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

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 ß (Aß) 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 Aß(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 Aß(1-40) and a high sensitivity. Furthermore, the incorporation of cholesterol into DMPC was effective to selectively detect Aß(1-40) in human serum, which effect was also checked by quartz crystal microbalance. Finally, Aß detection of 100-pM order was expected selectively in the serum by using the developed biosensor.

Miniaturization and High-Density Arrangement of Microcantilevers in Proximity and Tactile Sensor for Dexterous Gripping Control.

In this paper, in order to perform delicate and advanced grip control like human, a proximity and tactile combination sensor using miniaturized microcantilevers one-fifth the size of previous one as the detection part was newly developed. Microcantilevers were arranged with higher spatial density than in previous works and an interdigitated array electrode to enhance light sensitivity was added. It is found that the interdigitated array electrode can detect light with 1.6 times higher sensitivity than that in previous works and the newly fabricated microcantilevers have enough sensitivity to applied normal and shear loads. Therefore, more accurate detection of proximity distance and spatial distribution of contact force become available for dexterous gripping control to prevent 'overshooting', 'force control error', and 'slipping'.