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

Application of lipid-based nanoparticles in cancer immunotherapy

Immunotherapy is revolutionizing the clinical management of patients with different cancer types by sensitizing autologous or allogenic immune cells to the tumor microenvironment which eventually leads to tumor cell lysis without rapidly killing normal cells. Although immunotherapy has been widely demonstrated to be superior to chemotherapies, only a few populations of patients with specific cancer types respond to such treatment due to the failure of systemic immune activation. In addition, severe immune-related adverse events are rapidly observed when patients with very few responses are given higher doses of such therapies. Recent advances of lipid-based nanoparticles (NPs) development have made it possible to deliver not only small molecules but also mRNAs to achieve systemic anticancer immunity through cytotoxic immune cell activation, checkpoint blockade, and chimeric antigen receptor cell therapies, etc. This review summarized recent development and applications of LNPs in anticancer immunotherapy. The diversity of lipid-based NPs would encapsulate payloads with different structures and molecular weights to achieve optimal antitumor immunity through multiple mechanisms of action. The discussion about the components of lipid-based NPs and their immunologic payloads in this review hopefully shed more light on the future direction of anticancer immunotherapy.

Pressure-dependent fouling behavior during sterile filtration of mRNA-containing lipid nanoparticles

The COVID-19 pandemic has generated growing interest in the development of mRNA-based vaccines and therapeutics. However, the size and properties of the lipid nanoparticles (LNPs) used to deliver the nucleic acids can lead to unique phenomena during manufacturing that are not typical of other biologics. The objective of this study was to develop a more fundamental understanding of the factors controlling the performance of sterile filtration of mRNA-LNPs. Experimental filtration studies were performed with a Moderna mRNA-LNP solution using a commercially available dual-layer polyethersulfone sterile filter, the Sartopore 2 XLG. Unexpectedly, increasing the transmembrane pressure (TMP) from 2 to 20 psi provided more than a two-fold increase in filter capacity. Also surprisingly, the effective resistance of the fouled filter decreased with increasing TMP, in contrast to the pressure-independent behavior expected for an incompressible media and the increase in resistance typically seen for a compressible fouling deposit. The mRNA-LNPs appear to foul the dual-layer filter by blocking the pores in the downstream sterilizing-grade membrane layer, as demonstrated both by scanning electron microscopy (SEM) and derivative analysis of filtration data collected for the two layers independently. These results provide important insights into the mechanisms governing the filtration of mRNA-LNP vaccines and therapeutics. This article is protected by copyright. All rights reserved.

Efficient Genome Editing Achieved via Plug-and-Play Adenovirus Piggyback Transport of Cas9/gRNA Complex on Viral Capsid Surface

The capacity to efficiently deliver the gene-editing enzyme complex to target cells is favored over other forms of gene delivery as it offers one-time hit-and-run gene editing, thus improving precision and safety and reducing potential immunogenicity against edited cells in clinical applications. Here we performed a proof-of-mechanism study and demonstrated that a simian adenoviral vector for DNA delivery can be repurposed as a robust intracellular delivery platform for a functional Cas9/guide RNA (gRNA) complex to recipient cells. In this system, the clinically relevant adenovirus was genetically engineered with a plug-and-display technology based on SpyTag003/SpyCatcher003 coupling chemistry. Under physiological conditions, an off-the-shelf mixture of viral vector with SpyTag003 incorporated into surface capsid proteins and Cas9 fused with SpyCatcher003 led to a rapid titration reaction yielding adenovirus carrying Cas9SpyCatcher003 on the virus surface. The Cas9 fusion protein-conjugated viruses in the presence of a reporter gRNA delivered gene-editing functions to cells with an efficiency comparable to that of a commercial CRISPR/Cas9 transfection reagent. Our data fully validate the adenoviral "piggyback" approach to deliver an intracellularly acting enzyme cargo and, thus, warrant the prospect of engineering tissue-targeted adenovirus carrying Cas9/gRNA for in vivo gene editing.

Nonclinical safety evaluation of a novel ionizable lipid for mRNA delivery

mRNA vaccines hold tremendous potential in disease control and prevention for their flexibility with respect to production, application, and design. Recent breakthroughs in mRNA vaccination would have not been possible without major advances in lipid nanoparticles (LNPs) technologies. We developed an LNP containing a novel ionizable cationic lipid, Lipid-1, and three well known excipients. An in silico toxicity hazard assessment for genotoxicity, a genotoxicity assessment, and a dose range finding toxicity study were performed to characterize the safety profile of Lipid-1. The in silico toxicity hazard assessment, utilizing two prediction systems DEREK and Leadscope, did not find any structural alert for mutagenicity and clastogenicity, and prediction in the statistical models were all negative. In addition, applying a read-across approach a structurally very similar compound was tested negative in two in vitro assays confirming the low genotoxicity potential of Lipid-1. A dose range finding toxicity study in rabbits, receiving a single intramuscular injection of either different doses of an mRNA encoding Influenza Hemagglutinin H3 antigen encapsulated in the LNP containing Lipid-1 or the empty LNP, evaluated local tolerance and systemic toxicity during a 2-week observation period. Only rabbits exposed to the vaccine were able to develop a specific IgG response, indicating an appropriate vaccine take. The vaccine was well tolerated up to 250 μg mRNA/injection, which was defined as the No Observed Adverse Effect Level (NOAEL). These results support the use of the LNP containing Lipid-1 as an mRNA delivery system for different vaccine formulations and its deployment into clinical trials.

mRNA delivery technologies: Toward clinical translation

Messenger RNA (mRNA)-therapies have recently taken a huge step toward clinic thanks to the first mRNA-based medicinal products marketed. mRNA features for clinical purposes are improved by chemical modifications, but the inclusion in a delivery system is a regular requirement. mRNA nanomedicines must be designed for the specific therapeutic purpose, protecting the nucleic acid and facilitating the overcoming of biological barriers. Polymers, polypeptides, and cationic lipids are the main used materials to design mRNA delivery systems. Among them, lipid nanoparticles (LNPs) are the most advanced ones, and currently they are at the forefront of preclinical and clinical evaluation in several fields, including immunotherapy (against infectious diseases and cancer), protein replacement, gene editing and regenerative medicine. This chapter includes an overview on mRNA delivery technologies, with special interest in LNPs, and the most recent advances in their clinical application. Liposomes are the mRNA delivery technology with the highest clinical translation among LNPs, whereas the first clinical trial of a therapeutic mRNA formulated in exosomes has been recently approved for protein replacement therapy. The first mRNA products approved by the regulatory agencies worldwide are LNP-based mRNA vaccines against viral infections, specifically against the 2019 coronavirus disease (COVID-19). The clinical translation of mRNA-therapies for cancer is mainly focused on three strategies: anti-cancer vaccination by means of delivering cancer antigens or acting as an adjuvant, mRNA-engineered chimeric antigen receptors (CARs) and T-cell receptors (TCRs), and expression of antibodies and immunomodulators. Cancer immunotherapy and, more recently, COVID-19 vaccines spearhead the advance of mRNA clinical use.

