A new approach to advance nanomedicine, layer by layer

Short genetic fragments called small-interfering RNAs, or siRNAs, hold great promise as a tool for treating disease, as they can bind and silence specific messenger molecules that code for proteins. However, these molecules are easily degraded and their delivery to target cells remains difficult to achieve in practice. Now, NCCR Bio-Inspired Materials researchers at the Adolphe Merkle institute have developed an approach that overcomes some of the challenges associated with the targeting and delivery of siRNAs into cells.

The work, led by NCCR principal investigators Alke Fink and Barbara Rothen-Rutishauser, may help to optimize the controlled release of multiple therapeutic agents to treat cancer and other diseases.

To improve the targeting and delivery of siRNAs to cells, Fink and her PhD student Aaron Lee turned to a technique called layer-by-layer assembly. Taking advantage of interactions between molecules of opposite charge, the researchers coated silica nanoparticles with alternating layers of siRNAs, which are negatively charged, and a positively charged polymer that helps protect the RNA from degradation. The team also included an outer coating of hyaluronic acid, a molecule that binds to receptors found on most cells.

Exploiting the material properties, the researchers then assembled the nanoparticles on a specific surface. The surface, Fink says, “can be used as a local drug delivery depot.” For example, she adds, it could be used in implants to activate immune cells that fight bacterial infections.

To test whether their approach could work in practice, the researchers cultured cells expressing a green-fluorescent protein (GFP), which as the name says, emits bright green fluorescence, on a surface coated with nanoparticles containing siRNAs for silencing GFP. After the cells internalized the nanoparticles, their fluorescence intensity was reduced by about 50%. The particles didn’t have any strong adverse effects on cell health and proliferation. The findings were published in the journal ACS Applied Bio Materials.

The applications of the system are endless, as the nanoparticles can be customized to target specific cells and silence genes that are involved in different diseases. The particles could also be used for immunization to deliver antigens or nucleic acids that activate the immune system, or to carry drugs that induce death in cancer cells, Rothen-Rutishauser says.

The collaboration with Fink, who oversaw the design of the nanoparticles, was greatly facilitated by the NCCR Bio-Inspired Materials, says Rothen-Rutishauser, whose team identified the optimal cell type and marker to test whether the system worked.

In the future, the duo will continue to work together towards creating particle gradients that would allow researchers to generate a graded difference in physiological activity across cells on a surface.

Inducing a cell response at a specific site in the human body is often occurring in nature, for example when there’s local infection or disease, Rothen-Rutishauser says. “This locally controlled induction of the cell response was our inspiration.”

Reference: Lee, A.; Gosnell, N.; Milinkovic, D.; Taladriz-Blanco, P.; Rothen-Rutishauser, B.; Petri-Fink, A. Layer-by-layer siRNA particle assemblies for localized delivery of siRNA to epithelial cells through surface-mediated particle uptake, ACS Appl. Bio Mater., 2023, 6, 83–92. https://doi.org/10.1021/acsabm.2c00668 (open access)