Systemic delivery of messenger RNA for the treatment of pancreatic cancer using polyplex nanomicelles with a cholesterol moiety

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.

mRNA loading into ATP-responsive polyplex micelles with optimal density of phenylboronate ester crosslinking to balance robustness in the biological milieu and intracellular translational efficiency

Carriers for messenger RNA (mRNA) delivery require propensities to protect the mRNA from enzymatic degradation and to selectively release mRNA in the cytosol for smooth mRNA translation. To meet these requirements, we designed mRNA-loaded polyplex micelles (PMs) with ATP-responsive crosslinking in the inner core by complexing mRNA with poly(ethylene glycol)-polycation block copolymers derivatized with phenylboronic acid and polyol groups, which form crosslinking structures via spontaneous phenylboronate ester formation. PMs thus prepared are tolerable against enzymatic attack and, in turn, disintegrate in the cytosol to release mRNA when triggered by the cleavage of phenylboronate ester linkages in response to elevated ATP concentration. Two structural factors of the PM, including (i) the introduction ratios of phenylboronate ester crosslinkers and (ii) the structure and protonation degree of amino groups in the polycation segment, are critical for maximizing protein expression in cultured cells due to the optimized balance between the robustness in the biological milieu and the ATP-responsive mRNA release in the cytosol. The optimal PM formulation was further stabilized by installing cholesterol moieties into both the mRNA and ω-end of the block copolymer to elicit longevity in blood circulation after intravenous injection.

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.

Nanomedicine-Based Approaches for mRNA Delivery

Messenger RNA (mRNA) has immense potential for developing a wide range of therapies, including immunotherapy and protein replacement. As mRNA presents no risk of integration into the host genome and does not require nuclear entry for transfection, which allows protein production even in nondividing cells, mRNA-based approaches can be envisioned as safe and practical therapeutic strategies. Nevertheless, mRNA presents unfavorable characteristics, such as large size, immunogenicity, limited cellular uptake, and sensitivity to enzymatic degradation, which hinder its use as a therapeutic agent. While mRNA stability and immunogenicity have been ameliorated by direct modifications on the mRNA structure, further improvements in mRNA delivery are still needed for promoting its activity in biological settings. In this regard, nanomedicine has shown the ability for spatiotemporally controlling the function of a myriad of bioactive agents in vivo. Direct engineering of nanomedicine structures for loading, protecting, and releasing mRNA and navigating in biological environments can then be applied for promoting mRNA translation toward the development of effective treatments. Here, we review recent approaches aimed at enhancing mRNA function and its delivery through nanomedicines, with particular emphasis on their applications and eventual clinical translation.

Bundling of mRNA strands inside polyion complexes improves mRNA delivery efficiency in vitro and in vivo

RNA nanotechnology has promise for developing mRNA carriers with enhanced physicochemical and functional properties. However, the potential synergy for mRNA delivery of RNA nanotechnology in cooperation with established carrier systems remains unknown. This study proposes a combinational system of RNA nanotechnology and mRNA polyplexes, by focusing on mRNA steric structure inside the polyplexes. Firstly, several mRNA strands are bundled through hybridization with RNA oligonucleotide crosslinkers to obtain tight mRNA structure, and then the bundled mRNA is mixed with poly(ethylene glycol) (PEG)-polycation block copolymers to prepare PEG-coated polyplex micelles (PMs). mRNA bundling results in highly condensed mRNA packaging inside PM core with dense PEG chains on the surface, thereby, improving PM stability against polyion exchange reaction and ribonuclease (RNase) attack. Importantly, such stabilization effects are attributed to bundled structure of mRNA rather than the increase in total mRNA amount encapsulated in the PMs, as encapsulation of long mRNA strands without bundling fails to improve PM stability. Consequently, PMs loading bundled mRNA exhibit enhanced stability in mouse blood circulation, and induce efficient protein expression in cultured cells and mouse brain.

Polymeric Nanocarriers with Controlled Chain Flexibility Boost mRNA Delivery In Vivo through Enhanced Structural Fastening

Messenger RNA (mRNA) shows high therapeutic potential, though effective delivery systems are still needed for boosting its application. Nanocarriers loading mRNA via polyion complexation with block catiomers into core-shell micellar structures are promising systems for enhancing mRNA delivery. Engineering the interaction between mRNA and catiomers through polymer design can promote the development of mRNA-loaded micelles (mRNA/m) with increased delivery efficiency. Particularly, the polycation chain rigidity may critically affect the mRNA-catiomer interplay to yield potent nanocarriers, yet its effect remains unknown. Herein, the influence of polycation stiffness on the performance of mRNA/m by developing block complementary catiomers having polycation segments with different flexibility, that is, poly(ethylene glycol)-poly(glycidylbutylamine) (PEG-PGBA) and PEG-poly(L-lysine) (PEG-PLL) is studied. PEG-PGBA allows more than 50-fold stronger binding to mRNA than the relatively more rigid PEG-PLL, resulting in mRNA/m with enhanced protection against enzymatic attack and polyanions. mRNA/m from PEG-PGBA significantly enhances mRNA in vivo bioavailability and increased protein translation, indicating the importance of controlling polycation flexibility for forming stable polyion complexes with mRNA toward improved delivery.

