The Drug delivery system (DDS) consisted of several combination"s of the anticancer drug doxorubicin (DOX), polymeric drug carrier polyethylene glycol (PEG), drug spacer citric acid (CA) and targeting moiety sialic acid (SA) which was evaluated in vitro for cytotoxicity on human ovarian carcinoma cells (A2780). The targeted prodrug conjugates with two copies of SA and DOX showed enhanced cytotoxicity when compared with non-targeted prodrugs and free DOX. Targeting of the conjugate to cancer cells by sialic acid and an increase in number of copies of targeting moiety and anticancer drug enhanced prodrug uptake by cancer cells and cytotoxicity of the prodrug. Analysis of synthesized conjugates by 1NMR, MALDI/TOF, and HPLC showed the formation of the PEG prodrugs. More than 40% of the drug was released from its conjugate in presence of esterase enzyme, whereas the conjugate was stable at pH 7.4. The data obtained suggest that PAMAM G4-SA dendrimer represents a promising vehicle for...