Covalent binding of the components is undoubtedly the best option to maximize the structural integrity of drug delivery systems. However, this approach requires the presence of appropriate functional groups on the nanocarriers that enable this type of conjugation. An elegant approach in this regard is to coat the core-shell structure with another layer of PEG (PEGylation). The basic idea of PEGylation so far has been to avoid the components of blood circulation, thus reducing the degradation and rapid excretion of drugs from the body, as shown in the previous paragraph. At the same time, this approach decorates the surface of the nanocarrier with functional groups that pave the way for the conjugation of CPPs. Thus, the strategy of PEGylation is of utmost importance for two reasons.