RESUMO
The existence of beta-amyloid [Aß] peptides in the brain has been regarded as the most archetypal biomarker of Alzheimer's disease [AD]. Recently, an early clinical diagnosis has been considered a great importance in identifying people who are at high risk of AD. However, no microscale electronic sensing devices for the detection of Aß peptides have been developed yet. In this study, we propose an effective method to evaluate a small quantity of Aß peptides labeled with fluorescein isothiocyanate [FITC] using a photosensitive field-effect transistor [p-FET] with an on-chip single-layer optical filter. To accurately evaluate the quantity of Aß peptides within the cells cultured on the p-FET device, we measured the photocurrents which resulted from the FITC-conjugated Aß peptides expressed from the cells and measured the number of photons of the fluorochrome in the cells using a photomultiplier tube. Thus, we evaluated the correlation between the generated photocurrents and the number of emitted photons. We also evaluated the correlation between the number of emitted photons and the amount of FITC by measuring the FITC volume using AFM. Finally, we estimated the quantity of Aß peptides of the cells placed on the p-FET sensing area on the basis of the binding ratio between FITC molecules and Aß peptides.
