The density profiles of proteins adsorbed onto poly(ethylene glycol) (PEG) brushes grafted to phospholipid surfaces are characterized by neutron reflectometry (NR). PEG brushes are commonly used to suppress undesired protein adsorption to biotechnological surfaces .
Nevertheless brush failure leading to foreign body reaction is often reported. In contrast to conventional methods, NR with contrast variation allows to distinguish directly between primary protein adsorption at the grafting surfaces, secondary absorption at the brush outer edge and ternary adsorption to the polymer chains .
For protein adsorption from human blood serum significant primary adsorption into the lipid head group region is found, while at the same time pronounced ternary adsorption can be excluded. The profiles of anti-PEG antibodies are found to be significantly different for antibodies specific to the PEG end points and to the backbone. The unique structural insights obtained by NR may constitute a valuable basis for the rational design of protein-resistant surface functionalization for biotechnological applications.