Small interfering RNAs (siRNAs) are novel therapies that can be used to treat a wide range of diseases. This has led to a growing demand for selective, efficient, and safe ways to deliver siRNA into cells. Now, in a cooperation between the universities of Amsterdam and Leiden, the researchers have developed dedicated molecular nanocages for siRNA delivery. In a paper just published in Journal Chem, they present nanocages that are easy to prepare and show tunable siRNA delivery characteristics.
The nanocages were developed in the research group for homogeneous, supramolecular and bioinspired catalysis of Prof. Joost Reek and Bas de Bruin at the Van ‘t Hoff Institute for Molecular Sciences at the University of Amsterdam, and further studies in the group of Prof. Alexander Kros. at the Institute of Chemistry in Leiden. The researchers were motivated by the potential of siRNA in gene therapy, which necessitates the need for effective delivery systems. They set out to develop nanocages with functional groups on the outside, making the cages capable of binding siRNA strands. Since the binding is based on reversible bonds, siRNA can, in principle, be released into a cellular environment. To explore the delivery characteristics of their nanocages, the researchers conducted a laboratory study using several human cancer cells.
A range of nanocages
Nanocages are constructs of small molecular building blocks, so-called ditopic ligands, which are connected by metal atoms. A typical cage consists of 12 metal atoms and 24 ligands, hence the abbreviation M12L24. The researchers designed and synthesized five different ligands to form molecular cages with different binding affinities for siRNA. Next, they prepared a range of siRNA-binding nanocages using platinum or palladium as the linker metal. Palladium nanocages are less stable in a cellular environment, and decay is one of the mechanisms for siRNA release.
After evaluating the characteristics of the nanocage, such as stability and siRNA binding capacity, the delivery characteristics were put to the test in assays based on siRNA-mediated green fluorescent protein (GFP) silencing. The cages were used to deliver siRNA to human cells expressing GFP, so that fluorescence measurements could establish successful siRNA delivery. Two types of human cell lines were used: HeLa and U2Os.
Cage composition determines siRNA delivery
To their surprise, the researchers were not only able to demonstrate successful siRNA delivery, but also found remarkable differentiation depending on the metal used in the nanocage. where a platinum base spotThe 12L24 nanocage showed highly effective siRNA delivery to U2OS cells, it showed poor efficiency for HeLa. In contrast, the palladium base P.S.The 12L24 nanocage, derived from the same ligand building block, delivered siRNA to HeLa but not to U2OS. Such differentiation could not be observed in experiments using a commercially applied delivery system (lipofectamine). The M12L24 nanocages thus introduce the possibility of tuning siRNA delivery characteristics by adjusting the composition of the nanocage.
In their Chem paper, the researchers consider this unique cellular selectivity feature of nanoparticles a promising addition to the field of targeted RNA genetic material delivery, the full potential of which has yet to be discovered. Even though the current results were obtained in highly controlled laboratory research, they hope that the delivery of tunable RNA from their nanocages will lead to future developments of highly desirable RNA-selective nanomedicines.