Synthesis of silver nanoparticles for the dual delivery of doxorubicin and alendronate to cancer cells

We present the synthesis of a silver nanoparticle (AgNP) based drug-delivery system that achieves the simultaneous intracellular delivery of doxorubicin (Dox) and alendronate (Ald) and improves the anticancer therapeutic indices of both drugs. Water, under microwave irradiation, was used as the sole reducing agent in the size-controlled, bisphosphonate-mediated synthesis of stabilized AgNPs. AgNPs were coated with the bisphosphonate Ald, which templated nanoparticle formation and served as a site for drug attachment. The unreacted primary ammonium group of Ald remained free and was subsequently functionalized with either Rhodamine B (RhB), through amide formation, or Dox, through imine formation. The RhB-conjugated NPs (RhB-Ald@AgNPs) were studied in HeLa cell culture. Experiments involving the selective inhibition of cell membrane receptors were monitored by confocal fluorescence microscopy and established that macropinocytosis and clathrin-mediated endocytosis were the main mechanisms of cellular uptake. The imine linker of the Dox-modified nanoparticles (Dox-Ald@AgNPs) was exploited for acid-mediated intracellular release of Dox. We found that Dox-Ald@AgNPs had significantly greater anti-cancer activity in vitro than either Ald or Dox alone. Ald@AgNPs can accommodate the attachment of other drugs as well as targeting agents and therefore constitute a general platform for drug delivery.