Insights into the Structure of Comirnaty Covid-19 Vaccine: A Theory on Soft, Partially Bilayer-Covered Nanoparticles with Hydrogen Bond-Stabilized mRNA-Lipid Complexes

The mechanical properties of lipid nanoparticles depend on the type of biomacromolecule they are loaded with

For drug delivery systems, the mechanical properties of drug carriers are suspected to play a crucial role in the delivery process. However, there is a lack of reliable methods available to measure the mechanical properties of drug carriers, which hampers the establishment of a link between delivery efficiency and the mechanical properties of carriers. Lipid nanoparticles (LNPs) are advanced systems for delivering nucleic acids to target cell populations for vaccination purposes (mRNA) or the development of new drugs. Hence, it is crucial to develop reliable techniques to measure the mechanical properties of LNPs. In this article, we used AFM to image and probe the mechanical properties of LNPs which are loaded with two different biopolymers either pDNA or mRNA. Imaging the LNPs before and after indentation, as well as recording the retraction curve, enables us to obtain more insight into how the AFM tip penetrates into the particle and to determine whether the deformation of the LNPs is reversible. For pDNA, the indentation by the tip leads to irreversible rupture of the LNPs, while the deformation is reversible for the mRNA-loaded LNPs. Moreover, the forces reached for pDNA are higher than for mRNA. These results pave the way toward the establishment of the link between the LNP formulation and the delivery efficiency.

Mechanisms and Barriers in Nanomedicine: Progress in the Field and Future Directions

In recent years, steady progress has been made in synthesizing and characterizing engineered nanoparticles, resulting in several approved drugs and multiple promising candidates in clinical trials. Regulatory agencies such as the Food and Drug Administration and the European Medicines Agency released important guidance documents facilitating nanoparticle-based drug product development, particularly in the context of liposomes and lipid-based carriers. Even with the progress achieved, it is clear that many barriers must still be overcome to accelerate translation into the clinic. At the recent conference workshop "Mechanisms and Barriers in Nanomedicine" in May 2023 in Colorado, U.S.A., leading experts discussed the formulation, physiological, immunological, regulatory, clinical, and educational barriers. This position paper invites open, unrestricted, nonproprietary discussion among senior faculty, young investigators, and students to trigger ideas and concepts to move the field forward.

Determination of the interior pH of lipid nanoparticles using a pH-sensitive fluorescent dye-based DNA probe

Lipid nanoparticles (LNPs) containing ionizable cationic lipids are proven delivery systems for therapeutic nucleic acids, such as small interfering RNA (siRNA). It is important to understand the relationship between the interior pH of LNPs and the pH of the external environment to understand LNP formulation and function. Here, we developed a simple and rapid approach for determining the pH of the LNP core using a pH-sensitive fluorescent dye-based DNA probe. LNP siRNA systems containing pH-responsive DNA probes (LNP-siRNA&DNA) were generated by rapid mixing of lipids in ethanol and pH 4 aqueous buffer containing siRNA and DNA probes. We demonstrated that DNA probes were readily encapsulated in LNP systems and were sequestered into an environment at a high concentration as evidenced by an inter-probe FRET signal. It was shown that the pH of LNP encapsulated probes closely follows the pH increase or decrease of the external environment. This indicates that the clinically approved LNP RNA systems with similar lipid compositions (e.g., Onpattro and Comirnaty) are highly permeable to protons and that the pH of the interior environment closely mirrors the external environment. The pH-dependent response of the probe in LNPs was also confirmed under buffer conditions at various pHs. Furthermore, we showed that the pH-sensitive DNA probe can be incorporated into LNP systems at levels that allow the pH response to be monitored at a single LNP level using convex lens-induced confinement (CLiC) confocal microscopy. Direct visualization of the internal pH of single particles with the fluorescent DNA probe was achieved by CLiC for LNP-siRNA&DNA systems formulated under both high and normal ionic strength conditions.

Mesoscopic Structure of Lipid Nanoparticle Formulations for mRNA Drug Delivery: Comirnaty and Drug-Free Dispersions

