Aptamer-functionalized Fe3 O4 magnetic nanoparticles as a solid-phase extraction adsorbent for the selective extraction of berberine from Cortex phellodendri.

The extraction adsorbent was fabricated by immobilizing the highly specific recognition and binding of aptamer onto the surface of Fe3 O4 magnetic nanoparticles, which not only acted as recognition elements to recognize and capture the target molecule berberine from the extract of Cortex phellodendri, but also could favor the rapid separation and purification of the bound berberine by using an external magnet. The developed solid-phase extraction method in this work was useful for the selective extraction and determination of berberine in Cortex phellodendri extracts. Various conditions such as the amount of aptamer-functionalized Fe3 O4 magnetic nanoparticles, extraction time, temperature, pH value, Mg2+ concentration, elution time and solvent were optimized for the solid-phase extraction of berberine. Under optimal conditions, the purity of berberine extracted from Cortex phellodendri was as high as 98.7% compared with that of 4.85% in the extract, indicating that aptamer-functionalized Fe3 O4 magnetic nanoparticles-based solid-phase extraction method was very effective for berberine enrichment and separation from a complex herb extract. The applicability and reliability of the developed solid-phase extraction method were demonstrated by separating berberine from nine different concentrations of one Cortex phellodendri extract. The relative recoveries of the spiked solutions of all the samples were between 95.4 and 111.3%, with relative standard deviations ranging between 0.57 and 1.85%.

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

A sensitive and stable bioassay for the detection of Aß oligomer (Aßo), 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 Aßo aptamer (DNA1) and the complementary oligonucleotide of the Aßo 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 Aßo was introduced, the aptamer DNA1 preferentially bound with Aßo 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 Aßo in the range of 0.2-15nM with a detection limit of 36 pM. The developed method then was successfully applied to measure Aßo 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.