Cyclodextrin-Functionalized Chromatographic Materials Tailored for Reversible Adsorption

Novel dendronized silica substrates were synthesized. First- and second- generation polyaryl ether dendrons were appended to silica surfaces. Using Cu­(I) mediated cycloaddition “click” chemistry, β-cyclodextrin was tethered to the dendronized surfaces and to a nondendronized surface for comparison purposes. This synthesis strategy affords a modular, versatile method for surface functionalization in which the density of functional groups can be readily varied by changing the generation of dendron used. The surfaces, which are capable of adsorbing target analytes, have been characterized and studied using X-ray photoelectron spectroscopy (XPS) and vibrational sum frequency spectroscopy (VSFS). Fluorescence spectroscopy was used to study the surfaces’ ability to retain coumarin 152 (C152). These studies indicated that the β-cyclodextrin functionalized surfaces not only adsorbed C152 but also retained it through multiple aqueous washes. Furthermore, these observations were quantified and show that substrates functionalized with first-generation dendrons have a more than 6 times greater capacity to adsorb C152 than slides functionalized with monomeric β-cyclodextrin. The first-generation dendrons also have 2 times greater the capacity than the larger generation dendrons. This result is explained by describing a dendron that has an increased number of β-cyclodextrin monomers but, when covalently bound to silica, has a footprint too large to optimize the number of accessible monomers. Overall, both dendronized surfaces demonstrated an increased capacity to adsorb targeted analytes over the slides functionalized with monomeric β-cyclodextrin. The studies reported provide a methodology for characterizing and evaluating the properties of novel, highly functional surfaces

A global benchmark study using affinity-based biosensors

International audienceTo explore the variability in biosensor studies, 150 participants from 20 countries were given the same protein samples and asked to determine kinetic rate constants for the interaction. We chose a protein system that was amenable to analysis using different biosensor platforms as well as by users of different expertise levels. The two proteins (a 50-kDa Fab and a 60-kDa glutathione S-transferase [GST] antigen) form a relatively high-affinity complex, so participants needed to optimize several experimental parameters, including ligand immobilization and regeneration conditions as well as analyte concentrations and injection/dissociation times. Although most participants collected binding responses that could be fit to yield kinetic parameters, the quality of a few data sets could have been improved by optimizing the assay design. Once these outliers were removed, the average reported affinity across the remaining panel of participants was 620 pM with a standard deviation of 980 pM. These results demonstrate that when this biosensor assay was designed and executed appropriately, the reported rate constants were consistent, and independent of which protein was immobilized and which biosensor was used. (C) 2008 Elsevier Inc. All rights reserved