Cellular Trafficking of Nanotechnology‐Mediated mRNA Delivery

Abstract

Messenger RNA (mRNA)‐based therapy has emerged as a powerful, safe, and rapidly scalable therapeutic approach that involves technologies for both mRNA itself and the delivery vehicle. Although there are some unique challenges for different applications of mRNA therapy, a common challenge for all mRNA therapeutics is the transport of mRNA into the target cell cytoplasm for sufficient protein expression. This review is focused on the behaviors at the cellular level of nanotechnology‐mediated mRNA delivery systems, which have not been comprehensively reviewed yet. First, the four main therapeutic applications of mRNA are introduced, including immunotherapy, protein replacement therapy, genome editing, and cellular reprogramming. Second, common types of mRNA cargos and mRNA delivery systems are summarized. Third, strategies to enhance mRNA delivery efficiency during the cellular trafficking process are highlighted, including accumulation to the cell, internalization into the cell, endosomal escape, release of mRNA from the nanocarrier, and translation of mRNA into protein. Finally, the challenges and opportunities for the development of nanotechnology‐mediated mRNA delivery systems are presented. This review can provide new insights into the future fabrication of mRNA nanocarriers with desirable cellular trafficking performance.

Targeting Strategies for Site-Specific mRNA Delivery

“…For example, mRNA NPs with smaller sizes demonstrate enhanced tissue penetration, whereas those with larger sizes exhibit superior tissue accumulation and retention . The impact of surface charges on the in vivo tropism of mRNA NPs has been widely recognized, namely, highly positively charged mRNA NPs are more inclined to target the lungs, while negatively charged ones accumulate more in the spleens. , The surface properties, like poly­(ethylene glycol) (PEG) modification, also can influence NP pharmacokinetics and cell interactions . Notably, apart from direct impacts on in vivo organ/tissue/cell tropism, these physiochemical properties also influence surface protein adsorption and further affect endogenous targeting . , For example, NPs with negative charges (ζ < −10 mV) tend to bind to opsonins, resulting in rapid sequestration in mononuclear phagocyte system (MPS) organs.…”

“…Ligand-mediated active targeting can facilitate the binding of mRNA NPs with particular cell receptors and/or cellular internalization , thus achieving targeted delivery of mRNA to the cells of interest . Commonly used targeting ligands for site-specific mRNA delivery include small molecules, carbohydrates, nucleic acids, peptides, and antibodies. , These targeting ligands can be incorporated into mRNA nanocarriers through prefabrication modification strategies (suitable for tolerable entities such as small molecules and peptides) or postfabrication modification strategies (suitable for sensitive entities such as antibodies), driven by covalent coupling (e.g., esterification, amidation, thiol–maleimide Michael addition, azide–alkyne click chemistry, and Diels–Alder reaction) or noncovalent interactions (e.g., electrostatic interaction, hydrogen bonding, hydrophobic interaction, affinity avidin–biotin interaction, and host–guest interaction). , For instance, Robinson et al modified ionizable LNPs with CD3 or CD8 antibody for delivering mRNA to T cells . Another study identified a tumor-specific peptide through phage display, which facilitated active targeting of mRNA LNPs for hepatocellular carcinoma (HCC) therapy. , …”

“…The triumph of mRNA vaccines against COVID-19 has propelled mRNA therapy into a promising realm for genetic treatment, encompassing applications such as protein replacement, vaccine immunology, and regenerative medicine. , Despite the challenges posed by the fragility and negative charges of mRNA, various delivery systems have been explored to accelerate the development of mRNA therapeutics, with lipid nanoparticles (LNPs) emerging as the most successful and dominant nanocarriers in preclinical and clinical studies . To extend the success of these nanocarriers to more mRNA-based therapeutic areas, the key lies in enhancing efficacy while minimizing side effects, emphasizing the significance of precise mRNA delivery.…”

A polyamino acid-based phosphatidyl polymer library for in vivo mRNA delivery with spleen targeting ability

“…[5][6][7] To achieve effective mRNA therapies, it is imperative that the mRNAs reach the cytoplasm and be translated into therapeutic proteins. [7][8][9] However, the transfection effect of naked mRNA is limited due to defects such as rapid degradation by nucleases, restricted cellular uptake, and inherent immunogenicity. 10 Consequently, the creation of stable, efficacious, and safe delivery systems is crucial for mRNA application.…”

“…11 Common challenges for mRNA delivery platforms include improving translation efficiency, promoting high mRNA stability, possessing favourable pharmacokinetic profiles, achieving organ or cell selectivity and employing simple manufacturing and storage. 9 These all emphasize that a qualified mRNA delivery platform requires careful design. paved the way for extensive development of mRNA therapeutics.…”