Abstract
Classic immunohematology approaches, based on agglutination techniques,
have been used in manual and automated immunohematology laboratory
routines. Red blood cell (RBC) agglutination depends on intermolecular
attractive forces (hydrophobic bonds, Van der Walls, electrostatic
forces and hydrogen bonds) and repulsive interactions (zeta potential).
The aim of this study was to measure the force involved in RBC
aggregation using double optical tweezers, in normal serum, in the
presence of erythrocyte antibodies and associated to agglutination
potentiator solutions (Dextran, low ionic strength solution LISS and
enzymes). The optical tweezers consisted of a neodymium:yattrium
aluminium garnet (Nd:YAG) laser beam focused through a microscope
equipped with a minicam, which registered the trapped cell image in a
computer where they could be analyzed using a software. For measuring
RBC aggregation, a silica bead attached to RBCs was trapped and the
force needed to slide one RBC over the other, as a function of the
velocities, was determined. The median of the RBC aggregation force
measured in normal serum (control) was 1 x 10(-3) (0.1-2.5) poise. cm.
The samples analyzed with anti-D showed 2 x 10(-3) (1.0-4.0) poise. cm
(p<0.001). RBC diluted in potentiator solutions (Dextran 0.15%,
Bromelain and LISS) in the absence of erythrocyte antibodies, did not
present agglutination. High adherence was observed when RBCs were
treated with papain. Results are in agreement with the
imunohematological routine, in which non-specific results are not
observed when using LISS, Dextran and Bromelain. Nevertheless, false
positive results are frequently observed in manual and automated
microplate analyzer using papain enzyme. The methodology proposed is
simple and could provide specific information with the possibility of
meansuration regarding RBC interaction.
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