Cytosolic delivery of nucleic acids: The case of ionizable lipid nanoparticles

Straight to the point: targeted mRNA-delivery to immune cells for improved vaccine design

With the deepening of our understanding of adaptive immunity at the cellular and molecular level, targeting antigens directly to immune cells has proven to be a successful strategy to develop innovative and potent vaccines. Indeed, it offers the potential to increase vaccine potency and/or modulate immune response quality while reducing off-target effects. With mRNA-vaccines establishing themselves as a versatile technology for future applications, in the last years several approaches have been explored to target nanoparticles-enabled mRNA-delivery systems to immune cells, with a focus on dendritic cells. Dendritic cells (DCs) are the most potent antigen presenting cells and key mediators of B- and T-cell immunity, and therefore considered as an ideal target for cell-specific antigen delivery. Indeed, improved potency of DC-targeted vaccines has been proved in vitro and in vivo. This review discusses the potential specific targets for immune system-directed mRNA delivery, as well as the different targeting ligand classes and delivery systems used for this purpose.

Lipid Nanoparticle-Mediated Hit-and-Run Approaches Yield Efficient and Safe In Situ Gene Editing in Human Skin

Despite exciting advances in gene editing, the efficient delivery of genetic tools to extrahepatic tissues remains challenging. This holds particularly true for the skin, which poses a highly restrictive delivery barrier. In this study, we ran a head-to-head comparison between Cas9 mRNA or ribonucleoprotein (RNP)-loaded lipid nanoparticles (LNPs) to deliver gene editing tools into epidermal layers of human skin, aiming for in situ gene editing. We observed distinct LNP composition and cell-specific effects such as an extended presence of RNP in slow-cycling epithelial cells for up to 72 h. While obtaining similar gene editing rates using Cas9 RNP and mRNA with MC3-based LNPs (10-16%), mRNA-loaded LNPs proved to be more cytotoxic. Interestingly, ionizable lipids with a pKa ∼ 7.1 yielded superior gene editing rates (55%-72%) in two-dimensional (2D) epithelial cells while no single guide RNA-dependent off-target effects were detectable. Unexpectedly, these high 2D editing efficacies did not translate to actual skin tissue where overall gene editing rates between 5%-12% were achieved after a single application and irrespective of the LNP composition. Finally, we successfully base-corrected a disease-causing mutation with an efficacy of ∼5% in autosomal recessive congenital ichthyosis patient cells, showcasing the potential of this strategy for the treatment of monogenic skin diseases. Taken together, this study demonstrates the feasibility of an in situ correction of disease-causing mutations in the skin that could provide effective treatment and potentially even a cure for rare, monogenic, and common skin diseases.

RNA interference therapy in acute hepatic porphyrias

The acute hepatic porphyrias (AHPs) are inherited disorders of heme biosynthesis characterized by life-threatening acute neurovisceral attacks precipitated by factors that upregulate hepatic 5-aminolevulinic acid synthase 1 (ALAS1) activity. Induction of hepatic ALAS1 leads to the accumulation of porphyrin precursors, in particular 5-aminolevulinic acid (ALA), which is thought to be the neurotoxic mediator leading to acute attack symptoms such as severe abdominal pain and autonomic dysfunction. Patients may also develop debilitating chronic symptoms and long-term medical complications, including kidney disease and an increased risk of hepatocellular carcinoma. Exogenous heme is the historical treatment for attacks and exerts its therapeutic effect by inhibiting hepatic ALAS1 activity. The pathophysiology of acute attacks provided the rationale to develop an RNA interference therapeutic that suppresses hepatic ALAS1 expression. Givosiran is a subcutaneously administered N-acetylgalactosamine-conjugated small interfering RNA against ALAS1 that is taken up nearly exclusively by hepatocytes via the asialoglycoprotein receptor. Clinical trials established that the continuous suppression of hepatic ALAS1 mRNA via monthly givosiran administration effectively reduced urinary ALA and porphobilinogen levels and acute attack rates and improved quality of life. Common side effects include injection site reactions and increases in liver enzymes and creatinine. Givosiran was approved by the US Food and Drug Administration and European Medicines Agency in 2019 and 2020, respectively, for the treatment of patients with AHP. Although givosiran has the potential to decrease the risk of chronic complications, long-term data on the safety and effects of sustained ALAS1 suppression in patients with AHP are lacking.

Technological advances in the use of viral and non-viral vectors for delivering genetic and non-genetic cargos for cancer therapy

The burden of cancer is increasing globally. Several challenges facing its mainstream treatment approaches have formed the basis for the development of targeted delivery systems to carry and distribute anti-cancer payloads to their defined targets. This site-specific delivery of drug molecules and gene payloads to selectively target druggable biomarkers aimed at inducing cell death while sparing normal cells is the principal goal for cancer therapy. An important advantage of a delivery vector either viral or non-viral is the cumulative ability to penetrate the haphazardly arranged and immunosuppressive tumour microenvironment of solid tumours and or withstand antibody-mediated immune response. Biotechnological approaches incorporating rational protein engineering for the development of targeted delivery systems which may serve as vehicles for packaging and distribution of anti-cancer agents to selectively target and kill cancer cells are highly desired. Over the years, these chemically and genetically modified delivery systems have aimed at distribution and selective accumulation of drug molecules at receptor sites resulting in constant maintenance of high drug bioavailability for effective anti-tumour activity. In this review, we highlighted the state-of-the art viral and non-viral drug and gene delivery systems and those under developments focusing on cancer therapy.

Delivery of gene editing therapeutics

For the past decades, gene editing demonstrated the potential to attenuate each of the root causes of genetic, infectious, immune, cancerous, and degenerative disorders. More recently, Clustered Regularly Interspaced Short Palindromic Repeats-CRISPR-associated protein 9 (CRISPR-Cas9) editing proved effective for editing genomic, cancerous, or microbial DNA to limit disease onset or spread. However, the strategies to deliver CRISPR-Cas9 cargos and elicit protective immune responses requires safe delivery to disease targeted cells and tissues. While viral vector-based systems and viral particles demonstrate high efficiency and stable transgene expression, each are limited in their packaging capacities and secondary untoward immune responses. In contrast, the nonviral vector lipid nanoparticles were successfully used for as vaccine and therapeutic deliverables. Herein, we highlight each available gene delivery systems for treating and preventing a broad range of infectious, inflammatory, genetic, and degenerative diseases. STATEMENT OF SIGNIFICANCE: CRISPR-Cas9 gene editing for disease treatment and prevention is an emerging field that can change the outcome of many chronic debilitating disorders.

Deciphering Structural Determinants Distinguishing Active from Inactive Cell-Penetrating Peptides for Cytosolic mRNA Delivery

The formation of noncovalent complexes by mixing of positively charged polymers with negatively charged oligonucleotides (ONs) is a widely explored concept in nanomedicine to achieve cellular delivery of ONs. Uptake of ON complexes occurs through endocytosis, which then requires release of ON from endosomes. As one type of polymer, cell-penetrating peptides (CPPs) are being used which are peptides of about 8-30 amino acids in length. However, only a few CPPs yield effective cytosolic ON delivery and activity. Several strategies have been devised to increase cellular uptake and enhance endosomal release, among which an increase of osmotic pressure through the so-called proton sponge effect, disruption of membrane integrity through membrane activity, and disulfide-mediated polymerization. Here, we address the relevance of these concepts for mRNA delivery by incorporating structural features into the human lactoferrin-derived CPP, which shows uptake but not delivery. The incorporation of histidines was explored to address osmotic pressure and structural motifs of the delivery-active CPP PepFect14 (PF14) to address membrane disturbance, and finally, the impact of polymerization was explored. Whereas oligomerization increased the stability of polyplexes against heparin-induced decomplexation, neither this approach nor the incorporation of histidine residues to promote a proton-sponge effect yielded activity. Also, the replacement of arginine residues with lysine or ornithine residues, as in PF14, was without effect, even though all polyplexes showed cellular uptake. Ultimately, sufficient activity could only be achieved by transferring amphipathic sequence motifs from PF14 into the hLF context with some benefit of oligomerization demonstrating overarching principles of delivery for CPPs, lipid nanoparticles, and other types of delivery polymers.

