Polymeric capsules and micelles as promising carriers of anticancer drugs

Polymeric micelles and capsules are promising candidates for carriers of antineoplastic medications. Biodegradability and broadly defined biocompatibility are the key features that should always characterize polymers intended for medical applications. A well-designed delivery system ought to ensure the safe transport of chemotherapeutic agents to the target area and thus minimize systemic exposure to these drugs, limiting their toxic effect, preferably to the cancer cells. Polymeric micelles are often tailored for encapsulation of water-insoluble drugs. Micellar structures are usually fabricated as a result of self-assembly of various amphiphilic block copolymers in aqueous environment. More advanced methods are used to form capsules with a liquid core and a shell made of fused polymer nanoor microparticles. Such a coating can have homogeneous or heterogeneous composition. Janus and patchy capsules are usually characterized by more useful and advanced properties. Although some polymeric carriers are designed for a sustained release of the cargo, more sophisticated approaches involve payload liberation on demand under the influence of selected chemical or physical stimuli. The variety of available polymers and a wide range of possibilities of forming copolymers from different kind of monomers make polymeric materials ideal for the production of drug delivery systems with the desired properties. The aim of the present review is to sum up selected aspects of the use of polymeric micelles as carriers of cytostatic drugs, taking into account clinical applications. The additional objective is to show the studies on creating alternative systems based on stimuli-responsive capsules with shells made of polymeric particles.