Blood Dots: Hemoglobin-Derived Carbon Dots as Hydrogen Peroxide Sensors and Pro-Drug Activators

The present article highlights the preparation of hemoglobin-derived Fe2+-containing carbon dots, namely, blood dots (BD) and its simultaneous utilization in hydrogen peroxide (H2O2) sensing and pro-drug activation. The BD was characterized by different microscopic and spectroscopic techniques. The synthesized BD was highly water-soluble and exhibited strong blue emission under UV irradiation. This newly synthesized BD can efficiently split H2O2 to highly reactive hydroxyl/superoxide radicals which quench the intrinsic fluorescence of BD. Consequently, BD was utilized in H2O2 sensing with a limit of detection (LOD) of 1 mu M through fluorimetric assay. Notably, the reactive oxygen species (hydroxyl and superoxide radicals) generated from H2O2, upon interaction with BD, can damage DNA by oxidation. In this context, high accumulation of H2O2 is known to occur in cancer cells, because of the high enzymatic metabolism, in comparison to noncancer cells. In a similar way, the Fe2+-enriched BD can catalyze reactive oxygen species (ROS) generation from H2O2 within the cancer cell, which causes selective killing of the cancer cell via oxidative DNA damage. In addition, BD also has been used in bioimaging by exploiting its intrinsic fluorescence to distinguish between cancer and noncancer cells. The inclusion of BD in noncancerous cells illuminates bright blue fluorescence, while no significant emission of BD was observed in cancer cells, because of radical induced quenching of BD fluorescence in the presence of a high content of H2O2. Hence, the synthesized blood dot can be used in multitasking applications, including biosensing, bioimaging, and pro-drug activation for the selective killing of cancer cells.