A Single Methylene Group in Oligoalkylamine-Based Cationic Polymers and Lipids Promotes Enhanced mRNA Delivery

Mucosal IFNλ1 mRNA-based immunomodulation effectively reduces SARS-CoV-2 induced mortality in mice

RNA vaccines elicit protective immunity against SARS-CoV-2, but the use of mRNA as an antiviral immunotherapeutic is unexplored. Here, we investigate the activity of lipidoid nanoparticle (LNP)-formulated mRNA encoding human IFNλ1 (ETH47), which is a critical driver of innate immunity at mucosal surfaces protecting from viral infections. IFNλ1 mRNA administration promotes dose-dependent protein translation, induction of interferon-stimulated genes without relevant signs of unspecific immune stimulation, and dose-dependent inhibition of SARS-CoV-2 replication in vitro. Pulmonary administration of IFNλ1 mRNA in mice results in a potent reduction of virus load, virus-induced body weight loss and significantly increased survival. These data support the development of inhaled administration of IFNλ1 mRNA as a potential prophylactic option for individuals exposed to SARS-CoV-2 or at risk suffering from COVID-19. Based on the broad antiviral activity of IFNλ1 regardless of virus or variant, this approach might also be utilized for other respiratory viral infections or pandemic preparedness.

Module-combinatorial design and screening of multifunctional polymers based on polyaspartic acid for DNA delivery

It is crucial to develop non-viral gene vectors that can efficiently and safely transfect plasmid DNA into cells. Low transfection efficiency and high cytotoxicity of cationic polymers hinder their application as gene carriers. Modification of cationic polymers has emerged as an attractive strategy for efficient and safe nucleic acids delivery. In this study, a simple and rapid method is developed to synthesize a series of multifunctional polymers by utilizing biodegradable polyaspartic acid as the backbone and modifying it with three modules. This one-component polymer possesses capabilities for nucleic acid condensation, cellular uptake, and endosomal escape. Polymers containing imidazole, triazole, or pyridine group exhibited promising transfection activity. Substituted with dodecylamine or 2-hexyldecan-1-amine enhance cellular uptake and subsequent transfection. Furthermore, the influence of ionizable amine side chains on gene delivery is investigated. Two optimal polymers, combined with the avian encephalomyelitis virus (AEV) plasmid vaccine, induced robust specific antibody responses and cellular immune responses in mice and chickens. Through module-combination design and screening of polyaspartamide polymers, this study presents a paradigm for the development of gene delivery vectors.

Tailoring Highly Branched Poly(β-amino ester)s for Efficient and Organ-Selective mRNA Delivery

Development of mRNA therapeutics necessitates targeted delivery technology, while the clinically advanced lipid nanoparticles face difficulty for extrahepatic delivery. Herein, we design highly branched poly(β-amino ester)s (HPAEs) for efficacious organ-selective mRNA delivery through tailoring their chemical compositions and topological structures. Using an "A2+B3+C2" Michael addition platform, a combinatorial library of 219 HPAEs with varied backbone structures, terminal groups, and branching degrees are synthesized. The branched topological structures of HPAEs provide enhanced serum resistance and significantly higher mRNA expression in vivo. The terminal amine structures of HPAEs determine the organ-selectivity of mRNA delivery following systemic administration: morpholine facilitates liver targeting, ethylenediamine favors spleen delivery, while methylpentane enables mRNA delivery to the liver, spleen, and lungs simultaneously. This study represents a comprehensive exploration of the structure-activity relationship governing both the efficiency and organ-selectivity of mRNA delivery by HPAEs, suggesting promising candidates for treating various organ-related diseases.

Dynamic carriers for therapeutic RNA delivery

Carriers for RNA delivery must be dynamic, first stabilizing and protecting therapeutic RNA during delivery to the target tissue and across cellular membrane barriers and then releasing the cargo in bioactive form. The chemical space of carriers ranges from small cationic lipids applied in lipoplexes and lipid nanoparticles, over medium-sized sequence-defined xenopeptides, to macromolecular polycations applied in polyplexes and polymer micelles. This perspective highlights the discovery of distinct virus-inspired dynamic processes that capitalize on mutual nanoparticle-host interactions to achieve potent RNA delivery. From the host side, subtle alterations of pH, ion concentration, redox potential, presence of specific proteins, receptors, or enzymes are cues, which must be recognized by the RNA nanocarrier via dynamic chemical designs including cleavable bonds, alterable physicochemical properties, and supramolecular assembly-disassembly processes to respond to changing biological microenvironment during delivery.

Delivery of mRNA with Histidine-Lysine Peptides

Transfection with mRNA has been considered superior to that with plasmids since the mRNA can be translated to a protein in the cytosol without entering the nucleus. One disadvantage of using mRNA is its susceptibility to enzymatic biodegradability, and consequently, significant research has occurred to determine nonviral carriers that will sufficiently stabilize this nucleic acid for cellular transport. Histidine-lysine peptides (HK) are one such class of mRNA carriers, which we think serves as a model for other peptides and polymeric carrier systems. When the HK peptide and mRNA are mixed and interact through ionic and nonionic bonds, mRNA polyplexes are formed, which can transfect cells. In contrast to linear HK peptides, branched HK peptides protected and efficiently transfected mRNA into cells. After describing the preparation and biophysical characterization of these polyplexes, we will provide protocols for in vitro and in vivo transfection for these mRNA polyplexes.

Sequential Nitrile Amidination-Reduction as a Straightforward Procedure to Selective Linear Polyamine Preparation

A straightforward strategy toward the efficient synthesis of linear saturated polyamines containing 1,2-diaminoethane and/or 1,3-diaminopropane fragments has been developed. The procedure is based on the chemistry of 5- and 6-membered cyclic amidines, including their efficient synthesis from nitrile precursors and subsequent chemoselective reductive-opening by a borane-dimethyl sulfide complex. This two-step procedure provides a robust methodology for the synthesis of linear polyamine skeletons under nonharsh conditions and free of using selective protective groups or tedious workups.

