A Bio-Conjugated Fullerene as a Subcellular-Targeted and Multifaceted Phototheranostic Agent

Fullerenes are candidates for theranostic applications because of their high photodynamic activity and intrinsic multimodal imaging contrast. However, fullerenes suffer from low solubility in aqueous media, poor biocompatibility, cell toxicity, and a tendency to aggregate. C-70@lysozyme is introduced herein as a novel bioconjugate that is harmless to a cellular environment, yet is also photoactive and has excellent optical and optoacoustic contrast for tracking cellular uptake and intracellular localization. The formation, water-solubility, photoactivity, and unperturbed structure of C-70@lysozyme are confirmed using UV-visible and 2D H-1, N-15 NMR spectroscopy. The excellent imaging contrast of C-70@lysozyme in optoacoustic and third harmonic generation microscopy is exploited to monitor its uptake in HeLa cells and lysosomal trafficking. Last, the photoactivity of C-70@lysozyme and its ability to initiate cell death by means of singlet oxygen (O-1(2)) production upon exposure to low levels of white light irradiation is demonstrated. This study introduces C-70@lysozyme and other fullerene-protein conjugates as potential candidates for theranostic applications.

Automated summary

Fullerenes, specifically C-70@lysozyme, exhibit high photodynamic activity and excellent optical contrast, making them potential candidates for theranostic applications in monitoring cellular uptake and intracellular localization.