title: Tip-enhanced Raman scattering (TERS) from hemozoin crystals within a sectioned erythrocyte.
abstract: Tip-enhanced Raman scattering (TERS) is a powerful technique to obtain molecular information on a nanometer scale, however, the technique has been limited to cell surfaces, viruses, and isolated molecules. Here we show that TERS can be used to probe hemozoin crystals at less than 20 nm spatial resolution in the digestive vacuole of a sectioned malaria parasite-infected cell. The TERS spectra clearly show characteristic bands of hemozoin that can be correlated to a precise position on the crystal by comparison with the corresponding atomic force microscopy (AFM) image. These are the first recorded AFM images of hemozoin crystals inside malaria-infected cells and clearly show the hemozoin crystals protruding from the embedding medium. TERS spectra recorded of these crystals show spectral features consistent with a five-coordinate high-spin ferric heme complex, which include the electron density marker band ν(4) at 1373 cm(-1) and other porphyrin skeletal and ring breathing modes at approximately 1636, 1557, 1412, 1314, 1123, and 1066 cm(-1). These results demonstrate the potential of the AFM/TERS technique to obtain nanoscale molecular information within a sectioned single cell. We foresee this approach paving the way to a new independent drug screening modality for detection of drugs binding to the hemozoin surface within the digestive vacuole of the malaria trophozoite.
authors.affiliation: Centre for Biospectroscopy, School of Chemistry, Monash University, 3800 Victoria, Australia.
authors.forename: Bayden R
authors.initials: BR
authors.lastname: Wood
authors.forename: Elena
authors.initials: E
authors.lastname: Bailo
authors.forename: Mehdi Asghari
authors.initials: MA
authors.lastname: Khiavi
authors.forename: Leann
authors.initials: L
authors.lastname: Tilley
authors.forename: Samantha
authors.initials: S
authors.lastname: Deed
authors.forename: Tanja
authors.initials: T
authors.lastname: Deckert-Gaudig
authors.forename: Don
authors.initials: D
authors.lastname: McNaughton
authors.forename: Volker
authors.initials: V
authors.lastname: Deckert
mesh_terms: D000818:Animals; D003460:Crystallization; D004867:Equipment Design; D004912:Erythrocytes / Q000166:cytology* / Q000469:parasitology / Q000648:ultrastructure; D006420:Hemeproteins / Q000737:chemistry*; D006801:Humans; D008288:Malaria / Q000188:drug therapy; D018625:Microscopy, Atomic Force / Q000379:methods; D036103:Nanotechnology / Q000379:methods; D010963:Plasmodium falciparum / Q000378:metabolism; D013059:Spectrum Analysis, Raman / Q000379:methods*; D053058:Trophozoites / Q000737:chemistry
chemical_list: D006420:Hemeproteins; C020753:hemozoin