Unveiling the multifaceted applications of pamoic acid carbon dots (PACDs) in sensing and oncology.

In our research we explore the world of PACDs, carbon dots synthesized from pamoic acid through a single step pyrolysis method. Our findings reveal that PACDs have capabilities of serving as sensitive and selective sensors in both colorimetric and fluorescent modes. They are particularly effective, at colorimetrically and fluorometrically detecting ferric ions and can also act as fluorometric sensors for pH. When ferric ions are introduced an interesting transformation occurs. A noticeable change in color unfolds before our eyes, under 365 nm UV light the fluorescence shifts from green to blue while in daylight it changes from a yellow to a deep ink blue. Notably these detection techniques can precisely measure ferric ions within concentrations ranging from 5 µM to 80 µM with a detection limit of 0.1 µM for fluorescence response. Additionally, they can detect ferric ions colorimetrically within the range of 5 µM to 45 µM with a detection limit of 3.8 µM. Furthermore, the PACDs exhibit a capability to adapt to different pH levels. In alkaline environments with a pH range between 8 and 11 the fluorescence signal demonstrates a response that directly correlates with pH levels and slightly shifts its position. In contrast under acidic conditions a noticeable shift, towards blue is observed in the fluorescence signal leading to a change in color from green to blue when exposed to UV light. This shift persists as the fluorescence signal directly correlates with decreasing pH levels in settings. Apart from their proficiency in ferric ion detection and pH monitoring, the PACDs also demonstrate potential in cancer research. Through an assessment using the MTT assay it was discovered that the PACDs exhibit cytotoxic effects against five different cancer cell lines; HCT 116, MDA MB 231, Hep3B, MCF 7 and HeLa. The findings are promising as the PACDs show IC50 values of 12.5 µg/ml 6.25 µg/ml 25 µg/ml 50 µg/ml and 100 µg/ml for these cell lines. This research highlights the versatility and potential of PACDs as a tool, in both sensing applications and oncology research.

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Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.