Lipid nanoparticles for nucleic acid delivery: Current perspectives

Evolution of Vaccines Formulation to Tackle the Challenge of Anti-Microbial Resistant Pathogens

The increasing diffusion of antimicrobial resistance (AMR) across more and more bacterial species emphasizes the urgency of identifying innovative treatment strategies to counter its diffusion. Pathogen infection prevention is among the most effective strategies to prevent the spread of both disease and AMR. Since their discovery, vaccines have been the strongest prophylactic weapon against infectious diseases, with a multitude of different antigen types and formulative strategies developed over more than a century to protect populations from different pathogens. In this review, we review the main characteristics of vaccine formulations in use and under development against AMR pathogens, focusing on the importance of administering multiple antigens where possible, and the challenges associated with their development and production. The most relevant antigen classes and adjuvant systems are described, highlighting their mechanisms of action and presenting examples of their use in clinical trials against AMR. We also present an overview of the analytical and formulative strategies for multivalent vaccines, in which we discuss the complexities associated with mixing multiple components in a single formulation. This review emphasizes the importance of combining existing knowledge with advanced technologies within a Quality by Design development framework to efficiently develop vaccines against AMR pathogens.

Vaccine adjuvants: mechanisms and platforms

Adjuvants are indispensable components of vaccines. Despite being widely used in vaccines, their action mechanisms are not yet clear. With a greater understanding of the mechanisms by which the innate immune response controls the antigen-specific response, the adjuvants' action mechanisms are beginning to be elucidated. Adjuvants can be categorized as immunostimulants and delivery systems. Immunostimulants are danger signal molecules that lead to the maturation and activation of antigen-presenting cells (APCs) by targeting Toll-like receptors (TLRs) and other pattern recognition receptors (PRRs) to promote the production of antigen signals and co-stimulatory signals, which in turn enhance the adaptive immune responses. On the other hand, delivery systems are carrier materials that facilitate antigen presentation by prolonging the bioavailability of the loaded antigens, as well as targeting antigens to lymph nodes or APCs. The adjuvants' action mechanisms are systematically summarized at the beginning of this review. This is followed by an introduction of the mechanisms, properties, and progress of classical vaccine adjuvants. Furthermore, since some of the adjuvants under investigation exhibit greater immune activation potency than classical adjuvants, which could compensate for the deficiencies of classical adjuvants, a summary of the adjuvant platforms under investigation is subsequently presented. Notably, we highlight the different action mechanisms and immunological properties of these adjuvant platforms, which will provide a wide range of options for the rational design of different vaccines. On this basis, this review points out the development prospects of vaccine adjuvants and the problems that should be paid attention to in the future.

Cancer Vaccines: From the State of the Art to the Most Promising Frontiers in the Treatment of Colorectal Cancer

Colorectal cancer represents 10% of all new cancer cases each year and accounts for almost 10% of all cancer deaths. According to the WHO, by 2040 there will be a 60% increase in colorectal cancer cases. These data highlight the need to explore new therapeutic strategies. Classical interventions include surgical resection, chemotherapy and radiotherapy, which are invasive strategies that have many side effects on the patients and greatly affect their quality of life. A great advance in the treatment of this cancer type, as well as of all the others, could be the development of a vaccination strategy preventing the onset, the progression or the relapse of the pathology. In this review, we summarize the main vaccination strategies that are being studied for the treatment of colorectal cancer (CRC) and finally explore the possibility of using B-cells for the development of a new type of vaccine.

Multiomics analysis of naturally efficacious lipid nanoparticle coronas reveals high-density lipoprotein is necessary for their function

In terms of lipid nanoparticle (LNP) engineering, the relationship between particle composition, delivery efficacy, and the composition of the biocoronas that form around LNPs, is poorly understood. To explore this we analyze naturally efficacious biocorona compositions using an unbiased screening workflow. First, LNPs are complexed with plasma samples, from individual lean or obese male rats, and then functionally evaluated in vitro. Then, a fast, automated, and miniaturized method retrieves the LNPs with intact biocoronas, and multiomics analysis of the LNP-corona complexes reveals the particle corona content arising from each individual plasma sample. We find that the most efficacious LNP-corona complexes were enriched with high-density lipoprotein (HDL) and, compared to the commonly used corona-biomarker Apolipoprotein E, corona HDL content was a superior predictor of in-vivo activity. Using technically challenging and clinically relevant lipid nanoparticles, these methods reveal a previously unreported role for HDL as a source of ApoE and, form a framework for improving LNP therapeutic efficacy by controlling corona composition.

ASL mRNA-LNP Therapeutic for the Treatment of Argininosuccinic Aciduria Enables Survival Benefit in a Mouse Model

Argininosuccinic aciduria (ASA) is a metabolic disorder caused by a deficiency in argininosuccinate lyase (ASL), which cleaves argininosuccinic acid to arginine and fumarate in the urea cycle. ASL deficiency (ASLD) leads to hepatocyte dysfunction, hyperammonemia, encephalopathy, and respiratory alkalosis. Here we describe a novel therapeutic approach for treating ASA, based on nucleoside-modified messenger RNA (modRNA) formulated in lipid nanoparticles (LNP). To optimize ASL-encoding mRNA, we modified its cap, 5' and 3' untranslated regions, coding sequence, and the poly(A) tail. We tested multiple optimizations of the formulated mRNA in human cells and wild-type C57BL/6 mice. The ASL protein showed robust expression in vitro and in vivo and a favorable safety profile, with low cytokine and chemokine secretion even upon administration of increasing doses of ASL mRNA-LNP. In the ASL^Neo/Neo mouse model of ASLD, intravenous administration of the lead therapeutic candidate LNP-ASL CDS2 drastically improved the survival of the mice. When administered twice a week lower doses partially protected and 3 mg/kg LNP-ASL CDS2 fully protected the mice. These results demonstrate the considerable potential of LNP-formulated, modified ASL-encoding mRNA as an effective alternative to AAV-based approaches for the treatment of ASA.

Nanomaterials in tumor immunotherapy: new strategies and challenges

Tumor immunotherapy exerts its anti-tumor effects by stimulating and enhancing immune responses of the body. It has become another important modality of anti-tumor therapy with significant clinical efficacy and advantages compared to chemotherapy, radiotherapy and targeted therapy. Although various kinds of tumor immunotherapeutic drugs have emerged, the challenges faced in the delivery of these drugs, such as poor tumor permeability and low tumor cell uptake rate, had prevented their widespread application. Recently, nanomaterials had emerged as a means for treatment of different diseases due to their targeting properties, biocompatibility and functionalities. Moreover, nanomaterials possess various characteristics that overcome the defects of traditional tumor immunotherapy, such as large drug loading capacity, precise tumor targeting and easy modification, thus leading to their wide application in tumor immunotherapy. There are two main classes of novel nanoparticles mentioned in this review: organic (polymeric nanomaterials, liposomes and lipid nanoparticles) and inorganic (non-metallic nanomaterials and metallic nanomaterials). Besides, the fabrication method for nanoparticles, Nanoemulsions, was also introduced. In summary, this review article mainly discussed the research progress of tumor immunotherapy based on nanomaterials in the past few years and offers a theoretical basis for exploring novel tumor immunotherapy strategies in the future.