Enabling mRNA Therapeutics: Current Landscape and Challenges in Manufacturing

Recent advances and discoveries in the structure and role of mRNA as well as novel lipid-based delivery modalities have enabled the advancement of mRNA therapeutics into the clinical trial space. The manufacturing of these products is relatively simple and eliminates many of the challenges associated with cell culture production of viral delivery systems for gene and cell therapy applications, allowing rapid production of mRNA for personalized treatments, cancer therapies, protein replacement and gene editing. The success of mRNA vaccines during the COVID-19 pandemic highlighted the immense potential of this technology as a vaccination platform, but there are still particular challenges to establish mRNA as a widespread therapeutic tool. Immunostimulatory byproducts can pose a barrier for chronic treatments and different production scales may need to be considered for these applications. Moreover, long-term storage of mRNA products is notoriously difficult. This review provides a detailed overview of the manufacturing steps for mRNA therapeutics, including sequence design, DNA template preparation, mRNA production and formulation, while identifying the challenges remaining in the dose requirements, long-term storage and immunotolerance of the product.

Understanding structure activity relationships of Good HEPES lipids for lipid nanoparticle mRNA vaccine applications

Lipid nanoparticles (LNPs) have shown great promise as delivery vehicles to transport messenger ribonucleic acid (mRNA) into cells and act as vaccines for infectious diseases including COVID-19 and influenza. The ionizable lipid incorporated within the LNP is known to be one of the main driving factors for potency and tolerability. Herein, we describe a novel family of ionizable lipids synthesized with a piperazine core derived from the HEPES Good buffer. These ionizable lipids have unique asymmetric tails and two dissimilar degradable moieties incorporated within the structure. Lipids tails of varying lengths, degrees of unsaturation, branching, and the inclusion of additional ester moieties were evaluated for protein expression. We observed several key lipid structure activity relationships that correlated with improved protein production in vivo, including lipid tails of 12 carbons on the ester side and the effect of carbon spacing on the disulfide arm of the lipids. Differences in LNP physical characteristics were observed for lipids containing an extra ester moiety. The LNP structure and lipid bilayer packing, visualized through Cryo-TEM, affected the amount of protein produced in vivo. In non-human primates, the Good HEPES LNPs formulated with an mRNA encoding an influenza hemagglutinin (HA) antigen successfully generated functional HA inhibition (HAI) antibody titers comparable to the industry standards MC3 and SM-102 LNPs, demonstrating their promise as a potential vaccine.

Repositioning the antihistamine ebastine as an intracellular siRNA delivery enhancer

Small interfering RNAs (siRNAs) are promising therapeutics for the treatment of human diseases via the induction of sequence-specific gene silencing. To be functional, siRNAs require cytosolic delivery into target cells. However, state-of-the-art delivery systems mediate cellular entry through endocytosis and suffer from ineffective endosomal escape, routing a substantial fraction of the siRNA towards the lysosomal compartment. Cationic amphiphilic drugs (CADs) have been described to improve cytosolic siRNA delivery by the transient induction of lysosomal membrane permeabilization. In this work, we evaluated ebastine, an antihistamine CAD, for its ability to enhance cytosolic release of siRNA in a non-small cell lung cancer model. In particular, we demonstrated that ebastine can improve the siRNA-mediated gene silencing efficiency of a polymeric nanogel by 40-fold, outperforming other CAD compounds. Additionally, ebastine substantially enhanced gene knockdown of a cholesterol-conjugated siRNA, in two-dimensional (2D) cell culture as well as in three-dimensional (3D) tumor spheroids. Finally, ebastine could strongly promote siRNA delivery of lipid nanoparticles (LNPs) composed of a pH-dependent switchable ionizable lipid and with stable PEGylation, in contrast to state-of-the-art LNP formulations. Altogether, we identified ebastine as a potent and versatile siRNA delivery enhancer in cancer cells, which offers opportunities for drug combination therapy in oncology.

The potential role and mechanism of circRNAs in foam cell formation

Atherosclerosis is a significant risk factor for coronary heart disease (CHD) and myocardial infarction (MI). Atherosclerosis develops during foam cell generation, which is caused by an imbalance in cholesterol uptake, esterification, and efflux. LOX-1, SR-A1, and CD36 all increased cholesterol uptake. ACAT1 and ACAT2 promote free cholesterol (FC) esterification to cholesteryl esters (CE). The hydrolysis of CE to FC was aided by nCEH. FC efflux was promoted by ABCA1, ABCG1, ADAM10, and apoA-I. SR-BI promotes not only cholesterol uptake but also FC efflux. Circular RNAs (circRNAs), which are single-stranded RNAs with a closed covalent circular structure, have emerged as promising biomarkers and therapeutic targets for atherosclerosis due to their highly tissue, cell, and disease state-specific expression profiles. Numerous studies have shown that circRNAs regulate foam cell formation, acting as miRNA sponges to influence atherosclerosis development by regulating the expression of SR-A1, CD36, ACAT2, ABCA1, ABCG1, ADAM10, apoA-I, SR-B1. Several circRNAs, including circ-Wdr91, circ 0004104, circRNA0044073, circRNA_0001805, circDENND1B, circRSF1, circ 0001445, and circRNA 102682, are potential biomarkers for atherosclerosis to better evaluate cardiovascular risk. It is difficult to deliver synthetic therapeutic circRNAs to the desired target tissues. Nanotechnology, such as GA-RM/GZ/PL, may be an important solution to this problem. In this review, we focus on the potential role and mechanism of circRNA/miRNA axis in foam cell formation in the hopes of discovering new targets for the diagnosis, prevention, and treatment of atherosclerosis.

In vitro and in vivo evaluation of clinically-approved ionizable cationic lipids shows divergent results between mRNA transfection and vaccine efficacy

Ionizable cationic lipids (ICLs) play an essential role in the effectiveness of lipid nanoparticles (LNPs) for delivery of mRNA therapeutics and vaccines; therefore, critical evaluations of their biological performance would extend the existing knowledge in the field. In the present study, we examined the effects of the three clinically-approved ICLs, Dlin-MC3-DMA, ALC-0315 and SM-102, as well as DODAP, on the in vitro and in vivo performance of LNPs for mRNA delivery and vaccine efficacy. mRNA-LNPs containing these lipids were successfully prepared, which were all found to be very similar in their physicochemical properties and mRNA encapsulation efficiencies. Furthermore, the results of the in vitro studies indicated that these mRNA-LNPs were efficiently taken up by immortalized and primary immune cells with comparable efficiency; however, SM-102-based LNPs were superior in inducing protein expression and antigen-specific T cell proliferation. In contrast, in vivo studies revealed that LNPs containing ALC-0315 and SM-102 yielded almost identical protein expression levels in zebrafish embryos, which were significantly higher than Dlin-MC3-DMA-based LNPs. Additionally, a mouse immunization study demonstrated that a single-dose subcutaneous administration of the mRNA-LNPs resulted in a high production of intracellular cytokines by antigen-specific T cells, but no significant differences among the three clinically-approved ICLs were observed, suggesting a weak correlation between in vitro and in vivo outcomes. This study provides strong evidence that ICLs modulate the performance of mRNA-LNPs and that in vitro data does not adequately predict their behavior in vivo.

