For years, the distinctive optical and structural properties of single-walled carbon nanotubes (SWCNTs) have inspired the development of promising applications in the field of cell nanobiotechnology. In particular, the synergistic interaction of SWCNTs with photosynthetic organisms has the potential to enhance the native performance of biological machineries, paving the way for novel, renewable, and low cost solutions for light-harvesting, energy conversion, subcellular sensing, and DNA delivery. Recent studies have largely focused on enabling cellular uptake of SWCNTs by engineering the SWCNT surface through non-covalent side-wall functionalizations. Non-covalent functionalization with a rich variety of biomolecules and polymers has been shown to potentially increase SWCNT solubility and membrane translocation while endowing these nanostructures with enhanced biocompatibility.

We performed a systematic investigation of the effect of SWCNT functionalization on membrane penetration properties using a novel biological host. A custom-built optical setup was used for the unprecedented characterization of near-infrared fluorescence emissions of internalized SWCNTs. These results were used to inform fuctionalization design rules for SWCNT internalization, and more broadly, present a versatile approach towards imaging internalized SWCNTs in biological systems.