A poly(amidoamine)-based polymeric nanoparticle platform for efficient in vivo delivery of mRNA

Hurdles to healing: Overcoming cellular barriers for viral and nonviral gene therapy

Gene delivery offers great potential for treating various diseases, yet its success requires overcoming several biological barriers. These hurdles span from extracellular degradation, reaching the target cells, and inefficient cellular uptake to endosomal entrapment, cytoplasmic transport, nuclear entry, and transcription limitations. Viruses and non-viral vectors deal with these barriers via different mechanisms. Viral vectors, such as adenoviruses, adeno-associated viruses, and lentiviruses use natural mechanisms to efficiently deliver genetic material but face limitations including immunogenicity, cargo capacity, and production complexity. Nonviral vectors, including lipid nanoparticles, polymers, and protein-based systems, offer scalable and safer alternatives but often fall short in overcoming intracellular barriers and achieving high transfection efficiencies. Recent advancements in vector engineering have partially overcome several of these challenges. Ionizable lipids improve endosomal escape while minimizing toxicity. Biodegradable polymers balance efficacy with safety, and engineered protein systems, inspired by viral or bacterial entry mechanisms, integrate multifunctionality for enhanced delivery. Despite these advances, challenges, particularly in achieving robust in vivo translatability, scalability, and reduced immunogenicity, remain. This review synthesizes current knowledge of cellular barriers and the approaches to overcome them, providing a roadmap for designing more efficient gene delivery systems. By addressing these barriers, the field can advance toward safer, and more effective therapies.

The advent of clinical self-amplifying RNA vaccines

Self-amplifying RNA (saRNA) technology is an emerging platform for vaccine development, offering significant advantages over conventional mRNA vaccines. By enabling intracellular amplification of RNA, saRNA facilitates robust antigen expression at lower doses, thereby enhancing both immunogenicity and cost-effectiveness. This review examines the latest advancements in saRNA vaccine development, highlighting its applications in combating infectious diseases. This includes viral pathogens such as SARS-CoV-2, influenza, and emerging zoonotic threats. We discuss the design and optimization of saRNA vectors to maximize antigen expression while minimizing adverse immune responses. Recent studies demonstrating the safety, efficacy, and scalability of saRNA-based vaccines in clinical settings are also discussed. We address challenges related to delivery systems, stability, and manufacturing, along with novel strategies being developed to mitigate these challenges. As the global demand for rapid, flexible, and scalable vaccine platforms grows, saRNA presents a promising solution with enhanced potency and durability. This review emphasizes the transformative potential of saRNA vaccines to shape the future of immunization strategies, particularly in response to pandemics and other global health threats.

Improved tendon repair with optimized chemically modified mRNAs: Combined delivery of Pdgf-BB and IL-1Ra using injectable nanoparticles

Tendon injuries, common in both athletic and non-athletic populations, present significant challenges due to their slow healing and the formation of scar tissue, which impairs function and potentially increases the risk of (re-)rupture. Conventional treatments often yield suboptimal functional and structural repair. This study investigates the potential of mRNA-based therapeutics to enhance tendon healing by targeting 2 distinct pathways via the delivery of chemically modified ARCA-capped mRNAs (cmRNAs) encoding Interleukin-1 receptor antagonist (IL1RA) and Platelet-Derived Growth Factor-BB (PDGF-BB) using injectable nanoparticle (NP) carriers. In vitro experiments demonstrate successful cmRNA delivery and translation, resulting in increased tendon cell proliferation, migration, and anti-inflammatory responses. In vivo, cmRNA treatment notably enhances tendon repair in a rat patellar tendon defect model, by reducing pro-inflammatory cytokines and fibrotic markers while enhancing repair tissue structure. These findings suggest that NP-based cmRNA delivery represents a promising therapeutic strategy for improving tendon healing, offering better outcomes over existing treatments by targeting both inflammatory and regenerative pathways. STATEMENT OF SIGNIFICANCE: In this study, we investigate an mRNA-based therapeutic approach aimed at enhancing tendon healing in a small animal model. Utilizing bioreducible poly(amidoamine)-based polymeric nanoparticles (PAA PNPs) for the delivery of cmRNAs encoding Interleukin-1 receptor antagonist (IL1RA) and Platelet-Derived Growth Factor-BB (PDGF-BB), we demonstrate effective delivery and protein translation in vitro and ex vivo, resulting in enhanced tendon cell proliferation, migration, and robust anti-inflammatory responses. By combining these therapeutic cmRNAs, we show improved tendon repair in vivo, with accelerated tissue regeneration, better collagen fiber organization, and signs of reduced fibrotic scarring. These findings highlight the potential of nanoparticle-mediated cmRNA delivery targeting two distinct pathways to improve tendon healing, offering a promising alternative to current treatments that often yield suboptimal results.