Lipid nanoparticles (LNPs) for in vivo RNA delivery and their breakthrough technology for future applications

RNA therapeutics show a significant breakthrough for the treatment of otherwise incurable diseases and genetic disorders by regulating disease-related gene expression. The successful development of COVID-19 mRNA vaccines further emphasizes the potential of RNA therapeutics in the prevention of infectious diseases as well as in the treatment of chronic diseases. However, the efficient delivery of RNA into cells remains a challenge, and nanoparticle delivery systems such as lipid nanoparticles (LNPs) are necessary to fully realize the potential of RNA therapeutics. While LNPs provide a highly efficient platform for the in vivo delivery of RNA by overcoming various biological barriers, several challenges remain to be resolved for further development and regulatory approval. These include a lack of targeted delivery to extrahepatic organs and a gradual loss of therapeutic potency with repeated doses. In this review, we highlight the fundamental aspects of LNPs and their uses in the development of novel RNA therapeutics. Recent advances in LNP-based therapeutics and preclinical/clinical studies are overviewed. Lastly, we discuss the current limitations of LNPs and introduce breakthrough technologies that might overcome these challenges in future applications.

Recent Advances in Messenger Ribonucleic Acid (mRNA) Vaccines and Their Delivery Systems: A Review

Messenger ribonucleic acid (mRNA) was found as the intermediary that transfers genetic information from DNA to ribosomes for protein synthesis in 1961. The emergency use authorization of the two covid-19 mRNA vaccines, BNT162b2 and mRNA-1273, is a significant achievement in the history of vaccine development. Because they are generated in a cell-free environment using the in vitro transcription (IVT) process, mRNA vaccines are risk-free. Moreover, chemical modifications to the mRNA molecule, such as cap structures and changed nucleosides, have proved critical in overcoming immunogenicity concerns, achieving sustained stability, and achieving effective, accurate protein production in vivo. Several vaccine delivery strategies (including protamine, lipid nanoparticles (LNPs), polymers, nanoemulsions, and cell-based administration) were also optimized to load and transport RNA into the cytosol. LNPs, which are composed of a cationic or a pH-dependent ionizable lipid layer, a polyethylene glycol (PEG) component, phospholipids, and cholesterol, are the most advanced systems for delivering mRNA vaccines. Moreover, modifications of the four components that make up the LNPs showed to increase vaccine effectiveness and reduce side effects. Furthermore, the introduction of biodegradable lipids improved LNP biocompatibility. Furthermore, mRNA-based therapies are expected to be effective treatments for a variety of refractory conditions, including infectious diseases, metabolic genetic diseases, cancer, cardiovascular and cerebrovascular diseases. Therefore, the present review aims to provide the scientific community with up-to-date information on mRNA vaccines and their delivery systems.

Recent advances and prospects for lipid-based nanoparticles as drug carriers in the treatment of human retinal diseases

The delivery of cures for retinal diseases remains problematic. There are four main challenges: passing through multiple barriers of the eye, the delivery to particular retinal cell types, the capability to carry different forms of therapeutic cargo and long-term therapeutic efficacy. Lipid-based nanoparticles (LBNPs) are potent to overcome these challenges due to their unique merits: amphiphilic nanoarchitectures to pass biological barriers, vary modifications with specific affinity to target cell types, flexible capacity for large and mixed types of cargos and slow-release formulations for long-term treatment. We have reviewed the latest research on the applications of LBNPs for treating retinal diseases and categorized them by different payloads. Furthermore, we identified technical barriers and discussed possible future development for LBNPs to expand the therapeutic potential in treating retinal diseases.

Adjuvant physiochemistry and advanced nanotechnology for vaccine development

Vaccines comprising innovative adjuvants are rapidly reaching advanced translational stages, such as the authorized nanotechnology adjuvants in mRNA vaccines against COVID-19 worldwide, offering new strategies to effectively combat diseases threatening human health. Adjuvants are vital ingredients in vaccines, which can augment the degree, extensiveness, and longevity of antigen specific immune response. The advances in the modulation of physicochemical properties of nanoplatforms elevate the capability of adjuvants in initiating the innate immune system and adaptive immunity, offering immense potential for developing vaccines against hard-to-target infectious diseases and cancer. In this review, we provide an essential introduction of the basic principles of prophylactic and therapeutic vaccination, key roles of adjuvants in augmenting and shaping immunity to achieve desired outcomes and effectiveness, and the physiochemical properties and action mechanisms of clinically approved adjuvants for humans. We particularly focus on the preclinical and clinical progress of highly immunogenic emerging nanotechnology adjuvants formulated in vaccines for cancer treatment or infectious disease prevention. We deliberate on how the immune system can sense and respond to the physicochemical cues (e.g., chirality, deformability, solubility, topology, and chemical structures) of nanotechnology adjuvants incorporated in the vaccines. Finally, we propose possible strategies to accelerate the clinical implementation of nanotechnology adjuvanted vaccines, such as in-depth elucidation of nano-immuno interactions, antigen identification and optimization by the deployment of high-dimensional multiomics analysis approaches, encouraging close collaborations among scientists from different scientific disciplines and aggressive exploration of novel nanotechnologies.

Strategies for targeted gene delivery using lipid nanoparticles and cell-derived nanovesicles

Gene therapy is a promising approach for the treatment of many diseases. However, the effective delivery of the cargo without degradation in vivo is one of the major hurdles. With the advent of lipid nanoparticles (LNPs) and cell-derived nanovesicles (CDNs), gene delivery holds a very promising future. The targeting of these nanosystems is a prerequisite for effective transfection with minimal side-effects. In this review, we highlight the emerging strategies utilized for the effective targeting of LNPs and CDNs, and we summarize the preparation methodologies for LNPs and CDNs. We have also highlighted the non-ligand targeting of LNPs toward certain organs based on their composition. It is highly expected that continuing the developments in the targeting approaches of LNPs and CDNs for the delivery system will further promote them in clinical translation.

The use of RNA-based treatments in the field of cancer immunotherapy

Over the past several decades, mRNA vaccines have evolved from a theoretical concept to a clinical reality. These vaccines offer several advantages over traditional vaccine techniques, including their high potency, rapid development, low-cost manufacturing, and safe administration. However, until recently, concerns over the instability and inefficient distribution of mRNA in vivo have limited their utility. Fortunately, recent technological advancements have mostly resolved these concerns, resulting in the development of numerous mRNA vaccination platforms for infectious diseases and various types of cancer. These platforms have shown promising outcomes in both animal models and humans. This study highlights the potential of mRNA vaccines as a promising alternative approach to conventional vaccine techniques and cancer treatment. This review article aims to provide a thorough and detailed examination of mRNA vaccines, including their mechanisms of action and potential applications in cancer immunotherapy. Additionally, the article will analyze the current state of mRNA vaccine technology and highlight future directions for the development and implementation of this promising vaccine platform as a mainstream therapeutic option. The review will also discuss potential challenges and limitations of mRNA vaccines, such as their stability and in vivo distribution, and suggest ways to overcome these issues. By providing a comprehensive overview and critical analysis of mRNA vaccines, this review aims to contribute to the advancement of this innovative approach to cancer treatment.

Lipid Nanoparticle Delivery of Small Proteins for Potent In Vivo RAS Inhibition

Mutated RAS proteins are potent oncogenic drivers and have long been considered "undruggable". While RAS-targeting therapies have recently shown promise, there remains a clinical need for RAS inhibitors with more diverse targets. Small proteins represent a potential new therapeutic option, including K27, a designed ankyrin repeat protein (DARPin) engineered to inhibit RAS. However, K27 functions intracellularly and is incapable of entering the cytosol on its own, currently limiting its utility. To overcome this barrier, we have engineered a lipid nanoparticle (LNP) platform for potent delivery of functional K27-D30─a charge-modified version of the protein─intracellularly in vitro and in vivo. This system efficiently encapsulates charge-modified proteins, facilitates delivery in up to 90% of cells in vitro, and maintains potency after at least 45 days of storage. In vivo, these LNPs deliver K27-D30 to the cytosol of cancerous cells in the liver, inhibiting RAS-driven growth and ultimately reducing tumor load in an HTVI-induced mouse model of hepatocellular carcinoma. This work shows that K27 holds promise as a new cancer therapeutic when delivered using this LNP platform. Furthermore, this technology has the potential to broaden the use of LNPs to include new cargo types─beyond RNA─for diverse therapeutic applications.

