Quantum Bullets for Rapid Fire Gene Silencing

Scientists at the University of Washington Seattle, and Emory University have developed a rapid method of silencing gene expression by using quantum dots attached to small interfering RNA (si-RNA). The quantum dots carried the si-RNA into the cytoplasm, where it interacted with messenger RNA (mRNA) to prevent translation of genetic messages into proteins.

Quantum dots were dramatically better than existing techniques at stopping gene activity. In experiments, a cell's production of a test protein dropped to 2 percent when siRNA was delivered with quantum dots. By contrast, the test protein was produced at 13 percent to 51 percent of normal levels when the siRNA was delivered with one of three commercial reagents, or reaction-causing substances, now commonly used in laboratories.

Central to the finding is that fluorescent quantum dots allow scientists to watch the siRNA's movements. Previous siRNA trackers gave off light for less than a minute, while quantum dots, developed for imaging, emit light for hours at a time. In the experiments the authors were able to watch the process for many hours to track the gene-silencer's path.

The new approach is also five to 10 times less toxic to the cell than existing chemicals, meaning the quantum dot chaperones are less likely to harm cells. The ideal delivery vehicle would have no effect; the only biological change would be siRNA blocking cells' production of an unwanted protein. __Source_via_NextBigFuture

One key to the quantum dots ability to penetrate the cell wall so effectively, was the use of a "proton sponge" that coated the dots, giving them a positive charge which neutralised the negative charge of the siRNA.

This approach to influencing gene expression is temporary, but is typically easier than trying to change the genome--either genetically or epigenetically. This reversibility is a positive feature for short term gene silencing for specific purposes such as pre and post operative situations, serious acute trauma, shock, sepsis, or rehabilitation from severe illness or injury. Many more uses for this tool will crop up if its safety and efficacy remain high as reported.

DNA "Computer" Works Inside Living Cells, Suggests Possibilities

Although DNA computers have been made that can play simple games like tic-tac-toe, programming DNA computers to work inside living cells is much more interesting.

The goal is to inject human cells with DNA that can determine whether a cell is cancerous or otherwise diseased, based solely on the mix of molecules inside the cell. Sensing disease, the DNA might trigger a pinpoint dose of treatment in response. That technology, however, is a long way off. For now, researchers are testing different ways of turning DNA into versatile computers that can detect certain combinations of molecules and respond by producing other molecules.

...RNAi is something that cells do naturally. Cells produce what are known as short interfering RNA (siRNA) molecules, which recognize corresponding DNA sequences in genes and cause them to shut down.

Benenson and colleagues engineered a target gene to be sensitive to several different siRNAs of their own design. In the simplest case, they introduced a single siRNA molecule to switch off a target gene that encoded a fluorescent protein. In more complex cases, a pair of siRNAs or either of two siRNAs switched off another target gene, which in turn switched off a gene for a fluorescent protein. To make sure the system worked as intended, the researchers based their siRNAs on those of other species, they report in a paper published online today by Nature Biotechnology.

In principle, the RNAi technique can reach great heights of complexity, Benenson says, by making genes sensitive to more and more siRNAs in various combinations. "The scalability is very important, because eventually you want to make complex decisions," he says.

He says the next step is figuring out how to make the molecules inside a cell—such as those that are overproduced in cancer—trigger the production of siRNAs.

Source

This is a very simple approach to DNA "computing", but for all its conceptual simplicity it suggests possibilities that are much more complex. It is best to go very slowly and carefully. The type of control of gene expression hinted at here is not only promising as a cure for cancers, it is threatening.

This type of research appears ideal for a synthetic biological organism. At this time synthetic biologists are attempting to design the simplest possible cells, from other species, by including the smallest possible gene set for viability. Presumably, as the synth biologists master the simpler life forms, they will attempt to create more complex organisms.

Synthetic organisms could potentially become ideal biological models for studying various human diseases. Eventually, synthetic organisms and biological systems could replace most animal models--eliminating much of the need for animal research and testing.

This is yet another research field that bears close watching.

Fantastic Video of RNA Interference

If you liked The Inner Life of the Cell, you will be thrilled by RNAi, the video about RNA Interference a type of non-coding RNA. The narration in this video describes how RNAi participates in gene expression by blocking specific mRNAs from being translated.

Thanks again to Biosingularity Blog.

Contemplate what you learned from the above video when reading this newsrelease, describing a "masterswitch" for preserving adult stem cells in their primitive state.