Lipid nanoparticles (LNPs) produced by antisolvent precipitation (ASP) are used in formulations for mRNA drug delivery. The mesoscopic structure of such complex multicomponent and polydisperse nanoparticulate systems is most relevant for their drug delivery properties, medical efficiency, shelf life, and possible side effects. However, the knowledge on the structural details of such formulations is very limited. Essentially no such information is publicly available for pharmaceutical dispersions approved by numerous medicine agencies for the use in humans and loaded with mRNA encoding a mimic of the spike protein of the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) as, e.g., the Comirnaty formulation (BioNTech/Pfizer). Here, we present a simple preparation method to mimic the Comirnaty drug-free LNPs including a comparison of their structural properties with those of Comirnaty. Strong evidence for the liquid state of the LNPs in both systems is found in contrast to the designation of the LNPs as solid lipid nanoparticles by BioNTech. An exceptionally detailed and reliable structural model for the LNPs i.a. revealing their unexpected narrow size distribution will be presented based on a combined small-angle X-ray scattering and photon correlation spectroscopy (SAXS/PCS) evaluation method. The results from this experimental approach are supported by light microscopy, 1H NMR spectroscopy, Raman spectroscopy, cryogenic electron microscopy (cryoTEM), and simultaneous SAXS/SANS studies. The presented results do not provide direct insights on particle formation or dispersion stability but should contribute significantly to better understanding the LNP drug delivery process, enhancing their medical benefit, and reducing side effects.

mRNA-LNP COVID-19 Vaccine Lipids Induce Complement Activation and Production of Proinflammatory Cytokines: Mechanisms, Effects of Complement Inhibitors, and Relevance to Adverse Reactions

A small fraction of people vaccinated with mRNA-lipid nanoparticle (mRNA-LNP)-based COVID-19 vaccines display acute or subacute inflammatory symptoms whose mechanism has not been clarified to date. To better understand the molecular mechanism of these adverse events (AEs), here, we analyzed in vitro the vaccine-induced induction and interrelations of the following two major inflammatory processes: complement (C) activation and release of proinflammatory cytokines. Incubation of Pfizer-BioNTech's Comirnaty and Moderna's Spikevax with 75% human serum led to significant increases in C5a, sC5b-9, and Bb but not C4d, indicating C activation mainly via the alternative pathway. Control PEGylated liposomes (Doxebo) also induced C activation, but, on a weight basis, it was ~5 times less effective than that of Comirnaty. Viral or synthetic naked mRNAs had no C-activating effects. In peripheral blood mononuclear cell (PBMC) cultures supplemented with 20% autologous serum, besides C activation, Comirnaty induced the secretion of proinflammatory cytokines in the following order: IL-1α < IFN-γ < IL-1β < TNF-α < IL-6 < IL-8. Heat-inactivation of C in serum prevented a rise in IL-1α, IL-1β, and TNF-α, suggesting C-dependence of these cytokines' induction, although the C5 blocker Soliris and C1 inhibitor Berinert, which effectively inhibited C activation in both systems, did not suppress the release of any cytokines. These findings suggest that the inflammatory AEs of mRNA-LNP vaccines are due, at least in part, to stimulation of both arms of the innate immune system, whereupon C activation may be causally involved in the induction of some, but not all, inflammatory cytokines. Thus, the pharmacological attenuation of inflammatory AEs may not be achieved via monotherapy with the tested C inhibitors; efficacy may require combination therapy with different C inhibitors and/or other anti-inflammatory agents.

Lipid Nanoparticle (LNP) Delivery Carrier-Assisted Targeted Controlled Release mRNA Vaccines in Tumor Immunity

In recent years, lipid nanoparticles (LNPs) have attracted extensive attention in tumor immunotherapy. Targeting immune cells in cancer therapy has become a strategy of great research interest. mRNA vaccines are a potential choice for tumor immunotherapy, due to their ability to directly encode antigen proteins and stimulate a strong immune response. However, the mode of delivery and lack of stability of mRNA are key issues limiting its application. LNPs are an excellent mRNA delivery carrier, and their structural stability and biocompatibility make them an effective means for delivering mRNA to specific targets. This study summarizes the research progress in LNP delivery carrier-assisted targeted controlled release mRNA vaccines in tumor immunity. The role of LNPs in improving mRNA stability, immunogenicity, and targeting is discussed. This review aims to systematically summarize the latest research progress in LNP delivery carrier-assisted targeted controlled release mRNA vaccines in tumor immunity to provide new ideas and strategies for tumor immunotherapy, as well as to provide more effective treatment plans for patients.

Zwitterionic materials for nucleic acid delivery and therapeutic applications

Nucleic acid therapeutics have demonstrated substantial potential in combating various diseases. However, challenges persist, particularly in the delivery of multifunctional nucleic acids. To address this issue, numerous gene delivery vectors have been developed to fully unlock the potential of gene therapy. The advancement of innovative materials with exceptional delivery properties is critical to propel the clinical translation of nucleic acid drugs. Cationic vector materials have received extensive attention, while zwitterionic materials remain relatively underappreciated in delivery. In this review, we outline a diverse range of zwitterionic material nucleic acid carriers, predominantly encompassing zwitterionic lipids, polymers and peptides. Their respective chemical structures, synthesis approaches, properties, advantages, and therapeutic applications are summarized and discussed. Furthermore, we highlight the challenges and future opportunities associated with the development of zwitterionic vector materials. This review will aid to understand the zwitterionic materials in aiding gene delivery, contributing to the continual progress of nucleic acid therapeutics.

