PCSK9 Conjugated Liposomes for Targeted Delivery of Paclitaxel to the Cancer Cell: A Proof-of-concept Study

Ligand-based targeting of the receptors that are overexpressed explicitly on cancer cells represents an effective drug delivery approach to enhance the chemotherapeutic efficacy. Proprotein convertase subtilisin/kexin type 9 (PCSK9) which is a serine protease enzyme primarily produced by the liver cells, can potentially be used as a targeting ligand. PCSK9 binds to the LDL-r on hepatocytes' surface, leading to endocytosis and endosomal degradation. High LDL-r expression, which is believed to meet the higher demand of the cholesterol and phospholipids to build proliferating cancer cell membrane, ensures selective uptake of the PCSK9 conjugated liposomes. In the present work, the PCSK9 conjugated liposomal system was developed to deliver paclitaxel (PTX) to cancer cells. The protein was conjugated by EDC and NHS in a two-step coupling reaction to the li-posomes containing COOH-PEG2000-COOH lipid. Conjugation was confirmed by NMR, and liposomes were further characterized by SEM and zeta sizer. PCSK9-conjugated liposomes showed high encapsulation efficiency of 69.1% with a diameter of 90.0 & PLUSMN; 4.9 nm. Long-term stability (30 days) study (Zeta potential:-9.88) confirmed excellent constancy and significant drug retention (58.2%). Invitro cytotoxicity and targeting effi-ciency was explored using MTS assay in human embryonic kidney cells (HEK293), liver hepatocellular cells (HEPG2), and a human colon cancer cell line (HCT116) for 24 h. PCSK9 conjugated liposomes exhibited significantly higher growth inhibition than the unconjugated (control) liposomes in HCT116 cell line (p < 0.001). The novel PCSK9 conjugated liposomes presented potent and precise in vitro anticancer activity and, therefore, are suggested for the first time as a promising targeted delivery system for cancer treatment.