Temperature-Induced Ultradense PEG Polyelectrolyte Surface Grafting Provides Effective Long-Term Bioresistance against Mammalian Cells, Serum, and Whole Blood

We report a facile method of generating ultradense poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) surface by using high temperature alone, which in turn provides dramatic improvement in resisting nonspecific bioadsorption. X-ray photoelectron spectroscopy (XPS) revealed that the surface graft density increased  4 times higher on the surface prepared at 80 °C compared to 20 °C. The studies from small-angle X-ray scattering (SAXS) and the effect of varying ionic strength during/post assemblies at 20 and 80 °C indicated that the “cloud point grafting effect” is not the cause for obtaining high density grafting. Stringent long-term bioresistance tests have been conducted and the temperature-induced PLL-g-PEG surfaces have achieved (1) zero mammalian cell adsorption/migration for up to 36 days and (2) extremely close-to-zero protein adsorptions have been observed even after 36 days in 10% serum media and 24 h in whole blood within the ultrasensitive detection limit of time-of-flight secondary ion mass spectrometry (ToF-SIMS).