Antibody-Based Magnetic Nanoparticle Immunoassay for Quantification of Salivary Beta-Amyloid Peptides

Alzheimer's disease (AD) is a neurodegenerative disorder that leads to a decline in cognitive and intellectual ability and irreversible mental deterioration. Based on the multidisciplinary AD researches, the most universally accepted hypotheses on AD pathogenesis are the intracerebral aggregate formation of beta-amyloid (Aβ) peptides. According to medical paradigmatic transition from medical treatment to early diagnostic prevention, scientists have considered physiological body fluid as biomarker medium in which the promising AD biomarkers could be verified. Recently, use of saliva has been considered as one of the diagnostic fluids over the past decade with meaningful diagnostic potential.We utilized saliva as a biomarker medium to correlate the salivary Aβ levels to AD pathological aspects, especially to the MCI group among AD patients to verify our detecting system to be sensitive for early diagnostic tool. The identification of the salivary AD biomarkers using a facile microarraying method would motivate this study with the assistance of magnetically assembled antibody-conjugated nanoparticles and PMT as optical detector. This simple magnetoimmunoassay system measures the photo intensity generated by fluorescence, enables the quantification of the Aβ peptides from AD salivary samples, and consequently classifies the salivary Aβ levels into AD pathological aspects. This method demonstrates a facile approach enabling to simply detect salivary Aβ peptides at a concentration as low as ∼20 pg/ml. It is expected that our simple magnetoimmunoassay system may have a potential as a detector for low-level Aβ peptides with weak fluorescence emission.