Organic nanocarriers for cancer drug delivery

A major focus in translational cancer research is the study of nanocarriers as novel delivery systems for chemotherapeutics. Organic vesicular nanocarriers, such as liposomes and micelles, have the advantage of low toxicity and the versatility to carry diverse drugs and conjugate to targeting agents. This offers the potential for combining treatment and diagnosis (theranostics). Successful incorporation into these nanoformulations has been demonstrated for classical chemotherapeutic drugs that are mostly hydrophobic, small interfering RNA, biological therapeutics and specific nanoparticles, such as superparamagnetic nanoparticles. Liposomes and micelles appear to take advantage of the enhanced permeability and retention (EPR) effect in solid tumours to increase accumulation at the target site (passive targeting). This translates to the clinic, where liposomal drug formulations are reported to exhibit higher efficacy and less side effects. Multidrug formulations and combinations with other treatments, for example, radiation or radiofrequency ablation, to trigger drug release from the nanocarrier at the target site, are mostly at the pre-clinical stage. More complex formulations that incorporate treatment agents together with targeting (active targeting) and imaging molecules have also been investigated in in vivo models with encouraging results.

► Routine chemotherapy is often aggressive, but clinical outcomes remain suboptimal.
► Liposomes can encapsulate both hydrophilic and hydrophobic molecules.
► Liposomes and micelles are suitable for combining active targeting and therapy.
► Liposomes are the largest group of clinically approved cancer drug nanoformulations.