Selective regulation of protein bioactivity and cell adhesion and migration via PEG microdomains on biopolymers

It is well established that biomaterial surface chemistry plays a key role in modulating cell and tissue integration on polymeric implants. A commonly used model surface for inhibiting the bioadhesivity of materials is poly(ethylene glycol) (PEG). The incorporation, via surface treatment, grafting, or copolymerization, of PEG chains can obliterate the adhesive nature of a biomaterial. This effect of PEG is believed to be the result of steric interactions, which inhibit the adsorption of extracellular matrix (ECM) proteins. The nature of interactions between PEG-containing biomaterials, adsorbed ECM proteins and resultant cell functions, while pivotal to controlled responses of biomimetic materials, remain poorly understood. In this work the authors have studied these interactions, particularly focusing on cellular responses at intermediate PEG levels, in regimes where protein adsorption is allowed to occur. To this end, the authors have employed a series of polymers synthesized through random block copolymerization of a derivative of tyrosine with gradually increasing amounts of PEG. Despite the very different hydrophobic characters of the two monomers, no phase aggregation was observed at low PEG levels; instead, microdomains of hydrophilic PEG were distributed within the hydrophobic phase