A common feature found in many prodrug systems to obtain controlled response, is their dependency on linker units such as self-immolative spacers or a metabolically cleavable connection. Specifically, for self-immolative systems, prodrug constructs require at least one functional group that allows attachment to a targeting or depot scaffold. Several linker types have been developed, including oximes/imines 20 , hydrazone and disulfide bonds for a variety of drug candidates. Despite these advancements, many synthetic challenges remain, especially the incorporation of prodrugs into a carrier material. Indeed, the majority of prodrugs rely on carrier systems for water solubility. So far, material development for prodrugs is based either on non-covalent linkage, including encapsulation , self-assembly or is achieved through complex synthesis procedures, which is often limited to polymer conjugates or dendrimer systems .