A fluorinated ionizable lipid improves the mRNA delivery efficiency of lipid nanoparticles

The efficacy of messenger RNA (mRNA)-based vaccines or therapies relies on delivery vehicles that can transport them into the cytosol of cells. Lipid nanoparticles (LNPs) are the most clinically advanced carrier for mRNA. The chemical structure of an ionizable lipid is critical for the delivery efficiency of the LNPs. Herein, we synthesize a new ionizable lipid containing fluorinated alkyl chains (F-L319) and evaluate its mRNA delivery efficiency compared to its hydrocarbon counterpart (L319). While LNPs formulated with F-L319 alone showed decreased mRNA encapsulation and delivery efficiencies in comparison to the L319-LNP, we found that combining the appropriate ratios of F-L319 and L319 as hybrid ionizable lipids in LNPs (hybrid-LNPs) greatly enhanced mRNA delivery efficiency both in vitro and in vivo. Upon intravenous injection, the hybrid-LNP showed targeted mRNA expression in the spleen. Mechanistic studies indicate that the enhanced mRNA delivery of the hybrid-LNP is attributed to both improved mRNA encapsulation and cellular uptake. Collectively, fluorination of ionizable lipids represents a promising strategy to improve the delivery efficiency of LNPs.

Bioinspired Lipid Nanocarriers for RNA Delivery

RNA therapy is a disruptive technology comprising a rapidly expanding category of drugs. Further translation of RNA therapies to the clinic will improve the treatment of many diseases and help enable personalized medicine. However, in vivo delivery of RNA remains challenging due to the lack of appropriate delivery tools. Current state-of-the-art carriers such as ionizable lipid nanoparticles still face significant challenges, including frequent localization to clearance-associated organs and limited (1-2%) endosomal escape. Thus, delivery vehicles must be improved to further unlock the full potential of RNA therapeutics. An emerging strategy is to modify existing or new lipid nanocarriers by incorporating bioinspired design principles. This method generally aims to improve tissue targeting, cellular uptake, and endosomal escape, addressing some of the critical issues facing the field. In this review, we introduce the different strategies for creating bioinspired lipid-based RNA carriers and discuss the potential implications of each strategy based on reported findings. These strategies include incorporating naturally derived lipids into existing nanocarriers and mimicking bioderived molecules, viruses, and exosomes. We evaluate each strategy based on the critical factors required for delivery vehicles to succeed. Finally, we point to areas of research that should be furthered to enable the more successful rational design of lipid nanocarriers for RNA delivery.

A Straightforward Method for the Development of Positively Charged Gold Nanoparticle-Based Vectors for Effective siRNA Delivery

The therapeutic potential of short interfering RNA (siRNA) to treat many diseases that are incurable with traditional preparations is limited by the extensive metabolism of serum nucleases, low permeability through biological membrane barriers because of a negative charge, and endosomal trapping. Effective delivery vectors are required to overcome these challenges without causing unwanted side effects. Here, we present a relatively simple synthetic protocol to obtain positively charged gold nanoparticles (AuNPs) with narrow size distribution and the surface modified with Tat-related cell-penetrating peptide. The AuNPs were characterized using TEM and the localized surface plasmon resonance technique. The synthesized AuNPs showed low toxicity in experiments in vitro and were able to effectively form complexes with double-stranded siRNA. The obtained delivery vehicles were used for intracellular delivery of siRNA in an ARPE-19 cell line transfected with secreted embryonic alkaline phosphatase (SEAP). The delivered oligonucleotide remained intact and caused a significant knockdown effect on SEAP cell production. The developed material could be useful for delivery of negatively charged macromolecules, such as antisense oligonucleotides and various RNAs, particularly for retinal pigment epithelial cell drug delivery.

Key Design Features of Lipid Nanoparticles and Electrostatic Charge-Based Lipid Nanoparticle Targeting

Lipid nanoparticles (LNP) have gained much attention after the approval of mRNA COVID-19 vaccines. The considerable number of currently ongoing clinical studies are testament to this fact. These efforts towards the development of LNPs warrant an insight into the fundamental developmental aspects of such systems. In this review, we discuss the key design aspects that confer efficacy to a LNP delivery system, i.e., potency, biodegradability, and immunogenicity. We also cover the underlying considerations regarding the route of administration and targeting of LNPs to hepatic and non-hepatic targets. Furthermore, since LNP efficacy is also a function of drug/nucleic acid release within endosomes, we take a holistic view of charged-based targeting approaches of LNPs not only in the context of endosomal escape but also in relation to other comparable target cell internalization strategies. Electrostatic charge-based interactions have been used in the past as a potential strategy to enhance the drug release from pH-sensitive liposomes. In this review, we cover such strategies around endosomal escape and cell internalization in low pH tumor micro-environments.

Lipid Nanoparticles Deliver the Therapeutic VEGFA mRNA In Vitro and In Vivo and Transform Extracellular Vesicles for Their Functional Extensions

Lipid nanoparticles (LNPs) are currently used to transport functional mRNAs, such as COVID-19 mRNA vaccines. The delivery of angiogenic molecules, such as therapeutic VEGF-A mRNA, to ischemic tissues for producing new blood vessels is an emerging strategy for the treatment of cardiovascular diseases. Here, the authors deliver VEGF-A mRNA via LNPs and study stoichiometric quantification of their uptake kinetics and how the transport of exogenous LNP-mRNAs between cells is functionally extended by cells' own vehicles called extracellular vesicles (EVs). The results show that cellular uptake of LNPs and their mRNA molecules occurs quickly, and that the translation of exogenously delivered mRNA begins immediately. Following the VEGF-A mRNA delivery to cells via LNPs, a fraction of internalized VEGF-A mRNA is secreted via EVs. The overexpressed VEGF-A mRNA is detected in EVs secreted from three different cell types. Additionally, RNA-Seq analysis reveals that as cells' response to LNP-VEGF-A mRNA treatment, several overexpressed proangiogenic transcripts are packaged into EVs. EVs are further deployed to deliver VEGF-A mRNA in vitro and in vivo. Upon equal amount of VEGF-A mRNA delivery via three EV types or LNPs in vitro, EVs from cardiac progenitor cells are the most efficient in promoting angiogenesis per amount of VEGF-A protein produced. Intravenous administration of luciferase mRNA shows that EVs could distribute translatable mRNA to different organs with the highest amounts of luciferase detected in the liver. Direct injections of VEGF-A mRNA (via EVs or LNPs) into mice heart result in locally produced VEGF-A protein without spillover to liver and circulation. In addition, EVs from cardiac progenitor cells cause minimal production of inflammatory cytokines in cardiac tissue compared with all other treatment types. Collectively, the data demonstrate that LNPs transform EVs as functional extensions to distribute therapeutic mRNA between cells, where EVs deliver this mRNA differently than LNPs.

