Thiol Michael addition reaction: a facile tool for introducing peptides into polymer‐based gene delivery systems

Polymers, as widely used non‐viral gene carriers, suffer from high cytotoxicity and relatively low transfection efficiency. Such crucial drawbacks of polymers could be solved by incorporating short and bioactive peptides. The resulting synthetic polymer–peptide conjugates can not only maintain their own special characteristics, but also gain novel characteristics far beyond those of their parent polymer and peptide components to overcome barriers to gene delivery. There are various chemoselective reactions applied in the synthesis of polymer–peptide conjugates, such as Heck, Sonogashira and Suzuki coupling, Diels–Alder cycloaddition, click chemistry, Staudinger ligation, reductive alkylation and oxime/hydrazone chemistry. Among them, thiol–ene click reactions, including thiol–ene radical and thiol Michael addition reactions, are common methods for preparing peptide–polymer conjugates. In this review, we focus on thiol Michael addition reactions, elaborate on their mechanisms and highlight their applications in the synthesis of polymer–peptide conjugates for gene delivery. © 2017 Society of Chemical Industry