Functionalized Liposomes for Tumor Targeting as Advanced Tools for Cancer Therapy
Liposomes are self-closed, spherical structures composed of a phospholipid bilayer membrane that encapsulates an aqueous cavity. Liposomes are the most promising tools for controlled drug delivery, and are currently approved by the FDA as drug carriers for cancer treatment. Liposomes are able to retain large quantities of drugs and their PEGylation prevents their removal from circulation by macrophages. Although small liposomes have the capability to self-accumulate at tumor sites by extravasating the leaky blood vessels, this process is slow and uncontrollable. New methods of targeting tumors are necessary to increase the efficiency of liposome-based cancer treatments. Two liposome-based treatment systems are presented. In the first example, specific interactions between the over-expressed folate receptors in cancer cells and the folate-conjugated liposomes are utilized to target cancer cells without causing harm to normal tissues. In the second example, Anginex-conjugated liposomes are used to target endothelial cells as a method for specifically inhibiting vascular endothelial cell proliferation and halting angiogenic processes associated with the formation of new blood vessels at tumor sites. This work opens up new avenues for developing more effective treatment approaches for curing cancer.