[Fixation and immunological reactivity of parasitic protozoa in sol-gel matrices]

Parasitic protozoa have been entrapped within sol-gel silica matrices. Stationary phase promastigote cells of Leishmania donovani infantum are mixed with a silicon alkoxide solution. They remain trapped within the growing oxide network formed upon hydrolysis and condensation of the alkoxide. Electron microscopy shows the preservation of the cellular organization and the integrity of the plasma membrane of entrapped parasites. Specific antigen-antibody reactions have been performed within the sol-gel matrix via enzyme-linked immunosorbent assays (ELISA) currently used for the diagnostic of visceral leishmaniasis. A clear-cut difference in optical density was measured between positive and negative sera from dogs. Entrapped protozoa antigens are still able to react with specific antibodies through the open porosity of the silica network. These results suggest that sol-gel matrices could be used for the development of immunodiagnostic assays requiring whole cell parasites as antigens.