field of rare diseases, gene therapy is perhaps where the greatest potential lies and we anticipate that chitosans will be key players in the translation of research to the clinic.

Physical characterization and in vivo organ distribution of coated iron oxide nanoparticles

Citrate-stabilized iron oxide magnetic nanoparticles (MNPs) were coated with one of carboxymethyl dextran (CM-dextran), polyethylene glycol-polyethylene imine (PEG-PEI), methoxy-PEG-phosphate+rutin, or dextran. They were characterized for size, zeta potential, hysteresis heating in an alternating magnetic field, dynamic magnetic susceptibility, and examined for their distribution in mouse organs following intravenous delivery. Except for PEG-PEI-coated nanoparticles, all coated nanoparticles had a negative zeta potential at physiological pH. Nanoparticle sizing by dynamic light scattering revealed an increased nanoparticle hydrodynamic diameter upon coating. Magnetic hysteresis heating changed little with coating; however, the larger particles demonstrated significant shifts of the peak of complex magnetic susceptibility to lower frequency. 48 hours following intravenous injection of nanoparticles, mice were sacrificed and tissues were collected to measure iron concentration. Iron deposition from nanoparticles possessing a negative surface potential was observed to have highest accumulation in livers and spleens. In contrast, iron deposition from positively charged PEG-PEI-coated nanoparticles was observed to have highest concentration in lungs. These preliminary results suggest a complex interplay between nanoparticle size and charge determines organ distribution of systemically-delivered iron oxide magnetic nanoparticles.

Interfacial analysis of siRNA complexes with poly-ethylenimine (PEI) or PAMAM dendrimers in gene delivery

Solution and interfacial analysis has been employed to gain insight into the complexation of siRNA using either G4 PAMAM dendrimers or 25kDa branched poly-ethylenimine (bPEI). The size, charge and shape/structure of the complexing agents were probed using atomic force microscopy (AFM), circular dichroism spectrometry (CD), dynamic light scattering (DLS), and gel electrophoresis (GE). The binding capability of these cationic polymers to the siRNA molecule, subsequently controls the surface/adsorption behaviour of the complexes to a negatively charged surface. G4 PAMAM dendrimers bind to the major groove of the siRNA structure, while bPEI binds to both major and minor groove. PAMAM-siRNA complexes form a thin uniform surface film with adsorption of monomeric particles, whilst bPEI-siRNA complexes adsorb as particles in random orientations at low bPEI concentration and form network structures across the surface at high charge ratio. This is due to their ability to bind to both regions within siRNA. This new understanding of the interfacial behaviour of siRNA complexes correlates with observations of cellular transfection and can be used in the design of optimal transfection agents.

Tunable PEGylation of branch-type PEI/DNA polyplexes with a compromise of low cytotoxicity and high transgene expression: in vitro and in vivo gene delivery

Although PEGylated polyplexes for gene delivery are widespread, there is a need for an in-depth investigation of the role of the PEGylation degree on the delivery efficiency of the systems. For this, a low-toxicity series of polymers for gene delivery were designed via Michael addition of poly(ethylene glycol)methyl ether methacrylate (PEGMA) onto branched polyethylenimine PEI. The goal was to finely tune the PEGylation degree in order to determine the system offering the best compromise between low cytotoxicity and high transfection efficiency under both in vitro and in vivo conditions. From dynamic light scattering tests, zeta potential measurements and gel retardation assay, it was found that nanoparticle assembly of PEI-g-PEGMA and DNA exhibited stable complex formation when the PEGylation degree was below 2.9%. In addition, complexes formed from polymers with a PEGylation degree of at least 1.67% (from PEI-g-PEGMA-6 to PEI-g-PEGMA-18) all showed very low hemolysis activity. Transfection efficiencies of the prepared complexes were determined using the pEGFP-C3 vector and β-galactosidase. Complexes made of PEI-g-PEGMA-6 and PEI-g-PEGMA-10 at a polymer nitrogen/DNA phosphorus weight ratio (W_n/W_p) of 5 led to the best transfection efficiencies. Moreover, PEGylation ensured low cytotoxicity of the complexes in particular at high W_n/W_p ratios. In vivo tests in a mouse model confirmed the in vitro results obtained for PEI-g-PEGMA-6-based complexes, at all W_n/W_p ratios tested, but also showed that a high PEGylation degree (5.2% for PEI-g-PEGMA-18), though inefficient in vitro could still lead to successful delivery in vivo, due to a prolonged contact time between the complex and the cells, and to the change in the biological environment. Overall, provided a fine tuning of the grafting density of PEGMA onto PEI and the polymer nitrogen/DNA phosphorus weight ratio, our results prove that PEI-g-PEGMA polymers constitute an efficient platform for successful in vitro and in vivo gene delivery, and ensure low cytotoxicity and prolonged cell viability.