A computationally designed antigen eliciting broad humoral responses against SARS-CoV-2 and related sarbecoviruses

The threat of spillovers of coronaviruses associated with the severe acute respiratory syndrome (SARS) from animals to humans necessitates vaccines that offer broader protection from sarbecoviruses. By leveraging a viral-genome-informed computational method for selecting immune-optimized and structurally engineered antigens, here we show that a single antigen based on the receptor binding domain of the spike protein of sarbecoviruses elicits broad humoral responses against SARS-CoV-1, SARS-CoV-2, WIV16 and RaTG13 in mice, rabbits and guinea pigs. When administered as a DNA immunogen or by a vector based on a modified vaccinia virus Ankara, the optimized antigen induced vaccine protection from the Delta variant of SARS-CoV-2 in mice genetically engineered to express angiotensin-converting enzyme 2 and primed by a viral-vector vaccine (AZD1222) against SARS-CoV-2. A vaccine formulation incorporating mRNA coding for the optimized antigen further validated its broad immunogenicity. Vaccines that elicit broad immune responses across subgroups of coronaviruses may counteract the threat of zoonotic spillovers of betacoronaviruses.

Polymer nanoparticles deliver mRNA to the lung for mucosal vaccination

An inhalable platform for messenger RNA (mRNA) therapeutics would enable minimally invasive and lung-targeted delivery for a host of pulmonary diseases. Development of lung-targeted mRNA therapeutics has been limited by poor transfection efficiency and risk of vehicle-induced pathology. Here, we report an inhalable polymer-based vehicle for delivery of therapeutic mRNAs to the lung. We optimized biodegradable poly(amine-co-ester) (PACE) polyplexes for mRNA delivery using end-group modifications and polyethylene glycol. These polyplexes achieved high transfection of mRNA throughout the lung, particularly in epithelial and antigen-presenting cells. We applied this technology to develop a mucosal vaccine for severe acute respiratory syndrome coronavirus 2 and found that intranasal vaccination with spike protein-encoding mRNA polyplexes induced potent cellular and humoral adaptive immunity and protected susceptible mice from lethal viral challenge. Together, these results demonstrate the translational potential of PACE polyplexes for therapeutic delivery of mRNA to the lungs.

Polyplex designs for improving the stability and safety of RNA therapeutics

Nanoparticle-based delivery systems have contributed to the recent clinical success of RNA therapeutics, including siRNA and mRNA. RNA delivery using polymers has several distinct properties, such as enabling RNA delivery into extra-hepatic organs, modulation of immune responses to RNA, and regulation of intracellular RNA release. However, delivery systems should overcome safety and stability issues to achieve widespread therapeutic applications. Safety concerns include direct damage to cellular components, innate and adaptive immune responses, complement activation, and interaction with surrounding molecules and cells in the blood circulation. The stability of the delivery systems should balance extracellular RNA protection and controlled intracellular RNA release, which requires optimization for each RNA species. Further, polymer designs for improving safety and stability often conflict with each other. This review covers advances in polymer-based approaches to address these issues over several years, focusing on biological understanding and design concepts for delivery systems rather than material chemistry.

Precise and systematic end group chemistry modifications on PAMAM and poly(l-lysine) dendrimers to improve cytosolic delivery of mRNA

Here, we aimed to chemically modify PAMAM dendrimers using lysine as a site-selective anchor for successfully delivering mRNA while maintaining a low toxicity profile. PAMAM dendrimers were multi-functionalised by amidation reactions in a regioselective, quantitative and stepwise manner with carefully selected property-modifying surface groups. Alternatively, novel lysine-based dendrimers were prepared in the same manner with the aim to unlock their potential in gene delivery. The modified dendrimers were then formulated with Cy5-EGFP mRNA by bulk mixing via liquid handling robotics across different nitrogen to phosphate ratios. The resulting dendriplexes were characterised by size, charge, mRNA encapsulation, and mRNA binding affinity. Finally, their in-vitro delivery activity was systematically investigated across key cellular trafficking stages to relate chemical design to cellular effect. We demonstrate our findings in different cell lines and benchmarked relative to a commercially available transfection agent, jetPEI®. We demonstrate that specific surface modifications are required to generate small, reliable and well-encapsulated positively charged dendriplex complexes. Furthermore, we show that introduction of fusogenic groups is essential for driving endosomal escape and achieving cellular delivery and translation of mRNA in these cell lines.

Current knowledge on the tissue distribution of mRNA nanocarriers for therapeutic protein expression

Exogenously delivered mRNA-based drugs are emerging as a new class of therapeutics with the potential to treat several diseases. Over the last decade, advancements in the design of non-viral delivery tools have enabled mRNA to be evaluated for several therapeutic purposes including protein replacement therapies, gene editing, and vaccines. However, in vivo delivery of mRNA to targeted organs and cells remains a critical challenge. Evaluation of the biodistribution of mRNA vehicles is of utmost importance for the development of effective pharmaceutical candidates. In this review, we discuss the recent advances in the design of nanoparticles loaded with mRNA and extrapolate the key factors influencing their biodistribution following administration. Finally, we highlight the latest developments in the preclinical and clinical translation of mRNA therapeutics for protein supplementation therapy.

Applications and challenges of biomaterial mediated mRNA delivery

With the rapid development of gene therapy technology and the outbreak of coronavirus disease 2019 (COVID-19), messenger RNA (mRNA) therapeutics have attracted more and more attention, and the COVID-19 mRNA vaccine has been approved by the Food and Drug Administration (FDA) for emergency authorization. To improve the delivery efficiency of mRNA in vitro and in vivo, researchers have developed a variety of mRNA carriers and explored different administration routes. This review will systematically introduce the types of mRNA vectors, routes of administration, storage methods, safety of mRNA therapeutics, and the type of diseases that mRNA drugs are applied for. Finally, some suggestions are supplied on the development direction of mRNA therapeutic agents in the future.

mRNA-based modalities for infectious disease management

The novel coronavirus disease 2019 (COVID-19) is still rampant all over the world, causing incalculable losses to the world. Major pharmaceutical organizations around the globe are focusing on vaccine research and drug development to prevent further damage caused by the pandemic. The messenger RNA (mRNA) technology has got ample of attention after the success of the two very effective mRNA vaccines during the recent pandemic of COVID-19. mRNA vaccine has been promoted to the core stage of pharmaceutical industry, and the rapid development of mRNA technology has exceeded expectations. Beyond COVID-19, the mRNA vaccine has been tested for various infectious diseases and undergoing clinical trials. Due to the ability of constant mutation, the viral infections demand abrupt responses and immediate production, and therefore mRNA-based technology offers best answers to sudden outbreaks. The need for mRNA-based vaccine became more obvious due to the recent emergence of new Omicron variant. In this review, we summarized the unique properties of mRNA-based vaccines for infectious diseases, delivery technologies, discussed current challenges, and highlighted the prospects of this promising technology in the future. We also discussed various clinical studies as well preclinical studies conducted on mRNA therapeutics for diverse infectious diseases.

