Far-Red Fluorescent carbon nano-onions for high-resolution cellular imaging

The development of novel fluorescent systems for bio-imaging applications is a research field of increasing interest and many efforts have been made for the implementation of imaging agents for the biologically relevant... [ view full abstract ]

The development of novel fluorescent systems for bio-imaging applications is a research field of increasing interest and many efforts have been made for the implementation of imaging agents for the biologically relevant near-infra red (NIR) region, where tissues exhibit minimal absorbance. Carbon nano-onions (CNOs) are an emerging class of nanoparticles which showed great potential in a variety of different applications [1]. The functionalization of CNOs with different functional groups increases the ability to penetrate into the cells [2] and allows for the conjugation of different diagnostic and therapeutic agents, opening new avenues in theranostic applications [3].

Our recent reports showed that fluorescently labelled CNOs exhibit weak inflammatory potential and a low cytotoxicity [4] and are readily internalized by cancer cells and deposited in the lysosomes [5]. Moreover, in vivo studies on zebrafish larvae (Danio Rerio) during the development shown their biocompatibility and homogenous distribution in a vertebrate model system [6].

Here we report the development of a novel class of fluorescent nanoprobes with enhanced solubility in biological media and bright photoluminescence. The fluorescent CNOs (fluo-CNOs) have been characterized by different analytical techniques such as spectroscopy (Raman, x-ray photoelectron, fluorescence), thermogravimetric analysis (TGA), dynamic light scattering (DLS), zeta potential as well as microscopy.

The internalization and cytotoxicity of fluo-CNOs have been analyzed in human cervical carcinoma (HeLa) and human breast cancer (MCF-7) cells, showing any significant toxic effect on cell morphology and cell viability in both cell lines (Figure 1a). Moreover, the functionalized CNOs showed high fluorescence intensity even at very low concentration with partially localization in the lysosomes (Figure 1b) [7]. Our findings confirmed the excellent potentialities of these functionalized carbon nanomaterials as biocompatible platform for high-resolution cellular imaging.

References

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[5] Bartelmess, J. Nanoscale 2014, 6, 13761

[6] d’Amora, M. et al. Sci. Rep. 2016, 6, 33923 

[7] Lettieri, S. et al. RSC Adv. 2017, 7, 45676