Protein adsorption is the first event occurring in blood-material interactions. For medical implants and in vivo sensors, surface resistance to protein adsorption and cell adhesion from complex media is needed to prevent undesirable responses of the living system to a device or implant. This creates the need for surface modifications that have low reactivity with bloodborne proteins. Recently, zwitterionic materials have been shown to have ultra low protein adsorption. Previous studies have shown that surface packing density and film thickness are important for surface resistance to non-specific protein adsorption.

In this work, poly(sulfobetaine methacrylate) (polySBMA) and poly(carboxybetaine arylic amide) (polyCBAA) were grafted onto surfaces via atom transfer radical polymerization (ATRP) method. Film thickness is controlled between 10-100nm. Protein adsorption from single fibrinogen and lysozyme solutions, serum or plasma was investigated by surface plasmon resonance (SPR) sensors. Results show that protein adsorption strongly depends on grafted film thickness. In addition, the influence of ionic strength on protein adsorption was also studied. Results show that all of these surfaces are highly resistant to non-specific protein adsorption from single fibrinogen and lysozyme solutions and several of them can be considered as “ultra low fouling” surfaces (less than 5 ng/cm² protein adsorption) to 100% blood serum or plasma. This work provides a new in vitro evaluation standard for the application of biomaterials in vivo.