The interplay between noncoding RNAs and drug resistance in hepatocellular carcinoma: the big impact of little things

Hepatocellular carcinoma (HCC) is the leading cause of cancer-related death in people, and a common primary liver cancer. Lacking early diagnosis and a high recurrence rate after surgical resection, systemic treatment is still an important treatment method for advanced HCC. Different drugs have distinct curative effects, side effects and drug resistance due to different properties. At present, conventional molecular drugs for HCC have displayed some limitations, such as adverse drug reactions, insensitivity to some medicines, and drug resistance. Noncoding RNAs (ncRNAs), including microRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs), have been well documented to be involved in the occurrence and progression of cancer. Novel biomarkers and therapeutic targets, as well as research into the molecular basis of drug resistance, are urgently needed for the management of HCC. We review current research on ncRNAs and consolidate the known roles regulating drug resistance in HCC and examine the potential clinical applications of ncRNAs in overcoming drug resistance barriers in HCC based on targeted therapy, cell cycle non-specific chemotherapy and cell cycle specific chemotherapy.

Lipid-based nanoparticles for cancer immunotherapy

As the fourth most important cancer management strategy except surgery, chemotherapy and radiotherapy, cancer immunotherapy has been confirmed to elicit durable antitumor effects in the clinic by leveraging the patient's own immune system to eradicate the cancer cells. However, the limited population of patients who benefit from the current immunotherapies and the immune related adverse events hinder its development. The immunosuppressive microenvironment is the main cause of the failure, which leads to cancer immune evasion and immunity cycle blockade. Encouragingly, nanotechnology has been engineered to enhance the efficacy and reduce off-target toxicity of their therapeutic cargos by spatiotemporally controlling the biodistribution and release kinetics. Among them, lipid-based nanoparticles are the first nanomedicines to make clinical translation, which are now established platforms for diverse areas. In this perspective, we discuss the available lipid-based nanoparticles in research and market here, then describe their application in cancer immunotherapy, with special emphasis on the T cells-activated and macrophages-targeted delivery system. Through perpetuating each step of cancer immunity cycle, lipid-based nanoparticles can reduce immunosuppression and promote drug delivery to trigger robust antitumor response.

Cargo-selective and adaptive delivery of nucleic acid therapeutics by bola-amphiphilic dendrimers

Nucleic acid therapeutics are becoming an important drug modality, offering the unique opportunity to address "undruggable" targets, respond rapidly to evolving pathogens, and treat diseases at the gene level for precision medicine. However, nucleic acid therapeutics have poor bioavailability and are chemolabile and enzymolabile, imposing the need for delivery vectors. Dendrimers, by virtue of their well-defined structure and cooperative multivalence, represent precision delivery systems. We synthesized and studied bola-amphiphilic dendrimers for cargo-selective and on-demand delivery of DNA and small interfering RNA (siRNA), both important nucleic acid therapeutics. Remarkably, superior performances were achieved for siRNA delivery with the second-generation dendrimer, yet for DNA delivery with the third generation. We systematically studied these dendrimers with regard to cargo binding, cellular uptake, endosomal release, and in vivo delivery. Differences in size both of the dendrimers and their nucleic acid cargos impacted the cooperative multivalent interactions for cargo binding and release, leading to cargo-adaptive and selective delivery. Moreover, both dendrimers harnessed the advantages of lipid and polymer vectors, while offering nanotechnology-based tumor targeting and redox-responsive cargo release. Notably, they allowed tumor- and cancer cell-specific delivery of siRNA and DNA therapeutics for effective treatment in different cancer models, including aggressive and metastatic malignancies, outperforming the currently available vectors. This study provides avenues to engineer tailor-made vectors for nucleic acid delivery and precision medicine.

LXR signaling controls homeostatic dendritic cell maturation

Dendritic cells (DCs) mature in an immunogenic or tolerogenic manner depending on the context in which an antigen is perceived, preserving the balance between immunity and tolerance. Whereas the pathways driving immunogenic maturation in response to infectious insults are well-characterized, the signals that drive tolerogenic maturation during homeostasis are still poorly understood. We found that the engulfment of apoptotic cells triggered homeostatic maturation of type 1 conventional DCs (cDC1s) within the spleen. This maturation process could be mimicked by engulfment of empty, nonadjuvanted lipid nanoparticles (LNPs), was marked by intracellular accumulation of cholesterol, and was highly specific to cDC1s. Engulfment of either apoptotic cells or cholesterol-rich LNPs led to the activation of the liver X receptor (LXR) pathway, which promotes the efflux of cellular cholesterol, and repressed genes associated with immunogenic maturation. In contrast, simultaneous engagement of TLR3 to mimic viral infection via administration of poly(I:C)-adjuvanted LNPs repressed the LXR pathway, thus delaying cellular cholesterol efflux and inducing genes that promote T cell-mediated immunity. These data demonstrate that conserved cellular cholesterol efflux pathways are differentially regulated in tolerogenic versus immunogenic cDC1s and suggest that administration of nonadjuvanted cholesterol-rich LNPs may be an approach for inducing tolerogenic DC maturation.

Advances and Challenges of Stimuli-Responsive Nucleic Acids Delivery System in Gene Therapy

Gene therapy has emerged as a powerful tool to treat various diseases, such as cardiovascular diseases, neurological diseases, ocular diseases and cancer diseases. In 2018, the FDA approved Patisiran (the siRNA therapeutic) for treating amyloidosis. Compared with traditional drugs, gene therapy can directly correct the disease-related genes at the genetic level, which guarantees a sustained effect. However, nucleic acids are unstable in circulation and have short half-lives. They cannot pass through biological membranes due to their high molecular weight and massive negative charges. To facilitate the delivery of nucleic acids, it is crucial to develop a suitable delivery strategy. The rapid development of delivery systems has brought light to the gene delivery field, which can overcome multiple extracellular and intracellular barriers that prevent the efficient delivery of nucleic acids. Moreover, the emergence of stimuli-responsive delivery systems has made it possible to control the release of nucleic acids in an intelligent manner and to precisely guide the therapeutic nucleic acids to the target site. Considering the unique properties of stimuli-responsive delivery systems, various stimuli-responsive nanocarriers have been developed. For example, taking advantage of the physiological variations of a tumor (pH, redox and enzymes), various biostimuli- or endogenous stimuli-responsive delivery systems have been fabricated to control the gene delivery processes in an intelligent manner. In addition, other external stimuli, such as light, magnetic fields and ultrasound, have also been employed to construct stimuli-responsive nanocarriers. Nevertheless, most stimuli-responsive delivery systems are in the preclinical stage, and some critical issues remain to be solved for advancing the clinical translation of these nanocarriers, such as the unsatisfactory transfection efficiency, safety issues, complexity of manufacturing and off-target effects. The purpose of this review is to elaborate the principles of stimuli-responsive nanocarriers and to emphasize the most influential advances of stimuli-responsive gene delivery systems. Current challenges of their clinical translation and corresponding solutions will also be highlighted, which will accelerate the translation of stimuli-responsive nanocarriers and advance the development of gene therapy.

