Aminoporphyrin-Carbon Dot Nanocomposites for High-Efficiency Photodynamic Therapy

Carbon dots (CDs) are recognized for their excellent features, including chemical versatility, high biocompatibility, water solubility, low toxicity, minimal photobleaching, and efficient cellular internalization. The conjugation of porphyrins with CDs has emerged as a promising strategy to address the low solubility of these macrocycles in aqueous media and their lack of specificity for cancer cells, thereby expanding their potential as photosensitizers, particularly for photodynamic therapy. In this study, CDs synthesized from citric acid and tris(hydroxymethyl)aminomethane were successfully conjugated via covalent bonding to readily available 5,10,15,20-tetrakis(4-aminophenyl)porphyrin, affording a nanohybrid TAPP-Catris. The success of covalent functionalization was confirmed using Fourier Transform Infrared Spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Photochemical characterization confirmed that the nanohybrid effectively generated the reactive cytotoxic species, singlet oxygen (1O2). Biological assays on triple-negative breast cancer HCC1806 and skin malignant melanoma A375 cell lines revealed that TAPP-Catris exhibits high cytotoxicity under irradiation with filtered light (cutoff >560 nm), with IC50 of 3.22 and 3.88 μM respectively. May-Grünwald Giemsa staining confirmed that cell death was mediated by apoptosis. To the best of our knowledge, this porphyrin-based nanohybrid exhibits the highest photodynamic therapeutic activity, for these cell lines.