Identification of potential crucial genes associated with the pathogenesis and prognosis of pancreatic adenocarcinoma

Pancreatic adenocarcinoma (PAAD) is a type of malignant tumor with the highest mortality rate among all neoplasms worldwide, and its exact pathogenesis is still poorly understood. Timely diagnosis and treatment are of great importance in order to decrease the mortality rate of PAAD. Therefore, identifying new biomarkers for diagnosis and prognosis is essential to enable early detection of PAAD and to improve the overall survival (OS) rate. In order to screen and integrate differentially expressed genes (DEGs) between PAAD and normal tissues, a total of seven datasets were downloaded from the Gene Expression Omnibus database and the ‘limma’ and ‘robustrankggreg’ packages in R software were used. The Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis of the DEGs was performed using the Database for Annotation, Visualization and Integrated Discovery website, and the protein-protein interaction network analysis was performed using the Search Tool for the Retrieval of Interacting Genes/Proteins database. A gene prognostic signature was constructed using the Cox regression model. A total of 10 genes (CDK1, CCNB1, CDC20, ASPM, UBE2C, TPX2, TOP2A, NUSAP1, KIF20A and DLGAP5) that may be associated with pancreatic adenocarcinoma were identified. According to the differentially expressed genes in The Cancer Genome Atlas, the present study set up four prognostic signatures (matrix metalloproteinase 12, sodium voltage-gated channel α subunit 11, tetraspanin 1 and SH3 domain and tetratricopeptide repeats-containing 2), which effectively predicted OS. The hub genes that were highly associated with the occurrence, development and prognosis of PAAD were identified, which may be helpful to further understand the molecular basis of pancreatic cancer and guide the synthesis of drugs for PPAD.

Promising RNA-based cancer gene therapy using extracellular vesicles for drug delivery

INTRODUCTION

RNA-based cancer gene therapy shows potential in cancer treatment. However, the safe and efficient transfer of therapeutic RNA to target cells has always been a challenge. The ideal drug delivery system should be effective with low immunogenicity and toxicity. Besides, a high specificity of drug delivery is necessary to improve efficacy and avoid the side effects associated with tumor heterogeneity. As endogenous RNA vehicles, extracellular vesicles (EVs) have shown their advantages and potential as drug delivery systems in gene therapy.

AREAS COVERED

We summarize the performance of EVs as a drug delivery system in RNA-based cancer gene therapy and discuss the advantages, limitations, and potentials of this translational medicine. In addition, we compare the characteristics and differences of current drug delivery systems and expound the principles of selecting a drug delivery system suitable for cancer gene therapy.

EXPERT OPINION

EVs are highly biocompatible membrane structures with low cytotoxicity which provide a new choice for drug delivery in RNA-based cancer gene therapy. The specificity of engineered EVs and artificial EV-mimetics can be improved through peptide or polymer decoration. However, apart from therapeutic RNA, EVs naturally carry many molecules. This may lead to unpredictable effects and thus should be applied with caution.

Sugar-Nanocapsules Imprinted with Microbial Molecular Patterns for mRNA Vaccination

Innate immune cells recognize and respond to pathogen-associated molecular patterns. In particular, polysaccharides found in the microbial cell wall are potent activators of dendritic cells (DCs). Here, we report a new class of nanocapsules, termed sugar-capsules, entirely composed of polysaccharides derived from the microbial cell wall. We show that sugar-capsules with a flexible polysaccharide shell and a hollow core efficiently drain to lymph nodes and activate DCs. In particular, sugar-capsules composed of mannan (Mann-capsule) carrying mRNA (mRNA) promote strong DC activation, mRNA translation, and antigen presentation on DCs. Mann-capsules elicit robust antigen-specific CD4+ and CD8α+ T-cell responses with antitumor efficacy in vivo. The strategy presented in this study is generally applicable for utilizing pathogen-derived molecular patterns for vaccines and immunotherapies.

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.

Improving cancer immunotherapy using nanomedicines: progress, opportunities and challenges

Multiple nanotherapeutics have been approved for patients with cancer, but their effects on survival have been modest and, in some examples, less than those of other approved therapies. At the same time, the clinical successes achieved with immunotherapy have revolutionized the treatment of multiple advanced-stage malignancies. However, the majority of patients do not benefit from the currently available immunotherapies and many develop immune-related adverse events. By contrast, nanomedicines can reduce - but do not eliminate - the risk of certain life-threatening toxicities. Thus, the combination of these therapeutic classes is of intense research interest. The tumour microenvironment (TME) is a major cause of the failure of both nanomedicines and immunotherapies that not only limits delivery, but also can compromise efficacy, even when agents accumulate in the TME. Coincidentally, the same TME features that impair nanomedicine delivery can also cause immunosuppression. In this Perspective, we describe TME normalization strategies that have the potential to simultaneously promote the delivery of nanomedicines and reduce immunosuppression in the TME. Then, we discuss the potential of a combined nanomedicine-based TME normalization and immunotherapeutic strategy designed to overcome each step of the cancer-immunity cycle and propose a broadly applicable 'minimal combination' of therapies designed to increase the number of patients with cancer who are able to benefit from immunotherapy.