An imidazole modified lipid confers enhanced mRNA-LNP stability and strong immunization properties in mice and non-human primates

The mRNA vaccine technology has promising applications to fight infectious diseases as demonstrated by the licensing of two mRNA-based vaccines, Comirnaty® (Pfizer/BioNtech) and Spikevax® (Moderna), in the context of the Covid-19 crisis. Safe and effective delivery systems are essential to the performance of these vaccines and lipid nanoparticles (LNPs) able to entrap, protect and deliver the mRNA in vivo are considered by many as the current "best in class". Nevertheless, current mRNA/LNP vaccine technology has still some limitations, one of them being thermostability, as evidenced by the ultracold distribution chain required for the licensed vaccines. We found that the thermostability of mRNA/LNP, could be improved by a novel imidazole modified lipid, DOG-IM4, in combination with standard helper lipids. DOG-IM4 comprises an ionizable head group consisting of imidazole, a dioleoyl lipid tail and a short flexible polyoxyethylene spacer between the head and tail. Here we describe the synthesis of DOG-IM4 and show that DOG-IM4 LNPs confer strong immunization properties to influenza HA mRNA in mice and macaques and a remarkable stability to the encapsulated mRNA when stored liquid in phosphate buffered saline at 4 °C. We speculate the increased stability to result from some specific attributes of the lipid's imidazole head group.

Linear Poly(ethylenimine-propylenimine) Random Copolymers for Gene Delivery: From Polymer Synthesis to Efficient Transfection with High Serum Tolerance

Naturally occurring oligoamines, such as spermine, spermidine, and putrescine, are well-known regulators of gene expression. These oligoamines frequently have short alkyl spacers with varying lengths between the amines. Linear polyethylenimine (PEI) is a polyamine that has been widely applied as a gene vector, with various formulations currently in clinical trials. In order to emulate natural oligoamine gene regulators, linear random copolymers containing both PEI and polypropylenimine (PPI) repeat units were designed as novel gene delivery agents. In general, statistical copolymerization of 2-oxazolines and 2-oxazines leads to the formation of gradient copolymers. In this study, however, we describe for the first time the synthesis of near-ideal random 2-oxazoline/2-oxazine copolymers through careful tuning of the monomer structures and reactivity as well as polymerization conditions. These copolymers were then transformed into near-random PEI-PPI copolymers by controlled side-chain hydrolysis. The prepared PEI-PPI copolymers formed stable polyplexes with GFP-encoding plasmid DNA, as validated by dynamic light scattering. Furthermore, the cytotoxicity and transfection efficiency of polyplexes were evaluated in C2C12 mouse myoblasts. While the polymer chain length did not significantly increase the toxicity, a higher PPI content was associated with increased toxicity and also lowered the amount of polymers needed to achieve efficient transfection. The transfection efficiency was significantly influenced by the degree of polymerization of PEI-PPI, whereby longer polymers resulted in more transfected cells. Copolymers with 60% or lower PPI content exhibited a good balance between high plasmid-DNA transfection efficiency and low toxicity. Interestingly, these novel PEI-PPI copolymers revealed exceptional serum tolerance, whereby transfection efficiencies of up to 53% of transfected cells were achieved even under 50% serum conditions. These copolymers, especially PEI-PPI with DP500 and a 1:1 PEI/PPI ratio, were identified as promising transfection agents for plasmid DNA.

Inhalable polymer nanoparticles for versatile mRNA delivery and mucosal vaccination

An inhalable platform for mRNA therapeutics would enable minimally invasive and lung targeted delivery for a host of pulmonary diseases. Development of lung targeted mRNA therapeutics has been limited by poor transfection efficiency and risk of vehicle-induced pathology. Here we report an inhalable polymer-based vehicle for delivery of therapeutic mRNAs to the lung. We optimized biodegradable poly(amine-co-ester) polyplexes for mRNA delivery using end group modifications and polyethylene glycol. Our polyplexes achieved high transfection of mRNA throughout the lung, particularly in epithelial and antigen-presenting cells. We applied this technology to develop a mucosal vaccine for SARS-CoV-2. Intranasal vaccination with spike protein mRNA polyplexes induced potent cellular and humoral adaptive immunity and protected K18-hACE2 mice from lethal viral challenge.

One-sentence summary

Inhaled polymer nanoparticles (NPs) achieve high mRNA expression in the lung and induce protective immunity against SARS-CoV-2.

Efficient healing of large osseous segmental defects using optimized chemically modified messenger RNA encoding BMP-2

Large segmental osseous defects heal poorly. Recombinant, human bone morphogenetic protein-2 (rhBMP-2) is used clinically to promote bone healing, but it is applied at very high doses that cause adverse side effects and raise costs while providing only incremental benefit. We describe a previously unexplored, alternative approach to bone regeneration using chemically modified messenger RNA (cmRNA). An optimized cmRNA encoding BMP-2 was delivered to critical-sized femoral osteotomies in rats. The cmRNA remained orthotopically localized and generated BMP locally for several days. Defects healed at doses ≥25 μg of BMP-2 cmRNA. By 4 weeks, all animals treated with 50 μg of BMP-2 cmRNA had bridged bone defects without forming the massive callus seen with rhBMP-2. Moreover, such defects recovered normal mechanical strength quicker and initiated bone remodeling faster. cmRNA regenerated bone via endochondral ossification, whereas rhBMP-2 drove intramembranous osteogenesis; cmRNA provides an innovative, safe, and highly translatable technology for bone healing.

