Block copolymer micelles as a solution for drug delivery problems

Micelles, nanosized colloidal particles with a hydrophobic core and hydrophilic shell, can be successfully used for the solubilisation of various poorly soluble pharmaceuticals, and demonstrate a series of attractive properties as drug carriers. Polymeric micelles, such as micelles formed by amphiphilic block copolymers, are of a special interest as they possess high stability both in vitro and in vivo, and good biocompatibility. Drug-loaded micelles can spontaneously accumulate in body areas with compromised vasculature (tumours, infarcts) via the enhanced permeability and retention (EPR) effect. Micelles made of stimuli-responsive (pH- or temperature-sensitive) amphiphilic block copolymers can release their contents in pathological areas demonstrating hyperthermia or acidosis. Various specific targeting ligand molecules, such as antibodies, can be attached to the micelle surface and bring drug-loaded micelles to, and into, target cells (cancer cells being a primary target). Micelles carrying various reporter (contrast) groups may become the imaging agents of choice in different imaging modalities. This review will consider some recent trends in using micelles as pharmaceutical carriers.