Anionic polymer coating for enhanced delivery of Cas9 mRNA and sgRNA nanoplexes

Polymeric carriers have long been recognized as some of the most effective and promising systems for nucleic acid delivery. In this study, we utilized an anionic di-block co-polymer, PEG-PLE, to enhance the performance of lipid-modified PEI (C14-PEI) nanoplexes for delivering Cas9 mRNA and sgRNA targeting KRAS G12S mutations in lung cancer cells. Our results demonstrated that PEG-PLE, when combined with C14-PEI at a weight-to-weight ratio of 0.2, produced nanoplexes with a size of approximately 140 nm, a polydispersity index (PDI) of 0.08, and a zeta potential of around -1 mV. The PEG-PLE/C14-PEI nanoplexes at this ratio were observed to be both non-cytotoxic and effective in encapsulating Cas9 mRNA and sgRNA. Confocal microscopy imaging revealed efficient endosomal escape and intracellular distribution of the RNAs. Uptake pathway inhibition studies indicated that the internalization of PEG-PLE/C14-PEI primarily involves scavenger receptors and clathrin-mediated endocytosis. Compared to C14-PEI formulations, PEG-PLE/C14-PEI demonstrated a significant increase in luciferase mRNA expression and gene editing efficiency, as confirmed by T7EI and ddPCR, in A549 cells. Sanger sequencing identified insertions and/or deletions around the PAM sequence, with a total of 69% indels observed. Post-transfection, the KRAS-ERK pathway was downregulated, resulting in significant increases in cell apoptosis and inhibition of cell migration. Taken together, this study reveals a new and promising formulation for CRISPR delivery as potential lung cancer treatment.

Polymeric Nanoparticles Enable mRNA Transfection and Its Translation in Intervertebral Disc and Human Joint Cells, Except for M1 Macrophages

Chronic lower back pain caused by intervertebral disc degeneration and osteoarthritis (OA) are highly prevalent chronic diseases. Although pain management and surgery can alleviate symptoms, no disease-modifying treatments are available. mRNA delivery could halt inflammation and degeneration and induce regeneration by overexpressing anti-inflammatory cytokines or growth factors involved in cartilage regeneration. Here, we investigated poly(amidoamine)-based polymeric nanoparticles to deliver mRNA to human joint and intervertebral disc cells. Human OA chondrocytes, human nucleus pulposus (NP) cells, human annulus fibrosus (AF) cells, fibroblast-like synoviocytes (FLS) and M1-like macrophages were cultured and transfected with uncoated or PGA-PEG-coated nanoparticles loaded with EGFP-encoding mRNA. Cell viability and transfection efficiency were analyzed for all cell types. Nanoparticle internalization was investigated in FLS and M1-like macrophages. No significant decrease in cell viability was observed in most conditions. Only macrophages showed a dose-dependent reduction of viability. Transfection with either nanoparticle version resulted in EGFP expression in NP cells, AF cells, OA chondrocytes and FLS. Macrophages showed internalization of nanoparticles by particle-cell co-localization, but no detectable expression of EGFP. Taken together, our data show that poly (amidoamine)-based nanoparticles can be used for mRNA delivery into cells of the human joint and intervertebral disc, indicating its potential future use as an mRNA delivery system in OA and IVDD, except for macrophages.

Degradable Polymeric Bio(nano)materials and Their Biomedical Applications: A Comprehensive Overview and Recent Updates

Degradable polymers (both biomacromolecules and several synthetic polymers) for biomedical applications have been promising very much in the recent past due to their low cost, biocompatibility, flexibility, and minimal side effects. Here, we present an overview with updated information on natural and synthetic degradable polymers where a brief account on different polysaccharides, proteins, and synthetic polymers viz. polyesters/polyamino acids/polyanhydrides/polyphosphazenes/polyurethanes relevant to biomedical applications has been provided. The various approaches for the transformation of these polymers by physical/chemical means viz. cross-linking, as polyblends, nanocomposites/hybrid composites, interpenetrating complexes, interpolymer/polyion complexes, functionalization, polymer conjugates, and block and graft copolymers, are described. The degradation mechanism, drug loading profiles, and toxicological aspects of polymeric nanoparticles formed are also defined. Biomedical applications of these degradable polymer-based biomaterials in and as wound dressing/healing, biosensors, drug delivery systems, tissue engineering, and regenerative medicine, etc., are highlighted. In addition, the use of such nano systems to solve current drug delivery problems is briefly reviewed.