5. Conclusions
Drug and protein delivery by polymer conjugation has open new pathway of research. It is important to remember that the development of complex coupling strategies such as glycoPEGylation, a double-step enzymatic approach which generates conjugates, was considered impossible only a few decades ago. In the same way, what is now considered too complex or unsuitable for further investigation may quickly lead to new discoveries given the extraordinary progression we are witnessing in all fields of technology. It goes without saying then that researchers must continue to exert every effort to address and overcome all hurdles along the way exploiting the know-how gained from interdisciplinary research. The example of enzymatic PEGylation itself demonstrates that the collaboration between chemists and biologists can lead to the development of promising conjugates. The same can be said for the collaboration between molecular biologists and polymer chemists who are developing proteins with expanded genetic codes incorporating unnatural amino acids that will enrich the repertoire of useful tools available to science. These unnatural amino acids contain, in fact, a group suitable for click chemistry conjugation of a polymer [96]. Future developments will be facilitated by knowledge exchange and sharing that should be encouraged at all levels in view of producing safer, more tolerable, and efficacious drugs.