High-sensitivity Immunomagnetic System for "Liquid Biopsy" of Alzheimer's Disease

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Project Summary Alzheimer’s disease (AD) is a major healthcare and social-economic burden. With effective treatment yet to be developed, the early detection at the prodromal stage and surveillance of the progression are the best approach to control and intervene AD development. While non-invasive positron emission tomography (PET) can measure amyloid-β peptides (Aβs) and microtubule tau proteins in the brain to confirm the onset of AD, the availability of imaging equipment, diagnostic accuracy of single Aβ or tau specific radiotracer and the cost and exposure of radioactive materials limit imaging applications from early screening of large and diverse populations and repeated scans in monitoring disease progression. Therefore, there is an unmet need in developing robust, accessible and cost-effective in vitro diagnostic tools for detecting and measuring the levels of Aβs and tau proteins in cerebrospinal fluid or even blood samples of patients or at-risk individuals at the “point-of-care”. However, serum detection of these AD biomarker demands high sensitivity because of low concentrations of Aβs or tau proteins in blood samples and slow and gradual change of the levels of these biomarkers during disease progression. One major challenge to the current biospecimen based in vitro diagnostics is the biofouling effect, i.e., adsorption of proteins and biomolecules on the surface of the detecting agents and devices. This leads to the formation of the layer of unwanted molecules, which reduces the detection specificity and sensitivity by (1) blocking antibodies to the targeted biomarkers, and (2) causing high “background noise” from adsorbed non-specific proteins and other molecules interfering the detection of targeted biomarkers. We believe that these problems can be overcome by our innovative solutions, i.e., 1) the anti-biofouling polymer to coat nanoparticle capturing agents to block the non-specific protein adsorption, thus protecting the sensitivity and specificity of the targeting ligands/antibodies; 2) high magnetism magnetic iron oxide nanorods (IONRs) with nano-sized magnetic stir bar action to enhance mixing of capturing agents and targeted biomarkers in the microfluidic detection system. By integrating these technologies, our project aims to develop a multiplexing based “liquid biopsy” system with ultra-high sensitivity and specificity for serum detection of selected AD biomarkers, Aβ40, Aβ42, total-tau (tTau), phosphorylated-Tau (pTau)181 and amyloid precursor protein (APP) in one sample. We will make and optimize antibody-conjugated anti-biofouling IONRs with different aspect ratios for highly efficient fluid mixing and multiplex detection of spiked Aβ40, Aβ42, tTau and pTau proteins and APP669-711 in blood samples (Aim 1), coupled with developing a microfluidic device with effective nano-stir bar mixing for improved detection efficiency (Aim 2), and then evaluate and validate the developed “liquid biopsy” system by multiplexed measuring serum Aβ40, Aβ42, tTau, pTau proteins and APP669-711 levels in AD patients longitudinally, and comparing and correlating the serum measurement with results from Aβ and tau PET imaging and proteomics analysis done on the same patients (Aim 3).