Lipid-Nanoparticle-Based Delivery of CRISPR/Cas9 Genome-Editing Components

Gene editing mediated by CRISPR/Cas9 systems is due to become a beneficial therapeutic option for treating genetic diseases and some cancers. However, there are challenges in delivering CRISPR components which necessitate sophisticated delivery systems for safe and effective genome editing. Lipid nanoparticles (LNPs) have become an attractive nonviral delivery platform for CRISPR-mediated genome editing due to their low immunogenicity and application flexibility. In this review, we provide a background of CRISPR-mediated gene therapy, as well as LNPs and their applicable characteristics for delivering CRISPR components. We then highlight the challenges of CRISPR delivery, which have driven the significant development of new, safe, and optimized LNP formulations in the past decade. Finally, we discuss considerations for using LNPs to deliver CRISPR and future perspectives on clinical translation of LNP-CRISPR gene editing.

Clinical progress of nanomedicine-based RNA therapies

The clinical application of nanoparticles (NPs) to deliver RNA for therapy has progressed rapidly since the FDA approval of Onpattro® in 2018 for the treatment of polyneuropathy associated with hereditary transthyretin amyloidosis. The emergency use authorization or approval and widespread global use of two mRNA-NP based vaccines developed by Moderna Therapeutics Inc. and Pfizer-BioNTech in 2021 has highlighted the translatability of NP technology for RNA delivery. Furthermore, in clinical trials, a wide variety of NP formulations have been found to extend the half-life of RNA molecules such as microRNA, small interfering RNA, and messenger RNA, with limited safety issues. In this review, we discuss the NP formulations that are already used in the clinic to deliver therapeutic RNA and highlight examples of RNA-NPs which are currently under evaluation for human use. We also detail NP formulations that failed to progress through clinical trials, in hopes of guiding future successful translation of nanomedicine-based RNA therapeutics into the clinic.

The Progress and Promise of RNA Medicine─An Arsenal of Targeted Treatments

In the past decade, there has been a shift in research, clinical development, and commercial activity to exploit the many physiological roles of RNA for use in medicine. With the rapid success in the development of lipid-RNA nanoparticles for mRNA vaccines against COVID-19 and with several approved RNA-based drugs, RNA has catapulted to the forefront of drug research. With diverse functions beyond the role of mRNA in producing antigens or therapeutic proteins, many classes of RNA serve regulatory roles in cells and tissues. These RNAs have potential as new therapeutics, with RNA itself serving as either a drug or a target. Here, based on the CAS Content Collection, we provide a landscape view of the current state and outline trends in RNA research in medicine across time, geography, therapeutic pipelines, chemical modifications, and delivery mechanisms.

mRNA-based therapeutics: powerful and versatile tools to combat diseases

The therapeutic use of messenger RNA (mRNA) has fueled great hope to combat a wide range of incurable diseases. Recent rapid advances in biotechnology and molecular medicine have enabled the production of almost any functional protein/peptide in the human body by introducing mRNA as a vaccine or therapeutic agent. This represents a rising precision medicine field with great promise for preventing and treating many intractable or genetic diseases. In addition, in vitro transcribed mRNA has achieved programmed production, which is more effective, faster in design and production, as well as more flexible and cost-effective than conventional approaches that may offer. Based on these extraordinary advantages, mRNA vaccines have the characteristics of the swiftest response to large-scale outbreaks of infectious diseases, such as the currently devastating pandemic COVID-19. It has always been the scientists’ desire to improve the stability, immunogenicity, translation efficiency, and delivery system to achieve efficient and safe delivery of mRNA. Excitingly, these scientific dreams have gradually been realized with the rapid, amazing achievements of molecular biology, RNA technology, vaccinology, and nanotechnology. In this review, we comprehensively describe mRNA-based therapeutics, including their principles, manufacture, application, effects, and shortcomings. We also highlight the importance of mRNA optimization and delivery systems in successful mRNA therapeutics and discuss the key challenges and opportunities in developing these tools into powerful and versatile tools to combat many genetic, infectious, cancer, and other refractory diseases.

Toward Gene Transfer Nanoparticles as Therapeutics

Genetic medicine has great potential to treat the underlying causes of many human diseases with exquisite precision, but the field has historically been stymied by delivery as the central challenge. Nanoparticles, engineered constructs the size of natural viruses, are being designed to more closely mimic the delivery efficiency of viruses, while enabling the advantages of increased safety, cargo-carrying flexibility, specific targeting, and ease in manufacturing. The speed in which nonviral gene transfer nanoparticles are making progress in the clinic is accelerating, with clinical validation of multiple nonviral nucleic acid delivery nanoparticle formulations recently FDA approved for both expression and for silencing of genes. While much of this progress has been with lipid nanoparticle formulations, significant development is being made with other nanomaterials for gene transfer as well, with favorable attributes such as biodegradability, scalability, and cell targeting. This review highlights the state of the field, current challenges in delivery, and opportunities for engineered nanomaterials to meet these challenges, including enabling long-term therapeutic gene editing. Delivery technology utilizing different kinds of nanomaterials and varying cargos for gene transfer (DNA, mRNA, and ribonucleoproteins) are discussed. Clinical applications are presented, including for the treatment of genetic diseases such as cystic fibrosis.

A brief review of mRNA therapeutics and delivery for bone tissue engineering

The therapeutics for bone tissue regeneration requires constant advancements owing to the steady increase in the number of patients suffering from bone-related disorders, and also to find efficient and cost-effective treatment modalities. One of the major advancements in the field of therapeutics is the development of mRNAs. mRNAs, which have been extensively tested for the vaccines, could be very well utilized as a potential inducer for bone regeneration. The ability of mRNAs to enter the cells and instruct the cellular machinery to produce the required native proteins such as BMP or VEGF is a great way to avoid the issues faced with growth factor deliveries such as the production cost, loss of biological function etc. However, there have been a few hurdles for using mRNAs as an effective therapeutic agent, such as proper dosing, tolerating the degradation by RNases, improving the half-life, controlling the spatio-temporal release and reducing the off-target effects. This brief review discusses the various developments in the field of mRNA therapeutics especially for bone tissue engineering, how nano-formulations are being developed to effectively deliver the mRNAs into the cells by evading the immune responses, how researchers have developed certain strategies to increase the half-life, to successfully deliver the mRNAs to specific bone defect area and bring about effective bone regeneration.

