Fluorescent Carbon Nano-onion as Bioimaging Probe

Concentrically arranged multilayered fullerenes exhibiting onion-like morphology are popularly known as carbon nano-onion (CNO) and are useful in bioimaging application. On the basis of the origin of the fluorescence, the CNO-based nanoprobes are classified into type I and type IL The type I CNO-based nanoprobe needs a secondary moiety such as organic dyes or an amine functionalization at its surface to induce the fluorescence. On the other hand, the emission in type II does not originate from such an external surface passivating agent. The CNO-based system not only shows structural similarity to the well-known multiwalled carbon nanotube but is also a bit more advantageous because of its low cytotoxicity. These features enable their prolonged use in the biological system for imaging purposes. In particular, we have covered the aspects of synthesis, surface functionalization, the origin of fluorescence, and biocompatibility. In addition, recent developments directed toward in vitro and in vivo imaging studies by utilizing CNO-based nanoprobes are summarized here.

Automated summary

Carbon nano-onion (CNO) is a concentrically arranged multilayered fullerene with onion-like morphology, popular in bioimaging applications. Based on the origin of fluorescence, CNO-based nanoprobes are classified into type I and type II. While type I CNO-based nanoprobe requires a secondary moiety to induce fluorescence, type II emission does not originate from external passivating agents. CNO not only resembles multiwalled carbon nanotubes but also has lower cytotoxicity, making it suitable for long-term imaging in biological systems.