Amyloid Peptide Aggregation In Plugs Formed By Microfluidics

Abstract

We present a novel microfluidic device for amyloid peptide aggregation research. The device relies on the control of interfacial chemistry, which allows miniaturizing of aggregation measurements to nanoliter volumes. In traditional in vitro aggregation experiments, adsorption of amyloid peptides to various interfaces has been shown to nucleate and to enhance peptide aggregation. The problem of adsorption is even more pronounced upon miniaturization of aggregation experiments. Miniaturization leads to an increase of the surface-to-volume ratio, and concomitantly to an increase of amyloid peptide aggregation if the surface is not controlled. Nevertheless, miniaturization of aggregation experiments is desirable for samples available only in small volumes, as for example cerebrospinal fluid (CSF) from mice. CSF has recently gained interest in Alzheimer research, however CSF analytics has been hampered to due the small available volume.In order to miniaturize and control the interfacial chemistry of aggregation experiments we used a plug based microfluidic approach. Plugs are nanoliter sized aqueous droplets formed in the flow of immiscible fluids inside microfluidic channels. Upon peptide encapsulation into plugs, the unfavorable interfaces are exchanged for an adjustable liquid/liquid interface. We show for one prominent amyloid peptide, the Alzheimer's peptide Aβ(1-40), that aggregation in plugs has kinetics of orders of magnitude slower than under standard conditions. Further we show the applicability of this miniaturized system to aggregation experiments by testing the inhibitory potency of CSF from wild type and ceAPPswePS1ΔE9/TTR-/- mice on Aβ aggregation. Using the plug-based approach, we were able to perform over 750 experiments with a single mouse CSF sample of 5 μl in volume. The plug system offers many new opportunities to investigate in vitro aggregation studies, as for example time controlled aging of amyloid peptides, nucleation in a confined environment, and screening of drug components.