Versatile Design of Intracellular Protein-Responsive Translational Regulation System for Synthetic mRNA

Synthetic mRNA (mRNA) enables transgene expression without the necessity of nuclear import and the risk of insertional mutagenesis, which makes it an attractive tool for medical applications such as vaccination and protein replacement therapy. For further improvement of mRNA therapeutics, cell-selective translation is desirable, because transgene expression in nontarget cells sometimes causes adverse effects. In this study, we developed an intracellular protein-responsive translational regulation system based on Caliciviral VPg-based translational activator (CaVT) combined with inteins and target protein-binding nanobodies. This system enabled both translational activation and repression in a target protein-dependent manner. Importantly, the target protein can be altered by simply exchanging the nanobodies. The versatile design for target protein-responsive translational regulation holds promise for producing mRNA therapeutics with high safety.

Current advances and challenges in COVID-19 vaccine development: from conventional vaccines to next-generation vaccine platforms

The world is grappling with an unprecedented public health crisis COVID-19 pandemic caused by the novel coronavirus SARS-CoV-2. Due to the high transmission/mortality rates and socioeconomic impacts of the COVID-19, its control is crucial. In the absence of specific treatment, vaccines represent the most efficient way to control and stop the pandemic. Many companies around the world are currently making efforts to develop the vaccine to combat COVID-19. This review outlines key strategies for generating SARS-CoV-2 vaccine candidates, along with the mechanism of action, advantages, and potential limitations of each vaccine. The use of nanomaterials and nanotechnology for COVID-19 vaccines development will also be discussed.

Nonviral Delivery Systems of mRNA Vaccines for Cancer Gene Therapy

In recent years, the use of messenger RNA (mRNA) in the fields of gene therapy, immunotherapy, and stem cell biomedicine has received extensive attention. With the development of scientific technology, mRNA applications for tumor treatment have matured. Since the SARS-CoV-2 infection outbreak in 2019, the development of engineered mRNA and mRNA vaccines has accelerated rapidly. mRNA is easy to produce, scalable, modifiable, and not integrated into the host genome, showing tremendous potential for cancer gene therapy and immunotherapy when used in combination with traditional strategies. The core mechanism of mRNA therapy is vehicle-based delivery of in vitro transcribed mRNA (IVT mRNA), which is large, negatively charged, and easily degradable, into the cytoplasm and subsequent expression of the corresponding proteins. However, effectively delivering mRNA into cells and successfully activating the immune response are the keys to the clinical transformation of mRNA therapy. In this review, we focus on nonviral nanodelivery systems of mRNA vaccines used for cancer gene therapy and immunotherapy.

Strategies to deliver RNA by nanoparticles for therapeutic potential

The use of a variety of RNA molecules, including messenger RNA, small interfering RNA, and microRNA, has shown great potential for prevention and therapy of many pathologies. However, this therapeutic promise has historically been limited by short in vivo half-life, lack of targeted delivery, and safety issues. Nanoparticle (NP)-mediated delivery has been a successful platform to overcome these limitations, with multiple formulations already in clinical trials and approved by the FDA. Although there is a diversity of NPs in terms of material formulation, size, shape, and charge that have been proposed for biomedical applications, specific modifications are required to facilitate sufficient RNA delivery and adequate therapeutic effect. This includes optimization of (i) RNA incorporation into NPs, (ii) specific cell targeting, (iii) cellular uptake and (iv) endosomal escape ability. In this review, we summarize the methods by which NPs can be modified for RNA delivery to achieve optimal therapeutic effects.

In Vitro Engineering Chimeric Antigen Receptor Macrophages and T Cells by Lipid Nanoparticle-Mediated mRNA Delivery

Chimeric antigen receptor (CAR)-engineered adoptive cell therapy marks a revolution in cancer treatment based on the highly successful responses to CAR T cell therapy in the treatment of blood cancers. Due to the versatile structure of CARs, this technology can be easily adapted to other immune cell types, including macrophages and NKs, and applied in the treatment of many other cancers. However, high costs and fatal adverse effects represent significant concerns for future development. In vitro transcribed (IVT) mRNA therapeutics, which possess a high safety profile and straightforward production methods, could provide a useful alternative for CAR cell construction. However, the low stability and transfection efficiency of IVT-mRNA in immune cells limit further applications. In this work, we successfully engineered CAR macrophages (CAR-Ms) and CAR T cells with CAR mRNA using lipid nanoparticles (LNPs). Both the LNP formulations and mRNA modifications were optimized for in vitro mRNA transfection. More importantly, the CAR macrophages and CAR T cells both demonstrated significant cytotoxic effects on B lymphoma in vitro, underscoring the great potential of mRNA-engineered adoptive cell therapy.

Neurosurgery at the crossroads of immunology and nanotechnology. New reality in the COVID-19 pandemic

Neurosurgery as one of the most technologically demanding medical fields rapidly adapts the newest developments from multiple scientific disciplines for treating brain tumors. Despite half a century of clinical trials, survival for brain primary tumors such as glioblastoma (GBM), the most common primary brain cancer, or rare ones including primary central nervous system lymphoma (PCNSL), is dismal. Cancer therapy and research have currently shifted toward targeted approaches, and personalized therapies. The orchestration of novel and effective blood-brain barrier (BBB) drug delivery approaches, targeting of cancer cells and regulating tumor microenvironment including the immune system are the key themes of this review. As the global pandemic due to SARS-CoV-2 virus continues, neurosurgery and neuro-oncology must wrestle with the issues related to treatment-related immune dysfunction. The selection of chemotherapeutic treatments, even rare cases of hypersensitivity reactions (HSRs) that occur among immunocompromised people, and number of vaccinations they have to get are emerging as a new chapter for modern Nano neurosurgery.

Non-Viral Delivery of RNA Gene Therapy to the Central Nervous System

Appropriate gene delivery systems are essential for successful gene therapy in clinical medicine. Lipid-mediated nucleic acid delivery is an alternative to viral vector-mediated gene delivery and has the following advantages. Lipid-mediated delivery of DNA or mRNA is usually more rapid than viral-mediated delivery, offers a larger payload, and has a nearly zero risk of incorporation. Lipid-mediated delivery of DNA or RNA is therefore preferable to viral DNA delivery in those clinical applications that do not require long-term expression for chronic conditions. Delivery of RNA may be preferable to non-viral DNA delivery in some clinical applications, since transit across the nuclear membrane is not necessary, and onset of expression with RNA is therefore even faster than with DNA, although both are faster than most viral vectors. Delivery of RNA to target organ(s) has previously been challenging due to RNA's rapid degradation in biological systems, but cationic lipids complexed with RNA, as well as lipid nanoparticles (LNPs), have allowed for delivery and expression of the complexed RNA both in vitro and in vivo. This review will focus on the non-viral lipid-mediated delivery of RNAs, including mRNA, siRNA, shRNA, and microRNA, to the central nervous system (CNS), an organ with at least two unique challenges. The CNS contains a large number of slowly dividing or non-dividing cell types and is protected by the blood brain barrier (BBB). In non-dividing cells, RNA-lipid complexes demonstrated increased transfection efficiency relative to DNA transfection. The efficiency, timing of the onset, and duration of expression after transfection may determine which nucleic acid is best for which proposed therapy. Expression can be seen as soon as 1 h after RNA delivery, but duration of expression has been limited to 5-7 h. In contrast, transfection with a DNA lipoplex demonstrates protein expression within 5 h and lasts as long as several weeks after transfection.

