title: Discriminating the intraerythrocytic lifecycle stages of the malaria parasite using synchrotron FT-IR microspectroscopy and an artificial neural network.
abstract: Synchrotron Fourier transform infrared (FT-IR) spectra of fixed single erythrocytes infected with Plasmodium falciparum at different stages of the intraerythrocytic cycle are presented for the first time. Bands assigned to the hemozoin moiety at 1712, 1664, and 1209 cm(-1) are observed in FT-IR difference spectra between uninfected erythrocytes and infected trophozoites. These bands are also found to be important contributors in separating the trophozoite spectra from the uninfected cell spectra in principal components analysis. All stages of the intraerythrocytic lifecycle of the malarial parasite, including the ring and schizont stage, can be differentiated by visual inspection of the C-H stretching region (3100-2800 cm(-1)) and by using principal components analysis. Bands at 2922, 2852, and 1738 cm(-1) assigned to the nu(asym)(CH(2) acyl chain lipids), nu(sym)(CH(2) acyl chain lipids), and the ester carbonyl band, respectively, increase as the parasite matures from its early ring stage to the trophozoite and finally to the schizont stage. Training of an artificial neural network showed that excellent automated spectroscopic discrimination between P. falciparum-infected cells and the control cells is possible. FT-IR difference spectra indicate a change in the production of unsaturated fatty acids as the parasite matures. The ring stage spectrum shows bands associated with cis unsaturated fatty acids. The schizont stage spectrum displays no evidence of cis bands and suggests an increase in saturated fatty acids. These results demonstrate that different phases of the P. falciparum intraerthyrocytic life cycle are characterized by different lipid compositions giving rise to distinct spectral profiles in the C-H stretching region. This insight paves the way for an automated infrared-based technology capable of diagnosing malaria at all intraerythrocytic stages of the parasite's life cycle.
authors.affiliation: Centre for Biospectroscopy and School of Chemistry, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Grant T
authors.initials: GT
authors.lastname: Webster
authors.forename: Katherine A
authors.initials: KA
authors.lastname: de Villiers
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Egan
authors.forename: Samantha
authors.initials: S
authors.lastname: Deed
authors.forename: Leann
authors.initials: L
authors.lastname: Tilley
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Tobin
authors.forename: Keith R
authors.initials: KR
authors.lastname: Bambery
authors.forename: Don
authors.initials: D
authors.lastname: McNaughton
authors.forename: Bayden R
authors.initials: BR
authors.lastname: Wood
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D004912:Erythrocytes / Q000737:chemistry / Q000378:metabolism / Q000469:parasitology*; D006420:Hemeproteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008018:Life Cycle Stages; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D008288:Malaria / Q000175:diagnosis / Q000469:parasitology* / Q000473:pathology*; D016571:Neural Networks, Computer; D010963:Plasmodium falciparum / Q000254:growth & development* / Q000502:physiology; D025341:Principal Component Analysis; D017550:Spectroscopy, Fourier Transform Infrared; D017356:Synchrotrons
chemical_list: D015415:Biomarkers; D006420:Hemeproteins; D008055:Lipids; C020753:hemozoin