An Overview of the Stability and Delivery Challenges of Commercial Nucleic Acid Therapeutics

Nucleic acid (NA)-based biopharmaceuticals have emerged as promising therapeutic modalities. NA therapeutics are a diverse class of RNA and DNA and include antisense oligonucleotides, siRNA, miRNA, mRNA, small activating RNA, and gene therapies. Meanwhile, NA therapeutics have posed significant stability and delivery challenges and are expensive. This article discusses the challenges and opportunities for achieving stable formulations of NAs with novel drug delivery systems (DDSs). Here we review the current progress in the stability issues and the significance of novel DDSs associated with NA-based biopharmaceuticals, as well as mRNA vaccines. We also highlight the European Medicines Agency (EMA) and US Food and Drug Administration (FDA)-approved NA-based therapeutics with their formulation profiles. NA therapeutics could impact future markets if the remaining challenges and requirements are addressed. Regardless of the limited information available for NA therapeutics, reviewing and collating the relevant facts and figures generates a precious resource for formulation experts familiar with the NA therapeutics' stability profile, their delivery challenges, and regulatory acceptance.

Unsaturated, Trialkyl Ionizable Lipids are Versatile Lipid-Nanoparticle Components for Therapeutic and Vaccine Applications

Lipid nanoparticles (LNPs) have proven a successful platform for the delivery of nucleic acid (NA)-based therapeutics and vaccines, with the ionizable lipid component playing a key role in modulating potency and tolerability. Here, a library of 16 novel ionizable lipids is screened hypothesizing that short, branched trialkyl hydrophobic domains can improve LNP fusogenicity or endosomal escape, and potency. LNPs formulated with the top-performing trialkyl lipid (Lipid 10) encapsulating transthyretin siRNA elicit significantly greater gene silencing and are better tolerated than those with the benchmark Onpattro lipid DLin-MC3-DMA. Lipid 10 also demonstrates superior liver delivery of mRNA when compared to other literature ionizable lipids, is well tolerated, and successfully repeat-doses in nonhuman primates. In a prime-boost hemagglutinin rodent vaccine model, intramuscular administration of Lipid-10 LNP elicits comparable or better antibody titers to the SM-102 and ALC-0315 lipid compositions used in the U.S. Food and Drug Administration approved mRNA COVID vaccines. These data suggest that Lipid 10 is a particularly versatile ionizable lipid, well-suited for both systemic therapeutic and intramuscular vaccine applications and able to successfully deliver diverse NA payloads.

Shaping the future from the small scale: dry powder inhalation of CRISPR-Cas9 lipid nanoparticles for the treatment of lung diseases

INTRODUCTION

Most lung diseases are serious conditions resulting from genetic and environmental causes associated with high mortality and severe symptoms. Currently, treatments available have a palliative effect and many targets are still considered undruggable. Gene therapy stands as an attractive approach to offering innovative therapeutic solutions. CRISPRCas9 has established a remarkable potential for genome editing with high selectivity to targeted mutations. To ensure high efficacy with minimum systemic exposure, the delivery and administration route are key components that must be investigated.

AREAS COVERED

This review is focused on the delivery of CRISPRCas9 to the lungs, taking advantage of lipid nanoparticles (LNPs), the most clinically advanced nucleic acid carriers. We also aim to highlight the benefits of pulmonary administration as a local delivery route and the use of spray drying to prepare stable nucleic-acid-based dry powder formulations that can overcome multiple lung barriers.

EXPERT OPINION

Exploring the pulmonary administration to deliver CRISPRCas9 loaded in LNPs as a dry powder increases the chances to achieve high efficacy and reduced adverse effects. CRISPRCas9 loaded in LNP-embedded microparticles has not yet been reported in the literature but has the potential to reach and accumulate in target cells in the lung, thus, enhancing overall efficacy and safety.

Lysine-Derived Charge-Altering Releasable Transporters: Targeted Delivery of mRNA and siRNA to the Lungs

Targeted delivery of nucleic acid therapeutics to the lungs could transform treatment options for pulmonary disease. We have previously developed oligomeric charge-altering releasable transporters (CARTs) for in vivo mRNA transfection and demonstrated their efficacy for use in mRNA-based cancer vaccination and local immunomodulatory therapies against murine tumors. While our previously reported glycine-based CART-mRNA complexes (G-CARTs/mRNA) show selective protein expression in the spleen (mouse, >99%), here, we report a new lysine-derived CART-mRNA complex (K-CART/mRNA) that, without additives or targeting ligands, shows selective protein expression in the lungs (mouse, >90%) following systemic IV administration. We further show that by delivering siRNA using the K-CART, we can significantly decrease expression of a lung-localized reporter protein. Blood chemistry and organ pathology studies demonstrate that K-CARTs are safe and well-tolerated. We report on the new step economical, organocatalytic synthesis (two steps) of functionalized polyesters and oligo-carbonate-co-α-aminoester K-CARTs from simple amino acid and lipid-based monomers. The ability to direct protein expression selectively in the spleen or lungs by simple, modular changes to the CART structure opens fundamentally new opportunities in research and gene therapy.

Lipid-based colloidal nanoparticles for applications in targeted vaccine delivery

Bioactive molecules and their effects have been influenced by their solubility and administration route. In many therapeutic reagents, the performance of therapeutics is dependent on physiological barriers in the human body and delivery efficacy. Therefore, an effective and stable therapeutic delivery promotes pharmaceutical advancement and suitable biological usage of drugs. In the biological and pharmacological industries, lipid nanoparticles (LNPs) have emerged as a potential carrier to deliver therapeutics. Since studies reported doxorubicin-loaded liposomes (Doxil®), LNPs have been applied to numerous clinical trials. Lipid-based nanoparticles, including liposomes, solid lipid nanoparticles (SLNs), and nanostructured lipid nanoparticles, have also been developed to deliver active ingredients in vaccines. In this review, we present the type of LNPs used to develop vaccines with attractive advantages. We then discuss messenger RNA (mRNA) delivery for the clinical application of mRNA therapeutic-loaded LNPs and recent research trend of LNP-based vaccine development.

Designing supramolecular self-assembly nanomaterials as stimuli-responsive drug delivery platforms for cancer therapy

Stimuli-responsive nanomaterials have attracted substantial interest in cancer therapy, as they hold promise to deliver anticancer agents to tumor sites in a precise and on-demand manner. Interestingly, supramolecular chemistry is a burgeoning discipline that entails the reversible bonding between components at the molecular and nanoscale levels, and the recent advances in this area offer the possibility to design nanotherapeutics with improved controllability and functionality for cancer therapy. Herein, we provide a comprehensive summary of typical non-covalent interaction modes, which primarily include hydrophobic interaction, hydrogel bonding, host-guest interaction, π-π stacking, and electrostatic interaction. Special emphasis is placed on the implications of these interaction modes to design novel stimuli-responsive drug delivery principles and concepts, aiming to enhance the spatial, temporal, and dosage precision of drug delivery to cancer cells. Finally, future perspectives are discussed to highlight current challenges and future opportunities in self-assembly-based stimuli-responsive drug delivery nanotechnologies for cancer therapy.

Development and applications of mRNA treatment based on lipid nanoparticles

Nucleic acid-based therapies such as messenger RNA have the potential to revolutionize modern medicine and enhance the performance of existing pharmaceuticals. The key challenges of mRNA-based therapies are delivering the mRNA safely and effectively to the target tissues and cells and controlling its release from the delivery vehicle. Lipid nanoparticles (LNPs) have been widely studied as drug carriers and are considered to be state-of-the-art technology for nucleic acid delivery. In this review, we begin by presenting the advantages and mechanisms of action of mRNA therapeutics. Then we discuss the design of LNP platforms based on ionizable lipids and the applications of mRNA-LNP vaccines for prevention of infectious diseases and for treatment of cancer and various genetic diseases. Finally, we describe the challenges and future prospects of mRNA-LNP therapeutics.

