In vivo tumor-suppressing efficacy and cell internalization of doxorubicin loaded in liposomes bearing folate

Thioether Phosphatidylcholine Liposomes: A Novel ROS-Responsive Platform for Drug Delivery

Liposomes are the most valuable nanocarriers in clinical use because of their biocompatibility, biodegradation, and effective encapsulation of hydrophilic or hydrophobic drugs. However, their applications are limited by the structure and functions of the most common phospholipids used as the main component of the liposomes. In this work, novel series of thioether phosphatidylcholines (S-PCs) and S-PC-based liposomes (S-LPs) were developed for reactive oxygen species (ROS)-responsive drug release. First of all, S-PCs with different chain lengths were synthesized by a combination of click reaction and heterogeneous esterification. Differential scanning calorimetry studies indicated that S-PCs had different phase transition temperatures depending on their chain lengths. Their critical aggregation concentrations were measured by the fluorescence probe technique indicating the self-assembly ability. After that, S-PC-based stealth liposomes (S-LPs) containing DSPE-PEG₂₀₀₀ and cholesterol were prepared via a classic thin-film method. Doxorubicin (DOX) as a model drug was loaded in the stealth liposomes (DOX/S-LPs) by using the ammonium sulfate gradient method with high encapsulation efficiency. DOX/S-LPs were characterized by dynamic light scattering (DLS), transmission electron microscope (TEM), and cryogenic TEM, confirming their spherical structure with the bilayer thickness of about 4 nm. The ROS sensitivity of S-PCs and S-LPs was carefully evaluated in the presence of H₂O₂ by means of mass spectrometry, DLS, TEM, and ultraviolet spectroscopy and release study. The results indicated the significant structural change of S-LPs after H₂O₂ treatment, which demonstrated that S-LPs possessed an efficient ROS-triggered disintegration because of thioether oxidation of S-PCs. Finally, in vitro and in vivo anticancer efficiency assays revealed the improved drug potency of DOX/S-LPs, which can be attributed to ROS-triggered destruction of S-LPs after the uptake by tumor cells followed by rapid release of DOX. All together, as alternatives of traditional phosphatidylcholines, S-PC-based stealth liposomes are promising ROS-responsive carriers for the controlled delivery of drugs.

Folic acid-modified liposomal drug delivery strategy for tumor targeting of 5-fluorouracil

The aim of this study was to develop a liposomal formulation to selectively target cancer cells. Liposomes were prepared using thin layer method and folic acid (FA) was applied for targeted delivery of 5FU to cancer cells. Liposomes prepared were characterized for encapsulation efficiency (EE%), morphology and their particle size. Cellular uptake, cytotoxicity study and ROS production were evaluated using CT26 cell line. Hemolysis test was performed on rat red blood cells (RBCs). Moreover, the efficacy of targeted liposomes were investigated by in vivo antitumor activity and tissue toxicities were studied by histological examination. The EE% and average particle size of liposomes were 67.88±1.84% and 114.00±4.58nm, respectively. TEM image revealed that liposomes were spherical in shape. Targeted liposomes showed higher cellular uptake, lower IC₅₀ (12.02μM compared to 39.81μM for liposomal 5FU and 39.81μM for free 5FU) and higher ROS production than free drug (62,271.28 vs 2369.55 fluorescence intensity) on cancer cells. Results of hemolysis assay confirmed the blood biocompatibility of the liposomes. Moreover, folate targeted liposomes showed better tumor inhibition than free drug (88.75mm³ tumor volume vs 210.00mm³) and no tissue abnormalities were found in histological examination. It can be concluded that folate targeted liposomes provide an effective and safe strategy for colon cancer targeted chemotherapy.