A Versatile Approach to Unimolecular Water-Soluble Carriers : ATRP of PEGMA with Hydrophobic Star-Shaped Polymeric Core Molecules as an Alternative for PEGylation

New amphiphilic star-shaped architectures with dense hydrophilic shells were synthesized by a combination of ring-opening polymerization (ROP) of e-caprolactone (CL) and atom transfer radical polymerization (ATRP) of different poly(ethylene glycol) methacrylates (PEGMAs). The PCL hydrophobic cores with 4 and 6 arms were near-quantitatively functionalized to 4-, 6-, 8-, and 12-bromine end-capped starPCLs that were subsequently used as macroinitiators for ATRP, leading to the formation of well-defined 4-, 6-, 8-, and 12-arm starPCLpPEGMAs. The unimolecular behavior of all 4-12-arm star-shaped block copolymers was unambiguously demonstrated by dynamic light scattering (DLS) and analytical ultracentrifugation (AUC) measurements. Furthermore, no significant aggregation could be detected for the polymers loaded with different hydrophobic molecules as encapsulated guests, proving their carrier abilities in aqueous solutions. Cumulative advantages of the polyPEGMA functionalized systems, such as high hydrophilicity, tunable hydrophobic/hydrophilic balance, and molar masses, make the ATRP of PEGMA a straightforward alternative to the PEGylation approach for drug carrier systems. Furthermore, the dense PEGMA shell suppresses aggregation commonly observed for PEGylated carriers.