Carbon Nanodots-Squaraine conjugates as photodynamic therapy agents

Carbon dots (CDs) are a new class of fluorescent carbon-based nanoparticles with excellent properties such as strong emission, high chemical stability, aqueous solubility, excellent biocompatibility and low toxicity. As well, an impressive quality lies in the possibility to synthesize CDs from green precursors, making them an eco-friendly choice. Furthermore, CDs are considered outstanding materials for several fields, including biological applications, highlighting their potential as carriers in drug delivery, and in photodynamic therapy (PDT). PDT is a promising technique for the treatment of cancer conditions, involving systemic or topical administration of a photosensitizer (PS) excited at a specific wavelength with the aim to produce reactive oxygen species (ROS) and lead to cancer cell death. Photosensitizers, e.g., squaraines, are NIR organic dyes characterized by a strong absorption that perfectly match the therapeutic windows (650-850 nm). However, under physiological conditions, their chemical instability and self-aggregation properties limit their wide applications. In this context, the conjugation of these dyes on nanoparticles (NPs) is extremely important in order to prevent the formation of dye aggregates in an aqueous environment and protect their photophysical characteristics. The present contribution deals with the preparation and characterization of N-doped C-dots complexes with a Squaraine active in vitro PDT tests, to promote its use for the treatment of cancer. Purposes in the coming future should include folic acid-conjugated carbon dots making them more selective towards tumoral cells.