title: Fiber array based hyperspectral Raman imaging for chemical selective analysis of malaria-infected red blood cells.
abstract: A new setup for Raman spectroscopic wide-field imaging is presented. It combines the advantages of a fiber array based spectral translator with a tailor-made laser illumination system for high-quality Raman chemical imaging of sensitive biological samples. The Gaussian-like intensity distribution of the illuminating laser beam is shaped by a square-core optical multimode fiber to a top-hat profile with very homogeneous intensity distribution to fulfill the conditions of Koehler. The 30 m long optical fiber and an additional vibrator efficiently destroy the polarization and coherence of the illuminating light. This homogeneous, incoherent illumination is an essential prerequisite for stable quantitative imaging of complex biological samples. The fiber array translates the two-dimensional lateral information of the Raman stray light into separated spectral channels with very high contrast. The Raman image can be correlated with a corresponding white light microscopic image of the sample. The new setup enables simultaneous quantification of all Raman spectra across the whole spatial area with very good spectral resolution and thus outperforms other Raman imaging approaches based on scanning and tunable filters. The unique capabilities of the setup for fast, gentle, sensitive, and selective chemical imaging of biological samples were applied for automated hemozoin analysis. A special algorithm was developed to generate Raman images based on the hemozoin distribution in red blood cells without any influence from other Raman scattering. The new imaging setup in combination with the robust algorithm provides a novel, elegant way for chemical selective analysis of the malaria pigment hemozoin in early ring stages of Plasmodium falciparum infected erythrocytes.
authors.affiliation: Leibniz Institute of Photonic Technology, 07745 Jena, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Brückner
authors.affiliation: Justus Liebig University Giessen, Biochemistry and Molecular Biology, 35392 Giessen, Germany.
authors.forename: Katja
authors.initials: K
authors.lastname: Becker
authors.affiliation: Leibniz Institute of Photonic Technology, 07745 Jena, Germany; Friedrich Schiller University Jena, Institute for Physical Chemistry, 07745 Jena, Germany; Friedrich Schiller University Jena, Abbe Centre of Photonics, 07745 Jena, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Popp
authors.affiliation: Leibniz Institute of Photonic Technology, 07745 Jena, Germany; Friedrich Schiller University Jena, Institute for Physical Chemistry, 07745 Jena, Germany; Friedrich Schiller University Jena, Abbe Centre of Photonics, 07745 Jena, Germany. Electronic address: torsten.frosch@uni-jena.de.
authors.forename: Torsten
authors.initials: T
authors.lastname: Frosch
mesh_terms: D000465:Algorithms; D004912:Erythrocytes / Q000469:parasitology*; D006420:Hemeproteins / Q000737:chemistry; D006801:Humans; D057230:Limit of Detection; D016778:Malaria, Falciparum / Q000175:diagnosis*; D010963:Plasmodium falciparum; D013059:Spectrum Analysis, Raman; D046888:Tissue Array Analysis
chemical_list: D006420:Hemeproteins; C020753:hemozoin
keywords: Fiber based Raman; Hyperspectral imaging; Malaria pigment hemozoin; Raman imaging; Raman spectroscopy; Resonance Raman spectroscopy