Quantum dots: a new tool for anti-malarial drug assays

A range of QDs with different chemical coatings were tested for their ability to specifically bind iRBCs by immunofluorescence assay (IFA). One QD was selected and used to detect parasite growth and drug sensitivity by flow cytometry.PEGylated-cationic QD (PCQD) was found to specifically label infected erythrocytes preferentially with late stage parasites. The detection of QD-labelled infected erythrocytes by flow cytometry was sensitive enough to monitor chloroquine anti-malarial toxicity with a drug incubation period as short as 24 h (EC50 = 113nM). A comparison of our assay with another widely used anti-malarial drug screening assay, the pLDH assay, showed that PCQD-based assay had 50% improved sensitivity in detecting drug efficacy within a parasite life cycle. An excellent Z-factor of 0.8 shows that the QD assay is suitable for high-throughput screening.This new assay can offer a rapid and robust platform to screen novel classes of anti-malarial drugs.Malaria remains a major global health problem, threatening over 300 million people and causing nearly one million deaths annually [1]. It is still a major cause of death especially in children under five years of age and pregnant women in areas such as sub-Saharan Africa, which bear the greatest burden of the disease. Due to the emergence of resistance, the rate in which the available drugs fail in the treatment of malaria has increased. To worsen this situation, recent reports on the emergence of resistant strains to artemisinin-based combination therapy (ACT) [2,3] have accelerated the urgent need of new drugs.Recently, the CdSe/ZnS semiconductor nanocrystal known as quantum dot (QD) has been widely used for various bioimaging applications as well as in vitro diagnostics due to high photostability, large stokes shift, and tunable narrow emission spectral characteristics [4]. These particular interesting fluorescent properties of QDs allowed it to be used as a robust fluorophore for labelling bacteria [5], red bl