Influence of synthetic polycations on erythrocyte aggregation

DANIELI, VIRGINIA; FONTANA, A.; ALESSI, A.; GRANDFILS, C.; FORESTO, PATRICIA GLADYS; VALVERDE, JUANA ROSA; RIQUELME, BIBIANA DORIS

Montevideo, Uruguay

Conferencia; 6° Conferencia Internacional de Física Biológica; 2007

Sociedad Internacional de Biofísica

Polycations are oligomers or polymers of natural or synthetic origin, which bear a great number of positive charges at pH 7.4. Some of them are nowadays used in clinical medicine for different purposes, mainly in drug delivery. Another potential application of polycations is being investigated in order to mask the antigenic sites of cell membrane for cell therapies, in particular for erythrocytes in blood transfusion so as to prevent alloinmunization. In spite of their interesting pharmacological aspects, many polycations display a great cytotoxicity. In the last years, several efforts have been made to clarify the relationships existing between the macromolecular properties of these polymers (molecular weight, charge density, partition, flexibility, etc.) and their effects on blood cells. The aim of this work was to study the biocompatibility of two polycations-PEG copolymers on erythrocyte membrane. Particularly, we studied the influence of these polycations on erythrocyte aggregation, using digital image analysis. To do this, normal erythrocytes were incubated with the polycations-PEG copolymers Semo B86 and Semo B124 at two different concentrations. Polycation-treated and control RBCs were suspended in autologous plasma (to induce aggregation) and poured into an excavated slide, which was placed on the stage of an inverted microscope. Images were captured by a CCD camera, digitized and recorded to be numerically processed. The morphological characteristics and aggregate distribution in several visual fields were analyzed. The aggregate morphology was characterized by a dimensionless parameter called Aggregate Shape Parameter (ASP), which was obtained measuring the perimeter and the surface of the projected areas of the different aggregates. It was observed that polycation-treated and control RBCs readily form similar aggregate structures, because ASP values did not show any statistically significant difference between the two groups. Moreover, treated RBCs are morphologically normal, even at the highest polycation concentration investigated. A decreased aggregation with both polycations with respect to the control was observed, especially at the highest polycation concentration. This phenomenon was more marked with Semo B86. These results show different biocompatibilities of the polycations and could give more information on the interaction mechanisms of the polycations with the erythrocyte membrane so as to optimize them for several future therapeutic proposes.