Recent Advances in the Lipid Nanoparticle-Mediated Delivery of mRNA Vaccines

Lipid nanoparticles (LNPs) have recently emerged as one of the most advanced technologies for the highly efficient in vivo delivery of exogenous mRNA, particularly for COVID-19 vaccine delivery. LNPs comprise four different lipids: ionizable lipids, helper or neutral lipids, cholesterol, and lipids attached to polyethylene glycol (PEG). In this review, we present recent the advances and insights for the design of LNPs, as well as their composition and properties, with a subsequent discussion on the development of COVID-19 vaccines. In particular, as ionizable lipids are the most critical drivers for complexing the mRNA and in vivo delivery, the role of ionizable lipids in mRNA vaccines is discussed in detail. Furthermore, the use of LNPs as effective delivery vehicles for vaccination, genome editing, and protein replacement therapy is explained. Finally, expert opinion on LNPs for mRNA vaccines is discussed, which may address future challenges in developing mRNA vaccines using highly efficient LNPs based on a novel set of ionizable lipids. Developing highly efficient mRNA delivery systems for vaccines with improved safety against some severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants remains difficult.

Optimal delivery strategies for nanoparticle-mediated mRNA delivery

Messenger RNA (mRNA) has emerged as a new and efficient agent for the treatment of various diseases. The success of lipid nanoparticle-mRNA against the novel coronavirus (SARS-CoV-2) pneumonia epidemic has proved the clinical potential of nanoparticle-mRNA formulations. However, the deficiency in the effective biological distribution, high transfection efficiency and good biosafety are still the major challenges in clinical translation of nanomedicine for mRNA delivery. To date, a variety of promising nanoparticles have been constructed and then gradually optimized to facilitate the effective biodistribution of carriers and efficient mRNA delivery. In this review, we describe the design of nanoparticles with an emphasis on lipid nanoparticles, and discuss the manipulation strategies for nanoparticle-biology (nano-bio) interactions for mRNA delivery to overcome the biological barriers and improve the delivery efficiency, because the specific nano-bio interaction of nanoparticles usually remoulds the biomedical and physiological properties of the nanoparticles especially the biodistribution, mechanism of cellular internalization and immune response. Finally, we give a perspective for the future applications of this promising technology. We believe that the regulation of nano-bio interactions would be a significant breakthrough to improve the mRNA delivery efficiency and cross biological barriers. This review may provide a new direction for the design of nanoparticle-mediated mRNA delivery systems.

Delivery challenges for CRISPR-Cas9 genome editing for Duchenne muscular dystrophy

Duchene muscular dystrophy (DMD) is an X-linked neuromuscular disorder that affects about one in every 5000 live male births. DMD is caused by mutations in the gene that codes for dystrophin, which is required for muscle membrane stabilization. The loss of functional dystrophin causes muscle degradation that leads to weakness, loss of ambulation, cardiac and respiratory complications, and eventually, premature death. Therapies to treat DMD have advanced in the past decade, with treatments in clinical trials and four exon-skipping drugs receiving conditional Food and Drug Administration approval. However, to date, no treatment has provided long-term correction. Gene editing has emerged as a promising approach to treating DMD. There is a wide range of tools, including meganucleases, zinc finger nucleases, transcription activator-like effector nucleases, and, most notably, RNA-guided enzymes from the bacterial adaptive immune system clustered regularly interspaced short palindromic repeats (CRISPR). Although challenges in using CRISPR for gene therapy in humans still abound, including safety and efficiency of delivery, the future for CRISPR gene editing for DMD is promising. This review will summarize the progress in CRISPR gene editing for DMD including key summaries of current approaches, delivery methodologies, and the challenges that gene editing still faces as well as prospective solutions.

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.

Lipid-based nucleic acid therapeutics with in vivo efficacy

Synthetic vectors for therapeutic nucleic acid delivery are currently competing significantly with their viral counter parts due to their reduced immunogenicity, large payload capacity, and ease of manufacture under GMP-compliant norms. The approval of Onpattro, a lipid-based siRNA therapeutic, and the proven clinical success of two lipid-based COVID-19 vaccines from Pfizer-BioNTech, and Moderna heralded the specific advantages of lipid-based systems among all other synthetic nucleic acid carriers. Lipid-based systems with diverse payloads-plasmid DNA (pDNA), antisense oligonucleotide (ASO), small interfering RNA (siRNA), microRNA (miRNA), small activating RNA (saRNA), and messenger RNA (mRNA)-are now becoming a mature technology, with growing impact in the clinic. Research over four decades identified the key factors determining the therapeutic success of these multi-component systems. Here, we discuss the main nucleic acid-based technologies, presenting their mechanism of action, delivery barriers facing them, the structural properties of the payload as well as the component lipids that regulate physicochemical properties, pharmacokinetics and biodistribution, efficacy, and toxicity of the resultant nanoparticles. We further detail on the formulation parameters, evolution of the manufacturing techniques that generate reproducible and scalable outputs, and key manufacturing aspects that enable control over physicochemical properties of the resultant particles. Preclinical applications of some of these formulations that were successfully translated from in vitro studies to animal models are subsequently discussed. Finally, clinical success and failure of these systems starting from 1993 to present are highlighted, in a holistic literature review focused on lipid-based nucleic acid delivery systems. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

Gene knockdown in HaCaT cells by small interfering RNAs entrapped in grapefruit-derived extracellular vesicles using a microfluidic device

Small interfering RNAs (siRNAs) knockdown the expression of target genes by causing mRNA degradation and are a promising therapeutic modality. In clinical practice, lipid nanoparticles (LNPs) are used to deliver RNAs, such as siRNA and mRNA, into cells. However, these artificial nanoparticles are toxic and immunogenic. Thus, we focused on extracellular vesicles (EVs), natural drug delivery systems, for the delivery of nucleic acids. EVs deliver RNAs and proteins to specific tissues to regulate various physiological phenomena in vivo. Here, we propose a novel method for the preparation siRNAs encapsulated in EVs using a microfluidic device (MD). MDs can be used to generate nanoparticles, such as LNPs, by controlling flow rate to the device, but the loading of siRNAs into EVs using MDs has not been reported previously. In this study, we demonstrated a method for loading siRNAs into grapefruit-derived EVs (GEVs), which have gained attention in recent years for being plant-derived EVs developed using an MD. GEVs were collected from grapefruit juice using the one-step sucrose cushion method, and then GEVs-siRNA-GEVs were prepared using an MD device. The morphology of GEVs and siRNA-GEVs was observed using a cryogenic transmission electron microscope. Cellular uptake and intracellular trafficking of GEVs or siRNA-GEVs to human keratinocytes were evaluated by microscopy using HaCaT cells. The prepared siRNA-GEVs encapsulated 11% of siRNAs. Moreover, intracellular delivery of siRNA and gene suppression effects in HaCaT cells were achieved using these siRNA-GEVs. Our findings suggested that MDs can be used to prepare siRNA-EV formulations.

