Surface charge of Plasmodium falciparum merozoites as revealed by atomic force microscopy with surface potential spectroscopy

Abstract

Electric charges on the surface of Plasmodium falciparum merozoites and erythrocytes were investigated by atomic force microscopy with surface potential spectroscopy. The apical end of merozoites was positively charged, while the entire erythrocyte surface was negatively charged. Transmission electron microscopy also demonstrated that negatively charged nanogold particles attached to the apical end of merozoites, and cationized ferritin particles attached to the entire surface of the erythrocyte. This indicates that the surface charge at the apical end of the merozoite may play an important role in invasion of the erythrocyte. Materials and methodsParasite culture P. falciparum indochina-1 strain was cultivated in vitro according to the method of Trager and Jensen (1976). Culture was maintained Parasitol Res (2002) 88: 16±20

Comparisons of the topographic characteristics and electrical charge distributions among Babesia‐infected erythrocytes and extraerythrocytic merozoites using AFM

“…These results are in good agreement with studies in which positively and negatively charged labelling particles and conducting substrate were used to measure the surface potential of the blood cells (Danon et al ., ; Akaki et al ., ). Free merozoites also display a similar surface potential, whereas the erythrocyte target cells are known to possess an oppositely charged surface, likely due to the expression of negatively charged sialylated glycoproteins (Fernandes et al ., ), nanogold particles (Akaki et al ., ). The difference in potential found on the surface of merozoites is large enough to bring merozoite and the target erythrocyte cells together before chemical binding takes place.…”

“…Other studies of surface potential involved indicators such as negatively charged and positively charged particles to probe the surface potential of samples. For instance, Akaki investigated the surface charge of plasmodium falciparum merozoites by surface potential spectroscopy (SPS) and transmission electron microscopy (TEM) using indium tin oxide glass slide (ITO) as conducting base substrate and negatively charged nanogold and positively cationised ferritin particles to probe erythrocytes and merozoites surfaces (Akaki et al, 2002). Akaki's work demonstrated that the negatively charged particles attached to the apical end of merozoites and positively charged particles to the entire surface of the erythrocytes.…”

“…AFM was demonstrated to be able to provide a direct insight on the topography of the surface of B. bovis, and B. bigemina-infected erythrocytes (Hutchings et al, 2007;Gohil et al, 2010), but the surface characteristics of B. caballi-infected erythrocytes remain unexplored. In addition, Kelvin probe force microscopy (KPFM) technique was first used to measure the contact potential between different materials (Nonnenmacher et al, 1991;Melitz et al, 2011), and also to measure the surface potential difference in the external membrane of Plasmodium-infected erythrocytes (Aikawa et al, 1996;Akaki et al, 2002). Differential surface membrane potential may also be related to important biological functions such as the ability of the parasite and infected erythrocytes to interact with other cells and their environments.…”

Digital holographic microscopy for the evaluation of human sperm structure

“…Recently, several novel techniques have been developed for the identification of more detailed features of the cells. Differential interference contrast microscopy, scanning near-field optical microscopy, electrostatic force microscopy, atomic force microscopy and scanning thermal microscopy (Akaki et al ., 2002; Bartoov et al ., 2002; Rothery et al ., 2003). Most of these techniques involve biochemical processing that requires specific equipment and may also alter the vitality of the sperm analysed.…”

Insights into the Membranolytic Activity of Antimalarial Drug-Cell Penetrating Peptide Conjugates

“…Yet, the goal of this biophysical study was to answer more fundamental questions regarding the influence of the charge of the lipids (zwitterionic versus anionic) on the surface of the model membranes, considering that electrostatic interactions are fundamental in the first steps of a peptide-membrane interaction. Other factors providing useful insights into the unexpected lack of selectivity of CQ-TP10 conjugates for PiRBC should, however, be considered: firstly, the surface of both niRBC and PiRBC is negatively charged, due to the presence of several non-lipidic components [30]. It has been reported that glycophorins (proteins rich in negatively-charged sialic acid) present in the erythrocyte membrane surface are altered by an enzyme-like material released by the parasite upon invasion, to prevent further invasion by other parasites [9,31].…”