Harnessing Lignin-Derived Carbon Dots for Enhanced NIR Photothermal Ablation of Melanoma Cells

The integration of optical imaging modalities with photothermal therapy (PTT) enables simultaneous oncotherapy and bioimaging, offering improved therapeutic efficacy and enhanced treatment precision. As a result, this approach has emerged as a promising strategy for cancer treatment. Carbon dots (CDs) are highly stable, biocompatible materials with exceptional fluorescent properties, making them strong contenders for optical bioimaging and photothermal applications. However, challenges remain in synthesizing optimal CDs due to insufficient photothermal conversion efficiency, often requiring high laser power densities and higher CD concentrations for effective photothermal therapy (PTT). In this study, nitrogen-doped lignin-derived CDs (N-LCDs) are synthesized via a green, low-cost route using lignin as the carbon source and ethylenediamine as the nitrogen dopant. The resulting N-LCDs exhibit excellent absorption in the near-infrared (NIR) range, superior photothermal stability, and remarkable biocompatibility. Cellular uptake studies confirmed efficient internalization, while flow cytometry analysis revealed significant apoptosis upon NIR laser exposure, validating their photothermal therapeutic effect. The structural and optical characterization of N-LCDs demonstrates a high photothermal conversion efficiency (PCE ∼ 57.5%), highlighting their potential as effective and safe bioimaging and photothermal agents for in vitro cancer therapy.