Label-free, chronological and selective detection of aggregation and fibrillization of amyloid beta protein in serum by microcantilever sensor immobilizing cholesterol-incorporated liposome

摘要

To facilitate the early diagnosis of Alzheimer's disease and mild cognitive impairment patients, we developed a cantilever-based microsensor that immobilized liposomes of various phospholipids to detect a trace amount of amyloid beta (A beta) protein, and investigated its aggregation and fibrillization on model cell membranes in human serum. Three species of liposomes composed of different phospholipids of 1,2-dipalmtoyl-sn-glycero-3-phosphocholine (DPPC), DPPC/phosphatidyl ethanolamine and 1,2-dipalmitoyl-sn-glycero-3-phosphorylglycerol having varied hydrophilic groups were applied, which showed different chronological interactions with A beta(1-40) protein and varied sensitivities of the cantilever sensor, depending on their specific electrostatic charged conditions, hydrophilicity, and membrane fluidity. 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) having short hydrophobic carbon chains confirmed to show a large interaction with A beta(1-40) and a high sensitivity. Furthermore, the incorporation of cholesterol into DMPC was effective to selectively detect A beta(1-40) in human serum, which effect was also checked by quartz crystal microbalance. Finally, A beta detection of 100-pM order was expected selectively in the serum by using the developed biosensor.