ATOMIC-FORCE MICROSCOPY STUDY OF FINE-STRUCTURES OF THE ENTIRE SURFACE OF RED-BLOOD-CELLS

Glutaraldehyde-fixed red blood cells were imaged by tapping mode atomi c force microscopy (TMAFM) in air at room temperature. The results sho w that TMAFM can visualize the morphology of the red blood cell at bot h cellular and nanometer scales. The scan size covers the range from s everal hundred nanometers to more than one hundred micrometers. TMAFM not only has a higher resolution than the optical microscope, but also can observe biological samples without precoating as required for sca nning electron microscopy (SEM). The AFM images of the entire surface of an uncoated red blood cell with nanometer resolution are successful ly reconstructed by 28 AFM images of the preselected subareas on the s urface of the red blood cell. These images reveal directly the fine st ructures of the external surface of uncoated red blood cells in air. T he surface exhibits a characteristic structure composed of a large num ber of closely-packed nanometer particles with a size ranging from a f ew nanometers to tens of nanometers. These ''particulate'' components are evenly distributed, and no jumping protrusion or depression struct ures were found. These particles give rise to a very smooth surface of the red blood cell as shown in a large-scan AFM image. In addition, t he 28 AFM images obtained by the continuous scanning over 3 hours indi cate that TMAFM can image soft biological samples such as led blood ce lls stably and reproducibly.