Studying loading of 5-fluorouracil onto the surface of gold–silver nanocomposite utilizing DLS and UV–Vis spectroscopy

The antimetabolite drug 5-fluorouracil (5-Fu) is extensively applied to treat many cancerous tumors. However, in order to inhibit its severe side effects and maintain its clinical benefits and anticancer efficacy, this drug should be loaded onto a suitable nanovehicle. In this work, gold nanoparticles were synthesized using Turkevich reduction method, and then, the prepared particles coated with a thin layer of silver via re-reduction of a silver nitrate solution. XRD, EDS, DLS, TEM and UV–Visible measurements were performed to characterize gold and gold–silver nanoparticles. By taking the UV–Visible absorption spectrum, two plasmonic peaks found at 411 and 526 nm due to the localized surface plasmons of the spherical interfaces of the nanoparticles. By loading 5-fluorouracil molecules onto the surface of gold and fabrication of gold–silver nanocomposite, significant changes occurred in the TEM, DLS and UV–Vis outcomes that can be interpreted considering the re-decoration and aggregation of the nanoparticles. Moreover, both of the plasmonic peaks experienced a redshift. By adding different amounts of drug solution into the colloidal solution, a direct and meaningful relation was obtained between the absorption peaks and drug concentration, which can be used as a measuring tool to evaluate drug loading amount. This study revealed that 5-fluorouracil affects DLS and UV–Vis absorption characteristics of gold–silver nanocomposite and adsorption characteristics of the synthesized bimetallic Ag–Au nanocomposite leading to more suitable results compared to the single metal nanoparticles. It is concluded that measuring drug loading using gold–silver nanocomposite would be more precise than that of single metal nanoparticles. In addition, the drug release behavior of drug-loaded gold–silver nanocomposite was also investigated under in vitro conditions at pH 6.5 and 37 °C. This study revealed that ~ 72% of loaded drug was released after 70 h. Furthermore, the MTT assay was used to study the cytocompatibility of the loaded drug on the cancer cell line U251. This study showed that the drug-loaded nanoparticles have a higher anti-proliferative effect compared to that of the free drug against U251 glioma cancer cells.

Graphical abstract

5-Fluorouracil as an extensively used drug in the treatment of many cancers is delivered by gold–silver nanocomposite. Findings revealed that the bimetallic nanocomposite behaves much better than the corresponding single metal counterparts in the drug loading process. Loading of 5-fluorouracil molecules onto the surface of gold–silver nanoparticles significantly affects TEM, DLS and optical properties of the carrier, and therefore, a direct and meaningful relation can be obtained between the peak changes and drug concentration. In addition, the prepared nanoparticles showed acceptable anti-proliferative activity against the cancer cell line U251.