Non-viral delivery of the CRISPR/Cas system: DNA versus RNA versus RNP

Since its discovery, the CRISPR/Cas technology has rapidly become an essential tool in modern biomedical research. The opportunities to specifically modify and correct genomic DNA has also raised big hope...

mRNA Therapeutic Modalities Design, Formulation and Manufacturing under Pharma 4.0 Principles

In the quest for a formidable weapon against the SARS-CoV-2 pandemic, mRNA therapeutics have stolen the spotlight. mRNA vaccines are a prime example of the benefits of mRNA approaches towards a broad array of clinical entities and druggable targets. Amongst these benefits is the rapid cycle "from design to production" of an mRNA product compared to their peptide counterparts, the mutability of the production line should another target be chosen, the side-stepping of safety issues posed by DNA therapeutics being permanently integrated into the transfected cell's genome and the controlled precision over the translated peptides. Furthermore, mRNA applications are versatile: apart from vaccines it can be used as a replacement therapy, even to create chimeric antigen receptor T-cells or reprogram somatic cells. Still, the sudden global demand for mRNA has highlighted the shortcomings in its industrial production as well as its formulation, efficacy and applicability. Continuous, smart mRNA manufacturing 4.0 technologies have been recently proposed to address such challenges. In this work, we examine the lab and upscaled production of mRNA therapeutics, the mRNA modifications proposed that increase its efficacy and lower its immunogenicity, the vectors available for delivery and the stability considerations concerning long-term storage.

Recent Advances in the Noninvasive Delivery of mRNA

Over the past two decades, research on mRNA-based therapies has exploded, mainly because of the inherent advantages of mRNA, including a low integration probability, transient expression, and simple and rapid in vitro transcription production approaches. In addition, thanks to improved stability and reduced immunogenicity by advanced strategies, the application of mRNA has expanded from protein replacement therapy to vaccination, gene editing and other fields, showing great promise for clinical application. Recently, with the successive launch of two mRNA-based COVID-19 vaccines, mRNA technology has attracted an enormous amount of attention from scientific researchers as well as pharmaceutical companies. Because of the large molecular weight, hydrophilicity, and highly negative charge densities of mRNA, it is difficult to overcome the intracellular delivery barriers. Therefore, various delivery vehicles have been developed to achieve more effective mRNA delivery. In general, conventional mRNA administration methods are based on injection strategies, including intravenous, intramuscular, intradermal, and subcutaneous injections. Although these routes circumvent the absorption barriers to some extent, they bring about injection-related concerns such as safety issues, pain, low compliance, and difficulty in repeated dosing, increasing the need to explore alternative strategies for noninvasive delivery. The ideal noninvasive delivery systems are featured with easy to use, low risks of infection, and good patient compliance. At the same time, they allow patients to self-administer, reducing reliance on professional healthcare workers and interference with bodily functions and daily life. In particular, the noninvasive mucosal delivery of mRNA vaccines can induce mucosal immune responses, which are important for resisting pathogens infected through mucosal routes.Because of the potential clinical benefits mentioned above, we detailed the existing strategies for the noninvasive delivery of mRNA in this review, including delivery via the nasal, pulmonary, vaginal, and transdermal routes. First, we discussed the unique strengths and biological hindrances of each route on the basis of physiology. Next, we comprehensively summarized the research progress reported so far and analyzed the technologies and delivery vehicles used, hoping to provide some references for further explorations. Among these noninvasive routes, nasal and pulmonary delivery are the earliest and most intensively studied areas, mostly owing to their favorable physiological structures: the nasal or pulmonary mucosa is easily accessible, highly permeable and highly vascularized. In contrast, the development of vaginal mRNA delivery is relatively less reported, and the current research mainly focused on some local applications. In addition, microneedles have also been investigated to overcome skin barriers for mRNA delivery in recent years, making microneedle-based delivery an emerging alternative pathway. In summary, a variety of mRNA formulations and delivery strategies have been developed for noninvasive mRNA delivery, skillfully combining appropriate vehicles or physical technologies to enhance effectiveness. We surmise that continuous advances and technological innovations in the development of mRNA noninvasive delivery will accelerate the translation from experimental research to clinical application.

Dynamic mRNA polyplexes benefit from bioreducible cleavage sites for in vitro and in vivo transfer

Currently, messenger RNA (mRNA)-based lipid nanoparticle formulations revolutionize the clinical field. Cationic polymer-based complexes (polyplexes) represent an alternative compound class for mRNA delivery. After establishing branched polyethylenimine with a succinylation degree of 10% (succPEI) as highly effective positive mRNA transfection standard, a diverse library of PEI-like peptides termed sequence-defined oligoaminoamides (OAAs) was screened for mRNA delivery. Notably, sequences, which had previously been identified as potent plasmid DNA (pDNA) or small-interfering RNA (siRNA) carriers, displayed only moderate mRNA transfection activity. A second round of screening combined the cationizable building block succinoyl tetraethylene pentamine and histidines for endosomal buffering, tyrosine tripeptides and various fatty acids for mRNA polyplex stabilization, as well as redox-sensitive units for programmed intracellular release. For the tested OAA carriers, balancing of extracellular stability, endosomal lytic activity, and intracellular release capability was found to be of utmost importance for optimum mRNA transfection efficiency. OAAs with T-shape topology containing two oleic acids as well-stabilizing fatty acids, attached via a dynamic bioreducible building block, displayed superior activity with up to 1000-fold increased transfection efficiency compared to their non-reducible analogs. In the absence of the dynamic linkage, incorporation of shorter less stabilizing fatty acids could only partly compensate for mRNA delivery. Highest GFP expression and the largest fraction of transfected cells (96%) could be detected for the bioreducible OAA with incorporated histidines and a dioleoyl motif, outperforming all other tested carriers as well as the positive control succPEI. The good in vitro performance of the dynamic lead structure was verified in vivo upon intratracheal administration of mRNA complexes in mice.

Synthetic mRNA - emerging new class of drug for tissue regeneration

mRNA has the potential to be the next generation drug for tissue restoration in regenerative medicine. The variety of mRNAs that could be synthesized with the aim of increasing the expression of any required protein offers new opportunities. However, the intrinsic immunogenicity and lack of stability of mRNA has long restricted the potential of mRNA therapeutics. Fortunately, considerable progress has been made on synthetic mRNA modifications and relevant purification steps that have overcome these limitations. However, there remains a lack of efficient mRNA delivery strategies. Additionally, mRNA may need to be administered in situ via three-dimensional biomaterials. These materials, also known as transcript-activated matrices, require further consideration in terms of mRNA loading and release, immunogenicity, and other features. In this article, various limiting factors in mRNA synthesis, vector formulation, and local delivery to tissues are highlighted together with current developments and the future outlook for mRNA therapeutics in tissue regeneration.

