(444e) Effect of Entanglements in Lipid- and Polymer-Planar Membranes on Nucleation of Amyloid ? and Its Fibril Growth Behavior

Design of biosensor to detect amyloid β peptide (Aβ) from Alzheimer’s disease requires the biocompatible materials with high affinity to Aβ. We then used the biocompatible polymers polymetyl methacrylate (PMMA), polysulfone (PSf), poly(L-lactic acid) (PLLA), and polyvinylpyrrolidone (PVP), together with phospholipid from biomembranes such as 1,2-dioleoyl-phosphatidylcholine (DOPC) and 1,2-dipalmitoyl-phsphatidylcholine (DPPC). Phospholipid- and polymer-based membranes were prepared on the surface of Au electrode of the quartz crystal microbalance (QCM). The accumulated amount of Aβ based on the frequency change of QCM was in order of PSf > PLLA > DOPC > PMMA ~ PVP ~ DPPC. Generally, the accumulation of Aβ results in its fibrillation via a nucleation. The fibrillation behavior of Aβ on these planar membranes was then examined by using a total internal reflection fluorescence miscroscopy combined with a fluorescence probe thioflavin T (ThT). Because ThT can specifically bind to amyloid of Aβ. The nucleation rate of Aβ on planar membranes was determined from the reciprocal of lag time measured by ThT fluorescence intensity. Nucleation rate of Aβ was negatively correlated with the molecular weight of polymers. The slope of nucleation rate to molecular weight in the range of more than 100,000 was larger than that in the range below 100,000. This strongly suggested that the entanglements of polymers inhibited the nucleation process of Aβ. The entanglements within planar membranes is a key factor for regulating the formation of Aβ assemblies on membrane interfaces.