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

A new sample treatment approach for sensitive determination of three amyloid-beta peptides (A beta 1-42, A beta 1-40 and A beta 1-38) with capillary electrophoresis coupled with laser induced fluorescent detection is reported herein. These A beta peptides are considered an important family of biomarkers in the cerebrospinal fluid (CSF) for early diagnosis of Alzheimer's disease (AD). Due to their extremely low abundance in CSF (down to sub nM ranges), batch-wise preconcentration via magneto-immunocapture with enrichment factors up to 100 was implemented. The A beta peptides were first captured onto magnetic micro-beads. Then, on-beads fluorescent labeling of the captured A beta peptides were carried out to avoid the unwanted presence of extra fluorescent dye in the eluent as in the case of in-solution labeling. Finally thermal elution was performed and eluted labeled peptides were analyzed off line with CE-LIF. The A beta-capturing efficiencies of different commercially available antibodies grafted onto magnetic beads were tested. A beta peptides in CSF samples collected from AD's patients and healthy persons (used as controls) were measured and evaluated. As a proof of concept, the developed strategy was adapted into a miniaturized fluidized bed configuration that has the potential for coupling with a microchip separation system.