Lignin derived reduced fluorescence carbon dots with theranostic approaches: Nano-drug-carrier and bioimaging

This is the first study on synthesis of water-soluble reduced fluorescent carbon dots (r-FCDs) by using lignosulfonate lignin as carbon source. The resulted r-FCDs have been employed for curcumin nano-carrier and bioimaging applications. The r-FCDs were obtained within 10 min under microwave irradiation after reduction with NaBH4. The prepared carbon dots were characterized by various spectroscopic techniques, TEM, XRD, DLS & fluorescence microscopy. The maximum PL intensity was found at 475 nm on excitation at 440 nm with quantum yield (QYs) of 47.3%. TEM and DLS results showed that average diameter of r-FCDs was about 4.9 nm and were readily dispersed in water with strong photostability. XRD results suggested the amorphous nature of r-FCDs. The weak interaction found between an anticancer compound curcumin and surfaces of r-FCDs endowed them with the capacity to act as superior candidate for its capturing and releasing at physiological pH (7.4). The r-FCDs were efficiently up taken by cancerous cells (A549 and SW480) and illuminating the whole cell with a clear distinction between cytoplasm and nucleus. Good biocompatibility results were found with MTT and hemolysis assay. These attractive results indicate that prepared r-FCDs are promising probe for cancer diagnosis and treatment.