Detection of Pre-Existing Antibodies to Polyethylene Glycol and PEGylated Liposomes in Human Serum

Polyethylene glycol, or PEG, is common in consumer products, over-the-counter medications, food, and pharmaceutical products. Concerns about PEG immunogenicity and the subsequent negative impact of pre-existing and product-induced antibodies often shadow the benefits of using PEG in nanotechnology-based products. Such anti-PEG antibodies contribute to the accelerated blood clearance of PEGylated nanomedicines and result in premature drug release and antibody-mediated toxicities. Recent data demonstrated that using PEG in COVID-19 lipid nanoparticle-mRNA vaccines is associated with an induction of anti-PEG antibodies in healthy individuals, further contributing to the development or boosting of pre-existing antibodies and increasing the risks of antibody-mediated toxicities to other products containing PEG. Therefore, monitoring the levels of pre-existing and product-induced anti-PEG antibodies provides mechanistic insights for pharmacology, toxicology, and immunological studies of PEGylated drug products.

[Atomic Force Microscopy to Measure the Mechanical Property of Nanosized Lipid Vesicles and Its Applications]

Nanoparticles, including liposomes and lipid nanoparticles, have garnered global attention due to their potential applications in pharmaceuticals, vaccines, and gene therapies. These particles enable targeted delivery of new drug modalities such as highly active small molecules and nucleic acids. However, for widespread use of nanoparticle-based formulations, it is crucial to comprehensively analyze their characteristics to ensure both efficacy and safety, as well as enable consistent production. In this context, this review focuses on our research using atomic force microscopy (AFM) to study liposomes and lipid nanoparticles. Our work significantly contributes to the capability of AFM to measure various types of liposomes in an aqueous medium, providing valuable insights into the mechanical properties of these nanoparticles. We discuss the applications of this AFM technique in assessing the quality of nanoparticle-based pharmaceuticals and developing membrane-active peptides.

Bioinspired Spatiotemporal Management toward RNA Therapies

Ribonucleic acid (RNA)-based therapies have become an attractive topic in disease intervention, especially with some that have been approved by the FDA such as the mRNA COVID-19 vaccine (Comirnaty, Pfizer-BioNTech, and Spikevax, Moderna) and Patisiran (siRNA-based drug for liver delivery). However, extensive applications are still facing challenges in delivering highly negatively charged RNA to the targeted site. Therapeutic delivery strategies including RNA modifications, RNA conjugates, and RNA polyplexes and delivery platforms such as viral vectors, nanoparticle-based delivery platforms, and hydrogel-based delivery platforms as potential nucleic acid-releasing depots have been developed to enhance their cellular uptake and protect nucleic acid from being degraded by immune systems. Here, we review the growing number of viral vectors, nanoparticles, and hydrogel-based RNA delivery systems; describe RNA loading/release mechanism induced by environmental stimulations including light, heat, pH, or enzyme; discuss their physical or chemical interactions; and summarize the RNA therapeutics release period (temporal) and their target cells/organs (spatial). Finally, we describe current concerns, highlight current challenges and future perspectives of RNA-based delivery systems, and provide some possible research areas that provide opportunities for clinical translation of RNA delivery carriers.

Computational approaches to lipid-based nucleic acid delivery systems

Nucleic acid-based therapies have shown enormous effectiveness as vaccines against the recent COVID19 pandemics and hold great promises in the fight of a broad spectrum of diseases ranging from viral infections to cancer up to genetically transmitted pathologies. Due to their highly degradable polyanionic nature, nucleic acids need to be packed in sophisticate delivery vehicles which compact them up, protect them from early degradation and help delivery them to the right tissue/cells. Lipid-based nanoparticles (LNP) represent, at present, the main solution for nucleic acid delivery. They are made of a mixture of lipids whose key ingredient is an ionizable cationic lipid. Indeed, the interactions between the polyanionic nucleic acids and the ionizable cationic lipids, and their pH-dependent regulation in the life cycle of the nanoparticle, from production to cargo delivery, mostly determine the effectiveness of the therapeutic approach. Notwithstanding the large improvements in the delivery efficiency of LNPs in the last two decades, it is estimated that only a small fraction of the cargo is actually delivered, stimulating further research for the design of more effective LNP formulations. A rationally driven design would profit from the knowledge of the precise molecular structure of these materials, which is however still either missing or characterized by poor spatial resolution. Computational approaches have often been used as a molecular microscope either to enrich the available experimental data and provide a molecular-level picture of the LNPs or even simulate specific processes involving the formation and/or the molecular mechanisms of action of the LNP. Here, I review the recent literature in the field.