Eu-doped ZnAl-LDH as a Fluorescent Labeling Carrier for the Delivery and Controlled Release of Camptothecin

Europium doped Zinc-aluminum layered double hydroxide (Eu-doped ZnAl-LDH) as a fluorescent labeling carrier for the delivery and controlled release of camptothecin (CPT) has been studied. X-ray diffraction (XRD) patterns showed that the basal spacing of the Eu-doped ZnAl-LDH intercalated with CPT (2.27 nm) was larger than that of the initial Eu-doped ZnAl-LDH (0.88 nm), indicating the successful intercalation of CPT into the Eu-doped ZnAl-LDH carrier. X-ray photoelectron spectroscopy (XPS) suggested that some Eu(III) were reduced to Eu(II) after the intercalation of CPT into the Eu-doped ZnAl-LDH. The release of the CPT from drug carrier was carried out in a simulated medium. It was found that the cumulative concentration of the released CPT was exponential with releasing time, and well conformed to the exponential equation: C=A-Bexp(-kt). It took 720 minutes (min) for the complete release of CPT from drug carrier. Fluorescent analyses revealed that the fluorescence attributed to the drug delivery system changed from red, blue-green, to blue emission during delivery and release of CPT, which may be a favorable signal for "detecting" the delivery and release of CPT. Thus, the present Eu-doped ZnAl-LDH may be a feasible drug carrier with fluorescent labeling function.