Optimized workflow to modify microRNA expression in primary human intravascular cells

BACKGROUND

A comprehensive dissection of the role of microRNAs (miRNAs) in gene regulation and subsequent cell functions requires a specific and efficient knockdown or overexpression of the miRNA of interest; these are achieved by transfecting the cell of interest with a miRNA inhibitor or a miRNA mimic, respectively. Inhibitors and mimics of miRNAs with a unique chemistry and/or structural modifications are available commercially and require different transfection conditions. Here, we aimed to investigate how various conditions affect the transfection efficacy of two miRNAs with high and low endogenous expression, miR-15a-5p and miR-20b-5p respectively, in human primary cells.

RESULTS

MiRNA inhibitors and mimics from two commonly used commercial vendors were employed, i.e., mirVana (Thermo Fisher Scientific) and locked nucleic acid (LNA) miRNA (Qiagen). We systematically examined and optimized the transfection conditions of such miRNA inhibitors and mimics to primary endothelial cells and monocytes using either a lipid-based carrier (lipofectamine) for delivery or an unassisted uptake. Transfection of LNA inhibitors with either phosphodiester (PE)- or phosphorothioate (PS)-modified nucleotide bonds, delivered using a lipid-based carrier, efficiently downregulated the expression levels of miR-15a-5p already 24 h following transfection. MirVana miR-15a-5p inhibitor displayed a less efficient inhibitory effect, which was not improved 48 h following a single transfection or two consecutive transfections. Interestingly, LNA-PS miR-15a-5p inhibitor efficiently reduced the levels of miR-15a-5p when delivered without a lipid-based carrier in both ECs and monocytes. When using a carrier, mirVana and LNA miR-15a-5p and miR-20b-5p mimics showed similar efficiency 48 h following transfection to ECs and monocytes. None of the miRNA mimics effectively induced overexpression of the respective miRNA when given to primary cells without a carrier.

CONCLUSION

LNA miRNA inhibitors efficiently downregulated the cellular expression of miRNA, such as miR-15a-5p. Furthermore, our findings suggest that LNA-PS miRNA inhibitors can be delivered in the absence of a lipid-based carrier, whereas miRNA mimics need the aid of a lipid-based carrier to achieve sufficient cellular uptake.

Toxicological Assessments of a Pandemic COVID-19 Vaccine-Demonstrating the Suitability of a Platform Approach for mRNA Vaccines

The emergence of SARS-CoV-2 at the end of 2019 required the swift development of a vaccine to address the pandemic. Nonclinical GLP-compliant studies in Wistar Han rats were initiated to assess the local tolerance, systemic toxicity, and immune response to four mRNA vaccine candidates encoding immunogens derived from the spike (S) glycoprotein of SARS-CoV-2, encapsulated in lipid nanoparticles (LNPs). Vaccine candidates were administered intramuscularly once weekly for three doses at 30 and/or 100 µg followed by a 3-week recovery period. Clinical pathology findings included higher white blood cell counts and acute phase reactant concentrations, lower platelet and reticulocyte counts, and lower RBC parameters. Microscopically, there was increased cellularity (lymphocytes) in the lymph nodes and spleen, increased hematopoiesis in the bone marrow and spleen, acute inflammation and edema at the injection site, and minimal hepatocellular vacuolation. These findings were generally attributed to the anticipated immune and inflammatory responses to the vaccines, except for hepatocyte vacuolation, which was interpreted to reflect hepatocyte LNP lipid uptake, was similar between candidates and resolved or partially recovered at the end of the recovery phase. These studies demonstrated safety and tolerability in rats, supporting SARS-CoV-2 mRNA-LNP vaccine clinical development.

Effect of PEG Anchor and Serum on Lipid Nanoparticles: Development of a Nanoparticles Tracking Method

Polyethylene glycol (PEG) is used in Lipid Nanoparticles (LNPs) formulations to confer stealth properties and is traditionally anchored in membranes by a lipid moiety whose length significantly impacts the LNPs fate in vivo. C18 acyl chains are efficiently anchored in the membrane, while shorter C14 lipids are quickly desorbed and replaced by a protein corona responsible for the completely different fate of LNPs. In this context, a method to predict the biological behavior of LNPs depending on the lipid-PEG dissociation was developed using the Nanoparticle Tracking Analysis (NTA) method in serum. Two formulations of siRNA-containing LNPs were prepared including CSL3 or SM-102 lipids and were grafted with different lipids-PEG (C18, C14 lipids-PEG, and Ceramide-PEG). The impact of the lipid-PEG on the interactions between LNPs and serum components was demonstrated by monitoring the mean particle size and the concentration over time. In vitro, these formulations demonstrated low toxicity and efficient gene knockdown on tumor MDA-MB-231 cells, but serum was found to significantly impact the efficiency of C18-PEG-based LNPs, while it did not impact the efficiency of C14-PEG-based LNPs. The NTA method demonstrated the ability to discriminate between the behaviors of LNPs according to serum proteins' interactions. CSL3 lipid and Cer-PEG were confirmed to have promise for LNP formulation.

Methods for CRISPR-Cas as Ribonucleoprotein Complex Delivery In Vivo

The efficient delivery of CRISPR-Cas components is still a key and unsolved problem. CRISPR-Cas delivery in the form of a Cas protein+sgRNA (ribonucleoprotein complex, RNP complex), has proven to be extremely effective, since it allows to increase on-target activity, while reducing nonspecific activity. The key point for in vivo genome editing is the direct delivery of artificial nucleases and donor DNA molecules into the somatic cells of an adult organism. At the same time, control of the dose of artificial nucleases is impossible, which affects the efficiency of genome editing in the affected cells. Poor delivery efficiency and low editing efficacy reduce the overall potency of the in vivo genome editing process. Here we review how this problem is currently being solved in scientific works and what types of in vivo delivery methods of Cas9/sgRNA RNPs have been developed.

Physicochemical properties, pharmacokinetics, toxicology and application of nanocarriers

As a promising delivery nanosystem for drug controlled-release, nanocarriers (NCs) have been investigated widely. Although various studies have concentrated on the preparation and characterization of nanoparticles (NPs), clinical applications are rarely reported, due to the unclear distribution, absorption, metabolism, toxicology processes and drug release mechanism. The clinical application of NCs is therefore still a long way off. This review describes the effects of the properties of NCs (including size, shape, surface properties, porosity, elasticity and so on) on pharmacological and toxicological behaviours in vivo and medical applications. Moreover, this study is intended to help the readers understand the behaviours and mechanisms of NCs and positively face the challenges caused by the variety of complicated and limited processes of NCs in vivo. Importantly, this article provides some strategies for the clinical application of NCs and may provide ideas to enhance the therapeutic efficacy of NCs without increasing the toxicology, by introducing tracing technology, which can be more suitable in contributing to the development of safety and efficacy of NCs and the growth of nanotechnology.

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.

Lipid Microparticles Show Similar Efficacy With Lipid Nanoparticles in Delivering mRNA and Preventing Cancer

PURPOSE

Messenger RNA (mRNA) has shown great promise for vaccine against both infectious diseases and cancer. However, mRNA is unstable and requires a delivery vehicle for efficient cellular uptake and degradation protection. So far, lipid nanoparticles (LNPs) represent the most advanced delivery platform for mRNA delivery. However, no published studies have compared lipid microparticles (LMPs) with lipid nanoparticles (LNPs) in delivering mRNA systematically, therefore, we compared the impact of particle size on delivery efficacy of mRNA vaccine and subsequent immune responses.

