Photoacoustic and fluorescence lifetime imaging of diatoms

Julijana Cvjetinovic; Alexey I Salimon; Marina V Novoselova; Philipp V Sapozhnikov; Evgeny A Shirshin; Alexey M Yashchenok; Olga Yu Kalinina; Alexander M Korsunsky; Dmitry A Gorin

doi:10.1016/j.pacs.2020.100171

Photoacoustic and fluorescence lifetime imaging of diatoms

Photoacoustics. 2020 Mar 10:18:100171. doi: 10.1016/j.pacs.2020.100171. eCollection 2020 Jun.

Affiliations

¹ Center for Photonics and Quantum Materials, Skolkovo Institute of Science and Technology, 3 Nobelya Str., Moscow, 121205, Russia.
² Center for Energy Science and Technology, Skolkovo Institute of Science and Technology, 3 Nobelya Str., Moscow, 121205, Russia.
³ Shirshov Institute of Oceanology of Russian Academy of Sciences, 36 Nakhimovsky Prospekt, Moscow, 117997, Russia.
⁴ Lomonosov Moscow State University, 1/2 Leninskiye Gory, Moscow, 119991, Russia.
⁵ Institute of Spectroscopy of the Russian Academy of Sciences, 5 Fizicheskaya Str., Troitsk, Moscow, 108840, Russia.
⁶ Faculty of Geography, Lomonosov Moscow State University, 1 Leninskiye Gory, Moscow, 119991, Russia.
⁷ Department of Engineering Science, University of Oxford, Oxford, OX1 3PJ, United Kingdom.

Abstract

Photoacoustic and fluorescent methods are used intensely in biology and medicine. These approaches can also be used to investigate unicellular diatom algae that are extremely important for Earth's ecology. They are enveloped within silica frustules (exoskeletons), which can be used in drug delivery systems. Here, we report for the first time the successful application of photoacoustic (PA) and fluorescent visualization of diatoms. Chlorophyll a and c and fucoxanthin were found likely to be responsible for the photoacoustic effect in diatoms. The PA signal was obtained from gel drops containing diatoms and was found to increase with the diatom concentration. The fluorescence lifetime of the diatom chromophores ranged from 0.5 to 2 ns. The dynamic light scattering, absorbance, and SEM characterization techniques were also applied. The results were considered in combination to elucidate the nature of the photoacoustic signal. Possible biotechnological applications are proposed for the remote photoacoustic monitoring of algae.

Keywords: Absorbance; Diatoms; Dynamic light scattering; Fluorescence lifetime imaging microscopy; Fluorescence spectroscopy; Photoacoustic imaging; Scanning electron microscopy.