Light-triggered and nanocarrier properties of nitrogen-doped carbon nanodots

Abstract

Carbon nanodots (CDs) are an emerging class of nanomaterials that have recently attracted significant attention for applications in personalized diagnosis, therapy and theragnostics. Herein, we aimed to develop emissive and photothermal N-doped CDs obtained via one-pot thermal process from chitosan (CDs-chit) without the use of organic solvents and additional reagents. The CDs-chit nanostructures were characterized using spectroscopic techniques, including Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared spectroscopy (FTIR), X-rays Photoelectron spectroscopy (XPS), and Transmission Electron Microscopy (TEM). The CDs-chit showed excellent luminescence quantum yield (φ_420 nm = 6%), curcumin entrapment efficiency (12%), good photothermal conversion efficiency upon blue-light excitation (η_405 nm = 57.1%) and red-light excitation (η_808 nm = 16.2%). The photoxidation and photoreduction properties of CDs-chit nanostructures were also demonstrated through the photodegradation of methylene blue and the photogeneration of gold-nanostructures (CDs-chit/Au⁰), a tentative mechanism was proposed whereby CDs-chit act as both electron source and capping agent. In vitro experiments using MTT assay demonstrated the low cytotoxicity of CDs-chit. Confocal laser scanning microscopy imaged the cellular uptake of curcumin-loaded car-bon dots (CDs-chit/curc), while the absence of significant changes in gene expression confirmed the biocompatibility of the carbon dots. NIR light-triggered cell damages was observed upon photoexcitation of tumoral HCT 116 cells using an 808 nm laser source through a two-photon absorption mechanism. The ease of preparation, curcumin loading capacity, effective cellular uptake, and downregulation of pro-inflammatory IL-6 gene expression, photoluminescence and hyperthermia make CDs-chit nanomaterials attractive for further investigations in the field of biomedical research.