Added to pre-existing inflammation, mRNA-lipid nanoparticles induce inflammation exacerbation (IE)

Current nucleoside-modified RNA lipid nanoparticle (modmRNA-LNP) technology has successfully paved the way for the highest clinical efficacy data from next-generation vaccinations against SARS-CoV-2 during the COVID-19 pandemic. However, such modmRNA-LNP technology has not been characterized in common pre-existing inflammatory or immune-challenged conditions, raising the risk of adverse clinical effects when administering modmRNA-LNPs in such cases. Herein, we induce an acute-inflammation model in mice with lipopolysaccharide (LPS) intratracheally (IT), 1 mg kg⁻¹, or intravenously (IV), 2 mg kg⁻¹, and then IV administer modmRNA-LNP, 0.32 mg kg⁻¹, after 4 h, and screen for inflammatory markers, such as pro-inflammatory cytokines. ModmRNA-LNP at this dose caused no significant elevation of cytokine levels in naive mice. In contrast, shortly after LPS immune stimulation, modmRNA-LNP enhanced inflammatory cytokine responses, Interleukin-6 (IL-6) in serum and Macrophage Inflammatory Protein 2 (MIP-2) in liver significantly. Our report identifies this phenomenon as inflammation exacerbation (IE), which was proven to be specific to the LNP, acting independent of mRNA cargo, and was demonstrated to be time- and dose-dependent. Macrophage depletion as well as TLR3 −/− and TLR4−/− knockout mouse studies revealed macrophages were the immune cells involved or responsible for IE. Finally, we show that pretreatment with anti-inflammatory drugs, such as corticosteroids, can partially alleviate IE response in mice. Our findings characterize the importance of LNP-mediated IE phenomena in gram negative bacterial inflammation, however, the generalizability of modmRNA-LNP in other forms of chronic or acute inflammatory and immune contexts needs to be addressed.

mRNA, a Revolution in Biomedicine

The perspective of using messenger RNA (mRNA) as a therapeutic molecule first faced some uncertainties due to concerns about its instability and the feasibility of large-scale production. Today, given technological advances and deeper biomolecular knowledge, these issues have started to be addressed and some strategies are being exploited to overcome the limitations. Thus, the potential of mRNA has become increasingly recognized for the development of new innovative therapeutics, envisioning its application in immunotherapy, regenerative medicine, vaccination, and gene editing. Nonetheless, to fully potentiate mRNA therapeutic application, its efficient production, stabilization and delivery into the target cells are required. In recent years, intensive research has been carried out in this field in order to bring new and effective solutions towards the stabilization and delivery of mRNA. Presently, the therapeutic potential of mRNA is undoubtedly recognized, which was greatly reinforced by the results achieved in the battle against the COVID-19 pandemic, but there are still some issues that need to be improved, which are critically discussed in this review.

Delivery of synthetic mRNAs for tissue regeneration

In recent years, nucleic acid-based therapeutics have gained increasing importance as novel treatment options for disease prevention and treatment. Synthetic messenger RNAs (mRNAs) are promising nucleic acid-based drugs to transiently express desired proteins that are missing or defective. Recently, synthetic mRNA-based vaccines encoding viral proteins have been approved for emergency use against COVID-19. Various types of vehicles, such as lipid nanoparticles (LNPs) and liposomes, are being investigated to enable the efficient uptake of mRNA molecules into desired cells. In addition, the introduction of novel chemical modifications into mRNAs increased the stability, enabled the modulation of nucleic acid-based drugs, and increased the efficiency of mRNA-based therapeutic approaches. In this review, novel and innovative strategies for the delivery of synthetic mRNA-based therapeutics for tissue regeneration are discussed. Moreover, with this review, we aim to highlight the versatility of synthetic mRNA molecules for various applications in the field of regenerative medicine and also discuss translational challenges and required improvements for mRNA-based drugs.

Lipid Nanoparticles─From Liposomes to mRNA Vaccine Delivery, a Landscape of Research Diversity and Advancement

Lipid nanoparticles (LNPs) have emerged across the pharmaceutical industry as promising vehicles to deliver a variety of therapeutics. Currently in the spotlight as vital components of the COVID-19 mRNA vaccines, LNPs play a key role in effectively protecting and transporting mRNA to cells. Liposomes, an early version of LNPs, are a versatile nanomedicine delivery platform. A number of liposomal drugs have been approved and applied to medical practice. Subsequent generations of lipid nanocarriers, such as solid lipid nanoparticles, nanostructured lipid carriers, and cationic lipid-nucleic acid complexes, exhibit more complex architectures and enhanced physical stabilities. With their ability to encapsulate and deliver therapeutics to specific locations within the body and to release their contents at a desired time, LNPs provide a valuable platform for treatment of a variety of diseases. Here, we present a landscape of LNP-related scientific publications, including patents and journal articles, based on analysis of the CAS Content Collection, the largest human-curated collection of published scientific knowledge. Rising trends are identified, such as nanostructured lipid carriers and solid lipid nanoparticles becoming the preferred platforms for numerous formulations. Recent advancements in LNP formulations as drug delivery platforms, such as antitumor and nucleic acid therapeutics and vaccine delivery systems, are discussed. Challenges and growth opportunities are also evaluated in other areas, such as medical imaging, cosmetics, nutrition, and agrochemicals. This report is intended to serve as a useful resource for those interested in LNP nanotechnologies, their applications, and the global research effort for their development.

A novel mechanism for the loss of mRNA activity in lipid nanoparticle delivery systems

Lipid nanoparticle (LNP)-formulated mRNA vaccines were rapidly developed and deployed in response to the SARS-CoV-2 pandemic. Due to the labile nature of mRNA, identifying impurities that could affect product stability and efficacy is crucial to the long-term use of nucleic-acid based medicines. Herein, reversed-phase ion pair high performance liquid chromatography (RP-IP HPLC) was used to identify a class of impurity formed through lipid:mRNA reactions; such reactions are typically undetectable by traditional mRNA purity analytical techniques. The identified modifications render the mRNA untranslatable, leading to loss of protein expression. Specifically, electrophilic impurities derived from the ionizable cationic lipid component are shown to be responsible. Mechanisms implicated in the formation of reactive species include oxidation and subsequent hydrolysis of the tertiary amine. It thus remains critical to ensure robust analytical methods and stringent manufacturing control to ensure mRNA stability and high activity in LNP delivery systems.

Lipid nanoparticle delivery of mRNA vaccines has become of particular importance, however, mRNA stability is a major concern. Here, the authors report on a study of lipid impurity mRNA interactions using reverse phase ion pair HPLC to identify reactions which render the mRNA untranslatable, reducing vaccine efficiency.