Synthetic molecule libraries for nucleic acid delivery: Design parameters in cationic/ionizable lipids and polymers

Recent progress in the design of cationic lipids and polymers has successfully translated nucleic acid drugs into clinical applications, such as the treatment of liver diseases and the prevention of virus infection. Small or large libraries of delivery molecules have been used to find the key chemical structures to protect nucleic acids from nucleases in the extracellular milieu and to facilitate the endosomal escape after endocytosis. This review introduces three essential design parameters (i.e., acid dissociation constant, hydrophobicity, and biodegradability) to develop synthetic molecules for nucleic acid delivery. The significance and mechanism of each parameter are described based on the results obtained from in vitro and in vivo evaluations. Other design parameters were then discussed to create the next generation of delivery molecules for future nucleic acid therapeutics.

mRNA delivery via non-viral carriers for biomedical applications

As an emerging new class of nucleic acid drugs, messenger RNA (mRNA) has huge potential in immunotherapy, regenerative medicine, vaccine, and gene editing. Comparing with siRNA and pDNA, mRNA is more vulnerable to nucleases in vivo. However, the lack of effective and safe delivery methods impedes the broad application of mRNA-based therapeutics. Up to now, the delivery of mRNA remains largely unexplored, and therefore, is a hot topic in the field of gene therapy. In this review, we will summarize the ongoing challenges in mRNA-based therapeutics and unmet requirements for delivery vehicles in terms of the unique structure of mRNA. We then highlight the advancement in mRNA delivery in both fundamental research and clinical applications. Finally, a prospective will be proposed upon reviewing the current progress in mRNA delivery.

Nanotechnology-Assisted RNA Delivery: From Nucleic Acid Therapeutics to COVID-19 Vaccines

In recent years, the main quest of science has been the pioneering of the groundbreaking biomedical strategies needed for achieving a personalized medicine. Ribonucleic acids (RNAs) are outstanding bioactive macromolecules identified as pivotal actors in regulating a wide range of biochemical pathways. The ability to intimately control the cell fate and tissue activities makes RNA-based drugs the most fascinating family of bioactive agents. However, achieving a widespread application of RNA therapeutics in humans is still a challenging feat, due to both the instability of naked RNA and the presence of biological barriers aimed at hindering the entrance of RNA into cells. Recently, material scientists' enormous efforts have led to the development of various classes of nanostructured carriers customized to overcome these limitations. This work systematically reviews the current advances in developing the next generation of drugs based on nanotechnology-assisted RNA delivery. The features of the most used RNA molecules are presented, together with the development strategies and properties of nanostructured vehicles. Also provided is an in-depth overview of various therapeutic applications of the presented systems, including coronavirus disease vaccines and the newest trends in the field. Lastly, emerging challenges and future perspectives for nanotechnology-mediated RNA therapies are discussed.

Identification of a potent ionizable lipid for efficient macrophage transfection and systemic anti-interleukin-1β siRNA delivery against acute liver failure

RNA interference (RNAi) therapy has great potential for treating inflammatory diseases. However, the development of potent carrier materials for delivering siRNA to macrophages is challenging. Herein, we design a set of ionizable lipid nanoparticles (LNPs) to screen and identify a potent carrier of siRNA for silencing an essential pro-inflammatory cytokine, interleukin-1β (IL-1β) in macrophages. The top performance LNP (114-LNP), containing ionizable lipid with spermine as an amine-head group, facilitated efficient siRNA internalization via multiple endocytosis pathways and achieved effective endosome escape in macrophages. The optimized LNP/siIL-1β achieved strong silencing of IL-1β in both activated Raw 264.7 cells and primary macrophages. Furthermore, systematic administration of 114-LNP/siIL-1β complexes could effectively inhibit IL-1β expression in an acute liver failure model and significantly attenuated hepatic inflammation and liver damage. These results suggest that the optimized ionizable lipid nanoparticle represents a promising platform for anti-inflammation therapies.

Delivery Systems for Nucleic Acids and Proteins: Barriers, Cell Capture Pathways and Nanocarriers

Gene therapy has been used as a potential approach to address the diagnosis and treatment of genetic diseases and inherited disorders. In this line, non-viral systems have been exploited as promising alternatives for delivering therapeutic transgenes and proteins. In this review, we explored how biological barriers are effectively overcome by non-viral systems, usually nanoparticles, to reach an efficient delivery of cargoes. Furthermore, this review contributes to the understanding of several mechanisms of cellular internalization taken by nanoparticles. Because a critical factor for nanoparticles to do this relies on the ability to escape endosomes, researchers have dedicated much effort to address this issue using different nanocarriers. Here, we present an overview of the diversity of nanovehicles explored to reach an efficient and effective delivery of both nucleic acids and proteins. Finally, we introduced recent advances in the development of successful strategies to deliver cargoes.

Transcript-Activated Coatings on Titanium Mediate Cellular Osteogenesis for Enhanced Osteointegration

Osteointegration is one of the most important factors for implant success. Several biomolecules have been used as part of drug delivery systems to improve implant integration into the surrounding bone tissue. Chemically modified mRNA (cmRNA) is a new form of therapeutic that has been used to induce bone healing. Combined with biomaterials, cmRNA can be used to develop transcript-activated matrices for local protein production with osteoinductive potential. In this study, we aimed to utilize this technology to create bone morphogenetic protein 2 (BMP2) transcript-activated coatings for titanium (Ti) implants. Therefore, different coating methodologies as well as cmRNA incorporation strategies were evaluated. Three different biocompatible biomaterials were used for the coating of Ti, namely, poly-d,l-lactic acid (PDLLA), fibrin, and fibrinogen. cmRNA-coated Ti disks were assayed for transfection efficiency, cmRNA release, cell viability and proliferation, and osteogenic activity in vitro. We found that cmRNA release was significantly delayed in Ti surfaces previously coated with biomaterials. Consequently, the transfection efficiency was greatly improved. PDLLA coating improved the transfection efficiency in a concentration-dependent manner. Lower PDLLA concentration used for the coating of Ti resulted in higher transfection efficiency. Fibrin and fibrinogen coatings showed even higher transfection efficiencies compared to all PDLLA concentrations. In those disks, not only the expression was up to 24-fold higher but also the peak of maximal expression was delayed from 24 h to 5 days, and the duration of expression was also extended until 7 days post-transfection. For fibrin, higher transfection efficiencies were obtained in the coatings with the lowest thrombin amounts. Accordingly, fibrinogen coatings gave the best results in terms of cmRNA transfection. All biomaterial-coated Ti surfaces showed improved cell viability and proliferation, though this was more noticeable in the fibrinogen-coated disks. The latter was also the only coating to support significant amounts of BMP2 produced by C2C12 cells in vitro. Osteogenesis was confirmed using BMP2 cmRNA fibrinogen-coated Ti disks, and it was dependent of the cmRNA amount present. Alkaline phosphatase (ALP) activity of C2C12 increased when using fibrinogen coatings containing 250 ng of cmRNA or more. Similarly, mineralization was also observed that increased with increasing cmRNA concentration. Overall, our results support fibrinogen as an optimal material to deliver cmRNA from titanium-coated surfaces.