Hybrid nanovaccine for the co-delivery of the mRNA antigen and adjuvant

For efficient cancer vaccines, the antitumor function largely relies on cytotoxic T cells, whose activation can be effectively induced via antigen-encoding mRNA, making mRNA-based cancer vaccines an attractive approach for personalized cancer therapy. While the liposome-based delivery system enables the systemic delivery and transfection of mRNA, incorporating an adjuvant that is non-lipid like remains challenging, although the co-delivery of mRNA (antigen) and effective adjuvant is key to the activation of the cytotoxic T cells. This is because the presence of an adjuvant is important for dendritic cell maturation-another necessity for cytotoxic T cell activation. In the present work, we designed a poly (lactic-co-glycolic acid) (PLGA)-core/lipid-shell hybrid nanoparticle carrier for the co-delivery of mRNA and gardiquimod (adjuvant that cannot be incorporated into the lipid shell). We demonstrated in the present work that the co-delivery of mRNA and gardiquimod led to the effective antigen expression and DC maturation in vitro. The intravenous administration of the hybrid nanovaccine resulted in the enrichment of mRNA expression in the spleen and a strong immune response in vivo. The simultaneous delivery of the antigen and adjuvant both spatially and temporally via the core/shell nanoparticle carrier is found to be beneficial for tumor growth inhibition.

Present Scenario of Bioconjugates in Cancer Therapy: A Review

Cancer is one of the deadliest diseases and poses a risk to people all over the world. Surgery, chemo, and radiation therapy have been the only options available until today to combat this major problem. Chemotherapeutic drugs have been used for treatment for more than 50 years. Unfortunately, these drugs have inherent cytotoxicities and tumor cells have started inducing resistance against these drugs. Other common techniques such as surgery and radiotherapy have their own drawbacks. Therefore, such techniques are incompetent tools to alleviate the disease efficiently without any adverse effects. This scenario has inspired researchers to develop alternative techniques with enhanced therapeutic effects and minimal side effects. Such techniques include targeted therapy, liposomal therapy, hormonal therapy, and immunotherapy, etc. However, these therapies are expensive and not effective enough. Furthermore, researchers have conjugated therapeutic agents or drugs with different molecules, delivery vectors, and/or imaging modalities to combat such problems and enhance the therapeutic effect. This conjugation technique has led to the development of bioconjugation therapy, in which at least one molecule is of biological origin. These bioconjugates are the new therapeutic strategies, having prospective synergistic antitumor effects and have potency to overcome the complications being produced by chemo drugs. Herein, we provide an overview of various bioconjugates developed so far, as well as their classification, characteristics, and targeting approach for cancer. Additionally, the most popular nanostructures based on their organic or inorganic origin (metallic, magnetic, polymeric nanoparticles, dendrimers, and silica nanoparticles) characterized as nanocarriers are also discussed. Moreover, we hope that this review will provide inspiration for researchers to develop better bioconjugates as therapeutic agents.

Inside out: optimization of lipid nanoparticle formulations for exterior complexation and in vivo delivery of saRNA

Self-amplifying RNA (saRNA) is a promising biotherapeutic tool that has been used as a vaccine against both infectious diseases and cancer. saRNA has been shown to induce protein expression for up to 60 days and elicit immune responses with lower dosing than messenger RNA (mRNA). Because saRNA is a large (~9500 nt), negatively charged molecule, it requires a delivery vehicle for efficient cellular uptake and degradation protection. Lipid nanoparticles (LNPs) have been widely used for RNA formulations, where the prevailing paradigm is to encapsulate RNA within the particle, including the first FDA-approved small-interfering siRNA therapy. Here, we compared LNP formulations with cationic and ionizable lipids with saRNA either on the interior or exterior of the particle. We show that LNPs formulated with cationic lipids protect saRNA from RNAse degradation, even when it is adsorbed to the surface. Furthermore, cationic LNPs deliver saRNA equivalently to particles formulated with saRNA encapsulated in an ionizable lipid particle, both in vitro and in vivo. Finally, we show that cationic and ionizable LNP formulations induce equivalent antibodies against HIV-1 Env gp140 as a model antigen. These studies establish formulating saRNA on the surface of cationic LNPs as an alternative to the paradigm of encapsulating RNA.

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.