Increasing the siRNA knockdown efficiency of lipid nanoparticles by morphological transformation with the use of dihydrosphingomyelin as a helper lipid

Lipid nanoparticles (LNPs), comprising ionizable lipids, helper lipids, cholesterol, and PEG lipids, can act as delivery carriers for nucleic acids and have achieved clinical success in the delivery of siRNA and mRNA. It has been shown that the morphology of LNPs varies depending on their lipid composition, but the influence of their morphology on nucleic acid efficacy has not been fully elucidated. In this study, we used our previously developed novel lipid, dioleoylglycerophosphate-diethylenediamine conjugate (DOP-DEDA), to create pH-responsive LNPs (DOP-DEDA LNPs). We evaluated the morphology of DOP-DEDA LNPs composed of different helper lipids and the knockdown efficiency of small interfering RNA (siRNA). A distinctive difference in morphology was observed between DOP-DEDA LNPs of different helper lipids. Significant differences were also observed in the apparent pK_a of DOP-DEDA LNPs and the knockdown efficiency of siRNA, which may be due to the difference in the localization of DOP-DEDA molecules in DOP-DEDA LNPs. These findings suggest that changing helper lipids alters the morphology of the DOP-DEDA LNP system, which affects the apparent pK_a and knockdown efficiency of siRNA.

Use of a Liver-Targeting Immune-Tolerogenic mRNA Lipid Nanoparticle Platform to Treat Peanut-Induced Anaphylaxis by Single- and Multiple-Epitope Nucleotide Sequence Delivery

While oral desensitization is capable of alleviating peanut allergen anaphylaxis, long-term immune tolerance is the sought-after goal. We developed a liver-targeting lipid nanoparticle (LNP) platform to deliver mRNA-encoded peanut allergen epitopes to liver sinusoidal endothelial cells (LSECs), which function as robust tolerogenic antigen-presenting cells that induce FoxP3+ regulatory T-cells (Tregs). The mRNA strand was constructed by including nucleotide sequences encoding for nonallergenic MHC-II binding T-cell epitopes, identified in the dominant peanut allergen, Ara h2. These epitopes were inserted in the mRNA strand downstream of an MHC-II targeting sequence, further endowed in vitro with 5' and 3' capping sequences, a PolyA tail, and uridine substitution. Codon-optimized mRNA was used for microfluidics synthesis of LNPs with an ionizable cationic lipid, also decorated with a lipid-anchored mannose ligand for LSEC targeting. Biodistribution to the liver was confirmed by in vivo imaging, while ELISpot assays demonstrated an increase in IL-10-producing Tregs in the spleen. Prophylactic administration of tandem-repeat or a combination of encapsulated Ara h2 epitopes induced robust tolerogenic effects in C3H/HeJ mice, sensitized to and subsequently challenged with crude peanut allergen extract. In addition to alleviating physical manifestations of anaphylaxis, there was suppression of Th2-mediated cytokine production, IgE synthesis, and mast cell release, accompanied by increased IL-10 and TGF-β production in the peritoneum. Similar efficacy was demonstrated during LNP administration postsensitization. While nondecorated particles had lesser but significant effects, PolyA/LNP-Man lacked protective effects. These results demonstrate an exciting application of mRNA/LNP for treatment of food allergen anaphylaxis, with the promise to be widely applicable to the allergy field.

Design of lipid-based nanoparticles for delivery of therapeutic nucleic acids

The successful development of nonviral delivery systems for nucleic acids has been reported extensively over the past number of years. Among them, lipid-based nanoparticles (LNPs) represent the most advanced platform. This review provides an overview of the state-of-the-art in LNP technology, focusing on the delivery of a range of nucleic acids. Recent advances in the development of an efficient and safe lipid-based system are critically analyzed with a particular emphasis on the rationale behind the design of LNPs and on attempts to elucidate the resulting molecular assembly and structure, their interactions with cellular proteins and biodistribution. In addition, manufacturing methods including microfluidics and their potential to influence stability and scale-up are summarized.

Genome editing in cancer: Challenges and potential opportunities

Ever since its mechanism was discovered back in 2012, the CRISPR/Cas9 system have revolutionized the field of genome editing. While at first it was seen as a therapeutic tool mostly relevant for curing genetic diseases, it has been recently shown to also hold the potential to become a clinically relevant therapy for cancer. However, there are multiple challenges that must be addressed prior to clinical testing. Predominantly, the safety of the system when used for in-vivo therapies, including off-target activity and the effects of the double strand break induction on genomic stability. Here, we will focus on the inherent challenges in the CRISPR/Cas9 system and discuss various opportunities to overcoming these challenges.

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In recent years, several works have shown that knocking down key genes by CRISPR/Cas9 based could potentially be a new type of cancer therapy.

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This has been made possible due to advances in the fields of In-vivo delivery, such as lentiviral vectors and lipid nanoparticles.

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Limiting CRISPR/Cas9 activity to the tumor and minimizing off-target activity are challenges that must be overcome before proceeding to the clinic.

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We review approaches arising from multiple disciplines that could overcome these challenges.

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The combination of these multi-disciplinary approaches should be able to overcome the different challenges and open the way to the clinic.

Nonviral nanoparticle gene delivery into the CNS for neurological disorders and brain cancer applications

Nonviral nanoparticles have emerged as an attractive alternative to viral vectors for gene therapy applications, utilizing a range of lipid-based, polymeric, and inorganic materials. These materials can either encapsulate or be functionalized to bind nucleic acids and protect them from degradation. To effectively elicit changes to gene expression, the nanoparticle carrier needs to undergo a series of steps intracellularly, from interacting with the cellular membrane to facilitate cellular uptake to endosomal escape and nucleic acid release. Adjusting physiochemical properties of the nanoparticles, such as size, charge, and targeting ligands, can improve cellular uptake and ultimately gene delivery. Applications in the central nervous system (CNS; i.e., neurological diseases, brain cancers) face further extracellular barriers for a gene-carrying nanoparticle to surpass, with the most significant being the blood-brain barrier (BBB). Approaches to overcome these extracellular challenges to deliver nanoparticles into the CNS include systemic, intracerebroventricular, intrathecal, and intranasal administration. This review describes and compares different biomaterials for nonviral nanoparticle-mediated gene therapy to the CNS and explores challenges and recent preclinical and clinical developments in overcoming barriers to nanoparticle-mediated delivery to the brain. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Ionizable drug delivery systems for efficient and selective gene therapy

Gene therapy has shown great potential to treat various diseases by repairing the abnormal gene function. However, a great challenge in bringing the nucleic acid formulations to the market is the safe and effective delivery to the specific tissues and cells. To be excited, the development of ionizable drug delivery systems (IDDSs) has promoted a great breakthrough as evidenced by the approval of the BNT162b2 vaccine for prevention of coronavirus disease 2019 (COVID-19) in 2021. Compared with conventional cationic gene vectors, IDDSs can decrease the toxicity of carriers to cell membranes, and increase cellular uptake and endosomal escape of nucleic acids by their unique pH-responsive structures. Despite the progress, there remain necessary requirements for designing more efficient IDDSs for precise gene therapy. Herein, we systematically classify the IDDSs and summarize the characteristics and advantages of IDDSs in order to explore the underlying design mechanisms. The delivery mechanisms and therapeutic applications of IDDSs are comprehensively reviewed for the delivery of pDNA and four kinds of RNA. In particular, organ selecting considerations and high-throughput screening are highlighted to explore efficiently multifunctional ionizable nanomaterials with superior gene delivery capacity. We anticipate providing references for researchers to rationally design more efficient and accurate targeted gene delivery systems in the future, and indicate ideas for developing next generation gene vectors.

Recent Progress of Lipid Nanoparticles-Based Lipophilic Drug Delivery: Focus on Surface Modifications

Numerous drugs have emerged to treat various diseases, such as COVID-19, cancer, and protect human health. Approximately 40% of them are lipophilic and are used for treating diseases through various delivery routes, including skin absorption, oral administration, and injection. However, as lipophilic drugs have a low solubility in the human body, drug delivery systems (DDSs) are being actively developed to increase drug bioavailability. Liposomes, micro-sponges, and polymer-based nanoparticles have been proposed as DDS carriers for lipophilic drugs. However, their instability, cytotoxicity, and lack of targeting ability limit their commercialization. Lipid nanoparticles (LNPs) have fewer side effects, excellent biocompatibility, and high physical stability. LNPs are considered efficient vehicles of lipophilic drugs owing to their lipid-based internal structure. In addition, recent LNP studies suggest that the bioavailability of LNP can be increased through surface modifications, such as PEGylation, chitosan, and surfactant protein coating. Thus, their combinations have an abundant utilization potential in the fields of DDSs for carrying lipophilic drugs. In this review, the functions and efficiencies of various types of LNPs and surface modifications developed to optimize lipophilic drug delivery are discussed.

