Typing Blood Cells, One At A Time

Extract

We are all familiar with the 4 groups of human blood types; 0, A, B, and AB. Each group is characterized by specific molecules on the surface of the red blood cells (RBCs). Recently, Michel Grandbois, Wolfgang Dettmann, Martin Benoit, and Hermann Gaub have modified the atomic force microscope (AFM) to use the different affinities of these molecules to produce an image.

A key step was to specifically functionalize the scanning probe tip of the AFM. What this means is to covalently attach an active molecule to the tip. The active molecule they used was a Iectin derived from the snail Helix pomatia (this is the same snail valued by the French as escargot). This Iectin binds specifically to molecules found on the surface of RBCs in blood group A (N-acetylgalactosamine-terminated glycolipids), but these molecules are not found in blood group O. But if the Iectin was bound directly to the AFM tip, nonspecific adsorption to the specimens would occur.