title: Quantum dots: a new tool for anti-malarial drug assays.
abstract: BACKGROUND
  Malaria infects over 300 million people every year and one of the major obstacles for the eradication of the disease is parasite's resistance to current chemotherapy, thus new drugs are urgently needed. Quantum dot (QD) is a fluorescent nanocrystal that has been in the spotlight as a robust tool for visualization of live cell processes in real time. Here, a simple and efficient method using QD to directly label Plasmodium falciparum-infected erythrocytes (iRBCs) was searched in order to use the QD as a probe in an anti-malarial drug-screening assay.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  This new assay can offer a rapid and robust platform to screen novel classes of anti-malarial drugs.
authors.affiliation: Center for Neglected Diseases Drug Discovery, Institut Pasteur Korea, Seongnam-si, Gyeonggi-do, South Korea.
authors.forename: Min-Je
authors.initials: MJ
authors.lastname: Ku
authors.forename: Fernando M
authors.initials: FM
authors.lastname: Dossin
authors.forename: Youngseon
authors.initials: Y
authors.lastname: Choi
authors.forename: Carolina B
authors.initials: CB
authors.lastname: Moraes
authors.forename: Jiyoung
authors.initials: J
authors.lastname: Ryu
authors.forename: Rita
authors.initials: R
authors.lastname: Song
authors.forename: Lucio H
authors.initials: LH
authors.lastname: Freitas-Junior
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000494:pharmacology*; D004912:Erythrocytes / Q000469:parasitology*; D005434:Flow Cytometry / Q000379:methods; D019085:Fluorescent Antibody Technique, Direct / Q000379:methods; D006801:Humans; D021261:Parasitic Sensitivity Tests / Q000379:methods; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000254:growth & development*; D045663:Quantum Dots; D013997:Time Factors
chemical_list: D000962:Antimalarials