Surface modification of lipid-based nanocarriers for cancer cell-specific drug targeting

Targeted drug delivery systems using nanocarriers for anticancer drugs have been investigated for over several decades. Among the many nanocarrier systems, lipid-based nanocarriers such as liposomes, solid lipid nanoparticles, and nanostructured lipid carriers have afforded attention as a carrier system to improve the efficacy of anticancer drugs. Recent efforts have focused on cancer cell-specific drug delivery through the functionalization of the surface of lipid-based nanocarriers with various ligands such as targeting moieties, cell-penetrating peptides, and cell-penetrating homing peptides to overcome non-selectivity, minimize side effects, and enhance antitumor efficacy. However, the use of ligand modification has been limited because the nanocarriers were easily recognized by the mononuclear phagocyte system and thus rapidly removed from the blood circulation. To achieve prolonged systemic circulation, nanocarriers were further modified with protective polymers such as polyethylene glycol (PEG). Unexpectedly, this presented a PEG dilemma, as the interaction of ligands with the target was hindered and induced poor cellular uptake. Recently, stimuli-sensitive cleavage of the PEG coat, following recognition of the cancer cell microclimate, such as low pH, redox-potential, and over-expressed enzymes, was established to solve this problem. This review presents a comprehensive overview on the current state of surface-modified lipid-based nanocarriers for the improved delivery of anticancer drugs. © 2017, The Korean Society of Pharmaceutical Sciences and Technology.