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Highly sensitive quantification of Alzheimer's disease biomarkers by aptamer-assisted amplification.

ABSTRACT: Alzheimer's disease (AD), a chronic neurodegenerative disease associated with the loss of neurons in the brain, is the most pervasive type of dementia; 47 million people are affected, and the number is expected to increase to more than 131 million by 2050, according to Alzheimer's Disease International. Both early diagnosis and continuous monitoring are crucial for early intervention, symptomatic treatment, monitoring of the efficacy of intervention and improved patient function. Beta-amyloid peptide, tau, and phosphorylated tau are useful for screening and diagnosis; meanwhile, simultaneous assessment of multiple biomarkers is of paramount importance for accurate disease diagnosis. Methods: Herein, we report a direct, inexpensive and ultrasensitive aptamer-based multiplex assay for the quantification of trace amounts of AD biomarkers in both human serum and cerebrospinal fluid (CSF) samples. In this newly developed assay, molecular recognition of an antibody-aptamer pair provides high specificity in target detection, and the use of a DNA amplification strategy affords high sensitivity, allowing quantification of AD biomarkers in both biological fluids in 1.5 h with only a diminutive amount of the sample consumed. A tailor-made turn-on fluorophore, namely, SPOH, was employed to label the antibody-aptamer hybrids and provide a strong fluorescence signal, which was then detected with a total internal reflection fluorescence microscopy electron-multiplying charge-coupled device (TIRFM-EMCCD) imaging system. The simultaneous detection of biomarkers was achieved by a direct shape-coded method in which the nanoplatforms can be distinguished from one another by their morphologies. Results: This assay demonstrated a lower detection limit (in the femtomolar range) for AD biomarkers than the previously reported antibody-antibody method. Conclusion: The developed assay holds tremendous clinical potential for early diagnosis of AD and monitoring of its progression.

SUBMITTER: Chan HN

PROVIDER: S-EPMC6568170 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Highly sensitive quantification of Alzheimer's disease biomarkers by aptamer-assisted amplification.

Chan Hei-Nga HN Xu Di D Ho See-Lok SL He Dinggeng D Wong Man Shing MS Li Hung-Wing HW

Theranostics 20190509 10

Alzheimer's disease (AD), a chronic neurodegenerative disease associated with the loss of neurons in the brain, is the most pervasive type of dementia; 47 million people are affected, and the number is expected to increase to more than 131 million by 2050, according to Alzheimer's Disease International. Both early diagnosis and continuous monitoring are crucial for early intervention, symptomatic treatment, monitoring of the efficacy of intervention and improved patient function. Beta-amyloid pe ...[more]

PMID: 31244934

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Project description:BACKGROUND: Amyloid precursor protein (APP), a key molecule in Alzheimer's disease (AD), is metabolized in two alternative cleavages, generating either the amyloidogenic peptides involved in AD pathology or the soluble form of APP (sAPP?). The level of amyloidogenic peptides in human cerebrospinal fluid (CSF) is considered to be a biomarker of AD, whereas the level of sAPP? in CSF as a biomarker has not been clearly established. sAPP? has neurotrophic and neuroprotective properties. Stimulating its formation and secretion is a promising therapeutic target in AD research. To this end, very sensitive tests for preclinical and clinical research are required. METHODS: The tests are based on homogenous time-resolved fluorescence and require no washing steps. RESULTS: We describe two new rapid and sensitive tests for quantifying mouse and human sAPP?. These 20 ?l-volume tests quantify the levels of: i) endogenous mouse sAPP? in the conditioned medium of mouse neuron primary cultures, as well as in the CSF of wild-type mice, ii) human sAPP? in the CSF of AD mouse models, and iii) human sAPP? in the CSF of AD and non-AD patients. These tests require only 5??l of conditioned medium from 5 × 10(4) mouse primary neurons, 1??l of CSF from wild-type and transgenic mice, and 0.5??l of human CSF. CONCLUSIONS: The high sensitivity of the mouse sAPP? test will allow high-throughput investigations of molecules capable of increasing the secretion of endogenous sAPP? in primary neurons, as well as the in vivo validation of molecules of interest through the quantification of sAPP? in the CSF of treated wild-type mice. Active molecules could then be tested in the AD mouse models by quantifying human sAPP? in the CSF through the progression of the disease. Finally, the human sAPP? test could strengthen the biological diagnosis of AD in large clinical investigations. Taken together, these new tests have a wide field of applications in preclinical and clinical studies.

Dataset Information

Highly sensitive quantification of Alzheimer's disease biomarkers by aptamer-assisted amplification.

Publications

Highly sensitive quantification of Alzheimer's disease biomarkers by aptamer-assisted amplification.

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