In Vitro Detection of Beta-Amyloid Peptides using a Photo-Sensitive Field Effect Transistor Integrated with a Single Layer On-Chip Optical Filter

Abstract

The importance of early Alzheimer's disease (AD) detection has been recognized to diagnose people at high risk of AD. The existence of intra/extracellular beta-amyloid (Aβ) of brain neurons has been regarded as the most archetypal hallmark of AD. The existing computed-image-based methods have limitations on accurate quantification of nanoscale Aβ peptides due to optical diffraction during the imaging process. Therefore, we propose a new method that is capable of evaluating a small amount of Aβ peptides by using photo-sensitive field-effect transistor (p-FET) integrated with a single layer on-chip optical filter. Arsenic trisulfide (As2S3) layer has adequate optical functions that reflect the unwanted ranges ( 480 nm) from fluorochromes widely used for labeling Aβ peptides.We measured destructively decayed photo-currents from As2S3-coated p-FET compared with those from bare p-FET. We also measured the elevated photo-currents generated by the transmitted fluorescent emission when a small amount of fluorescein isothiocyanate (FITC) were placed on As2S3-coated p-FET, indicating that the As2S3 filtered p-FET would differentiate the optically tenuous fluorescent beam. Furthermore, we measured the photo-currents generated by FITC conjugated with Aβ peptides expressed on a cell line to investigate the applicability of our p-FET sensor to the actual detection of Aβ peptides existing in a biological material.