Folate-targeted PEGylated liposomes improve the selectivity of PDT with meta-tetra(hydroxyphenyl)chlorin (m-THPC).

The folate receptor (FR) is over-expressed in many human tumours and is being intensively studied also in the field of nanomedicine as a target to enhance the selectivity of drug delivery to cancer cells by using nanocarriers bearing folic acid (FA) on their surface. In this study we report the encapsulation of the photosensitizer (PS) meta-tetra(hydroxyphenyl)chlorin (m-THPC) in FA-targeted PEGylated liposomes used as a novel drug delivery system for photodynamic therapy (PDT) of cancer. Our in vitro investigations revealed that only a modest fraction of targeted liposomes were internalized by specific endocytosis in FR-positive KB cells. However, FA-liposomes doubled the uptake of the entrapped m-THPC with respect to un-targeted liposomes and enhanced the photo-induced cytotoxicity in KB cells. In contrast, in FR-negative A549 cells FA-targeted or un-targeted liposomes exhibited a very similar extent of internalization and as a consequence the same photo-killing efficiency.