METHODS

Herein, we prepared 3 different size lipid particles, from nano-sized to micro-sized, and they loaded similar amounts of mRNA. These lipid particles were investigated both in vitro and in vivo, followed by evaluating the impact of particle size on inducing cellular and humoral immune responses.

RESULTS

In this study, all mRNA vaccines showed a robust immune response and lipid microparticles (LMPs) show similar efficacy with lipid nanoparticles (LNPs) in delivering mRNA and preventing cancer. In addition, immune adjuvants, either toll like receptors or active molecules from traditional Chinese medicine, can improve the efficacy of mRNA vaccines.

CONCLUSIONS

Considering the efficiency of delivery and endocytosis, besides lipid nanoparticles with size smaller than 150 nm, lipid microparticles (LMPs) also have the potential to be an alternative and promising delivery system for mRNA vaccines.

Passive, active and endogenous organ-targeted lipid and polymer nanoparticles for delivery of genetic drugs

Genetic drugs based on nucleic acid biomolecules are a rapidly emerging class of medicines that directly reprogramme the central dogma of biology to prevent and treat disease. However, multiple biological barriers normally impede the intracellular delivery of nucleic acids, necessitating the use of a delivery system. Lipid and polymer nanoparticles represent leading approaches for the clinical translation of genetic drugs. These systems circumnavigate biological barriers and facilitate the intracellular delivery of nucleic acids in the correct cells of the target organ using passive, active and endogenous targeting mechanisms. In this Review, we highlight the constituent materials of these advanced nanoparticles, their nucleic acid cargoes and how they journey through the body. We discuss targeting principles for liver delivery, as it is the organ most successfully targeted by intravenously administered nanoparticles to date, followed by the expansion of these concepts to extrahepatic (non-liver) delivery. Ultimately, this Review connects emerging materials and biological insights playing key roles in targeting specific organs and cells in vivo.

Nanoparticle drug delivery systems for synergistic delivery of tumor therapy

Nanoparticle drug delivery systems have proved anti-tumor effects; however, they are not widely used in tumor therapy due to insufficient ability to target specific sites, multidrug resistance to anti-tumor drugs, and the high toxicity of the drugs. With the development of RNAi technology, nucleic acids have been delivered to target sites to replace or correct defective genes or knock down specific genes. Also, synergistic therapeutic effects can be achieved for combined drug delivery, which is more effective for overcoming multidrug resistance of cancer cells. These combination therapies achieve better therapeutic effects than delivering nucleic acids or chemotherapeutic drugs alone, so the scope of combined drug delivery has also been expanded to three aspects: drug-drug, drug-gene, and gene-gene. This review summarizes the recent advances of nanocarriers to co-delivery agents, including i) the characterization and preparation of nanocarriers, such as lipid-based nanocarriers, polymer nanocarriers, and inorganic delivery carriers; ii) the advantages and disadvantages of synergistic delivery approaches; iii) the effectual delivery cases that are applied in the synergistic delivery systems; and iv) future perspectives in the design of nanoparticle drug delivery systems to co-deliver therapeutic agents.

Does Patisiran Reduce Ocular Transthyretin Synthesis? A Pilot Study of Two Cases

BACKGROUND

Variant transthyretin-mediated amyloidosis (ATTR-v) is a well-characterized disease affecting the neurologic and cardiovascular systems. Patisiran has been approved for neurologic involvement as it reduces hepatic synthesis of transthyretin (TTR). Eye involvement is a lateonset feature increasing the risk of glaucoma and cataracts in patients.

AIMS

The aim of this case series was to assess whether patisiran can effectively reduce TTR synthesis in such a barrier-protected organ as the eye.

METHODS

Two patisiran-treated ATTR-v patients underwent serum and aqueous humor sampling to measure TTR levels detected by SDS-PAGE and immunoblotting. Serum samples were compared to healthy control (HC), whereas aqueous humor samples were compared to non-amyloidotic subjects affected by cataracts and glaucoma.

RESULTS

Serum TTR levels representative of hepatic synthesis were sharply lower in treated patients if compared to the HC (-87.5% and -93.75%, respectively). Aqueous humor TTR levels showed mild-tono reduction in treated patients compared to non-amyloidotic subjects with cataracts (-34.9% and +8.1%, respectively) and glaucoma (-41.1% and -2.1%).

CONCLUSION

Patisiran does not seem to be as effective in inhibiting ocular TTR synthesis as it is in inhibiting hepatic synthesis. Re-engineering the envelope could allow the drug to target RPE cells thus avoiding any ocular involvement.

Macrophages as potential targets in gene therapy for cancer treatment

Macrophages, as ubiquitous and functionally diverse immune cells, play a central role in innate immunity and initiate adaptive immunity. Especially, tumor-associated macrophages (TAMs) are crucial contributors to the tumorigenesis and development of cancer. Thus, macrophages are emerging potential targets for cancer treatment. Among the numerous targeted therapeutic options, gene therapy is one of the most potential therapeutic strategies via directly and specifically regulating biological functions of macrophages at the gene level for cancer treatment. This short review briefly introduces the characteristics of macrophage populations, the functions of TAM in the occurrence, and the progress of cancer. It also summarized some representative examples to highlight the current progress in TAM-targeted gene therapy. The review hopes to provide new insights into macrophage-targeted gene therapy for precision cancer therapy.

Use of gene therapy for optic nerve protection: Current concepts

Gene therapy has become an essential treatment for optic nerve injury (ONI) in recent years, and great strides have been made using animal models. ONI, which is characterized by the loss of retinal ganglion cells (RGCs) and axons, can induce abnormalities in the pupil light reflex, visual field defects, and even vision loss. The eye is a natural organ to target with gene therapy because of its high accessibility and certain immune privilege. As such, numerous gene therapy trials are underway for treating eye diseases such as glaucoma. The aim of this review was to cover research progress made in gene therapy for ONI. Specifically, we focus on the potential of gene therapy to prevent the progression of neurodegenerative diseases and protect both RGCs and axons. We cover the basic information of gene therapy, including the classification of gene therapy, especially focusing on genome editing therapy, and then we introduce common editing tools and vector tools such as Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) -Cas9 and adeno-associated virus (AAV). We also summarize the progress made on understanding the roles of brain derived neurotrophic factor (BDNF), ciliary neurotrophic factor (CNTF), phosphatase-tensin homolog (PTEN), suppressor of cytokine signal transduction 3 (SOCS3), histone acetyltransferases (HATs), and other important molecules in optic nerve protection. However, gene therapy still has many challenges, such as misalignment and mutations, immunogenicity of AAV, time it takes and economic cost involved, which means that these issues need to be addressed before clinical trials can be considered.

