High-throughput Peptide epitope mapping using carbon nanotube field-effect transistors

Spiral Countercurrent Chromatography Enrichment, Characterization, and Assays of Carbon Nanotube Chiralities for Use in Biosensors

Single-walled carbon nanotubes (SWCNTs) are synthetic materials that hold great promise for electronics that are smaller and more versatile than the current silica-based technologies. But as-produced SWCNTs are generally a mixture of nanotubes with different structures that have vastly different properties. Separating these SWCNTs from multiwalled and metallic carbon nanotubes is vital to explore their individual properties and commercial utility ranging from optics to semiconductors. Compounding the problem of commercial investigation is that the semiconducting SWCNTs are also a mixture of different diameters and/or chiralities with different properties. Analyzing properties of enriched semiconducting SWCNT chiralities has only recently been possible through separation techniques such as aqueous two-phase solvent systems. Our study illustrates a semipreparative spiral countercurrent chromatography (CCC) separation of a commercial mixture of SWCNTs into distinct enriched fractions. A new mixer-settler spiral disk rotor was applied in this study, in which we compare the enriched SWCNTs for their effectiveness in biosensors with a high-throughput model assay, followed by antibody-mediated detection of Escherichia coli. Our results demonstrate that CCC-enriched responsive SWCNTs for biosensors can be used in our model assay, as well as for the detection of E. coli. To date, we believe that this is the first study along with Liu et al. [Chirality-controlled synthesis of single-wall carbon nanotubes using vapour-phase epitaxy. Nat. Commun.2012, 3, 1199] to demonstrate a specific utility of separated SWCNT species.

Array-in-well binding assay for multiparameter screening of phage displayed antibodies

Phage display is a well-established and powerful tool for the development of recombinant antibodies. In a standard phage display selection process using a high quality antibody phage library, a large number of unique antibody clones can be generated in short time. However, the pace of the antibody discovery project eventually depends on the methodologies used in the next screening phase to identify the clones with the most promising binding characteristics e.g., in terms of specificity, affinity and epitope. Here, we report an array-in-well binding assay, a miniaturized and multiplexed immunoassay that integrates the epitope mapping to the evaluation of the binding activity of phage displayed antibody fragments in a single well. The array-in-well assay design used here incorporates a set of partially overlapping 15-mer peptides covering the complete primary sequence of the target antigen, the intact antigen itself and appropriate controls printed as an array with 10×10 layout at the bottom of a well of a 96-well microtiter plate. The streptavidin-coated surface of the well facilitates the immobilization of the biotinylated analytes as well-confined spots. Phage displayed antibody fragments bound to the analyte spots are traced using anti-phage antibody labelled with horseradish peroxidase for tyramide signal amplification based highly sensitive detection. In this study, we generated scFv antibodies against HIV-1 p24 protein using a synthetic antibody phage library, evaluated the binders with array-in-well binding assay and further classified them into epitopic families based on their capacity to recognize linear epitopes. The array-in-well assay enables the integration of epitope mapping to the screening assay for early classification of antibodies with simplicity and speed of a standard ELISA procedure to advance the antibody development projects.