A Silver Lining

A group from UCSB works with the precious metal to create nanoscale silver clusters with unique fluorescent properties. These properties are important for a variety of sensing applications including biomedical imaging.

 The scientists positioned silver clusters at programmed sites on a nanoscale breadboard, a construction base for prototyping of photonics and electronics.

The results of this novel form of DNA nanotechnology address the difficulty of achieving uniform particle sizes and shapes. "In order to make photonic arrays using a self-assembly process, you have to be able to program the positions of the clusters you are putting on the array," Stacy Copp a graduate student in UCSB's Department of Physics explained.

The colors of the clusters are largely determined by the DNA sequence that wraps around them and controls their size. To create a positionable silver cluster with DNA-programmed color, the researchers engineered a piece of DNA with two parts: one that wraps around the cluster and the other that attaches to the DNA nanotube. "Sticking out of the nanotube are short DNA strands that act as docking stations for the silver clusters' host strands,"

The research group's team of graduate and undergraduate researchers is able to tune the silver clusters to fluoresce in a wide range of colors, from blue-green all the way to the infrared -- an important achievement because tissues have windows of high transparency in the infrared. According to Copp, biologists are always looking for better dye molecules or other infrared-emitting objects to use for imaging through a tissue.

The modular design presented in this research means that its step-by-step process can be easily generalized to silver clusters of different sizes and to many types of DNA scaffolds. The paper walks readers through the process of creating the DNA that stabilizes silver clusters. This newly outlined protocol offers investigators a new degree of control and flexibility in the rapidly expanding field of nanophotonics.

The overarching theme of Copp's research is to understand how DNA controls the size and shape of the silver clusters themselves and then figure out how to use the fact that these silver clusters are stabilized by DNA in order to build nanoscale arrays.

Source: USCB