Optical trapping of microalgae at 735–1064nm: Photodamage assessment

• Published in: Journal of photochemistry and photobiology. B, Biology Vol. 121; pp. 27 - 31
• Main Authors: Pilát, Z., Ježek, J., Šerý, M., Trtílek, M., Nedbal, L., Zemánek, P.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.04.2013
• Subjects: absorption; light intensity; Microalgae; Optical trapping; PAM fluorescence microspectroscopy; photobiology; photochemistry; Photodamage; trapping; wavelengths; Optical trapping; PAM fluorescence microspectroscopy; Microalgae; Photodamage
• ISSN: 1011-1344; 1873-2682
• DOI: 10.1016/j.jphotobiol.2013.02.006

► Living microalgal cells were trapped in optical tweezers using laser wavelengths 735–1064nm. ► Photodamage was assessed by pulse amplitude modulation chlorophyll fluorescence microspectroscopy. ► Loss of fluorescence in Trachydiscus minutus was observed up to 885nm trapping laser wavelength. ► Wavelengths over 935nm caused no observable fluorescence loss, suggesting minimal photodamage. Living microalgal cells differ from other cells that are used as objects for optical micromanipulation, in that they have strong light absorption in the visible range, and by the fact that their reaction centers are susceptible to photodamage. We trapped cells of the microalga Trachydiscus minutus using optical tweezers with laser wavelengths in the range from 735nm to 1064nm. The exposure to high photon flux density caused photodamage that was strongly wavelength dependent. The photochemical activity before and after exposure was assessed using a pulse amplitude modulation (PAM) technique. The photochemical activity was significantly and irreversibly suppressed by a 30s exposure to incident radiation at 735, 785, and 835nm at a power of 25mW. Irradiance at 885, 935 and 1064nm had negligible effect at the same power. At a wavelength 1064nm, a trapping power up to 218mW caused no observable photodamage.