Fast multispectral imaging analysis as phenotyping platform: Effect of titanium dioxide nanoparticles on microalgae physiology

Abstract

Several types of nanoparticles have been developed and explored in agricultural applications and their environmental impact evaluated. However, no such study was carried out using fully dispersible ultrasmall titanium dioxide nanoparticles (us-TiO2). Therefore, we investigate the effects of fully dispersible 2.5 nm large us-TiO2 nanoparticles on the cellular metabolism of the microalgae Chlamydomonas reinhardtii using multispectral imaging analysis as a platform for the evaluation of their physiological responses. Our results indicate that us-TiO2 modulates the microalgae cell growth in a concentration-dependent manner. X-ray fluorescence analysis showed that the us-TiO2 strongly interacts with the cells in relatively low and constant amounts in the range of 0.05 g·L−1 to 1.5 g·L−1. Most nanoparticles were found on the cell surface, surrounding the microalgae cells dispersed in TAP medium, indicating a low trend of internalization. We further applied multispectral imaging analyses toward fast phenotyping of the alterations in the cell's physiology. Furthermore, higher concentrations of us-TiO2 (~1 g·L−1) positively affect the microalgae photosynthetic activity and growth. Thus, our results indicated the capacity to detect variations in cell physiology and indicated a possible role of us-TiO2 in modulating positively microalgae photosynthesis and growth in a concentration-dependent way. The mechanisms controlling such responses must be further investigated.