A team of researchers at the University of Minnesota Twin Cities Department of Chemistry has developed a new polymer-based vehicle for delivering DNA- and RNA-based therapies for the treatment of diseases.
Polymer-based vehicles have shown great promise for delivering nucleic acids to cells, but little was known about the mechanism involved in unpackaging their cargo. Now, for the first time, the researchers have demonstrated the exact mechanism used by these delivery vehicles and have shown how they interact with human cells to deliver their payloads.
The researchers developed a trackable delivery system using a quinine-containing polymer and used Raman chemical imaging to track the release of the nucleic acid payloads inside cells.
To make edits to genes to treat diseases, nucleic acids must be delivered into cells. This is usually achieved using engineered viruses as the carrier, exploiting the ability of the virus to enter human cells. While this approach is effective, there are limitations and the virus itself can trigger an immune response which can limit the effectiveness of the treatment.
DNA and RNA are susceptible to enzymatic degradation, so there is the possibility that the intact nucleic acid will not be delivered. The new technique, which involves encapsulating the DNA or RNA in long-chain molecules, protects the sensitive cargo and ensures it is delivered in one piece, akin to wrapping a present in bubble wrap and boxing it prior to mailing.
The researchers developed a copolymer based on quinine and 2-hydroxyethyl acrylate (HEA). The former is fluorescent which allows the package to be tracked, and the latter is water soluble which allows the payload to be easily delivered and degraded after delivery. Both substances are already widely used. Quinine is used in tonic water and has been used to prevent malaria and HEA is used in a variety of personal care and medical materials. The polymer-based vehicle is safe to use and is substantially cheaper than using viruses to deliver gene therapy.
The issue that was holding back use of polymers for delivering gene therapy was the uncertainty around how the payload is delivered and the mechanism of interaction with cells. The researchers showed that proteins in cells play an important role in unpackaging the payload inside cells and releasing the nucleic acid cargo, which the researchers were able to observe in real time using Ramen spectroscopy.
“It’s very satisfying to know how this is actually happening, what the process of delivery is, and to actually see that in real-time,” said associate professor Renee Frontiera Frontiera. “A key point is that these polymers also work very well. For all the beneficial attributes, they’re also incredibly effective at getting the payload into cells, and we were able to tell why, which doesn’t always happen in this field.”
You can read more about the study in the paper – Quinine copolymer reporters promote efficient intracellular DNA delivery and illuminate a protein-induced unpackaging mechanism – which was recently published in the journal Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.2016860117