Microchip Electrophoresis Profiling of Aβ Peptides in the Cerebrospinal Fluid of Patients with Alzheimer’s Disease

Abstract

The preferential aggregation of Aβ1-42 in amyloid plaques is one of the major neuropathological events in Alzheimer's disease. This is accompanied by a relative reduction of the concentration of Aβ1-42 in the cerebrospinal fluid (CSF) of patients developing the signs of Alzheimer's disease. Here, we describe a microchip gel electrophoresis method in polydimethylsiloxane (PDMS) chip that enables rapid profiling of major Aβ peptides in cerebrospinal fluid. To control the electroosmotic flow (EOF) in the PDMS channel and also to reduce the adsorption of the peptides to the surface of the channel, a new double coating using poly(dimethylacrylamide-co-allyl glycidyl ether) (PDMA-AGE) and methylcellulose-Tween-20 was developed. With this method, separation of five synthetic Aβ peptides (Aβ1-37, Aβ1-38, Aβ1-39, Aβ1-40, and Aβ1-42) was achieved, and relative abundance of Aβ1-42 to Aβ1-37 could be calculated in different standard mixtures. We applied our method for profiling of Aβ peptides in CSF samples from nonAlzheimer patients and patients with Alzheimer's disease. Aβ peptides in the CSF samples were captured and concentrated using a microfluidic system in which magnetic beads coated with anti-Aβ were self-organized into an affinity microcolumn under the a permanent magnetic field. Finally, we could detect two Aβ peptides (Aβ1-40 and Aβ1-42) in the CSF samples.

Development of a magnetic immunosorbent for on-chip preconcentration of amyloid β isoforms: Representatives of Alzheimer’s disease biomarkers

“…28 The electrophoresis chip has channel cross section dimensions of 100 lm  50 lm  35 mm. The channel surface was coated by introducing a 0.2% solution of a homemade copolymer PDMA-AGE in ddH 2 O.…”

“…28 Here, the MCE method was used for monitoring the lIP process by comparing the ratio of Ab isoforms in the sample before the lIP and in the elution fraction using two types of immunosorbents: one coated with mAb and one with pAb anti-Ab IgG (Fig. 8(a)).…”

“…27 Mohamadi et al also had introduced application of such immunocapture in combination with microchip electrophoresis in detecting 5 Ab isoforms. 28 It was concluded that a preconcentration step was essential for sensitive detection of such lowabundance analytes. In the present paper, therefore, results from an extensive study on the development of a magnetic anti-Ab IS and its characterization and validation for Ab peptides using various analytical tools ranging from conventional western blotting to newly developed microchip electrophoresis are presented.…”

Applications of microfluidics and microchip electrophoresis for potential clinical biomarker analysis

“…However, detection of these peptides in blood and urine is more difficult because their concentrations are 10-100 times smaller than in CSF (1 to 10 ng/mL). Mohamadi et al [53] described a two-step microchip analysis of five different β-amyloid peptides from CSF in PDMS devices. To enrich the target analytes, they performed immunocapture in a microchip and labeled the eluted analytes with fluorescent dye.…”

Field amplified sample stacking of amyloid beta (1-42) oligomers using capillary electrophoresis

“…34 Although electrophoresis in microfluidic chips has been used to study the amyloid beta protein, thus far it has not been used to study its aggregation. 35 Additionally, while these studies have indicated the value and potential for using capillary or microchip electrophoresis to improve our understanding of FIG. 1.…”