Protein-Based Systems for Translational Regulation of Synthetic mRNAs in Mammalian Cells

Synthetic mRNAs, which are produced by in vitro transcription, have been recently attracting attention because they can express any transgenes without the risk of insertional mutagenesis. Although current synthetic mRNA medicine is not designed for spatiotemporal or cell-selective regulation, many preclinical studies have developed the systems for the translational regulation of synthetic mRNAs. Such translational regulation systems will cope with high efficacy and low adverse effects by producing the appropriate amount of therapeutic proteins, depending on the context. Protein-based regulation is one of the most promising approaches for the translational regulation of synthetic mRNAs. As synthetic mRNAs can encode not only output proteins but also regulator proteins, all components of protein-based regulation systems can be delivered as synthetic mRNAs. In addition, in the protein-based regulation systems, the output protein can be utilized as the input for the subsequent regulation to construct multi-layered gene circuits, which enable complex and sophisticated regulation. In this review, I introduce what types of proteins have been used for translational regulation, how to combine them, and how to design effective gene circuits.

Role of nanostructures in allergy: Diagnostics, treatments and safety

Nanotechnology is science, engineering and technology conducted at the nanoscale, which is about 1-100 nm. It has led to the development of nanomaterials, which behave very differently from materials with larger scales and can have a wide range of applications in biomedicine. The physical and chemical properties of materials of such small compounds depend mainly on the size, shape, composition and functionalization of the system. Nanoparticles, carbon nanotubes, liposomes, polymers, dendrimers and nanogels, among others, can be nanoengineeried for controlling all parameters, including their functionalization with ligands, which provide the desired interaction with the immunological system, that is dendritic cell receptors to activate and/or modulate the response, as well as specific IgE, or effector cell receptors. However, undesired issues related to toxicity and hypersensitivity responses can also happen and would need evaluation. There are wide panels of accessible structures, and controlling their physico-chemical properties would permit obtaining safer and more efficient compounds for clinical applications goals, either in diagnosis or treatment. The application of dendrimeric antigens, nanoallergens and nanoparticles in allergy diagnosis is very promising since it can improve sensitivity by increasing specific IgE binding, mimicking carrier proteins or enhancing signal detection. Additionally, in the case of immunotherapy, glycodendrimers, liposomes, polymers and nanoparticles have shown interest, behaving as platforms of allergenic structures, adjuvants or protectors of allergen from degradation or having a depot capacity. Taken together, the application of nanotechnology to allergy shows promising facts facing important goals related to the improvement of diagnosis as well as specific immunotherapy.

mRNA vaccines for infectious diseases: principles, delivery and clinical translation

Over the past several decades, messenger RNA (mRNA) vaccines have progressed from a scepticism-inducing idea to clinical reality. In 2020, the COVID-19 pandemic catalysed the most rapid vaccine development in history, with mRNA vaccines at the forefront of those efforts. Although it is now clear that mRNA vaccines can rapidly and safely protect patients from infectious disease, additional research is required to optimize mRNA design, intracellular delivery and applications beyond SARS-CoV-2 prophylaxis. In this Review, we describe the technologies that underlie mRNA vaccines, with an emphasis on lipid nanoparticles and other non-viral delivery vehicles. We also overview the pipeline of mRNA vaccines against various infectious disease pathogens and discuss key questions for the future application of this breakthrough vaccine platform.

Microfluidic transfection of mRNA into human primary lymphocytes and hematopoietic stem and progenitor cells using ultra-fast physical deformations

Messenger RNA (mRNA) delivery provides gene therapy with the potential to achieve transient therapeutic efficacy without risk of insertional mutagenesis. Amongst other applications, mRNA can be employed as a platform to deliver gene editing molecules, to achieve protein expression as an alternative to enzyme replacement therapies, and to express chimeric antigen receptors (CARs) on immune cells for the treatment of cancer. We designed a novel microfluidic device that allows for efficient mRNA delivery via volume exchange for convective transfection (VECT). In the device, cells flow through a ridged channel that enforces a series of ultra-fast and large intensity deformations able to transiently open pores and induce convective transport of mRNA into the cell. Here, we describe efficient delivery of mRNA into T cells, natural killer (NK) cells and hematopoietic stem and progenitor cells (HSPCs), three human primary cell types widely used for ex vivo gene therapy applications. Results demonstrate that the device can operate at a wide range of cell and payload concentrations and that ultra-fast compressions do not have a negative impact on T cell function, making this a novel and competitive platform for the development of ex vivo mRNA-based gene therapies and other cell products engineered with mRNA.

Advances in mRNA non-viral delivery approaches

Messenger RNAs (mRNAs) present a great potential as therapeutics for the treatment and prevention of a wide range of human pathologies, allowing for protein replacement, vaccination, cancer immunotherapy, and genomic engineering. Despite advances in the design of mRNA-based therapeutics, a key aspect for their widespread translation to clinic is the development of safe and effective delivery strategies. To this end, non-viral delivery systems including peptide-based complexes, lipidic or polymeric nanoparticles, and hybrid formulations are attracting growing interest. Despite displaying somewhat reduced efficacy compared to viral-based systems, non-viral carriers offer important advantages in terms of biosafety and versatility. In this review, we provide an overview of current mRNA therapeutic applications and discuss key biological barriers to delivery and recent advances in the development of non-viral systems. Challenges and future applications of this novel therapeutic modality are also discussed.

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.

Advances in mRNA-based drug discovery in cancer immunotherapy

INTRODUCTION

Immune checkpoint inhibitors and adoptive T-cell therapy based on chimeric antigen receptors are the spearhead strategies to exploit the immune system to fight cancer. To take advantage of the full potential of the immune system, cancer immunotherapy must incorporate new biotechnologies such as mRNA technology that may synergize with already approved immunotherapies and act more effectively on immune targets.

AREAS COVERED

This review describes the basics of mRNA biotechnology and provides insight into the recent advances in the use of mRNA for the local and systemic delivery of immunostimulatory antibodies, proinflammatory cytokines or for optimizing adoptive T-cell therapy.