Development of Novel siRNA Therapeutics: A Review with a Focus on Inclisiran for the Treatment of Hypercholesterolemia

Over the past two decades, it was discovered that introducing synthetic small interfering RNAs (siRNAs) into the cytoplasm facilitates effective gene-targeted silencing. This compromises gene expression and regulation by repressing transcription or stimulating sequence-specific RNA degradation. Substantial investments in developing RNA therapeutics for disease prevention and treatment have been made. We discuss the application to proprotein convertase subtilisin/kexin type 9 (PCSK9), which binds to and degrades the low-density lipoprotein cholesterol (LDL-C) receptor, interrupting the process of LDL-C uptake into hepatocytes. PCSK9 loss-of-function modifications show significant clinical importance by causing dominant hypocholesterolemia and lessening the risk of cardiovascular disease (CVD). Monoclonal antibodies and small interfering RNA (siRNA) drugs targeting PCSK9 are a significant new option for managing lipid disorders and improving CVD outcomes. In general, monoclonal antibodies are restricted to binding with cell surface receptors or circulating proteins. Similarly, overcoming the intracellular and extracellular defenses that prevent exogenous RNA from entering cells must be achieved for the clinical application of siRNAs. N-acetylgalactosamine (GalNAc) conjugates are a simple solution to the siRNA delivery problem that is especially suitable for treating a broad spectrum of diseases involving liver-expressed genes. Inclisiran is a GalNAc-conjugated siRNA molecule that inhibits the translation of PCSK9. The administration is only required every 3 to 6 months, which is a significant improvement over monoclonal antibodies for PCSK9. This review provides an overview of siRNA therapeutics with a focus on detailed profiles of inclisiran, mainly its delivery strategies. We discuss the mechanisms of action, its status in clinical trials, and its prospects.

A Triazolium-Anchored Self-Immolative Linker Enables Self-Assembly-Driven siRNA Binding and Esterase-Induced Release

The increased importance of RNA-based therapeutics comes with a need to develop next-generation stimuli-responsive systems capable of binding, transporting and releasing RNA oligomers. In this work, we describe triazolium-based amphiphiles capable of siRNA binding and enzyme-responsive release of the nucleic acid payload. In aqueous medium, the amphiphile self-assembles into nanocarriers that can disintegrate upon the addition of esterase. Key to the molecular design is a self-immolative linker that is anchored to the triazolium moiety and acts as a positively-charged polar head group. We demonstrate that addition of esterase leads to a degradation cascade of the linker, leaving the neutral triazole compound unable to form complexes and therefore releasing the negatively-charged siRNA. The reported molecular design and overall approach may have broad utility beyond this proof-of-principle study, because the underlying CuAAC "click" chemistry allows bringing together three groups very efficiently as well as cleaving off one of the three groups under the mild action of an esterase enzyme.

Overcoming Pharmaceutical Bottlenecks for Nucleic Acid Drug Development

The outbreak of the coronavirus disease 2019 (COVID-19) pandemic and swift approval of two mRNA vaccines have put nucleic acid therapeutics in the spotlight of both the scientific community and the general public. Actually, in addition to mRNAs, multiple nucleic acid therapeutics have been successively commercialized over the past few years. The rapid development of nucleic acid drugs not only demonstrates their superior potency but also marks a new era of the field. Compared with conventional treatments targeting proteins rather than the root causes of diseases at the genetic level, nucleic acids are capable of achieving long-standing or even curative effects against undruggable disorders by modulating gene expression via inhibition, editing, addition, or replacement. This offers a terrific arsenal for expanding therapeutic access to diseases lacking current treatment options and developing vaccines to provide swift responses to emerging global health threats.Despite the stunning success and recent resurgence of interest in the field, the unfavorable physicochemical characteristics (i.e., the negative charge, large molecular weight, and hydrophilicity), susceptibility to nuclease degradation, off-target toxicity, and immunogenicity are a brake for moving nucleic acid therapeutics from bench to bedside. Currently, developing technologies to improve the circulation stability, targeting affinity, cellular entry, endolysosomal escape, efficacy, and safety of nucleic acid drugs still remains a major pharmaceutical bottleneck.In this Account, we outline the research efforts from our group on the development of technology platforms to overcome the pharmaceutical bottlenecks for nucleic acid therapeutics. We have engineered a variety of intelligent delivery platforms such as synthetic nanomaterials (i.e., lipid nanoparticles, polymers, and inorganic nanoparticles), physical delivery methods (i.e., electroporation), and naturally derived vehicles (i.e., extracellular vesicles), aiming at endowing nucleic acids with improved circulation stability, targeting affinity, and cellular internalization (Get in) and stimuli responsive endolysosomal escape capability (Get out). Moreover, we will discuss our progress in developing a series of modification strategies for sequence engineering of nucleic acids to endow them with enhanced nuclease resistance, translation efficiency, and potency while alleviating their off-target toxicity and immunogenicity (Sequence engineering). Integrating these technologies may promote the development of nucleic acid therapeutics with potent efficacy and improved safety (Efficacy & safety). With this Account, we hope to offer insights into rational design of cutting-edge nucleic acid therapeutic platforms. We believe that the continuing advances in nucleic acid technologies together with academic-industry collaborations in the clinic, will promise to usher in more clinically translatable nucleic acid therapeutics in the foreseeable future.

Potential of siRNA in COVID-19 therapy: Emphasis on in silico design and nanoparticles based delivery

Small interfering RNA (siRNA)-mediated mRNA degradation approach have imparted its eminence against several difficult-to-treat genetic disorders and other allied diseases. Viral outbreaks and resulting pandemics have repeatedly threatened public health and questioned human preparedness at the forefront of drug design and biomedical readiness. During the recent pandemic caused by the SARS-CoV-2, mRNA-based vaccination strategies have paved the way for a new era of RNA therapeutics. RNA Interference (RNAi) based approach using small interfering RNA may complement clinical management of the COVID-19. RNA Interference approach will primarily work by restricting the synthesis of the proteins required for viral replication, thereby hampering viral cellular entry and trafficking by targeting host as well as protein factors. Despite promising benefits, the stability of small interfering RNA in the physiological environment is of grave concern as well as site-directed targeted delivery and evasion of the immune system require immediate attention. In this regard, nanotechnology offers viable solutions for these challenges. The review highlights the potential of small interfering RNAs targeted toward specific regions of the viral genome and the features of nanoformulations necessary for the entrapment and delivery of small interfering RNAs. In silico design of small interfering RNA for different variants of SARS-CoV-2 has been discussed. Various nanoparticles as promising carriers of small interfering RNAs along with their salient properties, including surface functionalization, are summarized. This review will help tackle the real-world challenges encountered by the in vivo delivery of small interfering RNAs, ensuring a safe, stable, and readily available drug candidate for efficient management of SARS-CoV-2 in the future.

High-Precision Synthesis of RNA-Loaded Lipid Nanoparticles for Biomedical Applications

The recent development of RNA-based therapeutics in delivering nucleic acids for gene editing and regulating protein translation has led to the effective treatment of various diseases including cancer, inflammatory and genetic disorder, as well as infectious diseases. Among these, lipid nanoparticles (LNP) have emerged as a promising platform for RNA delivery and have shed light by resolving the inherent instability issues of naked RNA and thereby enhancing the therapeutic potency. These LNP consisting of ionizable lipid, helper lipid, cholesterol, and poly(ethylene glycol)-anchored lipid can stably enclose RNA and help them release into the cells' cytosol. Herein, the significant progress made in LNP research starting from the LNP constituents, formulation, and their diverse applications is summarized first. Moreover, the microfluidic methodologies which allow precise assembly of these newly developed constituents to achieve LNP with controllable composition and size, high encapsulation efficiency as well as scalable production are highlighted. Furthermore, a short discussion on current challenges as well as an outlook will be given on emerging approaches to resolving these issues.

