Aptamers, however, have advantages over antibodies in clinical testing. They are able to tolerate a wide range of pH (acid and base environments) and salt concentrations. They have high heat stability, are easily synthesized, and cost efficient.
For their demonstration, the researchers chose thrombin and thrombin-binding aptamers. Thrombin is a naturally occurring protein in humans that plays a role in clotting.
The researchers affixed the aptamers to a sensor surface, in this case a glass slide coated with a nanoscale layer of gold. As the blood sample is applied to the testing surface, the aptamer and their corresponding proteins latched together.
The next step is to actually determine if the couples pairing was successful. To make this detection, the researchers used a real-time optical sensing technique known as Surface Plasmon Resonance (SPR). A surface plasmon is a "virtual particle," created by the wave-motion of electrons on the surface of the sensor. If the protein is present and has bound to the aptamer, conditions for which resonance will occur at the gold layer will change. This resonance change is detected through a simple reflectance technique that is coupled to a linear detector.
"By monitoring these conditions, we can quantify the amount of the target protein that is present; even at very low concentrations," says Cameron. "This approach is very robust in that unique aptamers for almost any given protein can be identified. T
|Contact: Angela Stark|
Optical Society of America