title: Protein adsorption, desorption, and aggregation mediated by solid-liquid interfaces.
abstract: Adsorption of proteins to solid-fluid interfaces is often empirically found to promote formation of soluble aggregates and larger, subvisible, and visible particles, but key stages in this process are often difficult to probe directly. Aggregation mediated by adsorption to water-silicon oxide (SiOx) interfaces, akin to hydrated glass surfaces, was characterized as a function of pH and ionic strength for alpha-chymotrypsinogen (aCgn) and for a monoclonal antibody (IgG1). A flow cell permitted neutron reflectivity for protein layers adsorbed to clean SiOx surfaces, as well as after successive "rinse" steps. Aggregates recovered in solution after gently "rinsing" the surface were characterized by neutron scattering, microscopy, and fluorescence spectroscopy. IgG1 molecules oriented primarily "flat" against the SiOx surface, with the primary protein layer desorbed to a minimal extent, whereas a diffuse overlayer was easily rinsed off. aCgn molecules were resistant to desorption when they appeared to be unfolded at the interface, but were otherwise easily removed. For cases where strong binding occurred, protein that did desorb was a mixture of monomer and small amounts of HMW aggregates (for aCgn) or subvisible particles (for IgG1). Changes in adsorption and/or unfolding with pH indicated that electrostatic interactions were important in all cases.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Center for Molecular and Engineering Thermodynamics, University of Delaware, Newark, Delaware 19716; Centerfor Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Perevozchikova
authors.affiliation: Centerfor Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899; Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania.
authors.forename: Hirsh
authors.initials: H
authors.lastname: Nanda
authors.affiliation: Department of Biopharmaceutical Product Sciences, GlaxoSmithKline, King of Prussia, Pennsylvania 19406.
authors.forename: Douglas P
authors.initials: DP
authors.lastname: Nesta
authors.affiliation: Department of Chemical and Biomolecular Engineering, Center for Molecular and Engineering Thermodynamics, University of Delaware, Newark, Delaware 19716; Centerfor Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899. Electronic address: cjr@udel.edu.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Roberts
mesh_terms: D000327:Adsorption; D000818:Animals; D002417:Cattle; D002919:Chymotrypsinogen / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007074:Immunoglobulin G / Q000737:chemistry*; D008958:Models, Molecular; D033363:Neutron Diffraction; D009994:Osmolar Concentration; D010087:Oxides / Q000737:chemistry; D066329:Protein Aggregates; D011487:Protein Conformation; D055550:Protein Stability; D053838:Scattering, Small Angle; D017655:Silicon Compounds / Q000737:chemistry; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D007074:Immunoglobulin G; D010087:Oxides; D066329:Protein Aggregates; D017655:Silicon Compounds; D014867:Water; C116473:silicon monoxide; D002919:Chymotrypsinogen
keywords: adsorption; desorption; neutron reflectivity; particle sizing; protein aggregation; scattering; stability