doi:10.1038/nindia.2011.124 Published online 25 August 2011
Researchers have designed novel fluorescent nanocomposites from a conducting polymer, RNA and gold nanoparticles. The nanocomposites exhibited interesting optical and electrical properties that could be useful for detecting RNA and making nanosized electronic devices.
Nanobiocomposites of DNA and RNA have earlier been used to influence bone growth, wound healing, nerve regeneration and tumour treatment. However, in such hybrid systems, researchers often encounter a unique phenomenon that causes the electric current to decrease as the voltage is increased. This phenomenon — known as negative differential resistance — remains to be explored in RNA-based nanocomposite systems.
To demonstrate negative differential resistance in an RNA-mediated system, the researchers used polyaniline sulphonic acid (PSA), RNA and gold (Au) nanoparticles to produce three types of nanocomposite: PSA–Au, PSA–RNA–Au and PSA–RNA. They studied the conductivity of these nanocomposites and measured their photoluminescence.
The PSA–RNA–Au nanocomposites were more conductive than the PSA–RNA ones, as the presence of gold nanoparticles facilitates charge transport. The PSA–RNA hybrid exhibited negative differential resistance in the presence of nanoparticles. The photoluminescence intensity of the PSA–Au nanocomposite was nine times higher than that of the PSA hybrid. This increased 15-fold on the addition of RNA.
This is the first report of negative differential resistance in an RNA-mediated system. "This will be useful for the detection of RNA and the fabrication of optical biosensors, opening a new avenue for device fabrication," says lead researcher Arun K. Nandi.