The Skin You Are In: Design-of-Experiments Optimization of Lipid Nanoparticle Self-Amplifying RNA Formulations in Human Skin Explants

Messenger RNA (mRNA) is a promising tool for biotherapeutics, and self-amplifying mRNA (saRNA) is particularly advantageous, because it results in abundant protein expression and production is easily scalable. While mRNA therapeutics have been shown to be highly effective in small animals, the outcomes do not scale linearly when these formulations are translated to dose-escalation studies in humans. Here, we utilize a design of experiments (DoE) approach to optimize the formulation of saRNA lipid nanoparticles in human skin explants. We first observed that luciferase expression from saRNA peaked after 11 days in human skin. Using DoE inputs of complexing lipid identity, lipid nanoparticle dose, lipid concentration, particle concentration, and ratio of zwitterionic to cationic lipids, we optimized the saRNA-induced luciferase expression in skin explants. Lipid identity and lipid concentration were found to be significant parameters in the DoE model, and the optimized formulation resulted in ∼7-fold increase in luciferase expression, relative to initial 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) formulation. Using flow cytometry, we observed that optimized formulations delivered the saRNA to ∼2% of the resident cells in the human skin explants. Although immune cells comprise only 7% of the total population of cells in skin, immune cells were found to express ∼50% of the RNA. This study demonstrates the powerful combination of using a DoE approach paired with clinically relevant human skin explants to optimize nucleic acid formulations. We expect that this system will be useful for optimizing both formulation and molecular designs of clinically translational nucleic acid vaccines and therapeutics.

Precise tuning of disulphide crosslinking in mRNA polyplex micelles for optimising extracellular and intracellular nuclease tolerability

The major issues in messenger (m)RNA delivery are rapid mRNA degradation in the extracellular and intracellular spaces, which decreases the efficiency and duration for protein expression from mRNA. Stabilization of mRNA carriers using environment-responsive crosslinkings has promises to overcome these issues. Herein, we fine-tuned the structure of disulphide crosslinkings, which are selectively cleaved in the intracellular reductive environment, using the mRNA-loaded polyplex micelles (PMs) prepared from poly(ethylene glycol)-poly(L-lysine) (PEG-PLys) block copolymers, particularly by focussing on cationic charge density after the crosslinking. Primary amino groups in PLys segment were partially thiolated in two ways: One is to introduce 3-mercaptopropionyl (MP) groups via amide linkage, resulting in the decreased cationic charge density [PEG-PLys(MP)], and the other is the conversion of amino groups to 1-amidine-3-mercaptopropyl (AMP) groups with preserving cationic charge density [PEG-PLys(AMP)]. Compared to non-crosslinked and PEG-PLys(MP) PMs, PEG-PLys(AMP) PM attained tighter mRNA packaging in the PM core, thereby improving mRNA nuclease tolerability in serum and intracellular spaces, and providing enhanced protein expression in cultured cells at the optimal crosslinking density. These findings highlight the importance of cationic charge preservation in installing crosslinking moieties, providing a rationale for mRNA carrier design in the molecular level.

PEG-OligoRNA Hybridization of mRNA for Developing Sterically Stable Lipid Nanoparticles toward In Vivo Administration

Lipid nanoparticles (LNPs) exhibit high potential as carriers of messenger RNA (mRNA). However, the arduous preparation process of mRNA-loaded LNPs remains a huge obstacle for their widespread clinical application. Herein, we tackled this issue by mRNA PEGylation through hybridization with polyethylene glycol (PEG)-conjugated RNA oligonucleotides (PEG-OligoRNAs). Importantly, mRNA translational activity was preserved even after hybridization of 20 PEG-OligoRNAs per mRNA. The straightforward mixing of the PEGylated mRNA with lipofectamine LTX, a commercial lipid-based carrier, just by pipetting in aqueous solution, allowed the successful preparation of mRNA-loaded LNPs with a diameter below 100 nm, whereas the use of non-PEGylated mRNA provided large aggregates above 100- and 1000-nm. In vivo, LNPs prepared from PEG-OligoRNA-hybridized mRNA exhibited high structural stability in biological milieu, without forming detectable aggregates in mouse blood after intravenous injection. In contrast, LNPs from non-PEGylated mRNA formed several micrometer-sized aggregates in blood, leading to rapid clearance from blood circulation and deposition of the aggregates in lung capillaries. Our strategy of mRNA PEGylation was also versatile to prevent aggregation of another type of mRNA-loaded LNP, DOTAP/Chol liposomes. Together, our approach provides a simple and robust preparation method to LNPs for in vivo application.

New copolymers as hosts of ribosomal RNA

Functionalized copolymers were synthesized and are proposed as hosts of RNA. The copolymers are based on carboxymethyl cellulose and poly-(ethylene glycol)-OH. These copolymers were functionalized with two amino acids, either lysine or histidine, through amide bond formation. The functionalized copolymer was then used to adsorb ribosomal RNA. The RNA loading was based on the nature of the amino acid functionalization of the copolymer. The array of RNA-copolymers was observed to be soft sphere-like, where the density of spheres was a function of the molecular weight of the carboxymethyl cellulose and the nature of the amino acid. Such RNA-copolymer systems are very sensitive to changes in pH.

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.

