Carbonization of Human Fingernails: Toward the Sustainable Production of Multifunctional Nitrogen and Sulfur Codoped Carbon Nanodots with Highly Luminescent Probing and Cell Proliferative/Migration Properties

A simple yet effective method is employed to prepare multifunctional fluorescent carbon nanodots (CNDs) from human fingernails. The results demonstrate that the CNDs have excellent optical properties and a quantum yield of 81%, which is attributed to the intrinsic composition of the precursor material itself. The CNDs are used to develop an ultrasensitive fluorescent probe for the detection of hexavalent chromium (limit of detection: 0.3 nM) via a combined inner-filter and static mechanism. Moreover, the toxicity of the CNDs over four epithelial cell lines is assessed. A negligible toxicity is induced on the three of the cell lines, whereas an increase in HEK-293 cell viability is demonstrated, granting cell proliferation properties to the as-synthesized CNDs. According to cell cycle analysis, cell proliferation is achieved by enhancing the transition of cells from the S phase to the G2/M one. Interestingly, CNDs are found to significantly promote cell migration, maybe because of their free-radical scavenging ability, making the CNDs suitable for wound healing applications. In addition, relevant experiments have revealed the blood compatibility of the CNDs. Finally, the CNDs were found suitable for cell imaging applications, and all of the aforementioned merits make it possible for them to be used for extraordinary, more advanced biological applications.