Optimizing synthetic nucleic acid and protein nanocarriers: The chemical evolution approach

Optimizing synthetic nanocarriers is like searching for a needle in a haystack. How to find the most suitable carrier for intracellular delivery of a specified macromolecular nanoagent for a given disease target location? Here, we review different synthetic 'chemical evolution' strategies that have been pursued. Libraries of nanocarriers have been generated either by unbiased combinatorial chemistry or by variation and novel combination of known functional delivery elements. As in natural evolution, definition of nanocarriers as sequences, as barcode or design principle, may fuel chemical evolution. Screening in appropriate test system may not only provide delivery candidates, but also a refined understanding of cellular delivery including novel, unpredictable mechanisms. Combined with rational design and computational algorithms, candidates can be further optimized in subsequent evolution cycles into nanocarriers with improved safety and efficacy. Optimization of nanocarriers differs for various cargos, as illustrated for plasmid DNA, siRNA, mRNA, proteins, or genome-editing nucleases.

In vitro transcribed mRNA for expression of designer nucleases: Advantages as a novel therapeutic for the management of chronic HBV infection

Chronic infection with the hepatitis B virus (HBV) remains a significant worldwide medical problem. While diseases caused by HIV infection, tuberculosis and malaria are on the decline, new cases of chronic hepatitis B are on the rise. Because often fatal complications of cirrhosis and hepatocellular carcinoma are associated with chronic hepatitis B, the need for a cure is as urgent as ever. Currently licensed therapeutics fail to eradicate the virus and this is attributable to persistence of the viral replication intermediate comprising covalently closed circular DNA (cccDNA). Elimination or inactivation of the viral cccDNA is thus a goal of research aimed at hepatitis B cure. The ability to engineer nucleases that are capable of specific cleavage of a DNA sequence now provides the means to disable cccDNA permanently. The scientific literature is replete with many examples of using designer zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs) and RNA-guided endonucleases (RGENs) to inactivate HBV. However, important concerns about safety, dose control and efficient delivery need to be addressed before the technology is employed in a clinical setting. Use of in vitro transcribed mRNA to express therapeutic gene editors goes some way to overcoming these concerns. The labile nature of RNA limits off-target effects and enables dose control. Compatibility with hepatotropic non-viral vectors is convenient for the large scale preparation that will be required for advancing gene editing as a mode of curing chronic hepatitis B.

Location of a single histidine within peptide carriers increases mRNA delivery

BACKGROUND

Previously, we determined that four-branched histidine-lysine (HK) peptides were effective carriers of plasmids and small interfering RNA. In the present study, we compared several branched HK carriers and, in particular, two closely-related H3K4b and H3K(+H)4b peptides for their ability as carriers of mRNA. The H3K(+H)4b peptide differed from its parent analogue, H3K4b, by only a single histidine in each branch.

METHODS

A series of four-branched HK peptides with varied sequences was synthesized on a solid-phase peptide synthesizer. The ability of these peptides to carry mRNA expressing luciferase to MDA-MB-231 cells was investigated. With gel retardation and heparin displacement assays, the stability of HK polyplexes was examined. We determined the intracellular uptake of HK polyplexes by flow cytometry and fluorescence microscopy. The size and polydispersity index of the polyplexes in several media were measured by dynamic light scattering.

RESULTS

MDA-MB-231 cells transfected by H3K(+H)4b-mRNA polyplexes expressed 10-fold greater levels of luciferase than H3K4b polyplexes. With gel retardation and heparin displacement assays, the H3K(+H)4b polyplexes showed greater stability than H3K4b. Intracellular uptake and co-localization of H3K(+H)4b polyplexes within acidic endosomes were also significantly increased compared to H3K4b. Similar to H3K(+H)4b, several HK analogues with an additional histidine in the second domain of their branches were effective carriers of mRNA. When combined with DOTAP liposomes, H3K(+H)4b was synergistic in delivery of mRNA.

CONCLUSIONS

H3K(+H)4b was a more effective carrier of mRNA than H3K4b. Mechanistic studies suggest that H3K(+H)4b polyplexes were more stable than H3K4b polyplexes. Lipopolyplexes formed with H3K(+H)4b markedly increased mRNA transfection.

An Imidazolium-Based Lipid Analogue as a Gene Transfer Agent

A dicationic imidazolium salt is described and investigated towards its application for gene transfer. The polar head group and the long alkyl chains in the backbone contribute to a lipid-like behavior, while an alkyl ammonium group provides the ability for crucial electrostatic interaction for the transfection process. Detailed biophysical studies regarding its impact on biological membrane models and the propensity of vesicle fusion are presented. Fluorescence spectroscopy, atomic force microscopy and confocal fluorescence microscopy show that the imidazolium salt leads to negligible changes in lipid packing, while displaying distinct vesicle fusion properties. Cell culture experiments reveal that mixed liposomes containing the novel imidazolium salt can serve as plasmid DNA delivery vehicles. In contrast, a structurally similar imidazolium salt without a second positive charge showed no ability to support DNA transfection into cultured cells. Thus, we introduce a novel and variable structural motif for cationic lipids, expanding the field of lipofection agents.

Inhaled RNA Therapy: From Promise to Reality

RNA-based medicine is receiving growing attention for its diverse roles and potential therapeutic capacity. The largest obstacle in its clinical translation remains identifying a safe and effective delivery system. Studies investigating RNA therapeutics in pulmonary diseases have rapidly expanded and drug administration by inhalation allows the direct delivery of RNA therapeutics to the target site of action while minimizing systemic exposure. In this review, we highlight recent developments in pulmonary RNA delivery systems with the use of nonviral vectors. We also discuss the major knowledge gaps that require thorough investigation and provide insights that will help advance this exciting field towards the bedside.

