Abstract
Red blood cell (RBC) aggregation in the blood stream is prevented by the
zeta potential created by its negatively charged membrane. There are
techniques, however, to decrease the zeta potential and allow cell
agglutination, which are the basis of most of antigen-antibody tests
used in immunohematology. We propose the use of optical tweezers to
measure membrane viscosity, adhesion, zeta potential, and the double
layer thickness of charges (DLT) formed around the cell in an
electrolytic solution. For the membrane viscosity experiment, we trap a
bead attached to RBCs and measure the force to slide one RBC over the
other as a function of the velocity. Adhesion is quantified by
displacing two RBCs apart until disagglutination. The DLT is measured
using the force on the bead attached to a single RBC in response to an
applied voltage. The zeta potential is obtained by measuring the
terminal velocity after releasing the RBC from the trap at the last
applied voltage. We believe that the methodology proposed here can
provide information about agglutination, help to improve the tests
usually performed in transfusion services, and be applied for zeta
potential measurements in other samples. (C) 2008 Society of
Photo-Optical Instrumentation Engineers.
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