EXPERT OPINION

mRNA-based nanomedicines have great potential to expand the arsenal of immunotherapy tools due to their ability to simplify and accelerate drug development and their suitability for transient and local expression of immunostimulatory molecules, whose systemic and sustained expression would be toxic. The success of mRNA-based COVID-19 vaccines has highlighted the feasibility of this approach. Continuous advances in the delivery and construction of RNA-based vectors hold promise for improvements in clinical efficacy.

mRNA-Based Nanomedicinal Products to Address Corneal Inflammation by Interleukin-10 Supplementation

The anti-inflammatory cytokine Interleukin-10 (IL-10) is considered an efficient treatment for corneal inflammation, in spite of its short half-life and poor eye bioavailability. In the present work, mRNA-based nanomedicinal products based on solid lipid nanoparticles (SLNs) were developed in order to produce IL-10 to treat corneal inflammation. mRNA encoding green fluorescent protein (GFP) or human IL-10 was complexed with different SLNs and ligands. After, physicochemical characterization, transfection efficacy, intracellular disposition, cellular uptake and IL-10 expression of the nanosystems were evaluated in vitro in human corneal epithelial (HCE-2) cells. Energy-dependent mechanisms favoured HCE-2 transfection, whereas protein production was influenced by energy-independent uptake mechanisms. Nanovectors with a mean particle size between 94 and 348 nm and a positive superficial charge were formulated as eye drops containing 1% (w/v) of polyvinyl alcohol (PVA) with 7.1-7.5 pH. After three days of topical administration to mice, all formulations produced GFP in the corneal epithelium of mice. SLNs allowed the obtaining of a higher transfection efficiency than naked mRNA. All formulations produce IL-10, and the interleukin was even observed in the deeper layers of the epithelium of mice depending on the formulation. This work shows the potential application of mRNA-SLN-based nanosystems to address corneal inflammation by gene augmentation therapy.

Synthetic modified messenger RNA for therapeutic applications

Synthetic modified messenger RNA (mRNA) has manifested great potentials for therapeutic applications such as vaccines and gene therapies, with the recent mRNA vaccines for global pandemic COVID-19 (corona virus disease 2019) attracting the tremendous attention. The chemical modifications and delivery vehicles of synthetic mRNAs are the two key factors for their in vivo therapeutic applications. Chemical modifications like nucleoside methylation endow the synthetic mRNAs with high stability and reduced stimulation of innate immunity. The development of scalable production of synthetic mRNA and efficient mRNA formulation and delivery strategies in recent years have remarkably advanced the field. It is worth noticing that we had limited knowledge on the roles of mRNA modifications in the past. However, the last decade has witnessed not only new discoveries of several naturally occurring mRNA modifications but also substantial advances in understanding their roles on regulating gene expression. It is highly necessary to reconsider the therapeutic system made by synthetic modified mRNAs and delivery vectors. In this review, we will mainly discuss the roles of various chemical modifications on synthetic mRNAs, briefly summarize the progresses of mRNA delivery strategies, and highlight some latest mRNA therapeutics applications including infectious disease vaccines, cancer immunotherapy, mRNA-based genetic reprogramming and protein replacement, mRNA-based gene editing.

Statement of significance

The development of synthetic mRNA drug holds great promise but lies behind small molecule and protein drugs largely due to the challenging issues regarding its stability, immunogenicity and potency. In the last 15 years, these issues have beensubstantially addressed by synthesizing chemically modified mRNA and developing powerful delivery systems; the mRNA therapeutics has entered an exciting new era begun with the approved mRNA vaccines for the COVID-19 infection disease. Here, we provide recent progresses in understanding the biological roles of various RNA chemical modifications, in developing mRNA delivery systems, and in advancing the emerging mRNA-based therapeutic applications, with the purpose to inspire the community to spawn new ideas for curing diseases.

From influenza to COVID-19: Lipid nanoparticle mRNA vaccines at the frontiers of infectious diseases

Vaccination represents the best line of defense against infectious diseases and is crucial in curtailing pandemic spread of emerging pathogens to which a population has limited immunity. In recent years, mRNA vaccines have been proposed as the new frontier in vaccination, owing to their facile and rapid development while providing a safer alternative to traditional vaccine technologies such as live or attenuated viruses. Recent breakthroughs in mRNA vaccination have been through formulation with lipid nanoparticles (LNPs), which provide both protection and enhanced delivery of mRNA vaccines in vivo. In this review, current paradigms and state-of-the-art in mRNA-LNP vaccine development are explored through first highlighting advantages posed by mRNA vaccines, establishing LNPs as a biocompatible delivery system, and finally exploring the use of mRNA-LNP vaccines in vivo against infectious disease towards translation to the clinic. Furthermore, we highlight the progress of mRNA-LNP vaccine candidates against COVID-19 currently in clinical trials, with the current status and approval timelines, before discussing their future outlook and challenges that need to be overcome towards establishing mRNA-LNPs as next-generation vaccines. STATEMENT OF SIGNIFICANCE: With the recent success of mRNA vaccines developed by Moderna and BioNTech/Pfizer against COVID-19, mRNA technology and lipid nanoparticles (LNP) have never received more attention. This manuscript timely reviews the most advanced mRNA-LNP vaccines that have just been approved for emergency use and are in clinical trials, with a focus on the remarkable development of several COVID-19 vaccines, faster than any other vaccine in history. We aim to give a comprehensive introduction of mRNA and LNP technology to the field of biomaterials science and increase accessibility to readers with a new interest in mRNA-LNP vaccines. We also highlight current limitations and future outlook of the mRNA vaccine technology that need further efforts of biomaterials scientists to address.

Strategies for controlling the innate immune activity of conventional and self-amplifying mRNA therapeutics: Getting the message across

The recent approval of messenger RNA (mRNA)-based vaccines to combat the SARS-CoV-2 pandemic highlights the potential of both conventional mRNA and self-amplifying mRNA (saRNA) as a flexible immunotherapy platform to treat infectious diseases. Besides the antigen it encodes, mRNA itself has an immune-stimulating activity that can contribute to vaccine efficacy. This self-adjuvant effect, however, will interfere with mRNA translation and may influence the desired therapeutic outcome. To further exploit its potential as a versatile therapeutic platform, it will be crucial to control mRNA's innate immune-stimulating properties. In this regard, we describe the mechanisms behind the innate immune recognition of mRNA and provide an extensive overview of strategies to control its innate immune-stimulating activity. These strategies range from modifications to the mRNA backbone itself, optimization of production and purification processes to the combination with innate immune inhibitors. Furthermore, we discuss the delicate balance of the self-adjuvant effect in mRNA vaccination strategies, which can be both beneficial and detrimental to the therapeutic outcome.

Biomedical Applications of Antiviral Nanohybrid Materials Relating to the COVID-19 Pandemic and Other Viral Crises

The COVID-19 pandemic has driven a global research to uncover novel, effective therapeutical and diagnosis approaches. In addition, control of spread of infection has been targeted through development of preventive tools and measures. In this regard, nanomaterials, particularly, those combining two or even several constituting materials possessing dissimilar physicochemical (or even biological) properties, i.e., nanohybrid materials play a significant role. Nanoparticulate nanohybrids have gained a widespread reputation for prevention of viral crises, thanks to their promising antimicrobial properties as well as their potential to act as a carrier for vaccines. On the other hand, they can perform well as a photo-driven killer for viruses when they release reactive oxygen species (ROS) or photothermally damage the virus membrane. The nanofibers can also play a crucial protective role when integrated into face masks and personal protective equipment, particularly as hybridized with antiviral nanoparticles. In this draft, we review the antiviral nanohybrids that could potentially be applied to control, diagnose, and treat the consequences of COVID-19 pandemic. Considering the short age of this health problem, trivially the relevant technologies are not that many and are handful. Therefore, still progressing, older technologies with antiviral potential are also included and discussed. To conclude, nanohybrid nanomaterials with their high engineering potential and ability to inactivate pathogens including viruses will contribute decisively to the future of nanomedicine tackling the current and future pandemics.