Synthetic circular miR-21 RNA decoys enhance tumor suppressor expression and impair tumor growth in mice

Naturally occurring circular RNAs efficiently impair miRNA functions. Synthetic circular RNAs may thus serve as potent agents for miRNA inhibition. Their therapeutic effect critically relies on (i) the identification of optimal miRNA targets, (ii) the optimization of decoy structures and (iii) the development of efficient formulations for their use as drugs. In this study, we extensively explored the functional relevance of miR-21-5p in cancer cells. Analyses of cancer transcriptomes reveal that miR-21-5p is the by far most abundant miRNA in human cancers. Deletion of the MIR21 locus in cancer-derived cells identifies several direct and indirect miR-21-5p targets, including major tumor suppressors with prognostic value across cancers. To impair miR-21-5p activities, we evaluate synthetic, circular RNA decoys containing four repetitive binding elements. In cancer cells, these decoys efficiently elevate tumor suppressor expression and impair tumor cell vitality. For their in vivo delivery, we for the first time evaluate the formulation of decoys in polyethylenimine (PEI)-based nanoparticles. We demonstrate that PEI/decoy nanoparticles lead to a significant inhibition of tumor growth in a lung adenocarcinoma xenograft mouse model via the upregulation of tumor suppressor expression. These findings introduce nanoparticle-delivered circular miRNA decoys as a powerful potential therapeutic strategy in cancer treatment.

A Potent Branched-Tail Lipid Nanoparticle Enables Multiplexed mRNA Delivery and Gene Editing In Vivo

The clinical translation of messengerRNA (mRNA) drugs has been slowed by a shortage of delivery vehicles that potently and safely shuttle mRNA into target cells. Here, we describe the properties of a particularly potent branched-tail lipid nanoparticle that delivers mRNA to >80% of three major liver cell types. We characterize mRNA delivery spatially, temporally, and as a function of injection type. Following intravenous delivery, our lipid nanoparticle induced greater protein expression than two benchmark lipids, C12-200 and DLin-MC3-DMA, at an mRNA dose of 0.5 mg/kg. Lipid nanoparticles were sufficiently potent to codeliver three distinct mRNAs (firefly luciferase, mCherry, and erythropoietin) and, separately, Cas9 mRNA and single guide RNA (sgRNA) for proof-of-concept nonviral gene editing in mice. Furthermore, our branched-tail lipid nanoparticle was neither immunogenic nor toxic to the liver. Together, these results demonstrate the unique potential of this lipid material to improve the management of diseases rooted in liver dysfunction.

The challenge and prospect of mRNA therapeutics landscape

Messenger RNA (mRNA)-based therapeutics hold the potential to cause a major revolution in the pharmaceutical industry because they can be used for precise and individualized therapy, and enable patients to produce therapeutic proteins in their own bodies without struggling with the comprehensive manufacturing issues associated with recombinant proteins. Compared with the current therapeutics, the production of mRNA is much cost-effective, faster and more flexible because it can be easily produced by in vitro transcription, and the process is independent of mRNA sequence. Moreover, mRNA vaccines allow people to develop personalized medications based on sequencing results and/or personalized conditions rapidly. Along with the great potential from bench to bedside, technical obstacles facing mRNA pharmaceuticals are also obvious. The stability, immunogenicity, translation efficiency, and delivery are all pivotal issues need to be addressed. In the recently published research results, these issues are gradually being overcome by state-of-the-art development technologies. In this review, we describe the structural properties and modification technologies of mRNA, summarize the latest advances in developing mRNA delivery systems, review the preclinical and clinical applications, and put forward our views on the prospect and challenges of developing mRNA into a new class of drug.

Nanomedicines to Deliver mRNA: State of the Art and Future Perspectives

The use of messenger RNA (mRNA) in gene therapy is increasing in recent years, due to its unique features compared to plasmid DNA: Transient expression, no need to enter into the nucleus and no risk of insertional mutagenesis. Nevertheless, the clinical application of mRNA as a therapeutic tool is limited by its instability and ability to activate immune responses; hence, mRNA chemical modifications together with the design of suitable vehicles result essential. This manuscript includes a revision of the strategies employed to enhance in vitro transcribed (IVT) mRNA functionality and efficacy, including the optimization of its stability and translational efficiency, as well as the regulation of its immunostimulatory properties. An overview of the nanosystems designed to protect the mRNA and to overcome the intra and extracellular barriers for successful delivery is also included. Finally, the present and future applications of mRNA nanomedicines for immunization against infectious diseases and cancer, protein replacement, gene editing, and regenerative medicine are highlighted.

Improved Nucleic Acid Therapy with Advanced Nanoscale Biotechnology

Due to a series of systemic and intracellular obstacles in nucleic acid (NA) therapy, including fast degradation in blood, renal clearance, poor cellular uptake, and inefficient endosomal escape, NAs may need delivery methods to transport to the cell nucleus or cytosol to be effective. Advanced nanoscale biotechnology-associated strategies, such as controlling the particle size, charge, drug loading, response to environmental signals, or other physical/chemical properties of delivery carriers, have provided great help for the in vivo and in vitro delivery of NA therapeutics. In this review, we introduce the characteristics of different NA modalities and illustrate how advanced nanoscale biotechnology assists NA therapy. The specific features and challenges of various nanocarriers in clinical and preclinical studies are summarized and discussed. With the help of advanced nanoscale biotechnology, some of the major barriers to the development of NA therapy will eventually be overcome in the near future.

