exploited as drug delivery targets (Fig. 13.6). The idea behind this is that the nano­onion’s layers can be created to have particular chemical characteristics, with such affinity for a particular kind of cell or tissue. The medicine can be given precisely to the target cells or tissue by being encapsulated within the nano-onion. Increased medication bioavailability, less toxicity to organs other than the target, and enhanced pharmacokinetics are benefits of utilizing nano-onions as targeting agents. However, there may be certain disadvantages, such as the difficulty in producing and char­acterizing the nanoparticles and the possibility of immunogenicity. A noteworthy example is the development of hyaluronic acid-conjugated carbon nanomaterials for improved tumor targeting ability [58, 59]. Targeting tumor cells that overexpress the CD44 + receptor with chemo and photo thermal therapy uses hyaluronic acid. Carbon nanomaterial (CNM) carriers can effectively carry anticancer medications, such as doxorubicin and gemcitabine, to the tumor locations, thanks to HA-targeting hybrid systems. Using hyaluronic acid, carbon nano-onions have shown to be quite promising for the delivery of specific drugs [60]. A HA-phospholipid compound was used in the work by d’Amor et al. to target cancer cells that overexpress CD44 while improving the solubility of the nanostructure. In comparison to human ovariancancer cells with undetectable levels of CD44, non-covalently functionalized carbon nano­onions with HA-phospholipids conjugate exhibit outstanding in vitro cell survival in human breast carcinoma cells [61]. Additionally, they have a high level of in vivo biocompatibility in zebrafish (Daniorerio) at various developmental stages and are mostly found in the digestive system of zebrafish larvae. Mamidi et al. discovered that the nano-onions complex with other nanoparticles might thrive as a viable pH and temperature-triggered drug delivery platform for GI tract and colon focused drug delivery [62]. There are various instances of nanocarrier systems on the market that have received FDA approval, demonstrating the effectiveness of the nanocarrier method in this regard. This viewpoint confirms that carbon nano-onions have the potential to serve as nanocarriers for the delivery of drugs. Already described are the many standards and factors to take into account when constructing a nanocarrier [18].

A chemical called an imaging agent is used to improve the image quality in medical imaging procedures like computed tomography and magnetic resonance imaging, among others. The potential for using nano-onions, which are microscopic particles comprised of concentric layers of carbon, as imaging agents has been investigated. The idea behind employing nano-onions as imaging agents is that they are capable of being functionalized with targeting molecules like antibodies or peptides, which can then bind specifically to sick cells or tissues [63]. This makes it possible to image the targeted area of interest with greater accuracy and precision. Encapsulating the imaging agent within the onion-like structure’s layers at the nanoscale level, which can then be coated with a biocompatible substance to prevent degradation and boost

enabling focused therapy, controlled release, and imaging in the future. Further­more, their distinct features could be used in other biological applications like as tissue engineering and biosensing. Finally, carbon nano-onions have demonstrated remarkable potential as a medium for future drug delivery.

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