or during thiol-disulfide exchange reactions. 103 They are also relatively stable at physiological pH and are mainly reduced in the cytosol, which contains high thiol concentrations notably due to a high presence of GSH (Figure ). Interestingly, the relatively higher stability of disulfide bonds in biological fluids compared to pH-sensitive bonds could be advantageous for more controlled and effective delivery. 104 RAFT polymerization has been used to prepare disulfide-containing vorinostat-conjugated diblock copolymer micelles loaded with tamoxifen for combination therapy. The diblock copolymer consists of a POEGMA block connected to a polystyrene (PS) block to which vorinostat was conjugated on the para position of the styrene units via disulfide linkages.