A drug delivery system with red fluorescence for the delivery and release of 5-fluorouracil in vitro

A drug delivery system with red fluorescence, based on Eu3+-doped ZnAl-LDH, is used for the delivery and release of the 5-fluorouracil (5-Fu) which is an anticancer drug. The release of 5-Fu was carried out in simulated intestinal medium (phosphate buffer solutions with pH 7.4 and 37 °C). The release of 5-Fu shows an initial rapid release with the average rate of 4.48 × 10−4 g·L−1/min and 70.33% release within the first 240 min, followed by a slow release with the average rate of 9.79 × 10−5 g·L−1/min and 29.67% release between 240 and 720 min. The loading capacity of the Eu3+-doped ZnAl-LDH for the 5-Fu was estimated to be about 35.0% (namely 35.0 g of 5-Fu per 100 g Eu3+-doped LDH). Interestingly, the loading of 5-Fu into the Eu3+-doped ZnAl-LDH attenuated the red fluorescence of the Eu3+-doped ZnAl-LDH, and its fluorescence was recovered after the 5-Fu released. This red fluorescent change may be used for in situ probing of the delivery and release of 5-Fu at specific sites.