Nanoparticles-Based Oligonucleotides Delivery in Cancer: Role of Zebrafish as Animal Model

Oligonucleotide (ON) therapeutics are molecular target agents composed of chemically synthesized DNA or RNA molecules capable of inhibiting gene expression or protein function. How ON therapeutics can efficiently reach the inside of target cells remains a problem still to be solved in the majority of potential clinical applications. The chemical structure of ON compounds could affect their capability to pass through the plasma membrane. Other key factors are nuclease degradation in the extracellular space, renal clearance, reticulo-endothelial system, and at the target cell level, the endolysosomal system and the possible export via exocytosis. Several delivery platforms have been proposed to overcome these limits including the use of lipidic, polymeric, and inorganic nanoparticles, or hybrids between them. The possibility of evaluating the efficacy of the proposed therapeutic strategies in useful in vivo models is still a pivotal need, and the employment of zebrafish (ZF) models could expand the range of possibilities. In this review, we briefly describe the main ON therapeutics proposed for anticancer treatment, and the different strategies employed for their delivery to cancer cells. The principal features of ZF models and the pros and cons of their employment in the development of ON-based therapeutic strategies are also discussed.

Therapeutic Perspectives of Thermogenic Adipocytes in Obesity and Related Complications

There is a rapidly increasing prevalence of obesity and related metabolic disorders such as type 2 diabetes worldwide. White adipose tissue (WAT) stores excess energy, whereas brown and beige adipose tissues consume energy to generate heat in the process of thermogenesis. Adaptive thermogenesis occurs in response to environmental cues as a means of generating heat by dissipating stored chemical energy. Due to its cumulative nature, very small differences in energy expenditure from adaptive thermogenesis can have a significant impact on systemic metabolism over time. Targeting brown adipose tissue (BAT) activation and converting WAT to beige fat as a method to increase energy expenditure is one of the promising strategies to combat obesity. In this review, we discuss the activation of the thermogenic process in response to physiological conditions. We highlight recent advances in harnessing the therapeutic potential of thermogenic adipocytes by genetic, pharmacological and cell-based approaches in the treatment of obesity and metabolic disorders in mice and the human.

Intracellular Routing and Recognition of Lipid-Based mRNA Nanoparticles

Messenger RNA (mRNA) is being extensively used in gene therapy and vaccination due to its safety over DNA, in the following ways: its lack of integration risk, cytoplasmic expression, and transient expression compatible with fine regulations. However, clinical applications of mRNA are limited by its fast degradation by nucleases, and the activation of detrimental immune responses. Advances in mRNA applications, with the recent approval of COVID-19 vaccines, were fueled by optimization of the mRNA sequence and the development of mRNA delivery systems. Although delivery systems and mRNA sequence optimization have been abundantly reviewed, understanding of the intracellular processing of mRNA is mandatory to improve its applications. We will focus on lipid nanoparticles (LNPs) as they are the most advanced nanocarriers for the delivery of mRNA. Here, we will review how mRNA therapeutic potency can be affected by its interactions with cellular proteins and intracellular distribution.

Nano and Microparticles as Potential Oral Vaccine Carriers and Adjuvants Against Infectious Diseases

Mucosal surfaces are the first site of infection for most infectious diseases and oral vaccination can provide protection as the first line of defense. Unlike systemic administration, oral immunization can stimulate cellular and humoral immune responses at both systemic and mucosal levels to induce broad-spectrum and long-lasting immunity. Therefore, to design a successful vaccine, it is essential to stimulate the mucosal as well as systemic immune responses. Successful oral vaccines need to overcome the harsh gastrointestinal environment such as the extremely low pH, proteolytic enzymes, bile salts as well as low permeability and the low immunogenicity of vaccines. In recent years, several delivery systems and adjuvants have been developed for improving oral vaccine delivery and immunogenicity. Formulation of vaccines with nanoparticles and microparticles have been shown to improve antigen stability, availability and adjuvanticity as well as immunostimulatory capacity, target delivery and specific release. This review discusses how nanoparticles (NPs) and microparticles (MPs) as oral carriers with adjuvant characteristics can be beneficial in oral vaccine development.

The Importance of Apparent pKa in the Development of Nanoparticles Encapsulating siRNA and mRNA

Polymer and lipid nanoparticles have been extensively used as carriers to address the biological barriers encountered in siRNA and mRNA delivery. We summarize the crucial role of nanoparticle charge and ionizability in complexing RNAs, binding to biological components, escaping from the endosome, and releasing RNAs into the cytoplasm. We highlight the significant impact of the apparent pKa of nanoparticles on their efficacy and toxicity, and the importance of optimizing pKa in the development of lead formulations for RNAs. We also discuss the feasibility of fine-tuning the pKa in nanoparticles and the applications of this approach in the optimization of delivery systems for RNAs.

Use of Gene Therapy in Retinal Ganglion Cell Neuroprotection: Current Concepts and Future Directions

We systematically reviewed published translational research on gene-based therapy for retinal ganglion cell (RGC) neuroprotection. A search was conducted on Entrez PubMed on 23 December 2020 using the keywords "gene therapy", "retinal ganglion cell" and "neuroprotection". The initial search yielded 82 relevant articles. After restricting publications to those with full text available and in the English language, and then curating for only original articles on gene-based therapy, the final yield was 18 relevant articles. From the 18 papers, 17 of the papers utilized an adeno-associated viral (AAV) vector for gene therapy encoding specific genes of interest. Specifically, six of the studies utilized an AAV vector encoding brain-derived neurotrophic factor (BDNF), two of the studies utilized an AAV vector encoding erythropoietin (EPO), the remaining 10 papers utilized AAV vectors encoding different genes and one microRNA study. Although the literature shows promising results in both in vivo and in vitro models, there is still a significant way to go before gene-based therapy for RGC neuroprotection can proceed to clinical trials. Namely, the models of injury in many of the studies were more acute in nature, unlike the more progressive and neurodegenerative pathophysiology of diseases, such as glaucoma. The regulation of gene expression is also highly unexplored despite the use of AAV vectors in the majority of the studies reviewed. It is also expected that with the successful launch of messenger ribonucleic acid (mRNA)-based vaccinations in 2020, we will see a shift towards this technology for gene-based therapy in glaucoma neuroprotection.