Acidification-Induced Structure Evolution of Lipid Nanoparticles Correlates with Their In Vitro Gene Transfections

The rational design of lipid nanoparticles (LNPs) for enhanced gene delivery remains challenging because of incomplete knowledge of their formulation-structure relationship that impacts their intracellular behavior and consequent function. Small-angle neutron scattering has been used in this work to investigate the structure of LNPs encapsulating plasmid DNA upon their acidification (from pH 7.4 to 4.0), as would be encountered during endocytosis. The results revealed the acidification-induced structure evolution (AISE) of the LNPs on different dimension scales, involving protonation of the ionizable lipid, volume expansion and redistribution of aqueous and lipid components. A similarity analysis using an LNP's structural feature space showed a strong positive correlation between function (measured by intracellular luciferase expression) and the extent of AISE, which was further enhanced by the fraction of unsaturated helper lipid. Our findings reveal molecular and nanoscale changes occurring during AISE that underpin the LNPs' formulation-nanostructure-function relationship, aiding the rational design of application-directed gene delivery vehicles.

CNS Delivery of Nucleic Acid Therapeutics: Beyond the Blood-Brain Barrier and Towards Specific Cellular Targeting

Nucleic acid-based therapeutic molecules including small interfering RNA (siRNA), microRNA(miRNA), antisense oligonucleotides (ASOs), messenger RNA (mRNA), and DNA-based gene therapy have tremendous potential for treating diseases in the central nervous system (CNS). However, achieving clinically meaningful delivery to the brain and particularly to target cells and sub-cellular compartments is typically very challenging. Mediating cell-specific delivery in the CNS would be a crucial advance that mitigates off-target effects and toxicities. In this review, we describe these challenges and provide contemporary evidence of advances in cellular and sub-cellular delivery using a variety of delivery mechanisms and alternative routes of administration, including the nose-to-brain approach. Strategies to achieve subcellular localization, endosomal escape, cytosolic bioavailability, and nuclear transfer are also discussed. Ultimately, there are still many challenges to translating these experimental strategies into effective and clinically viable approaches for treating patients.

A tale of nucleic acid-ionizable lipid nanoparticles: Design and manufacturing technology and advancement

INTRODUCTION

Ionizable lipid nanoparticles (LNPs) have been proven to have high encapsulation, cellular uptake, and effective endosomal escape and are therefore promising for nucleic acid delivery. The combination of ionizable lipids, helper lipids, cholesterol, and PEG lipids advances nucleic acid-ionizable LNPs and distinguishes them from liposomes, SLNs, NLCs, and other lipid particles. Solvent injection and microfluidics technology are the primary manufacturing techniques for commercialized ionizable LNPs. Microfluidics technology limitations restrict the rapid industrial scale-up and therapeutic effectiveness of ionized LNPs. Alternative manufacturing technologies and target-specific lipids are urgently needed.

AREA COVERED

This article provides an in-depth update on the lipid compositions, clinical trials, and manufacturing technologies for nucleic acid-ionizable LNPs. For the first time, we updated the distinction between ionizable LNPs and other lipid particles. We also proposed an alternate thermocycling technology for high industrial scale-up and the stability of nucleic acid-ionizing LNPs.

EXPERT OPINION

Nucleic acid-ionizable LNPs have a promising future for delivering nucleic acids in a target-specific manner. Though ionizing LNPs are in their early stages, they face several challenges, including only hepatic delivery, a short shelf life, and ultra-cold storage. In our opinion, ligand-based, target-specific synthesized novel lipids and advanced manufacturing technologies can easily overcome the restrictions and open up a new approach for improved therapeutic efficacy for chronic disorders.

Antitumor Activity of Anti-miR-21 Delivered through Lipid Nanoparticles

The ability of lipid nanoparticles (LNPs) to deliver nucleic acids have shown a great therapeutic potential to treat a variety of diseases. Here, an optimized formulation of QTsome lipid nanoparticles (QTPlus) is utilized to deliver an anti-miR-21 (AM21) against cancer. The miR-21 downstream gene regulation and antitumor activity is evaluated using mouse and human cancer cells and macrophages. The antitumor activity of QTPlus encapsulating AM21 (QTPlus-AM21) is further evaluated in combination with erlotinib and atezolizumab (ATZ). QTPlus-AM21 demonstrates a superior miR-21-dependent gene regulation and eventually inhibits A549 non-small cell lung cancer growth in vitro. QTPlus-AM21 further induces chemo-sensitization of A549 cells to erlotinib with a combination index of 0.6 in inhibiting A549 cell growth. When systemically administers to MC38 tumor-bearing mouse model, QTPlus-AM21 exhibits an antitumor immune response with over 80% tumor growth inhibition (TGI%) and over twofold and fourfold PD-1 and PD-L1 upregulation in tumors and spleens. The combination therapy of QTPlus-AM21 and ATZ further shows a higher antitumor response (TGI% over 90%) and successfully increases M1 macrophages and CD8 T cells into TME. This study provides new insights into the antitumor mechanism of AM21 and shows great promise of QTPlus-AM21 in combination with chemotherapies and immunotherapies.

Structure and Function of Cationic and Ionizable Lipids for Nucleic Acid Delivery

Hereditary genetic diseases, cancer, and infectious diseases are affecting global health and become major health issues, but the treatment development remains challenging. Gene therapies using DNA plasmid, RNAi, miRNA, mRNA, and gene editing hold great promise. Lipid nanoparticle (LNP) delivery technology has been a revolutionary development, which has been granted for clinical applications, including mRNA vaccines against SARS-CoV-2 infections. Due to the success of LNP systems, understanding the structure, formulation, and function relationship of the lipid components in LNP systems is crucial for design more effective LNP. Here, we highlight the key considerations for developing an LNP system. The evolution of structure and function of lipids as well as their LNP formulation from the early-stage simple formulations to multi-components LNP and multifunctional ionizable lipids have been discussed. The flexibility and platform nature of LNP enable efficient intracellular delivery of a variety of therapeutic nucleic acids and provide many novel treatment options for the diseases that are previously untreatable.

Lipid Nanoparticles for Nucleic Acid Delivery to Endothelial Cells

Endothelial cells play critical roles in circulatory homeostasis and are also the gateway to the major organs of the body. Dysfunction, injury, and gene expression profiles of these cells can cause, or are caused by, prevalent chronic diseases such as diabetes, cardiovascular disease, and cancer. Modulation of gene expression within endothelial cells could therefore be therapeutically strategic in treating longstanding disease challenges. Lipid nanoparticles (LNP) have emerged as potent, scalable, and tunable carrier systems for delivering nucleic acids, making them attractive vehicles for gene delivery to endothelial cells. Here, we discuss the functions of endothelial cells and highlight some receptors that are upregulated during health and disease. Examples and applications of DNA, mRNA, circRNA, saRNA, siRNA, shRNA, miRNA, and ASO delivery to endothelial cells and their targets are reviewed, as well as LNP composition and morphology, formulation strategies, target proteins, and biomechanical factors that modulate endothelial cell targeting. Finally, we discuss FDA-approved LNPs as well as LNPs that have been tested in clinical trials and their challenges, and provide some perspectives as to how to surmount those challenges.