Manganese-coordinated mRNA vaccines with enhanced mRNA expression and immunogenicity induce robust immune responses against SARS-CoV-2 variants

It is urgent to develop more effective mRNA vaccines against the emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants owing to the immune escape. Here, we constructed a novel mRNA delivery system [IC8/Mn lipid nanoparticles (IC8/Mn LNPs)]with high immunogenicity, via introducing a stimulator of interferon genes (STING) agonist [manganese (Mn)] based on a newly synthesized ionizable lipid (IC8). It was found that Mn can not only promote maturation of antigen-presenting cells via activating STING pathway but also improve mRNA expression by facilitating lysosomal escape for the first time. Subsequently, IC8/Mn LNPs loaded with mRNA encoding the Spike protein of SARS-CoV-2 Delta or Omicron variant (IC8/Mn@D or IC8/Mn@O) were prepared. Both mRNA vaccines induced substantial specific immunoglobulin G responses against Delta or Omicron. IC8/Mn@D displayed strong pseudovirus neutralization ability, T helper 1-biased immune responses, and good safety. It can be concluded that IC8/Mn LNPs have great potential for developing Mn-coordinated mRNA vaccines with robust immunogenicity and good safety.

Influence of Lipid Composition of Cationic Liposomes 2X3-DOPE on mRNA Delivery into Eukaryotic Cells

The design of cationic liposomes for efficient mRNA delivery can significantly improve mRNA-based therapies. Lipoplexes based on polycationic lipid 1,26-bis(cholest-5-en-3β-yloxycarbonylamino)-7,11,16,20-tetraazahexacosane tetrahydrochloride (2X3) and helper lipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) were formulated in different molar ratios (1:1, 1:2, 1:3) to efficiently deliver model mRNAs to BHK-21 and A549. The objective of this study was to examine the effect of 2X3-DOPE composition as well as lipid-to-mRNA ratio (amino-to-phosphate group ratio, N/P) on mRNA transfection. We found that lipoplex-mediated transfection efficiency depends on both liposome composition and the N/P ratio. Lipoplexes with an N/P ratio of 10/1 showed nanometric hydrodynamic size, positive ζ potential, maximum loading, and transfection efficiency. Liposomes 2X3-DOPE (1:3) provided the superior delivery of both mRNA coding firefly luciferase and mRNA-eGFP into BHK-21 cells and A549 cells, compared with commercial Lipofectamine MessengerMax.

An Enzymatically Gated Catalytic Hairpin Assembly Delivered by Lipid Nanoparticles for the Tumor-Specific Activation of Signal Amplification in miRNA Imaging

MicroRNA (miRNA) imaging in disease sites is vital to elucidate their role in cancer progression. However, limited tumor specificity remains a major barrier for traditional amplification approaches due to associated background signal leakage. Here, we report a generalizable approach via the combination of enzymatically triggered catalytic hairpin assembly with lipid nanoparticles (LNPs)-based delivery strategy for tumor-specific activation of signal amplification and therefore sensitive miRNA imaging. The signal amplification is established via engineering of traditional catalytic hairpin assembly with enzymatically activated motifs to achieve triggable miRNA imaging in cancer cells. Furthermore, by the introduction of LNPs to combat biological barriers, we demonstrate that the system enables amplified miRNA imaging in vivo with reduced off-tumor signal, leading to enhanced tumor-to-background contrast compared with traditional methods. This approach that relies on specific triggers and controlled delivery to distinguish miRNA in cancer cells from normal cells should be useful in tumor diagnosis.

mRNA vaccines for cancer immunotherapy

Immunotherapy has emerged as a breakthrough strategy in cancer treatment. mRNA vaccines are an attractive and powerful immunotherapeutic platform against cancer because of their high potency, specificity, versatility, rapid and large-scale development capability, low-cost manufacturing potential, and safety. Recent technological advances in mRNA vaccine design and delivery have accelerated mRNA cancer vaccines' development and clinical application. In this review, we present various cancer vaccine platforms with a focus on nucleic acid vaccines. We discuss rational design and optimization strategies for mRNA cancer vaccine development. We highlight the platforms available for delivery of the mRNA vaccines with a focus on lipid nanoparticles (LNPs) based delivery systems. Finally, we discuss the limitations of mRNA cancer vaccines and future challenges.

Gene-activated titanium implants for gene delivery to enhance osseointegration

Osseointegration is the direct and intimate contact between mineralized tissue and titanium implant at the bone-implant interface. Early establishment and stable maintenance of osseointegration is the key to long-term implant success. However, in patients with compromised conditions such as osteoporosis and patients beginning early load-bearing activities such as walking, lower osseointegration around titanium implants is often observed, which might result in implant early failure. Gene-activated implants show an exciting prospect of combining gene delivery and biomedical implants to solve the problems of poor osseointegration formation, overcoming the shortcomings of protein therapy, including rapid degradation and overdose adverse effects. The conception of gene-activated titanium implants is based on "gene-activated matrix" (GAM), which means scaffolds using non-viral vectors for in situ gene delivery to achieve a long-term and efficient transfection of target cells. Current preclinical studies in animal models have shown that plasmid DNA (pDNA), microRNA (miRNA), and small interference RNA (siRNA) functionalized titanium implants can enhance osseointegration with safety and efficiency, leading to the expectation of applying this technique in dental and orthopedic clinical scenarios. This review aims to comprehensively summarize fabrication strategies, current applications, and futural outlooks of gene-activated implants, emphasizing nucleic acid targets, non-viral vectors, implant surface modification techniques, nucleic acid/vector complexes loading strategies.

Airway epithelial cell-specific delivery of lipid nanoparticles loading siRNA for asthma treatment

With specific and inherent mRNA cleaving activity, small interfering RNA (siRNA) has been deemed promising therapeutics to reduce the exacerbation rate of asthma by inhibiting the expression and release of proinflammatory cytokines from airway epithelial cells (AECs). To exert the therapeutic effects of siRNA drugs, nano-formulations with high efficiency and safety are required to deliver these nucleic acids to the target cells. Herein, we exploited novel inhaled lipid nanoparticles (LNPs) targeting intercellular adhesion molecule-1 (ICAM-1) receptors on the apical side of AECs. This delivery system is meant to enhance the specific delivery efficiency of siRNA in AECs to prevent the expression of proinflammatory cytokines in AECs and the concomitant symptoms in parallel. A cyclic peptide that resembles part of the capsid protein of rhinovirus and binds to ICAM-1 receptors was initially conjugated with cholesterol and subsequently assembled with ionizable cationic lipids to form the LNPs (Pep-LNPs) loaded with siRNA against thymic stromal lymphopoietin (TSLP siRNA). The obtained Pep-LNPs were subjected to thorough characterization and evaluations in vitro and in vivo. Pep-LNPs significantly enhanced cellular uptake and gene silencing efficiency in human epithelial cells expressing ICAM-1 in vitro, exhibited AEC-specific delivery and improved the gene silencing effect in ovalbumin-challenged asthmatic mice after pulmonary administration. More importantly, Pep-LNPs remarkably downregulated the expression of TSLP in AECs, effectively alleviated inflammatory cell infiltration, and reduced the secretion of other proinflammatory cytokines, including IL-4 and IL-13, as well as mucus production in asthmatic mice. This study demonstrates that Pep-LNPs are safe and efficient to deliver siRNA drugs to asthmatic AECs and could potentially alleviate allergic asthma by inhibiting the overexpression of proinflammatory cytokines in the airway.

