Specific Binding of Alzheimer's Aβ Peptide Fibrils to Single-Walled Carbon Nanotubes

Abstract

Amyloids constitute a class of protein and protein fragments believed to be involved in the pathologies associated with Alzheimer's, Parkinson's and CreutzfeldtJakob diseases. These proteins can self-assemble into unique fibrillar structures that are resistant to normal protein degradation. Interesting recent developments in the study of amyloid fibrils demonstrate that they bind carbon allotropes. In this study, using single-walled carbon nanotube fieldeffect transistors (SWCNT-FETs), we show that the fibrillar form of Alzheimer's amyloid β (1-40) and (1-42) peptides specifically bind non-functionalized SWCNT in a saturable manner. Both peptides exhibited near identical binding curves with half-maximal binding concentrations of approximately 12 g/ml. Binding of the peptides to SWCNTs was diminished by including dimethyl sulphoxide (DMSO) at concentrations that inhibits fibril formation. Lastly, a monoclonal antibody (BAM-10), which binds to the N-terminal region of Alzheimer's amyloid fibrils, recognizes the amyloid peptides adhering to SWCNTs in the absence of DMSO, but not in the presence of 75% DMSO. Taken together, these results suggest that the fibrillar form of the Alzheimer's amyloid peptides are specifically binding to SWCNTs.

High-Throughput Peptide Epitope Mapping Using Carbon Nanotube Field-Effect Transistors

“…The reason for this lack of a consensus sequence might be due to using nanotube preparations that are of varying purity, diameter, chirality, surface defects, and so forth, for the selection process [33–35]. Nevertheless, the 15-mer peptides immobilized on the SWCNTs are accessible for antibody binding as was observed for a monoclonal antibody binding to A β amyloid peptides immobilized on SWCNT-FET [20]. The epitope mapping required relatively high antibody concentrations, which could reflect a lower affinity for partial epitopes represented in the peptide library.…”

“…This gp160 sequence is not identical to the gp160 used to generate the antibodies. Stock solutions (1 mg/mL) of the peptides were made with 50% acetonitrile/diH 2 O. Optimal coating concentration of the peptides was determined by titrating them onto SWCNT-FET circuits, as described by Stefansson et al [20]. Coating concentrations were empirically chosen and ranged between 10 and 100 ng/ μ L (data not shown).…”

“…We have previously used SWCNT-FETs printed on 4 ″ semiconducting silica wafers to monitor macromolecular interactions [17–20]. Each of those wafers has 92 independent circuits and was used to measure many biological molecules including IGF-1 [17], glycated human serum albumin [18], E. coli O157:H7 [19], and the fibrillar forms of Alzheimer's A β 1–40 and A β 1–42 peptides [20].…”

“…Each of those wafers has 92 independent circuits and was used to measure many biological molecules including IGF-1 [17], glycated human serum albumin [18], E. coli O157:H7 [19], and the fibrillar forms of Alzheimer's A β 1–40 and A β 1–42 peptides [20]. However, each circuit on the 92 circuit wafer has to be measured independently, which limits productivity.…”

Purification of semiconducting single-walled carbon nanotubes by spiral counter-current chromatography

“…The chromatography samples were applied to the field-effect transistor (FET) circuits according to the procedures of Fuzbien Technology Institute [28][29] to determine semiconductor activity. [30].…”