Conjugated ternary doped carbon dots from vitamin B derivative: Multispectral nanoprobes for targeted melanoma bioimaging and photosensitization

Multi-color emissive carbon dots (CDs) with intrinsic ternary doping were synthesized by a hydrothermal process from a single precursor, vitamin B1 derivative, thiamine pyrophosphate or ThPP. The origin of the multi-color photoluminescence was ascribed to the hybrid doping (N, S, P) in a carbon framework. The subsequent conjugation of CDs with folic acid (FA) enabled targeted bioimaging and photosensitization of the human melanoma cancer cells, SK-MEL28. The unique excitation-dependent multi-color emission of CD-FA probes allowed wide spectral resolution and targeting for amplified whole cell bioimaging including the nucleus. The photosensitization of cancer cells in the multi-color window was accomplished in a deep tissue cell culture setting. The synthesized CD-FAs showed excellent biocompatibility, photostability, and notably, their cellular targeting with enhanced uptake by folate receptor positive (FR+) cancer cells, SK-MEL28 over folate receptor negative (FR-), HEK293T ones in a co-culture model having both diseased and normal cells. The results demonstrate excellent potential for melanoma diagnostic, mapping and phototherapeutic applications with multi-spectral sensitivity.