ABSTRACT
Poly(ethylene glycol) (PEG) is a polymer possessing unique physicochemical properties such as high water solubility and flexibility. From these characteristics it is known that PEG is bioinert, and it has attracted increasing attention in the sphere of biomedical applications. Since Abchowski et al. (1) reported that end-functionalized PEG can modify biologically active proteins, an interaction that caused not only lowered immunogenicity but also an alteration of pharmacokinetics, PEG modification chemistry has become increasingly important in the field of protein drugs. The modification of the protein by PEG is the so-called ‘‘PEGylation,’’
and the term has been utilized from the beginning of the 1990s (2,3). As can be seen in Figure 1, the number of publications on PEGylation chemistry is increasing significantly every year. Thus, the merits of PEGylation chemistry have been becoming clear to the research community.
