Estradiol Hemisuccinate-Modified Surface-Engineered Carbon Dots: Target-Specific Theranostic Agent

The present work highlights design and development of noncovalently surface-modified carbon dots by 17 beta-estradiol hemisuccinate that selectively stains estrogen receptor (ER)-rich cancer cells as well as kill ER (+) cancer cells by target-specific delivery of the anticancer drug doxorubicin. Positively surface-charged blue-emitting and green-emitting cationic carbon dots (CCDs) were prepared. Blue-emitting cationic carbon dots (CCDb) were prepared by the thermal coupling of tris(hydroxymethyl)aminomethane and betaine hydrochloride, while green-emitting cationic carbon dots (CCDg) were prepared by the thermal coupling of citric acid and ehylenediamine. Negatively charged estradiol hemisuccinate (E2) was synthesized from 17 beta-estradiol. Both CCDb and CCDg were noncovalently coupled with E2 through electrostatic interaction to prepare CCDb-E2 and CCDg-E2 hybrids, respectively. These surface-modified carbon dots were characterized by microscopic and spectroscopic techniques. Both CCD-E2 hybrids were highly water soluble. CCDb-E2 and CCDg-E2 exhibited enhanced emissions more than those of the respective native CCDs. Consequently, these CCDb-E2 and CCDg-E2 hybrids were utilized as selective cellular markers of estrogen receptor-rich (ER+) MCF7 cells over estrogen receptor negative (ER-) MDA-MB-231 cells and noncancerous CHO cells. Moreover, the anticancer drug doxorubicin (dox)-loaded CCDb-E2 and CCDg-E2 (CCDb-E2-dox and CCDg-E2-dox, respectively) showed selective killing of ER(+) MCF7 cells through a late apoptotic pathway by 2-fold higher efficacy compared to ER(-) MDA-MB-231 cells and noncancerous CHO cells.