No 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.

High loading on a porous support is important for preparing high-performance metal catalysts, but the increased loading often results in a loss of dispersion and limited mass transfer. We approached this problem by supporting a large amount of metal or metal oxide on a hierarchically porous zeolite. The supported catalyst formed an embedded network of nanowires along the zeolite mesopores. Although tightly filled in the mesopores, the catalyst was readily accessible through microporous windows at the encasing mesopore walls. Cobalt, nickel, and TiO 2 , supported in this manner, exhibited high catalytic performance in Fischer−Tropsch synthesis, benzene hydrogenation, and furfural-to-γ-valerolactone conversion, respectively.

Hierarchical macroporous–mesoporous diglycolamide-modified silica monolith used as a selective sorbent for continuous flow separation of Th(iv) from rare earth elements.