Researchers improve siRNA delivery

Researchers from the University of Washington and Emory University believe that by utilising nanotechnology known as quantum dots they have made the delivery 10 to 20 times more effective than existing methods. This technique could pave the way for more effective, targeted delivery of siRNA or small interfering RNA - used to selectively switch off target genes via a process known as gene silencing - into cells. Shuming Nie, co-author of the research, said: "This work helps to overcome the longstanding barrier in the siRNA field: How to achieve high silencing efficiency with low toxicity​." siRNA does not easily cross cell membranes but the researchers overcame this by using quantum dots as a chaperone. Quantum dots are 6nm wide fluorescent balls of semiconductor material, which emit different colours of light depending on their size. They are already a well-established technology in drug discovery, where they are used as reagents in assays and screening. Each quantum dot is surrounded by a positively charged proton sponge, which enables the negatively charged siRNA to traverse the cell membrane. Once inside the cell the siRNA is released from the endosome and acts to achieve the desired therapeutic effect through disruption of protein production. This technique resulted in production of a test protein falling to just 2 per cent, in comparison with 13 to 51 per cent when the experiment was run using one of three commercial reagents commonly used in laboratories. Another advantage is that this delivery method is five to 10 times less toxic to the cell than currently available techniques. The researchers are now planning on trying to achieve the same results without the use of quantum dots, which have not been approved for use in humans. Nontoxic iron oxide or biodegradable polymeric carriers are two potential alternatives as the research team seeks to advance the work. This could eventually lead to the technologies use in the treatment of a wide range of ailments, from cancer to deteriorating eyesight. Research into the use of siRNA is continuing apace, with the first clinical trial for the treatment of cancer using the technology commencing recently​. Improvements to the targeting and efficiency of siRNA delivery could play an important role in ensuring the widespread adoption of the technology.