Analysis of Amyloid-β Peptides in Cerebrospinal Fluid Samples by Capillary Electrophoresis Coupled with LIF Detection

Abstract

We report a CE-LIF method for the separation and detection of five synthetic amyloid-β peptides corresponding to an important family of CSF-biomarkers in the context of Alzheimer disease (AD). The presumed most relevant peptides (Aβ1-42, Aβ1-40, and Aβ1-38) that may support the differentiation between AD and healthy patients or other dementias were successfully detected in CSF by incorporating an immunoconcentration step prior to CE analysis of derivatized peptides. We labeled the Aβ peptides with a fluoroprobe dye before CE-LIF analysis. This reagent reacts with the amino groups of lysine residues and produced mostly ditagged Aβ peptides under the proposed experimental conditions. The labeling reaction displayed similar efficiency with each one of the five different synthetic Aβ peptides that were tested. The limit of detection of the CE-LIF method approached 280 attomoles of injected synthetic labeled Aβ peptides. We obtained excellent correlation between peak areas and peptide concentrations from 35 nM to 750 nM. For the detection of Aβ peptides in human CSF samples, we enriched the peptides by immunoprecipitation prior to the CE-LIF analysis. The comparison of the CE-LIF profiles obtained from CSF samples from 3 AD patients and 4 non-demented control subjects indicated noticeable differences, suggesting that this method, which relies on a multibiomarker approach, may have potential as a clinical diagnostic test for AD.

Neutral polymers as coatings for high resolution electrophoretic separation of Aβ peptides on glass microchips

“…The fully validated method was then applied to spiked CSF samples with no loss of resolution between the three Ab peptides (Ab 1-38, Ab 1-40 and Ab 1-42). Compared to the conventional CE method previously published, 26 this MCE strategy provides the ease of fast surface modication allowing six times faster separation of Ab peptides while keeping excellent repeatability, recovery and resolution for simultaneous quantication. The miniaturization solves the rst bottleneck of the development of a diagnostic tool, by demonstrating the possibility to separate these peptides in a microchip still with a high resolution.…”

“…25 A promising ratio combination, Ab 1-42/(Ab 1-42 + Ab 1-40 + Ab 1-38), producing a high discrimination between AD and nD patients has been also reported. 26 Besides these conventional Ab peptides, N-truncated ones have recently attracted the attention of several research groups (see ref. 27 for a review).…”

Advances and Pitfalls in the Capillary Electrophoresis Analysis of Aggregates of Beta Amyloid Peptides

“…To obtain specificity in the method, several Aβ peptides must be analyzed and their relative ratio must be determined before obtaining a clear picture of Aβ alteration [10,12,13]. The limitations of these approaches, focused on Aβ monomers quantification, led to the need to determine fibrils themselves.…”

Magneto-immunocapture with on-bead fluorescent labeling of amyloid-β peptides: towards a microfluidized-bed-based operation

“…2 On the other hand, low levels of Aβ 1-42 in CSF may be also associated with other neurodegenerative diseases (NDs), notably dementia with Lewy body (DLB), Parkinson's disease (PDD) or Creutzfeld-Jacob disease (CJD). Different proposed biomarker combinations for AD include Aβ 1-42 and Tau/p-Tau protein, 5,6 Aβ 1-42/Aβ 1-40 ratio, 6,7 Aβ 1-42, Aβ 1-40 and Aβ 1-38, 8,9 the ratio of Aβ 1-42/(Aβ 1-42 + Aβ 1-40 + Aβ 1-38), 10 the ratio Aβ 1-40/42 and those between Aβ 1-37, Aβ 1-38 and Aβ 1-39 11,12 and Aβ 1-42 together with Aβ 2-42. Different proposed biomarker combinations for AD include Aβ 1-42 and Tau/p-Tau protein, 5,6 Aβ 1-42/Aβ 1-40 ratio, 6,7 Aβ 1-42, Aβ 1-40 and Aβ 1-38, 8,9 the ratio of Aβ 1-42/(Aβ 1-42 + Aβ 1-40 + Aβ 1-38), 10 the ratio Aβ 1-40/42 and those between Aβ 1-37, Aβ 1-38 and Aβ 1-39 11,12 and Aβ 1-42 together with Aβ 2-42.…”

“…Capillary zone electrophoresis (CZE), being the simplest mode of this technique, was applied successfully for separation and quantification of a mixture of different Aβ peptides down to 300-500 nM with UV detection 28 and 35 nM with laser-induced fluorescent detection (LIF), 10 respectively. Capillary zone electrophoresis (CZE), being the simplest mode of this technique, was applied successfully for separation and quantification of a mixture of different Aβ peptides down to 300-500 nM with UV detection 28 and 35 nM with laser-induced fluorescent detection (LIF), 10 respectively.…”