title: Nanoscale glassification of gold substrates for surface plasmon resonance analysis of protein toxins with supported lipid membranes.
abstract: Surface plasmon resonance (SPR) spectroscopy, a powerful tool for biosensing and protein interaction analysis, is currently confined to gold substrates and the relevant surface chemistries involving dextran and functional thiols. Drawbacks of using self-assembled monolayers (SAMs) for SPR-related surface modification include limited stability, pinhole defects, bioincompatibility, and nonspecific protein adsorption. Here we report the development of stable nanometer-scale glass (silicate) layers on gold substrates for SPR analysis of protein toxins. The nanoscale silicate layers were built up with layer-by-layer deposition of poly(allylamine hydrochloride) and sodium silicate, followed by calcination at high temperature. The resulting silicate films have a thickness ranging from 2 to 15 nm and demonstrate outstanding stability in flow cell conditions. The use of these surfaces as a platform to construct supported bilayer membranes (SBMs) is demonstrated, and improved performance against protein adsorption on SBM-coated surfaces is quantified by SPR measurements. SBMs can be formed reproducibly on the silicate surface via vesicle fusion and quantitatively removed using injection of 5% Triton X-100 solution, generating a fresh surface for each test. Membrane properties such as lateral diffusion of the SBMs on the silicate films are characterized with photobleaching methods. Studies of protein binding with biotin/avidin and ganglioside/cholera toxin systems show detection limits lower than 1 microg/mL (i.e., nanomolar range), and the response reproducibility is better than 7% RSD. The method reported here allows many assay techniques developed for glass surfaces to be transferred to label-free SPR analysis without the need for adaptation of protocols and time-consuming synthetic development of thiol-based materials and opens new avenues for developing novel bioanalytical technologies for protein analysis.
authors.affiliation: Department of Chemistry, University of California, Riverside, California 92521, USA.
authors.forename: K Scott
authors.initials: KS
authors.lastname: Phillips
authors.forename: Jong-Ho
authors.initials: JH
authors.lastname: Han
authors.forename: Marilyn
authors.initials: M
authors.lastname: Martinez
authors.forename: Zhuangzhi
authors.initials: Z
authors.lastname: Wang
authors.forename: David
authors.initials: D
authors.lastname: Carter
authors.forename: Quan
authors.initials: Q
authors.lastname: Cheng
mesh_terms: D001360:Avidin / Q000737:chemistry; D001710:Biotin / Q000737:chemistry; D002772:Cholera Toxin / Q000502:physiology; D005732:Gangliosides / Q000502:physiology; D006046:Gold / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D011073:Polyamines / Q000737:chemistry; D011485:Protein Binding / Q000502:physiology; D017640:Silicates / Q000737:chemistry*; D020349:Surface Plasmon Resonance / Q000379:methods*
chemical_list: D005732:Gangliosides; D011073:Polyamines; D017640:Silicates; D001360:Avidin; C063994:polyallylamine; D001710:Biotin; D006046:Gold; D002772:Cholera Toxin