Design concepts of polyplex micelles for in vivo therapeutic delivery of plasmid DNA and messenger RNA

Nonviral delivery of plasmid (p)DNA or messenger (m)RNA is a safe and promising therapeutic option to continuously supply therapeutic proteins into diseased tissues. In most cases of in vivo pDNA and mRNA delivery, these nucleic acids are loaded into carriers based on cationic polymers and/or lipids to prevent nuclease-mediated degradation before reaching target cells. The carriers should also evade host clearance mechanisms, including uptake by scavenger cells and filtration in the spleen. Installation of ligands onto the carriers can facilitate their rapid uptake into target cells. Meanwhile, carrier toxicity should be minimized not only for preventing undesirable adverse responses in patients, but also for preserving the function of transfected cells to exert therapeutic effects. Long-term progressive improvement of platform technologies has helped overcome most of these issues, though some still remain hindering the widespread clinical application of nonviral pDNA and mRNA delivery. This review discusses design concepts of nonviral carriers for in vivo delivery and the issues to be overcome, focusing especially on our own efforts using polyplex micelles. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 978-990, 2019.

Induced packaging of mRNA into polyplex micelles by regulated hybridization with a small number of cholesteryl RNA oligonucleotides directed enhanced in vivo transfection

There has been a progressive interest in the molecular design of polymers and lipids as synthetic carriers for targeting therapeutic mRNA in vivo with the ability to circumvent nuclease attack for treating intractable diseases. Herein, we developed a simple approach to attain one order of magnitude higher nuclease tolerability of mRNA through the formation of polyplex micelles (PMs) by combining ω-cholesteryl (ω-Chol)-poly (ethylene-glycol) (PEG)-polycation block copolymers with mRNA pre-hybridized with cholesterol (Chol)-tethered RNA oligonucleotides (Chol (+)-OligoRNA). Even one or a few short Chol (+)-OligoRNA anchors harboring along the 46-fold longer mRNA strand was sufficient to induce tight mRNA packaging in the PM core, as evidenced by Förster resonance energy transfer (FRET) measurement as well as by a longitudinal relaxation time (T₁) measurement using NMR. These results suggest that Chol (+)-OligoRNA on mRNA strand serves as a node to attract ω-Chol moiety of the block copolymers to tighten the mRNA packaging in the PM core. These mRNA loaded PMs showed high tolerability against nuclease attack, and exerted appreciable protein translational activity in cultured cells without any inflammatory responses, achieved by shortening of the length of hybridizing Chol (+)-OligoRNAs to 17 nucleotides. Finally, the Chol (+)-OligoRNA-stabilized PM revealed efficient mRNA introduction into the mouse lungs via intratracheal administration, demonstrating in vivo utility of this formulation.

Reviewing two decades of nanomedicine implementations in targeted treatment and diagnosis of pancreatic cancer: An emphasis on state of art

Pancreatic cancer is nowadays the most life-threatening cancer type worldwide. The problem of poor diagnosis, anti-neoplastics resistance and biopharmaceutical drawbacks of effective anti-cancer drugs lead to worsen disease state. Nanotechnology-based carrier systems used in both imaging and treatment procedures had solved many of these problems. It is critical to develop advanced detection method to save patients from being too late diagnosed. Targeting the pancreatic cancer cells as well helped in decreasing the side effects associated with normal cells destruction. Drug resistance is another challenge in pancreatic cancer management that can be solved by thorough understanding of the microenvironment associated with the disease to design creative nanocarriers. This is the first article to review multifaceted approaches of nanomedicine in pancreatic cancer detection and management. Additionally, mortality rates in selected Arab and European countries were illustrated herein. An emphasis was given on therapeutic and diagnostic challenges and different nanotechnologies adopted to overcome. The four main approaches encompassed nanomedicine for herbal treatment, nanomedicine of synthetic anti-cancer drugs, metal nanoparticles as a distinct treatment policy and nanotechnology for cancer diagnosis. Future research perspectives have been finally proposed.

Messenger RNA Delivery for Tissue Engineering and Regenerative Medicine Applications

The ability to control cellular processes and precisely direct cellular reprogramming has revolutionized regenerative medicine. Recent advances in in vitro transcribed (IVT) mRNA technology with chemical modifications have led to development of methods that control spatiotemporal gene expression. Additionally, there is a current thrust toward the development of safe, integration-free approaches to gene therapy for translational purposes. In this review, we describe strategies of synthetic IVT mRNA modifications and nonviral technologies for intracellular delivery. We provide insights into the current tissue engineering approaches that use a hydrogel scaffold with genetic material. Furthermore, we discuss the transformative potential of novel mRNA formulations that when embedded in hydrogels can trigger controlled genetic manipulation to regenerate tissues and organs in vitro and in vivo. The role of mRNA delivery in vascularization, cytoprotection, and Cas9-mediated xenotransplantation is additionally highlighted. Harmonizing mRNA delivery vehicle interactions with polymeric scaffolds can be used to present genetic cues that lead to precise command over cellular reprogramming, differentiation, and secretome activity of stem cells-an ultimate goal for tissue engineering.

