Biosensing of interaction between phospholipid membrane of liposome as model cell membrane and amyloid-beta protein in human serum by dielectric dispersion analysis

摘要

We have investigated time course of interaction between phospholipid membrane of liposome and amyloid-beta (Aβ) protein, which is a causative agent of Alzheimer's Disease (AD), by Dielectric Dispersion Analysis (DDA), especially for frequency range of 1-6 GHz. Two dielectric relaxations derived from bound water on liposome are observed and one of their relaxation width (Δε) suggested chronological change dependent on Aβ aggregation and fibrillization. We have newly used normal human serum as a solvent to investigate the interaction between the liposome and Aβ in the serum. Time course of interaction between the liposome and Aβ(1-40) in the human serum, thereafter the change of relaxation width (Δ(Δε)) as a parameter of Aβ concentration showed dynamic behavior of Δε, related to the aggregation and fibrillization of Aβ(1-40). In particular, a low concentration of Aβ (1 μM) has been successfully discriminated this time. Compared to the Aβ concentration in the blood (e.g. 50-200 nM) or cerebrospinal fluid (e.g. 700-4000 nM) of an AD patient, we consider that this DDA technique enables to evaluate Aβ and diagnose AD from the cerebrospinal fluid and would also be available from the blood by improving the sensitivity several times.