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Ultra Low Fouling Zwitterionic Polymers with Biomimetic Adhesive Groups

Guozhu Li, Department of Chemical Engineering, University of Washington, Box 351750, Seattle, WA 98105 and Shaoyi Jiang, Chemical Engineering, University of Washington, Benson Hall, Box 351750, Seattle, WA 98195.

Catechol derivatives inspired from the adhesive proteins found in mussels have been used for the functional modification of material surfaces. This is a very promising method for attaching functional groups to a wide range of surfaces. In recent years, we have developed ultra low fouling polymers based on zwitterionic materials, such as poly(sulfobetaine methacrylate) (polySBMA) and poly(carboxybetaine methacrylate) (polyCBMA). They show strong resistance to non-specific protein adsorption from a single protein solution such as fibrinogen and lysozyme and from complex media such as human serum and plasma. Catechol derivatives are desirable as a versatile grafting way for the efficient, convenient and stable anchoring of ultra low fouling groups onto surfaces.

In this work, we prepared zwitterionic-catechol conjugates. Atom transfer radical polymerization (ATRP) was employed to produce multiple-catechol initiators or catechol-g-zwitterionic polymers with controlled molecular weights. Bindings of these zwitterionic-catechol conjugates to various self-assembly monolayer (SAM) surfaces terminated with CH3, OH, COOH, NH2 have been studied to reveal binding mechanisms. Results are compared with those from bare gold surfaces. Protein adsorption from a single protein solution or blood serum/plasma onto these surfaces grafted with zwitterionic groups was tested by a surface plasmon resonance (SPR) sensor. Results show excellent nonfouling properties of these modified surfaces. Effects of multi-catechol anchor, buffer, ionic strength and temperature on the adhesion were also investigated. This work demonstrates a new, convenient and efficient way for surface modification to achieve ultra low fouling.