Subtle changes in surface-tethered groups on PEGylated DNA nanoparticles significantly influence gene transfection and cellular uptake

Gold Nanoparticles Coated with Nucleic Acids: An Overview of the Different Bioconjugation Pathways

Gold-based nanomaterials have marked the last few decades with the emergence of new medical technologies presenting unique features. For instance, the conjugation of gold nanoparticles (AuNPs) and nucleic acids has allowed the creation of nanocarriers with immense promise for gene therapy applications. Although the use of lipid particles as RNA delivery vectors has been broadly explored, this review aims to focus on the limited models reported for the conjugation of RNA with AuNPs. This is nonetheless unexpected regarding the manifold strategies existing to conjugate DNA to gold nanoparticles, which are exhaustively listed in this paper. Furthermore, new processes such as fast microwave and freezing methods have been described very recently, and it therefore seemed necessary to review these recent but promising conjugation pathways and to pick out those applicable to RNA. Indeed, RNA is considerably more attractive than DNA for therapeutic purposes, but its low stability involves numerous difficulties in the construction of effective nanodevices. However, from the many approaches developed for DNA, it turns out that just two of them are frequently used for the building of RNA delivery platforms based on gold: the salt-aging method with thiolated RNA strands and physisorption. However, both approaches present strong limitations such as the low stability of the Au-S bond and the potential cytotoxicity of polycations. To conclude, this general assessment highlights that the exploration of innovating approaches implying different chemistries is needed for the creation of more robust and shapeable AuNPs-RNA conjugates.

Pharmaceutical strategies for optimized mRNA expression

Messenger RNA (mRNA)-based immunotherapies and protein in situ production therapies hold great promise for addressing theoretically all the diseases characterized by aberrant protein levels. The safe, stable, and precise delivery of mRNA to target cells via appropriate pharmaceutical strategies is a prerequisite for its optimal efficacy. In this review, we summarize the structural characteristics, mode of action, development prospects, and limitations of existing mRNA delivery systems from a pharmaceutical perspective, with an emphasis on the impacts from formulation adjustments and preparation techniques of non-viral vectors on mRNA stability, target site accumulation and transfection efficiency. In addition, we introduce strategies for synergistical combination of mRNA and small molecules to augment the potency or mitigate the adverse effects of mRNA therapeutics. Lastly, we delve into the challenges impeding the development of mRNA drugs while exploring promising avenues for future advancements.

mRNA nanodelivery systems: targeting strategies and administration routes

With the great success of coronavirus disease (COVID-19) messenger ribonucleic acid (mRNA) vaccines, mRNA therapeutics have gained significant momentum for the prevention and treatment of various refractory diseases. To function efficiently in vivo and overcome clinical limitations, mRNA demands safe and stable vectors and a reasonable administration route, bypassing multiple biological barriers and achieving organ-specific targeted delivery of mRNA. Nanoparticle (NP)-based delivery systems representing leading vector approaches ensure the successful intracellular delivery of mRNA to the target organ. In this review, chemical modifications of mRNA and various types of advanced mRNA NPs, including lipid NPs and polymers are summarized. The importance of passive targeting, especially endogenous targeting, and active targeting in mRNA nano-delivery is emphasized, and different cellular endocytic mechanisms are discussed. Most importantly, based on the above content and the physiological structure characteristics of various organs in vivo, the design strategies of mRNA NPs targeting different organs and cells are classified and discussed. Furthermore, the influence of administration routes on targeting design is highlighted. Finally, an outlook on the remaining challenges and future development toward mRNA targeted therapies and precision medicine is provided.

Zn(ii)-Dipicolylamine analogues with amphiphilic side chains endow low molecular weight PEI with high transfection performance

To investigate the effect of amphiphilic balance of Zn(ii)-dipicolylamine analogues on the transfection process, we fabricated a series of Zn(ii)-dipicolylamine functional modules (DDAC-Rs) with different hydrophilic-phobic side chains to modify low molecular weight PEI (Zn-DP-Rs) by the Michael addition reaction. Zn-DP-Rs with hydrophilic terminal hydroxy group side chains demonstrate superior overall performance compared to those of hydrophobic alkyl side chains. In terms of the influence of the chain lengths in DDAC-Rs, from Zn-DP-A/OH-3 to Zn-DP-A/OH-5, the corresponding transfection efficiency shows an upward trend as the lengths increase. However, decreasing efficacy is observed with further increase in the length of side chains. In addition, the Zn-DP-Rs with amphiphilic side chains show prominent performance in every respect, highlighting the significance of balance in the amphipathy of side chains in DDAC-Rs. This work is of great significance for the development of polycationic gene carrier materials with excellent performance.

Surface-Functionalized PEGylated Nanoparticles Deliver Messenger RNA to Pulmonary Immune Cells

Nanoparticles designed as messenger RNA (mRNA) carriers to deliver gene medicine have shown great potential to change the way lung disease states are managed. Controlling their delivery to the lung and the transgene expression in a specific population of cells remains a challenge. Here, we developed a series of nanoparticles with polyethylene glycol (PEG) corona prepared by condensing mRNA with PEG-grafted-polyethyleneimine (PEI-g-PEG) with different PEG terminal functional groups and grafting ratios. PEGylated nanoparticles (PEG grafting ratio was 0.5%) with amino or amino acid terminal groups showed the highest transgene expression levels in the lung following systemic administration, and cell profiling analysis indicated that pulmonary immune cells contributed to the majority of expression. We also showed that these nanoparticles can be prepared by the flash nanocomplexation method, which is a scalable and reproducible process, yielding lyophilizable nanoparticles that were stable for at least 4 months at -20 °C. These results suggest that these surface-functionalized PEGylated nanoparticles may serve as desirable carriers to deliver mRNA to the lung for pulmonary immunomodulation.