Abstract
Carbon nanotubes (CNTs) are among the most exploited carbon allotropes in the emerging technologies of molecular sensing and bioengineering. However, the advancement of algal nanobiotechnology and nanobionics is hindered by the lack of methods for the straightforward visualization of the CNTs inside the cell. Herein, we present a handy and label-free experimental strategy based on visible Raman microscopy to assess the internalization of single-walled carbon nanotubes (SWCNTs) using the model photosynthetic alga Chlamydomonas reinhardtii as a recipient. The relationship between the properties of SWCNTs and their biological behavior was demonstrated, along with the occurrence of excitation energy transfer from the excited chlorophyll molecules to the SWCNTs. The non-radiative deactivation of the chlorophyll excitation promoted by the SWCNTs enables the recording of Raman signals originating from cellular compounds located near the nanotubes, such as carotenoids, polyphosphates, and starch. Furthermore, the outcome of this study unveils the possibility to exploit SWCNTs as spectroscopic probes in photosynthetic and non-photosynthetic systems where the fluorescence background hinders the acquisition of Raman scattering signals.
Highlights
The latest advances in phyto-nanotechnology and plant nano-bionics brought to light the ability of single-walled carbon nanotubes (SWCNTs) to deliver into plants small molecules, fertilizers, or pesticides [1,2,3,4,5], to improve plant defense [6,7,8] or even to turn plant tissues into molecular sensors [9,10]
These methods enabled both tracing the spatiotemporal behavior of SWCNTs and their localization inside plant cells
Chlamydomonas mutant, the entry of SWCNTs into the cell could be further facilitated due to the minute amount of the cell wall produced by this strain [32,33]
Summary
The latest advances in phyto-nanotechnology and plant nano-bionics brought to light the ability of single-walled carbon nanotubes (SWCNTs) to deliver into plants small molecules, fertilizers, or pesticides [1,2,3,4,5], to improve plant defense [6,7,8] or even to turn plant tissues into molecular sensors [9,10]. To the best of our knowledge, this is the first repost using Raman spectroscopy to track CNTs inside algae and to survey their interaction with the photosynthetic machinery This achievement could deepen the knowledge on the relationship between the physicochemical properties of the nanotubes and their biological effects in microalgae, supporting the development of biotechnological applications of SWCNTs. the outcome of this study highlights the possibility to exploit SWCNTs as spectroscopic probes in systems where the fluorescence background of the specimen obstructs the acquisition of Raman scattering signals (Appendix A)
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