Aim Peptides as ligands have shown the active targeting properties to the receptors like integrins, a family of receptors over-expressed in cancers. The present study was to develop and characterize two peptides modified drug-containing liposomes. Methods Argine-glycine-aspartic acid （RGD） tripeptide and glycine-argine-glycine-aspartic acid-serine （GRGDS） pentapeptide were used for modifications on the doxorubicin-loaded sterically stabilized liposomes （SSL-doxorubicin） for the liposome preparation, RGD-SSL-doxorubicin and GRGDS-SSL-doxorubicin, respectively. Characterizations were performed by measurements of the encapsulation efficiency, particle size and zeta potential, release rates in a simulated in vivo environment, and cytotoxicity to ovarian cancer cells. Cell uptake was investigated by flow cytometry and confocal microscopy methods. Results All encapsulation efficiencies of the liposomes were above 95%, and the modifications using RGD or GRGDS did not affect the final encapsulation efficiency. Average particle sizes of the liposomes Were in the range between 105.7 ± 3.5 nm and 130.5 ± 3.0 nm, and zeta potential values were between -3.3 ± 0.3 and -6.1 ± 0.3 mV. Approximately 2/5 of doxorubicin was released from liposomes before 12 h in the simulated in vivo environment containing fetal bovine serum. Inhibitory rates to cancer cells of the modified liposomes were slightly lower as compared to free doxorubicin. Similar phenomena were observed in the uptake measured by flow cytometry and confocal assay. After uptake applying various formulations on the cancer cells, doxorubicin was mainly distributed in the nuclei of SKOV-3 cells. Conclusion Two new doxorubicin-contained liposomes were successfully prepared and modified with argine-glycine-aspartic acid （RGD） tripeptide and glycine-argine-glycine- aspartic acid-serine （GRGDS） pentapeptide. In vitro characterization indicated that modifications did not alter significantly the properties of the sterically stabilized liposomes.
