Delivering siRNA is not straightforward due to the instability of mRNA that results from degradation, non-specific binding, and liver targeting after intravenous administration. Supi Das, Professor of Pharmaceutics & Drug Delivery at Butler University, also pointed out the need for endosomal escape to enable effective delivery to target tissues. Development of ionisable lipids and peptides has improved over time, but cracking the code of endosomal escape is yet to take place.
Das has worked with cationic liposomes, nanostructures, PLGA, chitosan nanoparticles, and polymer micelles. He has also worked on various functionalisations for lipid-based and polymer-based nanoparticles like PEGylation, RGD peptides, and cell-penetrating peptides to boost stability, circulation time, and targeting efficiency for gene delivery.
Das added that cell-penetrating peptides with dual or triple type actions can enhance cellular uptake. When it comes to endosome escape, the team has used different arginine substitutions and nuclear localisation concepts to improve endosomal escape.
To optimise lipid nanoparticle formulation, lipid molar ratio is critical to keep in mind because it determines the size, the polydispersity, and thus opsonisation. Optimising lipid-oligonucleotide weight ratio also maintains the protection of the oligos as well as smooth delivery (i.e., ensuring that the lipid can fuse with the cell membrane). Nitrogen-oligonucleotide phosphate ratio must also be factored in to improve ionisation of the lipids.
Furthermore, Das mentioned that the team uses microfluidics and ethanol injection methods to produce nanoparticles under 100nm. Das introduced his study on survivin and in vitro cell lines. Survivin is a member of the BIRC5 gene and it contains around 142 amino acids and is roughly 142 amino acids. It also inhibits apoptosis and promotes angiogenesis. The goal of the study was to reduce the level of survivin in cancer cells.
The group demonstrated successful siRNA delivery to silence genes like survivin in cancer cell lines and the mutant Huntingtin gene in neurodegenerative models. The results showed more prominent therapeutic effects when combined with drugs like paclitaxel or cisplatin.
