Comparative evaluation of synchronization methods for Plasmodium falciparum: Efficiency, practicality and experimental applicability

The study of Plasmodium falciparum intraerythrocytic developmental cycle relies on synchronized parasite cultures. This study aimed to quantitatively evaluate 4 common synchronization methods for the culture of P. falciparum 3D7, incorporating a novel nanomaterial-based tool to objectively assess late-stage parasite enrichment. The 4 methods including 5% D-sorbitol, isosmotic Percoll-Sorbitol (60% PS), discontinuous Percoll-Sorbitol gradients (70%–40% PS), and the Plasmion method. Synchronization efficiency was assessed through microscopic examination and flow cytometry. In addition to SYBR Green I as the stain for flow cytometry, we innovatively employed 20 nm polystyrene fluorescent microspheres (PFMs20), which bind to parasites following the production of new permeability pathways, to provide an objective validating the enrichment of mature stages. The binding rate was defined as the ratio of PFMs20 positivity to SYBR Green I positivity. Microscopic examination of Giemsa-stained blood smears served as the gold standard for assessing the stage-specific profiles achieved by each synchronization method. The 4 methods yielded distinct efficiency profiles: 5% D-sorbitol achieved 88.37% ring-stage purity; 60% PS demonstrated high late-stage enrichment with PFMs20 binding rates reaching 87.47%; 70%–40% PS uniquely enabled visible hemozoin-rich layer separation and showed 88.12% binding efficiency in its schizont-enriched fraction; while Plasmion yielded a binding rate of 73.37% in its late-stage fraction. Our results formulate a clear decision matrix for synchronization protocol selection. The sorbitol method is ideal for basic ring-stage studies, Percoll-based gradients support rigorous stage-specific investigations, and the Plasmion method is well-suited for resource-limited settings. This comparative analysis provides preliminary guidelines for synchronization method selection that require validation in diverse laboratory and field contexts.