Using an AFM as the base, researchers added micro and nano-electrodes into the tip. This allows researchers to get biological and chemical information via scanning electrochemical microscopy (SECM) simultaneously with topographical information provided by AFM.
"The problem with conventional AFM imaging is that you get topographical information, but only limited information on the chemical processes occurring at the cell surface," said Kranz. "With SECM, you can get information on electro-activity, but this information may be convoluted with the topographical information. Also SECM still suffers from limited resolution. We combined the two techniques to give us high resolution topography as well as the chemistry that's going on at the cell surface."
Researchers tested their new technique by integrating biosensors for glucose into AFM tips. They imaged, as a synthetic model, glucose transport through track-etched membranes. In another test, a biosensor based on horse radish peroxidase was integrated into the AFM tip. They were able to faithfully measure the chemical activity and image the process to a resolution of 200 nanometers.
The tool promises to be valuable for a wide range of biomedical and biotechnological applications. In an NIH-funded project in collaboration with Emory University, Kranz and Boris Mizaikoff are currently using this technique to study cystic fibrosis and the role errors in regulating adenosine triphosphate (ATP), a chemical involved in transporting energy to cells, might play in the disease.