Poly(lactic acid) nanoparticles and cell-penetrating peptide potentiate mRNA-based vaccine expression in dendritic cells triggering their activation

Messenger RNA-based vaccines have the potential to trigger robust cytotoxic immune responses, which are essential for fighting cancer and infectious diseases like HIV. Dendritic Cells (DCs) are choice targets for mRNA-based vaccine strategies, as they link innate and adaptive immune responses and are major regulators of cytotoxic and humoral adaptive responses. However, efficient delivery of antigen-coding mRNAs into DC cytosol has been highly challenging. In this study, we developed an alternative to lipid-based mRNA delivery systems, using poly(lactic acid) nanoparticles (PLA-NPs) and cationic cell-penetrating peptides as mRNA condensing agent. The formulations are assembled in two steps: (1) formation of a polyplex between mRNAs and amphipathic cationic peptides (RALA, LAH4 or LAH4-L1), and (2) adsorption of polyplexes onto PLA-NPs. LAH4-L1/mRNA polyplexes and PLA-NP/LAH4-L1/mRNA nanocomplexes are taken up by DCs via phagocytosis and clathrin-dependent endocytosis, and induce strong protein expression in DCs in vitro. They modulate DC innate immune response by activating both endosome and cytosolic Pattern Recognition Receptors (PRRs), and induce markers of adaptive responses in primary human DCs in vitro, with prevalent Th1 signature. Thus, LAH4-L1/mRNA and PLA-NP/LAH4-L1/mRNA represent a promising platform for ex vivo treatment and mRNA vaccine development.

mRNA Polyplexes with Post-Conjugated GALA Peptides Efficiently Target, Transfect, and Activate Antigen Presenting Cells

Vaccines based on mRNA have emerged as potent systems to elicit CD8⁺ T cell responses against various cancers and viral infectious diseases. The efficient intracellular delivery of mRNA molecules encoding antigens into the cytosol of antigen-presenting cells (APCs) is still challenging, requiring cell attachment, active uptake, and subsequent endosomal escape. Here, we report a facile approach for the formulation of peptide-functionalized mRNA polyplexes using copper-free click chemistry to promote presentation of mRNA antigen by dendritic cells (DCs). After screening different membrane active peptides, GALA modified mRNA polyplexes (PPx-GALA) with a size around 350 nm and with a slightly negative surface charge (−7 mV), exhibited the highest EGFP-mRNA transfection in RAW 246.7 macrophages (∼36%) and D1 dendritic cells (∼50%) as compared to polyplexes decorated with melittin or LEDE peptides. Interestingly, we found that PPx-GALA enters DCs through sialic acid mediated endo/phagocytosis, which was not influenced by DC maturation. The PPx-GALA formulation exhibited 18-fold higher cellular uptake compared to a lipofectamine mRNA formulation without inducing cytotoxicity. Live cell imaging showed that PPx-GALA that were taken up by endocytosis induced calcein release from endosomes into the cytosol. DCs treated with PPx-GALA containing mRNA encoding for OVA displayed enhanced T cell responses and DC maturation. Collectively, these data provide a strong rationale for further study of this PPx-GALA formulation in vivo as a promising mRNA vaccine platform.

Biomedical applications of mRNA nanomedicine

As an attractive alternative to plasmid DNA, messenger RNA (mRNA) has recently emerged as a promising class of nucleic acid therapeutics for biomedical applications. Advances in addressing the inherent shortcomings of mRNA and in the development of nanoparticle-based delivery systems have prompted the development and clinical translation of mRNA-based medicines. In this review, we discuss the chemical modification strategies of mRNA to improve its stability, minimize immune responses, and enhance translational efficacy. We also highlight recent progress in nanoparticle-based mRNA delivery. Considerable attention is given to the increasingly widespread applications of mRNA nanomedicine in the biomedical fields of vaccination, protein-replacement therapy, gene editing, and cellular reprogramming and engineering.

Block Copolymer Micelles in Nanomedicine Applications

Polymeric micelles are demonstrating high potential as nanomedicines capable of controlling the distribution and function of loaded bioactive agents in the body, effectively overcoming biological barriers, and various formulations are engaged in intensive preclinical and clinical testing. This Review focuses on polymeric micelles assembled through multimolecular interactions between block copolymers and the loaded drugs, proteins, or nucleic acids as translationable nanomedicines. The aspects involved in the design of successful micellar carriers are described in detail on the basis of the type of polymer/payload interaction, as well as the interplay of micelles with the biological interface, emphasizing on the chemistry and engineering of the block copolymers. By shaping these features, polymeric micelles have been propitious for delivering a wide range of therapeutics through effective sensing of targets in the body and adjustment of their properties in response to particular stimuli, modulating the activity of the loaded drugs at the targeted sites, even at the subcellular level. Finally, the future perspectives and imminent challenges for polymeric micelles as nanomedicines are discussed, anticipating to spur further innovations.

Factors relating to the biodistribution & clearance of nanoparticles & their effects on in vivo application

Nanoparticles have promising biomedical applications for drug delivery, tumor imaging and tumor treatment. Pharmacokinetics are important for the in vivo application of nanoparticles. Biodistribution and clearance are largely defined as the key points of pharmacokinetics to maximize therapeutic efficacy and to minimize side effects. Different engineered nanoparticles have different biodistribution and clearance processes. The interactions of organs with nanoparticles, which are determined by the characteristics of the organs and the biochemical/physical properties of the nanoparticles, are a major factor influencing biodistribution and clearance. In this review, the clearance functions of organs and the properties related to pharmacokinetics, including nanoparticle size, shape, biodegradation and surface modifications are discussed.

