Ultrasensitive probeless capacitive biosensor for amyloid beta (Aβ1-42) detection in human plasma using interdigitated electrodes

Progressive aggregation and protein misfolding are the initial fundamental indicators of neurodegenerative disorders such as Alzheimer's disease (AD). In this study, a highly sensitive and novel method to detect amyloid beta (Aβ) biomarkers, which are a hallmark of AD, using an immunoassay platform-based interdigitated capacitive biosensor, has been explored. For several decades, aptamers have classified as a novel class of molecular recognition probes comprising single-stranded complementary DNA sequences that bind to their identified targets with high specificity and affinity by an in vitro technique called SELEX (systematic evolution of exponential and enrichment). Aptamers, often referred to as "chemical antibodies", possess several highly obvious features for clinical use. The proposed sensing bio-device was fabricated and glazed with oligomeric Aβ (oAβ) aptamer and anti-oAβ antibody, functionalized onto a Pt/Ti-featured SiO2 substrate. Subsequently, analytical studies were conducted to confirm that the specificity, sensitivity, and selective detection of the oAβ-based bioengineered surfaces facilitate a label-free approach. The bionic capacitive sensor achieved real-time detection within 5 s (faster response than ELISA) under the femto-molar range concentrations of oAβ peptide in plasma using anti-oAβ antibody and oAβ aptamer with ultra-high affinity. Furthermore, the prepared capacitive biochip was selective against plasma-borne antigens and standby for 100 days at 4 °C. The developed biosensor is suitable for point-of-care (POC) diagnostic applications owing to its portability and scalability. Furthermore, the superior efficacy of oAβ in identifying AD has huge potential for biomedical applications.