Drug and gene delivery based on supramolecular assembly of PEG-polypeptide hybrid block copolymers

Recently, polypeptide hybrid polymers, particularly poly(ethylene glycol) (PEG)-polypeptide block copolymers, have been attracting significant interest for polymeric therapeutics, such as drug and gene delivery systems, utilizing their most relevant feature, that is the formation of micelles with a distinguished core-shell architecture. Of particular interest in the polypeptides is that a variety of functional groups, such as carboxyl groups and amino groups, are available as a side chain, and that they have propensities of low toxicity and biodegradability. The segregated polypeptide core of the micelle embedded in the hydrophilic palisade serves as a reservoir for a variety of drugs as well as of genes with diverse characteristics. The micelles have been developed with various functions, such as biocompatibility, stimuli- and environment-sensitivity, and targetability, aimed at their clinical use. Smart micelles have emerged as promising carriers that enhance the effect of drugs and genes with minimal side effects. in this review, recent advances in drug and gene delivery by polypeptide hybrid micelles, mostly accomplished in our group, are comprehensively described. Focus is placed on the design of PEG-polypeptide hybrid block copolymers, starting from the development of the drug-loading micelle systems to current efforts to establish a gene delivery system with a polyion complex (PIC) micelle, one of the most attractive topics in nanomedicine.