Current Status of Messenger RNA Delivery Systems

Messenger RNA is emerging as a highly versatile biological construct for creation of impactful medicines. mRNA vaccines directed toward infectious disease and cancer are in clinical development with encouraging early reads on tolerability and efficacy. The use of mRNA to direct intense but transient expression of paracrine factors is finding utility in reprogramming progenitor cells for wound healing and cardiac regeneration and for stimulation of antitumor immune responses, at least preclinically as we await clinical results. The use of mRNA for prolonged and repeated expression of proteins and enzymes to treat rare, typically monogenic disease is nearing clinical entry. These uses of mRNA require delivery solutions, and the application of and improvement to existing nanoparticle nucleic acid delivery systems have jump started the pace of development and reenergized the field of particle based nucleic acid delivery. The current status of mRNA delivery is reviewed in this article with an eye toward clinical tractability.

Prolonging pulse duration in ultrasound-mediated gene delivery lowers acoustic pressure threshold for efficient gene transfer to cells and small animals

While ultrasound-mediated gene delivery (UMGD) has been accomplished using high peak negative pressures (PNPs) of 2 MPa or above, emerging research showed that this may not be a requirement for microbubble (MB) cavitation. Thus, we investigated lower-pressure conditions close to the MB inertial cavitation threshold and focused towards further increasing gene transfer efficiency and reducing associated cell damage. We created a matrix of 21 conditions (n = 3/cond.) to test in HEK293T cells using pulse durations spanning 18 μs-36 ms and PNPs spanning 0.5-2.5 MPa. Longer pulse duration conditions yielded significant increase in transgene expression relative to sham with local maxima between 20 J and 100 J energy curves. A similar set of 17 conditions (n = 4/cond.) was tested in mice using pulse durations spanning 18 μs-22 ms and PNPs spanning 0.5-2.5 MPa. We observed local maxima located between 1 J and 10 J energy curves in treated mice. Of these, several low pressure conditions showed a decrease in ALT and AST levels while maintaining better or comparable expression to our positive control, indicating a clear benefit to allow for effective transfection with minimized tissue damage versus the high-intensity control. Our data indicates that it is possible to eliminate the requirement of high PNPs by prolonging pulse durations for effective UMGD in vitro and in vivo, circumventing the peak power density limitations imposed by piezo-materials used in US transducers. Overall, these results demonstrate the advancement of UMGD technology for achieving efficient gene transfer and potential scalability to larger animal models and human application.

Characterization of the complexation phenomenon and biological activity in vitro of polyplexes based on Tetronic T901 and DNA

The complexation process and underlying mechanisms that rule the interaction of DNA with the cationic block copolymer Tetronic T901 to form polyplexes and their potential transfection efficiency have been studied under different solution conditions. We noted that T901 favors the formation of self-assembled structures with partially condensed DNA at smaller polymer concentrations than other Pluronic™/Tetronic™-type copolymers previously analysed. The observed polyplexes display sizes from the nano- to the micro- range as derived from DLS, electronic and optical microscopies. Also, copolymer micelles are observed at concentrations below the copolymer critical micellar concentration (cmc) induced by the presence of DNA. The complexation process is dependent on solution conditions, with electrostatic and ionic interactions being more important at acidic pH thanks to the predominant diprotonated form of the block copolymer which is less aggregation-prone, whilst dispersive forces are increasingly enhanced under basic conditions or when rising the solution temperature. Whatever the case, the complexation is mainly governed by entropic contributions, as denoted from ITC data. In vitro transfection experiments after complexing T901 with a pDNA encoding the expression of green fluorescein protein, GFP, show a relative successful fluorescence of transfected HeLa cells, which confirms the uptake, internalization and release of the genetic material within the cells at suitable [N]/[P] ratios with relatively low cytotoxicity. Despite the observed successful outcomes, the obtained transfection efficacies are slightly lower than those obtained with Lipofectamine2000, so further optimization of the polyplex formation conditions is envisaged in future studies.

mRNA vaccines - a new era in vaccinology

mRNA vaccines represent a promising alternative to conventional vaccine approaches because of their high potency, capacity for rapid development and potential for low-cost manufacture and safe administration. However, their application has until recently been restricted by the instability and inefficient in vivo delivery of mRNA. Recent technological advances have now largely overcome these issues, and multiple mRNA vaccine platforms against infectious diseases and several types of cancer have demonstrated encouraging results in both animal models and humans. This Review provides a detailed overview of mRNA vaccines and considers future directions and challenges in advancing this promising vaccine platform to widespread therapeutic use.