Quantum Biotech and Internet of Virus Things: Towards a Theoretical Framework

Quantumization, the process of converting information into quantum (qubit) format, is a key enabler for propelling a new and distinct infrastructure in the pharmaceutical space. Quantum messenger RNA (QmRNA) technology, an indispensable constituent of quantum biotech (QB), is a compelling alternative to conventional vaccine methods because of its capacity for rapid development, high efficacy, and low-cost manufacturing to combat infectious diseases. Internet of Virus Things (IoVT), a biological version of Internet of Things (IoT), comprises applications to fight against pandemics and provides effective vaccine administration. The integration of QB and IoVT constitutes the QBIoVT system to advance the prospect of QmRNA vaccine discovery within a few days. This research disseminates the QBIoVT system paradigm, including architectural aspects, priority areas, challenges, applications, and QmRNA research engine design to accelerate QmRNA vaccines discovery. A comprehensive review of the literature was accomplished, and a context-centered methodology was applied to the QBIoVT paradigm forensic investigations to impel QmRNA vaccine discovery. Based on the above rumination, the principal motive for this study was to develop a novel QBIoVT theoretical framework which has not been produced through earlier theories. The proposed framework shall inspire future QBIoVT system research activities to improve pandemics detection and protection.

Neoantigen vaccine platforms in clinical development: understanding the future of personalized immunotherapy

INTRODUCTION

Derived from genetic alterations, cancer neoantigens are proteins with novel amino acid sequences that can be recognized by the immune system. Recent evidence demonstrates that cancer neoantigens represent important targets of cancer immunotherapy. The goal of cancer neoantigen vaccines is to induce neoantigen-specific immune responses and antitumor immunity, while minimizing the potential for autoimmune toxicity. Advances in sequencing technologies, neoantigen prediction ?algorithms,? and other technologies have dramatically improved the ability to identify and prioritize cancer neoantigens. These advances have generated considerable enthusiasm for ?the ?development of neoantigen vaccines. Several neoantigen vaccine platforms are currently being evaluated in early phase clinical trials including the synthetic long peptide (SLP), RNA, dendritic cell (DC), and DNA vaccine platforms.

AREAS COVERED

In this review, we describe, evaluate the mechanism(s) of action, compare the advantages and disadvantages, and summarize early clinical experience with each vaccine platform. We provide perspectives on the future directions of the neoantigen vaccine field. All data are derived from PubMed and ClinicalTrials search updated in October 2020.

EXPERT OPINION

Although the initial clinical experience is promising, significant challenges to the success of neoantigen vaccines include limitations in neoantigen identification and the need to successfully target the immunosuppressive tumor microenvironment.

Delivery of cancer therapies by synthetic and bio-inspired nanovectors

BACKGROUND

As a complement to the clinical development of new anticancer molecules, innovations in therapeutic vectorization aim at solving issues related to tumor specificity and associated toxicities. Nanomedicine is a rapidly evolving field that offers various solutions to increase clinical efficacy and safety. MAIN: Here are presented the recent advances for different types of nanovectors of chemical and biological nature, to identify the best suited for translational research projects. These nanovectors include different types of chemically engineered nanoparticles that now come in many different flavors of 'smart' drug delivery systems. Alternatives with enhanced biocompatibility and a better adaptability to new types of therapeutic molecules are the cell-derived extracellular vesicles and micro-organism-derived oncolytic viruses, virus-like particles and bacterial minicells. In the first part of the review, we describe their main physical, chemical and biological properties and their potential for personalized modifications. The second part focuses on presenting the recent literature on the use of the different families of nanovectors to deliver anticancer molecules for chemotherapy, radiotherapy, nucleic acid-based therapy, modulation of the tumor microenvironment and immunotherapy.

CONCLUSION

This review will help the readers to better appreciate the complexity of available nanovectors and to identify the most fitting "type" for efficient and specific delivery of diverse anticancer therapies.

Perspectives of nano-carrier drug delivery systems to overcome cancer drug resistance in the clinics

Advanced cancer is still considered an incurable disease because of its metastatic spread to distal organs and progressive gain of chemoresistance. Even though considerable treatment progress and more effective therapies have been achieved over the past years, recurrence in the long-term and undesired side effects are still the main drawbacks of current clinical protocols. Moreover, a majority of chemotherapeutic drugs are highly hydrophobic and need to be diluted in organic solvents, which cause high toxicity, in order to reach effective therapeutic dose. These limitations of conventional cancer therapies prompted the use of nanomedicine, the medical application of nanotechnology, to provide more effective and safer cancer treatment. Potential of nanomedicines to overcome resistance, ameliorate solubility, improve pharmacological profile, and reduce adverse effects of chemotherapeutical drugs is thus highly regarded. Their use in the clinical setting has increased over the last decade. Among the various existing nanosystems, nanoparticles have the ability to transform conventional medicine by reducing the adverse effects and providing a controlled release of therapeutic agents. Also, their small size facilitates the intracellular uptake. Here, we provide a closer review of clinical prospects and mechanisms of action of nanomedicines to overcome drug resistance. The significance of specific targeting towards cancer cells is debated as well.

Improved multidetector asymmetrical-flow field-flow fractionation method for particle sizing and concentration measurements of lipid-based nanocarriers for RNA delivery

Lipid-based nanoparticles for RNA delivery (LNP-RNA) are revolutionizing the nanomedicine field, with one approved gene therapy formulation and two approved vaccines against COVID-19, as well as multiple ongoing clinical trials. As for other innovative nanopharmaceuticals (NPhs), the advancement of robust methods to assess their quality and safety profiles-in line with regulatory needs-is critical for facilitating their development and clinical translation. Asymmetric-flow field-flow fractionation coupled to multiple online optical detectors (MD-AF4) is considered a very versatile and robust approach for the physical characterisation of nanocarriers, and has been used successfully for measuring particle size, polydispersity and physical stability of lipid-based systems, including liposomes and solid lipid nanoparticles. However, the unique core structure of LNP-RNA, composed of ionizable lipids electrostatically complexed with RNA, and the relatively labile lipid-monolayer coating, is more prone to destabilization during focusing in MD-AF4 than previously characterised nanoparticles, resulting in particle aggregation and sample loss. Hence characterisation of LNP-RNA by MD-AF4 needs significant adaptation of the methods developed for liposomes. To improve the performance of MD-AF4 applied to LNP-RNA in a systematic and comprehensive manner, we have explored the use of the frit-inlet channel where, differently from the standard AF4 channel, the particles are relaxed hydrodynamically as they are injected. The absence of a focusing step minimizes contact between the particle and the membrane, reducing artefacts (e.g. sample loss, particle aggregation). Separation in a frit-inlet channel enables satisfactory reproducibility and acceptable sample recovery in the commercially available MD-AF4 instruments. In addition to slice-by-slice measurements of particle size, MD-AF4 also allows to determine particle concentration and the particle size distribution, demonstrating enhanced versatility beyond standard sizing measurements.