Diatoms: where photoacoustics meets fluorescence
Julijana Cvjetinovic - Skolkovo Institute of Science and Technology, Moscow, Russia
Dmitry Gorin - Skolkovo Institute of Science and Technology, Moscow, Russia
Alexey Salimon - Skolkovo Institute of Science and Technology, Moscow, Russia
Alexander Korsunsky - Skolkovo Institute of Science and Technology, Moscow, Russia; Department of Engineering Science, University of Oxford, Oxford, United Kingdom
Marina Novoselova - Skolkovo Institute of Science and Technology, Moscow, Russia
Philipp Sapozhnikov - Shirshov Institute of Oceanology of Russian Academy of Sciences, Moscow, Russia
Olga Kalinina - Faculty of Geography, Lomonosov Moscow State University, Moscow, Russia
Evgeny Shirshin - Lomonosov Moscow State University, Skolkovo Institute of Science and Technology, Moscow, Russia
Alexey Yashchenok - Skolkovo Institute of Science and Technology, Moscow, Russia
Abstract
Diatoms, unicellular microalgae, have attracted significant attention and interest in the scientific community due to their distinctive highly porous silica cell walls and unique morphological, chemical, mechanical, and optical properties. As natural photosensitizers, they contain a tremendous amount of chromophores, such as chlorophylls and carotenoids, which paves the way for their photoacoustic and fluorescence lifetime visualization. Our results demonstrated, for the first time, a strong concentration-dependent photoacoustic response from Karayevia amoena diatom cells mixed with an agarose gel. The study was conducted by using a raster scanning optoacoustic mesoscopy (RSOM) Explorer P50 setup (iThera Medical GmbH, Germany), which utilizes laser excitation at 532 nm [1]. We additionally investigated other types of diatom algae, such as Fragilaria radians and Achnanthidium sibiricum, and confirmed the presence of living cells in the colonies. To prove the success of this method for imaging other photosynthetic objects we also examined green algae and cyanobacteria grown on an agar plate and obtained a robust photoacoustic effect. A fluorescence lifetime of diatom chromophores, namely chlorophyll a, ranges from 0.5 to 5 ns at excitation wavelengths of 402 nm and 638 nm. The variety in lifetimes is most likely a consequence of different pigment concentrations and the complex physiology of the cell itself. We believe that photoacoustic imaging is a suitable method for remote and rapid monitoring of the growth of these photosynthetic organisms in bioreactors, as well as in their natural environment, without complicated sample preparation.
[1] J. Cvjetinovic, A.I. Salimon, M. V. Novoselova, P. V. Sapozhnikov, E.A. Shirshin, A.M. Yashchenok, O.Y. Kalinina, A.M. Korsunsky, D.A. Gorin, Photoacoustic and fluorescence lifetime imaging of diatoms, Photoacoustics 18, 2020,
https://doi.org/10.1016/j.pacs.2020.100171.
Speaker
Julijana Cvjetinovic
Skolkovo Institute of Science and Technology, Moscow, Russia
Russia
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