Delivering the right message: Challenges and opportunities in lipid nanoparticles-mediated modified mRNA therapeutics-An innate immune system standpoint

mRNA molecules hold tremendous potential as a tool for gene therapy of a wide range of diseases. However, the main hurdle in implementation of mRNA for therapeutics, the systemic delivery of mRNA molecules to target cells, remains a challenge. A feasible solution for this challenge relies in the rapidly evolving field of nucleic acid-loaded nanocarriers and specifically in the established family of lipid-based nanoparticles (LNPs). Herein, we will discuss the main factors, which determine the fate of modified mRNA (mmRNA)-loaded LNPs in-vivo, and will focus on their interactions with the innate immune system as a main consideration in the design of lipid-based mmRNA delivery platforms.

Quantitative Phosphoproteomic Analysis Reveals Key Mechanisms of Cellular Proliferation in Liver Cancer Cells

Understanding the mechanisms of uncontrolled proliferation in cancer cells provides valuable insights into tumor development and is benefit for discovering efficient methods in cancer treatment. In this study, we identified and quantified 2,057 phosphoproteins and 9,824 unique phosphosites in three liver cell lines with high (QGY, Hep3B) and low (L02) proliferative potentials and disclosed the wide variations in phosphorylation sites and levels among them. We found that the number of identified phosphoproteins and phosphosites in these cells were negatively correlated with their proliferative abilities. The function analysis suggested that the aberrant phosphorylation of SR proteins and activation of MAPK pathway might be two critical factors to promote cancer cell proliferation. Meanwhile, the phosphorylation status of mini-chromosome maintenance (MCM) and nuclear pore (NPC) complexes are significantly different between cell lines with high and low proliferative potentials. Furthermore, the phosphosites targeted by kinase families of CDK, STE and HIPK in the proteins coded by cancer driver genes showed distinct profiles between caner and normal cell lines. These results present key phosphorylation networks involving in abnormal proliferation of cancer cells and uncovered potential molecular markers for estimating the proliferation ability of liver cancer cells.

Nanomaterial-Enabled Cancer Therapy

While cancer remains the major cause of death worldwide, nanomaterial (NM)-based diagnosis and treatment modalities are showing remarkable potential to better tackle clinical oncology by effectively targeting therapeutic agents to tumors. NMs can selectively accumulate in solid tumors, and they can improve the bioavailability and reduce the toxicity of encapsulated cytotoxic agents. Additional noteworthy functions of NMs in cancer treatment include the delivery of contrast agents to image tumor sites, delivery of genetic materials for gene therapy, and co-delivery of multiple agents to achieve combination therapy or simultaneous diagnostic and therapeutic outcomes. Although several NM therapeutics have been successfully translated to clinical applications, the gap between the bench and the bedside remains ominously wide. Tumor heterogeneity and the disparity between pre-clinical and clinical studies have been identified as two of the major translational challenges of NM-based cancer therapies. Herein, we review a handful of recent research studies on the use of NMs in cancer therapy and imaging, with a limited discussion on the consequences of tumor heterogeneity and pre-clinical studies on translational research of NM-based delivery systems and propositions in the literature to overcome these challenges.

Targeting Splicing in the Treatment of Human Disease

The tightly regulated process of precursor messenger RNA (pre-mRNA) alternative splicing (AS) is a key mechanism in the regulation of gene expression. Defects in this regulatory process affect cellular functions and are the cause of many human diseases. Recent advances in our understanding of splicing regulation have led to the development of new tools for manipulating splicing for therapeutic purposes. Several tools, including antisense oligonucleotides and trans-splicing, have been developed to target and alter splicing to correct misregulated gene expression or to modulate transcript isoform levels. At present, deregulated AS is recognized as an important area for therapeutic intervention. Here, we summarize the major hallmarks of the splicing process, the clinical implications that arise from alterations in this process, and the current tools that can be used to deliver, target, and correct deficiencies of this key pre-mRNA processing event.

mRNA-Based Therapeutics - Advances and Perspectives

In this review we discuss features of mRNA synthesis and modifications used to minimize immune response and prolong efficiency of the translation process in vivo. Considerable attention is given to the use of liposomes and nanoparticles containing lipids and polymers for the mRNA delivery. Finally we briefly discuss mRNAs which are currently in the clinical trials for cancer immunotherapy, vaccination against infectious diseases, and replacement therapy.

How to Tackle the Challenge of siRNA Delivery with Sequence-Defined Oligoamino Amides

RNA interference (RNAi) as a mechanism of gene regulation provides exciting opportunities for medical applications. Synthetic small interfering RNA (siRNA) triggers the knockdown of complementary mRNA sequences in a catalytic fashion and has to be delivered into the cytosol of the targeted cells. The design of adequate carrier systems to overcome multiple extracellular and intracellular roadblocks within the delivery process has utmost importance. Cationic polymers form polyplexes through electrostatic interaction with negatively charged nucleic acids and present a promising class of carriers. Issues of polycations regarding toxicity, heterogeneity, and polydispersity can be overcome by solid-phase-assisted synthesis of sequence-defined cationic oligomers. These medium-sized highly versatile nucleic acid carriers display low cytotoxicity and can be modified and tailored in multiple ways to meet specific requirements of nucleic acid binding, polyplex size, shielding, targeting, and intracellular release of the cargo. In this way, sequence-defined cationic oligomers can mimic the dynamic and bioresponsive behavior of viruses.