Monodispersity of Poly(ethylene glycol) Matters for Low-Fouling Coatings

Poly(ethylene glycol) (PEG) is the most used hydrophilic polymer for low-fouling coatings to minimize nonspecific interactions. The PEG molecular weight or its length as well as surface density are typically considered as the main impacts on the control over low-fouling properties. However, the influence of PEG monodispersity on such investigations is typically ignored and rarely reported. Herein, we report the assembly of PEGylated coatings on planar surfaces and Au nanorods (AuNRs) using a series of monodisperse PEG (Mono-PEG) with exact molecular weights and commonly used polydisperse PEG (Poly-PEG) to investigate the effect of the PEG molecular weight and monodispersity on the low-fouling properties. Nonspecific interactions with proteins or cells on PEGylated planar surfaces can be significantly reduced when Mono-PEG with a molecular weight of 752 Da and above is used, while a higher average molecular weight of 2000 Da is required for Poly-PEG-modified surfaces. Cell association of PEGylated AuNRs further confirms that a low molecular weight of Mono-PEG is sufficient to achieve low-fouling properties. This study provides an insight and general guidance into the engineering of low-fouling surfaces by the appropriate choice based on the PEG monodispersity and/or molecular weights.