Objectives: This study tried to achieve active targeting of Muc1 in cancer; the surface of PEGylated liposomal doxorubicin (PLD/Doxil®) was decorated with FA12 peptide. Methods: According to docking results, FA12 was selected for this study, among four different peptides. MD simulation was also conducted as an additional confirmation of the binding interaction between FA12 and Muc1. Liposomal formulations were prepared; 1HNMR and HPLC techniques were used to verify peptide conjugation to DSPE-PEG2000-COOH. Afterward, DSPE-PEG2000-FA12 was postinserted into the PLD at 50, 100, 200, and 400 peptides per liposome. The size, zeta potential, release profile, cytotoxicity (IC50), and cell uptake (using fluorescence microscopy and flow cytometry) were evaluated. In vivo biodistribution and antitumor activities were studied on mice bearing C-26 colon carcinoma. Results: Cell uptake and cytotoxicity results revealed that PLD-100 (targeted PLD with 100 FA12 per liposome) could significantly enhance cellular binding. Furthermore, PLD-100 demonstrated higher antitumor efficacy, indicating more remarkable survival compared to PLD and other targeted PLDs. PLD-100 exhibited higher doxorubicin tumor accumulation compared to PLD. Conclusions: FA12 peptide is a promising targeting ligand for PLD to treat cancers with a high level of Muc1 expression and merits further investigations.

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