title: Strong resistance of a thin crystalline layer of balanced charged groups to protein adsorption.
abstract: Resistance of mixed self-assembled monolayers (SAMs) with various counter-charged terminal groups of different valence and protonation/deprotonation states to nonspecific protein adsorption is investigated. It is demonstrated that excellent nonfouling surfaces can be readily constructed from mixed positively and negatively charged components of equal valence in a wide range of thiol solution compositions. Furthermore, the lattice structure of one of the mixed SAM systems studied is revealed by atomic force microscopy (AFM) to be (5.2 +/- 0.2 A x 5.2 +/- 0.2 A)60 degrees . Results indicate that the packing structure of mixed charged SAMs is determined by strong charge-charge interactions of the terminal groups rather than S-Au and chain-chain interactions. This work provides direct evidence that conformational flexibility is not required for protein resistance of a surface and even a single compact layer of charged groups of balanced charge with a crystalline structure can resist nonspecific protein adsorption, suggesting that tightly bound water molecules on the topmost part of the mixed SAMs play a dominant role in surface resistance to nonspecific protein adsorption.
authors.affiliation: Department of Chemical Engineering, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Shengfu
authors.initials: S
authors.lastname: Chen
authors.forename: Fuchen
authors.initials: F
authors.lastname: Yu
authors.forename: Qiuming
authors.initials: Q
authors.lastname: Yu
authors.forename: Yi
authors.initials: Y
authors.lastname: He
authors.forename: Shaoyi
authors.initials: S
authors.lastname: Jiang
mesh_terms: D000327:Adsorption; D003460:Crystallization; D006046:Gold / Q000737:chemistry; D018625:Microscopy, Atomic Force; D008956:Models, Chemical; D011506:Proteins / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013455:Sulfur / Q000737:chemistry; D013499:Surface Properties
chemical_list: D011506:Proteins; D013438:Sulfhydryl Compounds; D013455:Sulfur; D006046:Gold