Eager to avoid the complications that may arise if viral vectors are used to deliver components of the CRISPR/Cas9 gene-editing system, researchers have been busy developing nonviral nanoparticle carriers, such as lipid, polymeric, and gold nanoparticles. Now, at MIT, researchers have developed a new lipid nanoparticle that has an interesting twist: It packs chemically modified single guide RNA (sgRNA). By enhancing sgRNA, the researchers hope to protect it against nuclease degradation, and thereby boost efficiency of the overall CRISPR/Cas9 gene-editing system.

According to the MIT team, which was led by Daniel G. Anderson, Ph.D., an associate professor of chemical engineering and a member of MIT’s Koch Institute, the new delivery technique cut out certain genes in about 80% of liver cells, the best success rate ever achieved with CRISPR in adult animals.

Details about the new delivery system appeared November 13 in the journal Nature Biotechnology, in an article entitled “Structure-Guided Chemical Modification of Guide RNA Enables Potent Non-Viral In Vivo Genome Editing.” According to this article, the new delivery system could sidestep some of the complications encountered with delivery via viral vectors.

For example, once a particular virus is used, the patient may develop antibodies to it, so that it cannot be used again. Also, some patients have pre-existing antibodies to the viruses being tested as CRISPR/Cas9 delivery vehicles.

The researchers analyzed the structure of the complex formed by Cas9 and the sgRNA to figure out which sections of the sgRNA strand could be chemically modified without interfering with the binding of the two molecules. Based on this analysis, they created and tested many possible combinations of modifications.