The therapeutic prospects of N-acetylgalactosamine-siRNA conjugates

RNA interference has become increasingly used for genetic therapy following the rapid development of oligonucleotide drugs. Significant progress has been made in its delivery system and implementation in the treatment of target organs. After a brief introduction of RNA interference technology and siRNA, the efficiency and stability of GalNAc-siRNA conjugates are highlighted since several oligonucleotide drugs of GalNAc have been approved for clinical use in recent years. The structure and features of GalNAc-siRNA conjugates are studied and the clinical efficiency and limitations of oligonucleotide-based drugs are summarized and investigated. Furthermore, another delivery system, lipid nanoparticles, that confer many advantages, is concluded, includ-ing stability and mass production, compared with GalNAc-siRNA conjugates. Importantly, developing new approaches for the use of oligonucleotide drugs brings hope to genetic therapy.

Therapeutic and diagnostic applications of nanoparticles in the management of COVID-19: a comprehensive overview

In December 2019, Coronavirus Disease 2019 (COVID-19) was reported in Wuhan, China. Comprehensive strategies for quick identification, prevention, control, and remedy of COVID-19 have been implemented until today. Advances in various nanoparticle-based technologies, including organic and inorganic nanoparticles, have created new perspectives in this field. These materials were extensively used to control COVID-19 because of their specific attribution to preparing antiviral face masks, various safety sensors, etc. In this review, the most current nanoparticle-based technologies, applications, and achievements against the coronavirus were summarized and highlighted. This paper also offers nanoparticle preventive, diagnostic, and treatment options to combat this pandemic.

Cancerous pH-responsive polycarboxybetaine-coated lipid nanoparticle for smart delivery of siRNA against subcutaneous tumor model in mice

Lipid nanoparticles (LNPs) have been commonly used as a vehicle for nucleic acids, such as small interfering RNA (siRNA); the surface modification of LNPs is one of the determinants of their delivery efficiency especially in systemic administration. However, the applications of siRNA-encapsulated LNPs are limited due to a lack effective systems to deliver to solid tumors. Here, we report a smart surface modification using a charge-switchable ethylenediamine-based polycarboxybetaine for enhancing tumor accumulation via interaction with anionic tumorous tissue constituents due to selective switching to cationic charge in response to cancerous acidic pH. Our polycarboxybetaine-modified LNP could enhance cellular uptake in cancerous pH, resulting in facilitated endosomal escape and gene knockdown efficiency. After systemic administration, the polycarboxybetaine-modified LNP accomplished high tumor accumulation in SKOV3-luc and CT 26 subcutaneous tumor models. The siPLK-1-encapsulated LNP thereby accomplished significant tumor growth inhibition. This study demonstrates a promising potential of the pH-responsive polycarboxybetaine as a material for modifying the surface of LNPs for efficient nucleic acid delivery.

Relative risk reduction: Misinformative measure in clinical trials and COVID-19 vaccine efficacy

Treatment and vaccine efficacy in clinical trials are often reported in the media and medical journals as the relative risk reduction. The present article explains why the relative risk reduction is a misinformative measure that promotes disinformation when reporting efficacy in clinical research studies such as randomized controlled trials for COVID-19 vaccines. The relative risk reduction is based on the relative risk, a proportional measure or ratio used in epidemiologic studies to estimate the probability of a disease associated with an exposure. The present article demonstrates how the relative risk reduction and relative risk obscure the magnitude of disease risk reduction in clinical research. The absolute risk reduction is shown to be a more precise and reliable measure of treatment and vaccine efficacy in clinical research studies. The absolute risk reduction reciprocal also measures the number needed to treat or vaccinate, and is a more accurate measure than the relative risk reduction for comparing risk reductions of clinical studies. Additionally, the present article reviews consequences of COVID-19 vaccine efficacy misinformation disseminated through media reports. The article concludes that relative risk reduction should not be used to measure treatment and vaccine efficacy in clinical trials.

What is new?

•Unreliability of relative measures in clinical trials is graphically illustrated, demonstrating constant relative measures as absolute measures change.•Misuse of relative measures in clinical research is historically linked to misinterpretation of Jerome Cornfield's advice on measuring causative and associative effects.•Consequences of disinformation and misinformation related to COVID-19 vaccine efficacy and modern clinical medicine are described.•The proper use of absolute measures in meta-analyses is explained.

Mechanisms and challenges of nanocarriers as non-viral vectors of therapeutic genes for enhanced pulmonary delivery

With the rapid development of biopharmaceuticals and the outbreak of COVID-19, the world has ushered in a frenzy to develop gene therapy. Therefore, therapeutic genes have received enormous attention. However, due to the extreme instability and low intracellular gene expression of naked genes, specific vectors are required. Viral vectors are widely used attributed to their high transfection efficiency. However, due to the safety concerns of viral vectors, nanotechnology-based non-viral vectors have attracted extensive investigation. Still, issues of low transfection efficiency and poor tissue targeting of non-viral vectors need to be addressed. Especially, pulmonary gene delivery has obvious advantages for the treatment of inherited lung diseases, lung cancer, and viral pneumonia, which can not only enhance lung targeting and but also reduce enzymatic degradation. For systemic diseases therapy, pulmonary gene delivery can enhance vaccine efficacy via inducing not only cellular, humoral immunity but also mucosal immunity. This review provides a comprehensive overview of nanocarriers as non-viral vectors of therapeutic genes for enhanced pulmonary delivery. First of all, the characteristics and therapeutic mechanism of DNA, mRNA, and siRNA are provided. Thereafter, the advantages and challenges of pulmonary gene delivery in exerting local and systemic effects are discussed. Then, the inhalation dosage forms for nanoparticle-based drug delivery systems are introduced. Moreover, a series of materials used as nanocarriers for pulmonary gene delivery are presented, and the endosomal escape mechanisms of nanocarriers based on different materials are explored. The application of various non-viral vectors for pulmonary gene delivery are summarized in detail, with the perspectives of nano-vectors for pulmonary gene delivery.

Transformable nanoparticles to bypass biological barriers in cancer treatment

Nanomedicine based drug delivery platforms provide an interesting avenue to explore for the future of cancer treatment. Here we discuss the barriers for drug delivery in cancer therapeutics and how nanomaterials have been designed to bypass these blockades through stimuli responsive transformation in the most recent update. Nanomaterials that address the challenges of each step provide a promising solution for new cancer therapeutics.

Delivery of RNAs to Specific Organs by Lipid Nanoparticles for Gene Therapy

Gene therapy holds great promise in the treatment of genetic diseases. It is now possible to make DNA modifications using the CRISPR system. However, a major problem remains: the delivery of these CRISPR-derived technologies to specific organs. Lipid nanoparticles (LNPs) have emerged as a very promising delivery method. However, when delivering LNPs intravenously, most of the cargo is trapped by the liver. Alternatively, injecting them directly into organs, such as the brain, requires more invasive procedures. Therefore, developing more specific LNPs is crucial for their future clinical use. Modifying the composition of the lipids in the LNPs allows more specific deliveries of the LNPs to some organs. In this review, we have identified the most effective compositions and proportions of lipids for LNPs to target specific organs, such as the brain, lungs, muscles, heart, liver, spleen, and bones.

Synergetic Thermal Therapy for Cancer: State-of-the-Art and the Future

As a safe and minimal-invasive modality, thermal therapy has become an effective treatment in cancer treatment. Other than killing the tumor cells or destroying the tumor entirely, the thermal modality results in profound molecular, cellular and biological effects on both the targeted tissue, surrounding environments, and even the whole body, which has triggered the combination of the thermal therapy with other traditional therapies as chemotherapy and radiation therapy or new therapies like immunotherapy, gene therapy, etc. The combined treatments have shown encouraging therapeutic effects both in research and clinic. In this review, we have summarized the outcomes of the existing synergistic therapies, the underlying mechanisms that lead to these improvements, and the latest research in the past five years. Limitations and future directions of synergistic thermal therapy are also discussed.