Recent Advances in Lipid Nanoparticles for Delivery of mRNA

Messenger RNA (mRNA), which is composed of ribonucleotides that carry genetic information and direct protein synthesis, is transcribed from a strand of DNA as a template. On this basis, mRNA technology can take advantage of the body's own translation system to express proteins with multiple functions for the treatment of various diseases. Due to the advancement of mRNA synthesis and purification, modification and sequence optimization technologies, and the emerging lipid nanomaterials and other delivery systems, mRNA therapeutic regimens are becoming clinically feasible and exhibit significant reliability in mRNA stability, translation efficiency, and controlled immunogenicity. Lipid nanoparticles (LNPs), currently the leading non-viral delivery vehicles, have made many exciting advances in clinical translation as part of the COVID-19 vaccines and therefore have the potential to accelerate the clinical translation of gene drugs. Additionally, due to their small size, biocompatibility, and biodegradability, LNPs can effectively deliver nucleic acids into cells, which is particularly important for the current mRNA regimens. Therefore, the cutting-edge LNP@mRNA regimens hold great promise for cancer vaccines, infectious disease prevention, protein replacement therapy, gene editing, and rare disease treatment. To shed more lights on LNP@mRNA, this paper mainly discusses the rational of choosing LNPs as the non-viral vectors to deliver mRNA, the general rules for mRNA optimization and LNP preparation, and the various parameters affecting the delivery efficiency of LNP@mRNA, and finally summarizes the current research status as well as the current challenges. The latest research progress of LNPs in the treatment of other diseases such as oncological, cardiovascular, and infectious diseases is also given. Finally, the future applications and perspectives for LNP@mRNA are generally introduced.

Single pot organic solvent-free thermocycling technology for siRNA-ionizable LNPs: a proof-of-concept approach for alternative to microfluidics

Ionizable LNPs are the latest trend in nucleic acid delivery. Microfluidics technology has recently gained interest owing to its rapid mixing, production of nucleic acid-ionizable LNPs, and stability of nucleic acid inside the body. Industrial scale-up, nucleic acid-lipid long-term storage instability, and high production costs prompted scientists to seek alternate solutions to replace microfluidic technology. We proposed a single-pot, organic solvent-free thermocycling technology to efficiently and economically overcome most of the limitations of microfluidic technology. New thermocycling technology needs optimization of process parameters such as sonication duration, cooling–heating cycle, number of thermal cycles, and lipid:aqueous phase ratio to formulate precisely sized particles, effective nucleic acid encapsulation, and better shelf-life stability. Our research led to the formulation of siRNA-ionizable LNPs with particle sizes of 104.2 ± 34.7 nm and PDI 0.111 ± 0.109, with 83.3 ± 4.1% siRNA encapsulation. Thermocycling siRNA-ionizable LNPs had comparable morphological structures with commercialized microfluidics ionizable LNPs imaged by TEM and cryo-TEM. When compared to microfluidics ionizable LNPs, thermocycling siRNA-ionizable LNPs had a longer shelf life at 4°C. Our thermocycling technology showed an effective alternative to microfluidics technology in the production of nucleic acid–ionizable LNPs to meet global demand.

Thermocycling technology is a low-energy, low-temperature, self-assembling cooling–heating process in which lipid droplets spontaneously break apart into much smaller droplets to form siRNA-ionizable LNPs.

The new technology is an alternative to multistep, costly, and complex microfluidics technology for the formulation and bulk up of siRNA-ionizable LNPs economically.

Thermocycling siRNA-ionizable LNPs formulation focused on optimizing process parameters such as thermal cycle rate, number of thermal cycles, and lipid:aqueous phase ratio.

The thermocycling technology is able to overcome the limitations of the storage stability limitations of commercialized ionizable LNPs.

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.

Enhancing the Effect of Nucleic Acid Vaccines in the Treatment of HPV-Related Cancers: An Overview of Delivery Systems

Prophylactic vaccines against human papillomavirus (HPV) have proven efficacy in those who have not been infected by the virus. However, they do not benefit patients with established tumors. Therefore, the development of therapeutic options for HPV-related malignancies is critical. Third-generation vaccines based on nucleic acids are fast and simple approaches to eliciting adaptive immune responses. However, techniques to boost immunogenicity, reduce degradation, and facilitate their capture by immune cells are frequently required. One option to overcome this constraint is to employ delivery systems that allow selective antigen absorption and help modulate the immune response. This review aimed to discuss the influence of these different systems on the response generated by nucleic acid vaccines. The results indicate that delivery systems based on lipids, polymers, and microorganisms such as yeasts can be used to ensure the stability and transport of nucleic acid vaccines to their respective protein synthesis compartments. Thus, in view of the limitations of nucleic acid-based vaccines, it is important to consider the type of delivery system to be used-due to its impact on the immune response and desired final effect.

Structural and biochemical characteristics of mRNA nanoparticles determine anti-SARS-CoV-2 humoral and cellular immune responses

The coronavirus disease 2019 (COVID-19) pandemic underlines the urgent need for effective mRNA vaccines. However, current understanding of the immunological outcomes of mRNA vaccines formulated under different nanoplatforms is insufficient. Here, severe acute respiratory syndrome coronavirus 2 receptor binding domain mRNA delivered via lipid nanoparticle (LNP), cationic nanoemulsion (CNE), and cationic liposome (Lipo) was constructed. Results demonstrated that the structural and biochemical characteristics of nanoparticles shaped their tissue dissemination, cellular uptake, and intracellular trafficking, which eventually determined the activation of antiviral humoral and cellular immunity. Specifically, LNP was mainly internalized by myocyte and subsequently circumvented lysosome degradation, giving rise to humoral-biased immune responses. Meanwhile, CNE and Lipo induced cellular-preferred immunity, which was respectively attributed to the better lysosomal escape in dendritic cells and the superior biodistribution in secondary lymphoid organs. Overall, this study may guide the design and clinical use of mRNA vaccines against COVID-19.

Advances in vaccinia virus-based vaccine vectors, with applications in flavivirus vaccine development

Historically, virulent variola virus infection caused hundreds of millions of deaths. The smallpox pandemic in human beings has spread for centuries until the advent of the attenuated vaccinia virus (VV) vaccine, which played a crucial role in eradicating the deadly contagious disease. Decades of exploration and utilization have validated the attenuated VV as a promising vaccine vehicle against various lethal viruses. In this review, we focus on the advances in VV-based vaccine vector studies, including construction approaches of recombinant VV, the impact of VV-specific pre-existing immunity on subsequent VV-based vaccines, and antigen-specific immune responses. More specifically, the recombinant VV-based flaviviruses are intensively discussed. Based on the publication data, this review aims to provide valuable insights and guidance for future VV-based vaccine development.

On the Influence of Nucleic Acid Backbone Modifications on Lipid Nanoparticle Morphology

Nucleic acid therapeutics represent a major advance toward treating diseases at their root cause. However, nucleic acids are prone to degradation by serum endonucleases, clearance through the immune system, and rapid degradation in complex medium. To overcome these barriers, nucleic acids frequently include chemical modifications to improve stability or decrease immune responses. Lipid nanoparticles (LNPs) have enabled a dramatic reduction in the dose required to achieve a therapeutic effect by protecting these nucleic acids and improving their intracellular delivery. It has been assumed thus far that nonspecific ionic interactions drive LNP formation and chemical modifications to the nucleic acid backbone to confer improved stability do not impact LNP delivery in any way. Here, we demonstrate that these chemical modifications do impact LNP morphology substantially, and phosphorothioate modifications produce stronger interactions with ionizable amino lipids, resulting in enhanced entrapment. This work represents a major first step toward greater understanding of the interaction between the lipid components and nucleic acids within an LNP.