Core–shell drug carriers: liposomes, polymersomes, and niosomes

Effective therapies require an efficient method for drug delivery. The main goals of drug delivery systems, or carriers, is to enhance therapeutic efficiency by targeting specific tissue, and to provide control over the rate of drug release. Core–shell vesicle drug carriers are based on bilayer-forming amphiphiles: liposomes composed of phospholipid bilayers, polymersomes composed of copolymers, and niosomes from nonionic surfactants. Designed to carry hydrophilic drugs, they offer, in addition to targeting and controlled release, protection of drugs from degradation, prolonged circulation time in vivo, and administration routes that are incompatible with the unmodified drugs. Extensive studies link delivery efficiency to the carrier size, shape, and surface chemistry and charge, as well as environmental conditions (temperature, pH) and cell type. This review discusses the three types of formulations and summarizes studies of their performance in biomedical applications such as cancer therapy (tumor targeting) or transport through the blood–brain barrier (BBB).