In vitro siRNA delivery via diethylenetriamine- and tetraethylenepentamine-modified carboxyl group-terminated Poly(amido)amine generation 4.5 dendrimers

The recent discovery of small interfering RNAs (siRNAs) has opened new avenues for designing personalized treatment options for various diseases. However, the therapeutic application of siRNAs has been confronted with many challenges because of short half-life in circulation, poor membrane penetration, difficulty in escaping from endosomes, and insufficient release into the cytosol. To overcome these challenges, we designed a diethylenetriamine (DETA)- and tetraethylenepentamine (TEPA)-modified polyamidoamine dendrimer generation 4.5 (PDG4.5), and characterized it using ¹H nuclear magnetic resonance (NMR), ¹³C NMR, correlation spectroscopy (COSY), heteronuclear single-quantum correlation spectroscopy (HSQC), and Fourier transform infrared (FTIR) spectroscopy followed by conjugation with siRNA. The PDG4.5-DETA and PDG4.5-TEPA polyplexes exhibited spherical nanosize, ideal zeta potential, and effective siRNA binding ability, protected the siRNA from nuclease attack, and revealed less cytotoxicity of PDG4.5-DETA and PDG4.5-TEPA in HeLa cells. More importantly, the polyplexes also revealed good cellular internalization and facilitated translocation of the siRNA into the cytosol. Thus, PDG4.5-DETA and PDG4.5-TEPA can act as potential siRNA carriers in future medical and pharmaceutical applications.

Hydrogen-Bond Cyclization Programming of Ultrasensitive Esters and Its Application in Gene Delivery

The ester bond as a universal linker has recently been applied in gene delivery systems owing to its efficient gene release by electrostatic repulsion after its cleavage. However, the ester bond is nonlabile and is difficult to cleave in cells. This work reports a method in which a secondary amine was introduced to the β-position of the ester bond to generate a hydrogen-bond cyclization (HBC) structure that can make the ester bond hydrolysis ultrafast. A series of molecules comprising ultrasensitive esters that can be activated by H₂ O₂ were synthesized, and it was found that those able to form an HBC structure showed complete ester hydrolysis within 5 h in both water and phosphate-buffered saline solution, which was several times faster than other methods reported. Then, a series of amphiphilic poly(amidoamine) dendrimers were constructed, comprising the ultrasensitive ester groups for gene delivery; it was found that they could effectively release genes under quite a low concentration of H₂ O₂ (<200 μm) and transport them into the nucleus within 2 h in Hela cells with high safety. Their gene transfection efficiencies were higher than that of PEI_25k . The results demonstrated that the hydrogen-bond-induced ultrasensitive esters could be powerfully applied to construct gene delivery systems.

RNA delivery biomaterials for the treatment of genetic and rare diseases

Genetic and rare diseases (GARDs) affect more than 350 million patients worldwide and remain a significant challenge in the clinic. Hence, continuous efforts have been made to bridge the significant gap between the supply and demand of effective treatments for GARDs. Recent decades have witnessed the impressive progress in the fight against GARDs, with an improved understanding of the genetic origins of rare diseases and the rapid development in gene therapy providing a new avenue for GARD therapy. RNA-based therapeutics, such as RNA interference (RNAi), messenger RNA (mRNA) and RNA-involved genome editing technologies, demonstrate great potential as a therapy tool for treating genetic associated rare diseases. In the meantime, a variety of RNA delivery vehicles were established for boosting the widespread applications of RNA therapeutics. Among all the RNA delivery platforms which enable the systemic applications of RNAs, non-viral RNA delivery biomaterials display superior properties and a few biomaterials have been successfully exploited for achieving the RNA-based gene therapies on GARDs. In this review article, we focus on recent advances in the development of novel biomaterials for delivery of RNA-based therapeutics and highlight their applications to treat GARDs.

Delivering the Messenger: Advances in Technologies for Therapeutic mRNA Delivery

mRNA has broad potential as a therapeutic. Current clinical efforts are focused on vaccination, protein replacement therapies, and treatment of genetic diseases. The clinical translation of mRNA therapeutics has been made possible through advances in the design of mRNA manufacturing and intracellular delivery methods. However, broad application of mRNA is still limited by the need for improved delivery systems. In this review, we discuss the challenges for clinical translation of mRNA-based therapeutics, with an emphasis on recent advances in biomaterials and delivery strategies, and we present an overview of the applications of mRNA-based delivery for protein therapy, gene editing, and vaccination.

Nanoscale platforms for messenger RNA delivery

Messenger RNA (mRNA) has become a promising class of drugs for diverse therapeutic applications in the past few years. A series of clinical trials are ongoing or will be initiated in the near future for the treatment of a variety of diseases. Currently, mRNA-based therapeutics mainly focuses on ex vivo transfection and local administration in clinical studies. Efficient and safe delivery of therapeutically relevant mRNAs remains one of the major challenges for their broad applications in humans. Thus, effective delivery systems are urgently needed to overcome this limitation. In recent years, numerous nanoscale biomaterials have been constructed for mRNA delivery in order to protect mRNA from extracellular degradation and facilitate endosomal escape after cellular uptake. Nanoscale platforms have expanded the feasibility of mRNA-based therapeutics, and enabled its potential applications to protein replacement therapy, cancer immunotherapy, therapeutic vaccines, regenerative medicine, and genome editing. This review focuses on recent advances, challenges, and future directions in nanoscale platforms designed for mRNA delivery, including lipid and lipid-derived nanoparticles, polymer-based nanoparticles, protein derivatives mRNA complexes, and other types of nanomaterials. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Biology-Inspired Nanomaterials > Lipid-Based Structures Biology-Inspired Nanomaterials > Nucleic Acid-Based Structures.

Branched-Tail Lipid Nanoparticles Potently Deliver mRNA In Vivo due to Enhanced Ionization at Endosomal pH

The potential of mRNA therapeutics will be realized only once safe and effective delivery systems are established. Unfortunately, delivery vehicle development is stymied by an inadequate understanding of how the molecular properties of a vehicle confer efficacy. Here, a small library of lipidoid materials is used to elucidate structure-function relationships and identify a previously unappreciated parameter-lipid nanoparticle surface ionization-that correlates with mRNA delivery efficacy. The two most potent materials of the library, 306O₁₀ and 306O_i10 , induce substantial luciferase expression in mice following a single 0.75 mg kg^-1 mRNA dose. These lipidoids, which have ten-carbon tails and identical molecular weights, vary only in that the 306O₁₀ tail is straight and the 306O_i10 tail has a one-carbon branch. Remarkably, this small difference in structure conferred a tenfold improvement in 306O_i10 efficacy. The enhanced potency of this branched-tail lipidoid is attributed to its strong surface ionization at the late endosomal pH of 5.0. A secondary lipidoid library confirms that O_i10 materials ionize more strongly and deliver mRNA more potently than lipidoids containing linear tails. Together, these data highlight the exquisite control that lipid chemistry exerts on the mRNA delivery process and show that branched-tail lipids facilitate protein expression in animals.