Detection of Aβ oligomers based on magnetic-field-assisted separation of aptamer-functionalized Fe3O4 magnetic nanoparticles and BaYF5:Yb,Er nanoparticles as upconversion fluorescence labels

• Published in: Talanta (Oxford) 2017-08, Vol.170, p.350-357
• Main Authors: Jiang, Ling-Feng, Chen, Bo-Cheng, Chen, Ben, Li, Xue-Jian, Liao, Hai-Lin, Huang, Hong-Miao, Guo, Zhan-Jing, Zhang, Wen-Yan, Wu, Lin
• Format: Article
• Language: English
• Subjects: Aptamer; Aβ oligomers; Fe3O4 magnetic nanoparticles; Upconversion nanoparticles
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/j.talanta.2017.04.021

A sensitive and stable bioassay for the detection of Aβ oligomer (Aβo), a potentially promising candidate biomarker for Alzheimer's disease (AD) diagnosis, was developed using Fe3O4 magnetic nanoparticles (MNPs) as the recognition and concentration elements and BaYF5:Yb,Er upconversion nanoparticles (UCNPs) as highly sensitive labels, conjugated with the Aβo aptamer (DNA1) and the complementary oligonucleotide of the Aβo aptamer (DNA2), respectively. The DNA1 hybridized with DNA2 to form the duplex structure on the surface of the MNPs/UCNPs nanocomposites probe. When the target Aβo was introduced, the aptamer DNA1 preferentially bound with Aβo and caused the dissociation of some complementary DNA2, liberating some UCNP-labeled complementary DNA2 and leading to a decreased upconversion fluorescent intensity on the surface of MNPs. The decreased fluorescence intensity of UCNPs was related to the concentration of Aβo in the range of 0.2–15nM with a detection limit of 36 pM. The developed method then was successfully applied to measure Aβo in artificial cerebrospinal fluid. Benefiting from the magnetic separation and concentration effect of MNPs, the high sensitivity of UCNPs, as well as the selectivity and stability of the aptamer, the present strategy offered valuable information related to early diagnosis of AD process. We developed a sensitive and stable bioassay for detection of Aβ oligomers (Aβo), a potentially promising candidate biomarker for Alzheimer's disease (AD) diagnosis. We first prepared the amino-functionalized Fe3O4 magnetic nanoparticles (MNPs) and BaYF5:Yb,Er upconversion nanoparticles (UCNPs), which were conjugated with avidin by a classical glutaraldehyde method. Then the biotinylated Aβo aptamer DNA1 was immobilized on avidin-conjugated MNPs, and its complementary DNA2 was linked to avidin-conjugated UCNPs, all through the biotin–avidin affinity reaction, in order to prepare the DNA1-functionalized MNPs and DNA2-functionalized UCNPs. Then the aptamer DNA1 hybridized with its part complementary DNA2 to form the duplex structure on the surface of the MNPs/UCNPs nanoprobe, therefore were assembled onto the surface of MNPs giving a background upconversion fluorescent signal. In the presence of Aβo, the aptamer DNA1 preferentially bound with Aβo and caused the dissociation of some complementary DNA2, liberating some UCNP-labeled complementary DNA2 and leading to a decreased upconversion fluorescent signal on the surface of MNPs. Then after ma