Preparation of ds-DNA functionalized magnetic nanobaits for screening of bioactive compounds from medicinal plant.

A novel magnetic nanocomposite (MNPs@DNA) was synthesized by bonding double strand DNA (ds-DNA) onto Fe3O4 magnetic nanoparticles (MNPs) directly. MNPs@DNA was characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV), Fourier transform infrared spectroscopy (FT-IR) and thermo-gravimetric analysis (TGA), which indicated that ds-DNA was immobilized onto MNPs. Vibrating sample magnetometer (VSM) analysis indicated that the MNPs@DNA had a high saturation magnetization of 42.97emu/g. A novel method for screening of active compounds from natural sources was developed by employing MNPs@DNA as a nanobait and high-performance liquid chromatography-mass spectrometry as detecting system. Columbamine, palmatine, jateorhizine, epiberberine and berberine were identified as DNA binders from the extract of Rhizoma coptidis. In addition, a comparison of the binding abilities among MNPs with different DNA strand lengths (25, 200 and 1200bp) showed that the shortest one exhibited the highest binding ability. This is the first report on fast chemical characterization of active ingredients in medicinal plant using ds-DNA immobilized on magnetic nano-baits. This method can be used not only for screening of DNA binders from complex herbal matrices, but also for assessing the affinities between a specific ds-DNA and its potential binders.